text:
\section{Introduction}
\label{sec:intro}

Feedback from massive stars ($M$\,$>$\,8\,\mbox{\rm $M_{\odot}$}) plays a major role in
shaping the appearance of their surroundings. Their strong ultraviolet
radiation fields ionise the local interstellar medium (ISM), and their
intense stellar winds and eventual supernova explosions drive the dynamics
of the ISM, while also enriching it with heavy elements from the products
of nuclear fusion.
However, despite their dominant role in galactic evolution, the
formation of massive stars is still not well understood.

Two main models have been proposed to explain the formation of massive
stars: monolithic collapse \citep{McKee2003} or competitive accretion
\citep{Bonnell2001}\footnote{See \citet{Tan2014} and
  \citet{Krumholz2015} for recent reviews.}. In the first, the
formation scenario is similar to that in low-mass stars but with high
accretion rates (and accretion disks), while in the latter the
protostars grow in mass from a surrounding gas reservoir (via
filamentary feeding) depending on their position in the clump. To
understand which model and/or process is the main agent in the
formation of massive stars, it is important to observe them, and their
host clusters, in their earliest phases. However, due to the nature of
the stellar initial mass function \citep[IMF;][]{Salpeter1955},
massive stars are inherently rare objects.

The earliest phases of massive stars evolve on short timescales
($\sim$10$^5$\,yr) and occur deeply embedded in their natal clumps,
making them difficult to observe \citep{Churchwell2002, Lada2003}. In
this context, recent wide-area, near-infrared (NIR) surveys with the
UKIRT and VISTA telescopes \citep[e.g.][]{Lawrence2007,
  Minniti2010,Cioni2011} have enabled detections of numerous candidate
star clusters and star-forming regions
\citep[e.g.][]{Borissova2011,Piatti2014,Romita2016}. But
characterising the stellar content of such clusters remains an
observational challenge, mainly due to limitations in angular
resolution and sensitivity, which become even more critical in
extragalactic systems.

The Large Magellanic Cloud (LMC) contains a rich sample of molecular
clouds, and its distance
\citep[$\sim$50\,kpc, e.g.][]{Pietrzynski2013,deGrijs2014} is small
enough to allow study of individual objects within those clouds.  The
LMC is also sufficiently far from the Galactic plane
($b$\,$\sim$$-$33$^\circ$) that foreground extinction is relatively
small. As such, the LMC provides an excellent system in which to study
massive star-formation regions in an extragalactic environment
\citep[with a metallicity about half of the solar value,
e.g.][]{Dufour1982,Smith1999}

\begin{figure}
   \centering
 \includegraphics[width=\hsize]{N159-N160.png}
  \includegraphics[width=8.5cm]{N159_Sptizer_4.png}
  \caption[]{Overview of the N159/N160 complex. Top: Composite VISTA
    image \citep{Cioni2011}, combining $Y$ (blue), $J$ (green) and
    \mbox{$K_{\rm s}$}\/ (red) bands.  Bottom: Composite {\em Spitzer} image of N159E
    and N159W, combining 3.6\,$\mu$m (blue), 4.5\,$\mu$m (green) and
    8\,$\mu$m (red). The N159W field targetted by GeMS/GSAOI is shown
    by the yellow square. Compact clusters discussed in the paper are
    labelled C1-C5. The positions of the close X-ray binary LMC X-1 and  the SNR 0540 – 697 (\cite{Chen2010a}) are marked in dash-dotted cyan line and red cross respectively.}  \label{fig:vista}
\end{figure}

One of the richest star-forming regions in the LMC is the N159/N160
complex (see Fig.~\ref{fig:vista}), with its H\,{\footnotesize II}~ regions first
catalogued by \citet{Henize1956}. The complex is located in a ridge of
molecular CO gas \citep{Ott2008}, approximately 600\,pc (in
projection) south from the spectacular 30~Doradus region, and is the
location of the first extragalactic protostar, discovered by
\cite{Gatley1981}, as well as the first known type~I extragalactic OH
maser \citep{Caswell1981}. An overview of the structural components of
the complex was given by \citet{Bolatto2000}, who described it as
three distinct, well-separated regions (spanning
$\sim$15$'$/220\,pc), as follows:
\begin{enumerate}
\item {{\it N160:} associated with H\,{\footnotesize II}~ regions and young stellar
    clusters, where massive-star formation is in a relatively evolved
    stage and the parent clouds are almost entirely photodissociated
    and dissipated.}
\item {{\it N159:} associated with H\,{\footnotesize II}~ regions and young stellar
    clusters, but still closely linked with molecular gas and active
    star formation. N159 hosts massive embedded young stellar objects
    (YSOs), a maser source, and several ultracompact H\,{\footnotesize II}~
    (UCHII) regions \citep{Chen2010a}. N159 harbours
    two giant molecular clouds: N159E and N159W, located on the
    eastern and south-western sides of N159, respectively
    \citep{Johansson1998,Jones2005,Fukui2008}. CO observations also
    reveal a very high concentration of molecular gas at the location
    of N159W \citep{Cohen1988,Johansson1998,Bolatto2000}.}
\item {{\it N159S:} a giant molecular cloud $\sim$60\,pc south of N159
    (thus not included in Fig.~\ref{fig:vista}), with seemingly little
    star-formation activity \citep{Bolatto2000,Galametz2013}, although
    the detection of candidate Herbig Ae/Be stars at its northern tip
    suggests cluster formation might just be starting
    \citep{Nakajima2005}.}
\end{enumerate}

The morphology described above suggests sequential star-formation
southwards through the complex. This is supported by NIR imaging from
\citet{Nakajima2005}, who suggested that star formation in N160 may
have been initiated by a supergiant shell (SGS~19, with its centre
north-northeast of N160) with subsequent star formation in N159 and
the tip of N159S. This scenario is also supported by \cite{Farina2009}
from spectroscopic observations of massive stars across the region.

Early studies of the stellar content and exciting stars from optical
observations of N159 were presented by \citet{HMT1982} and
\citet{Deharveng1992}. From observations with the {\em Spitzer Space
  Telescope} Infrared Array Camera (IRAC), \citet{Jones2005} argued
that the different components in N159 have a common star-forming
history, with a wind-blown bubble ($\sim$1-2\,Myr old) initiating star
formation at the rim. The Papillon Nebula \citep{Meynadier2004} in the
the northeast of the bubble and the C2 and C5 compact clusters (see
below) are located on the edge of this bubble (indicated by the
$\sim$40\,pc diameter circle in the lower panel of
Fig.~\ref{fig:vista}). These arguments are substantiated by the map of
star-formation rate from \citet{Galametz2013}.

From analysis of {\em Spitzer} observations with the Multiband
Infrared Photometer, \cite{Chen2010a} proposed a more complicated
pattern of star formation in N159, where the expansion of the H\,{\footnotesize II}~
region could have triggered the star formation in N159E but not in
N159W. They concluded this from a comparison of the distribution of
YSOs and massive stars in both regions, and suggested that star
formation in N159W may have started spontaneously (or was triggered by
a force that is no longer detectable, e.g. an old supernova remnant).

A first high-resolution NIR study of N159W, taking advantage of
adaptive optics (AO), was presented by \citet{Testor2006}, who
resolved some of the candidate YSOs/clusters into multiple components
for the first time. More recently, $^{13}$CO\,(J=2--1) observations of
N159W with the Atacama Large Millimetre Array (ALMA) have discovered
the first two extragalactic protostellar molecular outflows
\citep{Fukui2015}.

In this paper we investigate the stellar content of N159W, using deep,
high angular-resolution {\mbox{$JHK_{\rm s}$}}-band images obtained
with the Gemini South Adaptive Optics Imager
\citep[GSAOI,][]{McGregor2004,Carrasco2011a}, fed by the Gemini
Multi-conjugate adaptive optics System \citep[GeMS,][]
{Rigaut2014,Neichel2014a}.  The observed field covered a field of
$\sim$90$''$ across (as shown in Fig.~\ref{fig:vista}).  These
observations cover a wider field than the previous AO-corrected
imaging, at finer angular resolution, and reach some 2-3\,mag deeper.
This combination of high angular-resolution and excellent sensitivity
in the NIR provides us with an unprecedented view of N159W, to
investigate its stellar content and ongoing star formation.

The paper is organised as follows. In Sect.~2 we present the
observations, data reduction, and completeness and contamination
analysis. Sect.~3 discusses the morphology of the region, and
colour-colour and colour-magnitude diagrams from the data are used to
identify candidate YSOs. In Sect.~4 we derive the luminosity function,
and associated IMF of the central cluster.  Sect.~5 discusses the
star-formation scenario in the N159W complex, with a closing summary
in Sect.~6.

\section{Observations and data reduction}

\subsection{Observations}

\begin{figure*}
   \centering
 \includegraphics[width=\hsize]{ds9_N159W_copie2.jpg}
 \caption{Three-colour GeMS/GSAOI image of N159W combining $J$ (blue),
   $H$ (green), and \mbox{$K_{\rm s}$}\/ (red); north is up and east is left. The
   width of the image (east to west) is 90$''$ ($\sim$22\,pc). Compact
   clusters discussed in the paper are labelled C1-C5, and the white
   circle indicates the H\,{\footnotesize II} bubble enclosing the
   central star cluster.}
              \label{fig:threecolor}%
\end{figure*}

The data were obtained with the Gemini South Adaptive Optics Imager
\citep[GSAOI,][]{McGregor2004,Carrasco2011a}, fed by the Gemini
Multi-conjugate adaptive optics System \citep[GeMS,][]
{Rigaut2014,Neichel2014a} on 2014 December 8 as part of
programme GS-2014B-C-2 (P.I. B.~Neichel). GSAOI provides images of a
85$''$\,$\times$\,85$''$ field of view, at a plate scale of
$\sim$20\,mas/pixel \citep[see][]{McGregor2004,Carrasco2011a}.  The
focal plane is imaged by a 2\,$\times$\,2 mosaic of Hawaii-2RG
2048\,$\times$\,2048 pixel arrays, with 3\farcs0 gaps between each
array.

The observations are summarized in Table~\ref{tab1} and the final
three-colour ({\mbox{$JHK_{\rm s}$}}) image is shown in
Figure~\ref{fig:threecolor}. Each science observation was randomly
dithered around the central pointing by 5$''$ to fill-in the
detector gaps, and adjacent sky frames were taken 2\farcm5 from the
science field. The average resolution obtained over the field, as
measured by the full-width half maximum (FWHM) of the stars on
single-exposure frames, is reported in Table~\ref{tab1}, as is the
natural seeing at the time of the observations (measured at zenith).
The average FWHM in the \mbox{$K_{\rm s}$}-band was 105\,mas, while the average
Strehl ratio (SR) obtained was 15\,\%. These performances are slightly
worse than those expected for such good-seeing conditions, but are
consistent with observations at low altitude (airmass between 1.3 and
1.6), as is the case for the LMC as seen from Cerro Pachon. The
coordinates of the field centre were $\alpha$\,=\,05$^h$39$^m$40$^s$,
$\delta$\,$=$\,$-$69\degr45\arcmin 55\arcsec (J2000), chosen to span
two star-forming regions of interest and to overlap with the field
observed by \cite{Testor2006}.

\begin{table*}
\begin{center}
  \caption{Observational details and {\sc starfinder} parameters used
    for the star detection and photometry for each filter. The quoted
    full width half maximum (FWHM) and Strehl ratio (SR) of the
    point-spread functions (and their corresponding standard
    deviations) are the means from measurements of over 200 stars
    uniformly distributed over the field, from all the individual
    frames. The exposure time for each image was 80\,s. The two/three
    values given for the {\sc starfinder} threshold mean that the
    algorithm does two/three iterations, with a relative threshold at
    $N$-sigma each.}\label{tab1}
\begin{tabular}{lccccccccc}
\hline
\hline
Date &Filter & Number of & $<$FWHM$>$ & $\sigma_{\rm{FWHM}}$ & $<$SR$>$ & $\sigma_{\rm{SR}}$ & Natural seeing
& {\sc starfinder} & {\sc starfinder} \\
     &       & frames  &  (mas)  & (mas) & (\%) & (\%) & (@ 0.55$\mu$m) & Threshold & Correlation \\
\hline
2014 Dec 8 & $J$  & 17  & 145  & 15 & $\phantom{1}$3 & 1 & 0\farcs55 & [5,2] & 0.7$\phantom{5}$ \\
           & $H$  & 14  & 100  & 20 & $\phantom{1}$9 & 2 & 0\farcs60 & [5,3] & 0.7$\phantom{5}$ \\
           & \mbox{$K_{\rm s}$}  & 17  & 105  & 15 &             14 & 3 & 0\farcs55 & [5, 4, 2] & 0.75 \\
\hline
\end{tabular}
\end{center}
\end{table*}

\subsection{Data reduction}
\label{subsec:red}

The data were reduced using the same methods as those from
\citet{Neichel2015a}, using home-made procedures developed in {\sc
  yorick} \citep{Munro1995}. The relevant steps were: (i) creation of a
master flatfield, based on sky-flat images taken during twilight of
the same night; (ii) creation of a master sky-frame based on the
dedicated sky images; (iii) correction of the science frames using the
relevant master flats/skies, as well as for detector non-linearities
and different gains between each detector.

In addition, it was necessary to apply an instrumental distortion
correction. An initial distortion map was derived from GeMS/GSAOI
observations of the Galactic globular cluster NGC\,288, that were
correlated with images from the Advanced Camera for Surveys on the
{\em Hubble Space Telescope (HST)}. This distortion map lead to a
residual positioning accuracy of $\sim$0\farcs2, which is not good
enough for the image quality of the GeMS/GSAOI images here.  Moreover,
this calibration only accounts for the static instrumental distortion
-- a dynamical component, which depends on the constellation of
natural guide stars and environmental factors like the telescope
pointing, still needs to be taken into account.

The dynamical contribution to the distortion map has to be corrected
frame by frame, selecting one frame as the primary astrometric
reference. By using high-order polynomials and the position of
relatively bright stars common to all the frames, we were able to
cross-register the images by the following steps: (i)
creation of a polynomial base $(P)_i$ of distortion modes as
$P_i(x,y)= C_{i,0} + C_{i,1}x + C_{i,2}y + C_{i,3}x^2 + C_{i,4}xy +
C_{i,6}y^2 + ... $~; (ii) measurement of the vectors $V_x$ and $V_y$
of the positional difference between each image and the reference frame,
for each of the bright ($<$\,21\,mag) stars common to all frames;
(iii) perform a Levenberg--Marquardt fit of the $V_x$ and $V_y$
vectors on the polynomial base and determination of the $\alpha_i$ and
$\beta_i$ coefficients such that: $V_x=\sum \alpha_i P_i $ and $
V_y=\sum \beta_i P_i$; (iv) application of the inverse distortion map
to the full image.

Of course, the quality of the above corrections depends on the number of
stars available for the procedure. The N159W observations provided a large
number of reference stars and, by using 15 degrees of freedom per axis, we
obtained corrected frames with a typical precision of 0.1\,pixel. Following
the procedure described above, each individual image was reduced
and combined by filter to produce three final reduced images.

\subsection{{\sc starfinder} photometry}
\label{subsec:starfinder}

Photometry for the stars in the observed field was obtained using the
{\sc starfinder} package \citep{Diolaiti2000}. Because of the complex
structure of AO-corrected point spread functions (PSFs), and their
spatial and temporal variations, photometry of AO images requires
PSF-fitting algorithms that provide more accurate results than regular
aperture photometry \citep[see, e.g.][]{Neichel2015a}.

{\sc starfinder} builds an empirical PSF by combining results for
several stars in an image. In the case of spatial variations of the
PSF across a field, it is usually divided into subfields, with {\sc
  starfinder} then used on each subfield in turn. There is naturally a
trade-off between having enough stars in each subfield so that an
accurate PSF model can be extracted, versus keeping the subfield as
small as possible to minimize PSF variations.  We experimented with a
range of subfield sizes for N159W.  The minimum residual was obtained
for subfields of 16$''$\,$\times$\,16$''$, shifted by 8$''$ (in x or
y) to introduce an overlap between the frames. Each star was then
measured several times, using different sets of PSFs, which were then
used to investigate the photometric errors.

The other critical aspect of tuning the {\sc starfinder} analysis is
the choice of the number of iterations, the relative threshold, and
the correlation threshold for star extraction at each iteration. These
parameters are summarized in Table~\ref{tab1}. Note that {\sc
  starfinder} goes through several iterations of star detection,
removing the detected stars at each iteration. We can then adjust
different threshold levels, pushing toward low signal-to-noise over
the iterations. The numbers given in the ninth column of
Table~\ref{tab1} are the thresholds used for each iteration.

We adjusted the {\sc starfinder} parameters so that single faint stars
were detected without too much contamination from remaining bad/hot
pixels or from structures in the background. Our three final reduced
images ($J$, $H$, and \mbox{$K_{\rm s}$}) have different characteristics in terms of
noise and resolution, so the {\sc starfinder} parameters have been
optimized for each filter. To detect as many of the faint stars as
possible we used 2\,$\times$\,2 binned images. This enabled the
detection of faint stars more robustly and, as the pixel size is
20\,mas and the typical resolution was $\sim$100\,mas, the binned
images are still well sampled, with no loss of spatial information.
Three bright stars were saturated in the $H$- and \mbox{$K_{\rm s}$}-band
observations (with pixel counts in excess of 50\,000\,e$^-$). These
were excluded from the PSF definition and photometry, with their
magnitudes adopted from observations of N159/N160 with the Infra-Red
Survey Facility (IRSF) by \citet{Nakajima2005}. The final
photometric catalogue contains magnitudes for 2185 stars in $J$, 4187
in $H$ and 3912 in \mbox{$K_{\rm s}$}.

\subsection{Photometric and astrometric calibration}
\label{subsec:zp}

To calibrate the instrumental magnitudes we evaluated the photometric
zero-points, employing values for 40 well-isolated stars in the
observed field from the IRSF observations \citep{Nakajima2005}.  A
reasonable match is found, with a zero-point uncertainty of 0.06\,mag
in $J$ and $H$, and 0.08\,mag in \mbox{$K_{\rm s}$}.

As an independent check, we also attempted to derive a zero-point
using the 2MASS catalogue \citep{Skrutskie2006}. The pixel size of the
2MASS cameras was only $\sim$2$''$, so there is a large mismatch
compared with the GSAOI images, and only 10 of the isolated stars used
above could be securely identified. The zero-point uncertainties from
calibration with the 2MASS stars were 0.2\,mag in $J$ and $H$, and
0.1\,mag in \mbox{$K_{\rm s}$}.  Given the smaller number of stars availale, we
therefore adopted the zero-points determined using the IRSF
catalogue\footnote{Corrections between the IRSF and 2MASS systems are
  small, amounting to $<$\,0.05\,mag for ($J$\,$-$\,\mbox{$K_{\rm s}$})$_{\rm
    IRSF}$\,$<$\,1.7\,mag \citep{Kuc2008}, so are neglected when
  estimating the final photometric error.}.

The world-coordinate system was also calibrated using the same 40
isolated stars from the IRSF catalogue \citep[for which the quoted
astrometric accuracy is 0.5$''$;][] {Nakajima2005}. The astrometric
solution of the GSAOI images was set using the x/y (pixel) positions
of each star cf. the IRSF positions, resulting in a mean astrometric
dispersion of 5\,mas (i.e. less than the typical FWHM of the images,
so no confusion is expected).

\subsection{Photometric error and completeness}
\label{subsec:comp}

After calibration, we undertook a series of completeness tests in each
filter to estimate the depth and photometric uncertainties of our
images. The detectability of a source depends on the local stellar
density and the {\sc starfinder} settings, and may also be affected by
diffuse background in the case of a region like N159W. To determine
the completeness of our images we used simulated stars inserted in the
real images. As for the PSF analysis, we divided the image in
subfields and used the corresponding local PSF from {\sc starfinder}
to construct simulated stars which mimic the real variations across
the field.

A set of 1000 artificial stars was inserted at random positions in
each subfield, following the method from \citep{Neichel2015a}. Random
magnitudes (in steps of 0.5\,mag) between 14.0 and 22.0 were assigned
for each filter. The {\sc starfinder} source detections were then run
using the exact parameters as those in Table~\ref{tab1}, and the number
of artificial stars successfully recovered was used to estimate the
photometric completeness. At the same time we also estimated
the photometric error by computing the standard deviation of the
difference between the measured and simulated magnitudes.

Results of these tests are shown in the upper panel of
Fig.~\ref{fig:mag_uncert}, with 90\,\% completeness obtained at
$J$\,$=$\,21.55, $H$\,$=$\,21.85, and
\mbox{$K_{\rm s}$}\,$=$\,21.85\,mag\footnote{This is 2.55, 3.85, and 4.50\,mag deeper
  than the respective limiting \mbox{$JHK_{\rm s}$}~ magnitudes of the IRSF data
  \citep{Nakajima2005}.}. Results for the photometric uncertainties
are shown in the lower panel of Fig.~\ref{fig:mag_uncert}; the final
photometric uncertainties are given by these errors combined in
quadrature with the zero-point errors estimated above.

\begin{figure}
\begin{center}
\begin{minipage}[c]{.45\textwidth}
\includegraphics[width=\hsize]{Completeness_N159paper-eps-converted-to.pdf}
\includegraphics[width=\hsize]{mag_uncert_N159paper-eps-converted-to.pdf}
\end{minipage}
\caption{Completeness (upper panel) and photometric uncertainties (lower panel) for
  each filter estimated from the completeness tests.}\label{fig:mag_uncert}
\end{center}
\end{figure}

\section{Results}

\subsection{Morphology of the N159W complex}
\label{ssec:morphology}

The composite GeMS/GSAOI image of N159W is shown in
Fig.~\ref{fig:threecolor}. Toward the south of the observed field we
can clearly identify the ionised H\,{\footnotesize II}~ region, forming an almost
circular nebula (as indicated by the white circle in the figure).
There are two bright stars separated by $\sim$0\farcs9 at the centre
of the nebula, with $J$\,$=$\,14.15 and 14.85\,mag (with the northern
star the brightest, as shown in the lower-right panel of Fig.
\ref{fig:objA7}); these are thought to be the primary ionising sources
of the H\,{\footnotesize II}~ region \citep{Deharveng1992}.  Optical spectroscopy from
\cite{Conti1991} classified the (then unresolved) composite spectrum
as O3-6~V, while also suggesting that it might well be a small compact
cluster. \cite{Deharveng1992} classified the two stars as O5-6 and
O7-O8, and \cite{Testor2006} obtained a NIR spectrum of the brightest
star, confirming it as an O star of type O5-6, with an estimated
extinction of \mbox{$A_{\rm V}$~} = 3.54\,mag.  For completeness, we note that
\cite{Farina2009} classified their spectrum of the central source(s)
as O8\footnote{Their observed coordinates are $\sim$0\farcs3 from the
  position of the brighter star so their spectrum was likely dominated
  by this object, albeit contaminated by the other star given their
  quoted pixel scale and slitwidth.}. The cluster associated with
these two massive stars, within the surrounding nebula, is hereafter
referred to as the central cluster.

Three compact clusters are observed at the edge of the nebula,
identified as C1, C2 and C3 in Fig.~\ref{fig:threecolor}. These are
located symmetrically around the nebula, at an almost equidistant
projected distance from the centre. Another compact cluster
(identified as C4) is located to the north-east of C3, and further
north there is a very embedded region, labelled as C5. The properties
of each of these are now discussed in turn.

\subsubsection{Compact cluster C1}
This corresponds to a class~II YSO (053940.78$-$694632.0) identified
by \citet{Chen2010a}, which was also classified as a Herbig Ae/Be star
by \citet{Nakajima2005}. Our observations reveal a compact cluster
(see Fig.~\ref{fig:objA7}), with the reddest star consistent with the
position of the previously reported YSO/Herbig object. The clump that
hosts this cluster has a somewhat cometary shape, with a
limb-brightened rim, and is further discussed in
Sect.~\ref{sec:scenario}.

\subsubsection{Compact cluster C2}
This compact cluster is source P2 from \citet{Jones2005}, and N159A7
from \citet[][resolved by their observations into their sources 121,
121a, 123, and 123a]{Testor2006}. This also corresponds to a
class~I/II YSO (053941.89$-$694612.0) from \cite{Chen2010a}, who
estimated its mass to be 33.7\,$\pm$\,2.6\,\mbox{\rm $M_{\odot}$}, with
\mbox{$A_{\rm V}$~}\,$=$\,12.7\,mag (while also noting it had multiple components).

The expanded view of C2 from the GeMS/GSAOI images is shown in
Fig.~\ref{fig:objA7}, revealing two dominating components and several
other sources, all embedded in a diffuse nebula with a diameter of
$\sim$0.55\,pc. The two main components have comparable \mbox{$K_{\rm s}$}-band
magnitudes, while the redder source (123 from \citeauthor{Testor2006})
is probably the source dominating the YSO luminosity and mass estimate
from \citeauthor{Chen2010a}; spectroscopy of this source from
\citeauthor{Testor2006} confirms that it is in a very early stage
(class~0/I YSO), so it is unlikely to have started ionising its
surroundings. Interestingly, C2 is one of the two high-mass sources
with a reported outflow from the ALMA observations by
\citet{Fukui2015}. They suggest that star formation in this compact
cluster was likely triggered by the collision of two thin filaments of
gas $\sim$10$^5$\,yrs ago.

\begin{figure*}
   \centering
 \includegraphics[width=\hsize]{mosaic_arxiv.png}
 \caption{Details of the five compact clusters (C1-5) and central two
   O-type stars (thought to ionise the central cluster) from the
   three-colour GeMS/GSAOI image; $J$ (blue), $H$ (green),
   and \mbox{$K_{\rm s}$}\/ (red).}\label{fig:objA7}
\end{figure*}

\subsubsection{Compact cluster C3}
This cluster was detected as a compact radio source by \citet[][their
source~5]{Hunt1994} and \cite{Indebetouw2004}. It corresponds to
053937.53$-$694609.8 from \citet{Chen2010a}, who classified it as a
type I/II YSO (with multiple components). Their mass estimate was
31.2\,$\pm$\,2.9\,\mbox{\rm $M_{\odot}$}, with an inferred spectral type of O7~V (cf.
the spectral type of O7.5~V inferred from the analysis of radio
data by \citeauthor{Indebetouw2004}). C3 is also N159A5 from
\citet{Testor2006}, who described it as a tight cluster of
five stars (their nos. 133, 136, 137, 138 140), with an estimated
extinction of $A_V$\,$=$\,8-12\,mag.

All the components are embedded in nebulosity with a diameter of
1\farcs9 (0.5\,pc). Our GeMS/GSAOI data resolve C3 into even more
components than past observations with $\sim$20 sources (see
Fig.~\ref{fig:objA7}). \citet{Jones2005} described the cluster as a
compact H\,{\footnotesize II}~ region with one or more OB-type stars, and spectroscopy
from \citet{Testor2006} of the brightest member (hence likely dominant
source of ionising photons) revealed a late O-type star \citep[also
see][]{Martin-Hernandez2005}.

\subsubsection{Compact cluster C4}
This corresponds to N159A6 from \citet{Testor2006}, who resolved it
into six stars embedded in nebulosity with a diameter of 0.45\,pc.
Our observations resolve C4 into at least 12 stars, as shown in the
lower-left panel of Fig.~\ref{fig:objA7}. In particular, star 155 from
\citeauthor{Testor2006} (in the centre of the image) is now resolved
into a double star. C4 is also source 053935.99$-$694604.1 from
\citet{Chen2010a}, who classified it as a type I YSO and noted it
having multiple components. Indeed, using the photometry from
\citeauthor{Testor2006} (their star 151, the bright, red object on the
western edge of C4 in Fig.~\ref{fig:objA7}), \citeauthor{Chen2010a}
estimated a mass of 18.5\,$\pm$\,1.4\,\mbox{\rm $M_{\odot}$}, with
$A_V$\,$=$\,2.5\,mag; this object was also classified as a Herbig
Ae/Be star by \cite{Nakajima2005}.

\subsubsection{Compact cluster C5 }

C5 is a very red region which appears to be deeply obscured with
nebulosity detected fin the $H$- and \mbox{$K_{\rm s}$}-bands (see
Figs.~\ref{fig:threecolor} and \ref{fig:objA7}). It is the most
intense 6\,cm (4.8\,GHz) continuum source seen in observations with
the Australia Telescope Compact Array (ATCA) of N159
\citep{Hunt1994,Indebetouw2004}, and has the highest dust
surface-densities in the whole N159/N160 complex, and one of the
highest star-formation rates \citep{Galametz2013}.

The {\em Spitzer} observations from \citet{Chen2010a} revealed the
presence of an embedded YSO in C5, which they classified as type~I,
estimating a mass of 34.8\,$\pm$\,8.4\,\mbox{\rm $M_{\odot}$}, with an inferred
spectral type of O6~V. More recently, ALMA observations of the dense
CO gas in C5 revealed a complex structure \citep[their
`N159W-N';][]{Fukui2015}, with several filaments which are generally
elongated in the northeast-southwest direction, and the detection of a
blue-shifted lobe of an outflow, thought to be associated with the YSO.
Taking into account longer-wavelength data from the {\em Herschel Space
  Observatory}, \citeauthor{Fukui2015} estimated the mass and
luminosity of the YSO (their `YSO-N') to be 31\,$\pm$\,8\,\mbox{\rm $M_{\odot}$}\/ and
(1.4\,$\pm$\,0.4)\,$\times$\,10$^5$\,\mbox{\rm $L_{\odot}$}, respectively.

No stars are detected in our GeMS/GSAOI images at the location of the
YSO \citep{Chen2010a,Fukui2015} or the UCHII region
\citep{Indebetouw2004}. Indeed, only one very red star (with
$J$\,$=$\,21.9, $H$\,$=$\,18.4 and \mbox{$K_{\rm s}$}\,$=$\,16.2\,mag) is detected
in/near the clump, some 2$''$ (0.5\,pc) south of the UCHII region.

\subsection{Identification and distribution of young stellar sources}

\subsubsection{Near-IR colour-colour diagram}
\label{subsec:ccd}

To investigate the nature of the stellar population of N159W, in the
left-hand panel of Fig.~\ref{fig:cc-diag} we show the $(H-\mbox{$K_{\rm s}$})$ vs.
$(J-H)$ colour-colour diagram (CCD) for the 1386 sources detected in
each of the $JHK_{\rm s}$ bands (for which the photometric error is
lower than 0.2\,mag). Overlaid on the CCD are curves
representing the main sequence (MS) and giant branch \citep[shown in
red and orange, respectively;][]{Bessell1988}, and the locus of
T~Tauri stars \citep[TTS, shown in blue;][]{Meyer1997}\footnote{In
  which the MS and TTS loci have been converted to the 2MASS system
  using the relations from \cite{Carpenter2001}.}.

Reddening vectors are also overplotted in Fig.~\ref{fig:cc-diag} (as
dashed red lines), drawn from the tip of the giant branch (left), from
the base of the MS (middle), and from the reddest TTS (right). In each of
these we calculate the reddening adopting a normal extinction law,
with: $A_J/A_V$\,$=$\,0.282, $A_H/A_V$\,$=$\,0.175,
$A_K/A_V$\,$=$\,0.112 \citep{Rieke1985}. Shifting the brightest stars
along the reddening vector to the MS, we find that they are consistent
with the expected colours of O4-O5 stars, in good agreement with the
spectroscopy of the central stars discussed above.

\begin{figure*}
\centering{
\includegraphics[width=8.5cm,height=8.5cm]{N159_new_JHK-eps-converted-to.pdf}
\includegraphics[width=8.5cm,height=8.5cm]{N159_new_JHK_control-eps-converted-to.pdf}}
\caption{Colour-colour diagrams for the cluster region in N159W
  (left-hand panel) and the control region (right), with the loci of
  the main sequence (MS), giant branch, and T~Tauri stars (TTS)
  overlaid in red, orange and blue, respectively. Also shown are
  reddening vectors (dashed red lines) drawn from the tip of the giant
  brach (left), from the base of the MS (middle), and from the reddest
  TTS (right). Cluster sources with a NIR excess are indicated in the
  left-hand panel by the blue circles. The error bars in the
  lower-right corner show the average uncertainties in the colour
  terms.}
\label{fig:cc-diag}
\end{figure*}

Most of the sources in the left-hand panel of Fig.~\ref{fig:cc-diag}
are within the reddening band of the MS, which could be a mixture of
reddened field stars and sources with warm circumstellar dust, a
standard characteristic of young pre-main-sequence (PMS) objects
\citep{Lada1992}. In contrast, stars lying redwards of the middle
reddening vector are expected to be associated with NIR-excess from
optically-thick circumstellar disks. We can therefore use the CCD
for a first identification of NIR-excess objects.

To understand the potential contamination from background/foreground
stars, the same CCD is shown for the control field in the
right-hand panel of Fig.~\ref{fig:cc-diag}. Most of the sources are
also within the MS reddening band, and only a few objects are found further
redwards, which could be due to unresolved binaries.

Thus, to try to identify candidate YSOs which are associated with the
cluster we applied the following two criteria:
\begin{enumerate}
\item{$H-\mbox{$K_{\rm s}$}$\,$>$\,1\,$\sigma$ (where $\sigma$ is
the error on the colour term) from the MS reddening vector.}
\item{$J-H$\,$>$\,0.65\,mag to avoid the region in the control field
which contains other sources.}
\end{enumerate}
We may have missed a few candidates using these criteria, but we aimed
to minimise the contamination by non-cluster members in the final
sample. The 36 candidate YSOs with NIR excesses identified using these
criteria are indicated in Fig.~\ref{fig:cc-diag} with blue circles.

We comment that 2256 sources were detected only in the $H$- and \mbox{$K_{\rm s}$}-bands;
while these are not included in Fig.~\ref{fig:cc-diag}, some may also
be YSO candidates with NIR excesses. Equally, some YSOs appear
relatively normal in the NIR, but are found to display excesses when
going to even longer wavelengths, e.g. from {\em Spitzer} observations
\citep{Ojha2011,Chavarria2014,Saral2015}. Thus, the number of YSO
candidates identified from our analysis is knowingly an underestimate
of the likely total in the region. Either deeper $J$-band observations
and/or high spatial-resolution $L$- and $M$-band observations are
needed to recover all the candidates.  Nevertheless, in the next
section we attempt to recover some of these embedded sources from
their $H-\mbox{$K_{\rm s}$}$ colours.

\subsubsection{Near-IR colour-magnitude diagram}
\label{subsec:cmd}

The colour-magnitude diagram (CMD) of the 2256 sources detected only
in the $H$- and \mbox{$K_{\rm s}$}-bands (with photometric errors of $<$\,0.2\,mag)
is shown in Fig.~\ref{fig:KHK} (black points), together with stars
observed in the control field overlaid (black points with green circles). Also plotted
are the zero-age main sequence (solid blue lines) and the 1\,Myr PMS
isochrone from \citet[][dotted red lines]{Siess2000}\footnote{We
  employed the isochrones from \citet{Siess2000} as they are the only
  PMS evolutionary models available which extend to a mass limit of
  0.1\,\mbox{\rm $M_{\odot}$}\/ and with a subsolar metallicity (calculated for
  $Z$\,$=$\,0.01, cf. the slightly lower metallicity of the LMC of
  $Z$\,$=$\,0.008).}  for extinctions of A$_V$\,$=$\,0 and 15\,mag.
In contrast with the control field, N159W has a significant number of
stars with $(H-K)$\,$>$\,0.7\,mag, which could be associated with the
young population of the cluster. However, trying to disentangle young
stars from reddened background stars from such a CMD is complex, so we
adopted the following approach. We considered the maximal extinction
seen in the direction of N159W, and applied this to the intrinsic
colour of a dwarf star. We then considered all sources redder than
this as potential NIR-excess sources associated with the cluster
region.

\begin{figure}
\centering{
\includegraphics[trim=0cm 0cm 0cm 2cm, width=11cm,height=9.8cm]{Fig_KHK__ref-eps-converted-to.pdf}}
\caption{Colour-magnitude diagram of sources in N159W detected in only
  the $H$- and \mbox{$K_{\rm s}$}-bands (black points) and those in the control field
  (black points with green circles). Also plotted are the zero-age main sequence (solid
  blue lines) and the 1\,Myr PMS isochrone from \citet[][dotted red
  lines]{Siess2000} for extinctions of A$_V$\,$=$\,0 and 15\,mag.  Red
  circles highlight candidate YSOs identified from our colour cut (see
  text for details). Blue circles highlight candidate YSOs previously identified from the CCD (Fig. \ref{fig:cc-diag}).}\label{fig:KHK}
\end{figure}

We estimated the maximum extinction using the 21\,cm H\,{\footnotesize
  I} ATCA observations from \citet[][which had an angular resolution
of $\sim$7$''$]{Dickey1994}.
From the H\,{\footnotesize I} absorption in the direction of N159W
they estimated N(H\,{\footnotesize
  I})\,$=$\,9.62\,$\times\,$10$^{22}$\,\cmsq. The gas-to-dust ratio,
$N_{\rm H}/E(B-V)$, in the LMC is several times larger than the
Galactic value \citep{Lequeux1989,Clayton1985}. Using the conversion
$N_{\rm H}/E(B-V)$ = 2 $\times $ 10$^{22}$ atoms \cmsq mag$^{-1}$ from
\cite{Lequeux1989} and \mbox{$R_{\rm V}$~} = $A_V/E(B-V)$ = 3.1, we estimated a
maximal visual extinction toward N159W of
$A_V$\,$\sim$15\,mag\footnote{This agrees with the maximum value from
  the YSO analyses by \citet{Chen2010a}}. The resulting $E(H-K)$ for a background star
is $\sim$0.9\,mag \citep[from
$A_V$\,$=$\,15.9\,$\times$\,$E(H-K)$,][]{Rieke1985}. Considering the
intrinsic $H-\mbox{$K_{\rm s}$}$ colour of 1\,Myr PMS stars is $\sim$0.1\,mag (see
Fig.~\ref{fig:KHK}), $A_V$\,$=$\,15\,mag would shift their location to
maximum of $(H-\mbox{$K_{\rm s}$})$\,$\sim$\,1\,mag.

Thus, we considered sources with $H-\mbox{$K_{\rm s}$}$\,$>$\,1\,mag as candidate
YSOs, with intrinsic excesses from disks and/or envelopes.  In our
sample selection we employed a slightly more conservative colour cut,
only selecting those sources with $H-\mbox{$K_{\rm s}$}$\,$>$\,1\,$+$\,$\sigma$,
where $\sigma$ was the estimated uncertainty on the colour term.
Applying this method we identified 68 additional candidates, as shown
by red circles in Fig.~\ref{fig:KHK}, although we acknowledge that a
small number of these might be highly-reddened background sources.
This gives 104 candidate YSOs in total: 36 from analysis of the CCD,
and 68 additional candidates from the CMD.

\subsubsection{Spatial distribution of candidate YSOs}
The spatial distribution of YSOs in a star-forming complex provides an
excellent tracer of recent star formation. The locations of our
candidate YSOs in the region of the central cluster and the C5 clump
are shown in the left- and right-hand panels of
Fig.~\ref{fig:spatial-loc}, respectively, including candidates from
analysis of the CCD (blue circles) and CMD (red circles). Also shown
are intensity contours of 8\,$\mu$m emission from the {\em Spitzer}
IRAC data \citep{Jones2005}. The locations of the candidate
YSOs are generally correlated with the 8\,$\mu$m emission, which also
corresponds to dense clumps of molecular gas
\citep[e.g.][]{Seale2012}. In contrast, there are only a few
candidate YSOs in the central cluster region (indicated by the white
circle in Fig.~\ref{fig:spatial-loc}), where the 8\,$\mu$m emission is
less intense.

\begin{figure*}
\begin{tabular}{cc}
\includegraphics[width=8.5cm,height=8.5cm]{Fig7a.jpg} &
\includegraphics[width=8.5cm,height=8.5cm]{Fig7b.pdf} \\
\end{tabular}
\caption{Locations of the candidate YSOs in the GeMS/GSAOI \mbox{$K_{\rm s}$}-band
  image, compared with the intensity of 8\,$\mu$m emission from {\em
    Spitzer} observations \citep[green contours,][]{Jones2005}; north
  is up and east is left. The blue circles show YSO candidates from
  analysis of the colour-colour diagram, red circles are those from
  analysis of the colour-magnitude diagram, see text for details. The
  left-hand panel shows the region around the central cluster
  (indicated by the white circle), with the yellow arc showing the
  location of an apparently limb-brightended rim; the right-hand panel
  shows the region around the C5 compact
  clump.}\label{fig:spatial-loc}
\end{figure*}

The 8\,$\mu$m morphology around the cluster resembles many Galactic
bubbles associated with H\,{\footnotesize II}~ regions \citep[e.g.][]{Deharveng2011}.
The 8\,$\mu$m IRAC band contains emission features at 7.7 and
8.6\,$\mu$m which are commonly attributed to polycyclic aromatic
hydrocarbons \citep[PAHs; e.g.][]{Peeters2004}.  PAHs are believed to
be destroyed in ionised gas \citep{Pavlyuchenkov2013}, but are thought
to be excited in the photo-dissociation region at the interface of a
H\,{\footnotesize II}~ region and a molecular cloud, by the absorption of far-UV photons
from the exciting stars of the H\,{\footnotesize II}~ region.  In particular, PAH
emission is thought to be a good tracer of the formation of B-type
stars \citep{Peeters2004}, which heat the surrounding dust to high
temperatures, exciting the PAH bands and fine-structure lines.
Indeed, bright, compact emission around B-type stars has been seen in
Galactic bubbles
\citep[e.g.][]{Zavagno2007,Samal2014,Dewangan2015,Kerton2015}.

In summary, the locations of the candidate YSOs support the idea that
the compact 8\,$\mu$m emission and molecular clumps in N159W appear to
be associated with recent massive-star formation, \citep[see
also][]{Jones2005,Testor2006}. In contrast, the relative absence of
YSOs in the central cluster suggests it was formed earlier. Possible
scenarios for the history of the region are discussed in
Sect.~\ref{sec:scenario}.

\section{Properties of the central cluster}

We now discuss the properties of the central cluster, defined as the
sources detected within the white circle in Figs.~\ref{fig:threecolor}
and \ref{fig:spatial-loc}.

\subsection{Age}\label{sect:age}

We estimated the age of the central cluster using the CMD of its
member stars (see Fig.~\ref{fig:JJH}). We preferred to use the
$J$-band here rather than $H$ or \mbox{$K_{\rm s}$}\/ to minimize the effect of
potential NIR-excesses on the age estimate. The zero-age main sequence
\citep[blue line,][]{Marigo2008} and PMS isochrones for ages of
0.5-3\,Myr \citep{Siess2000} are also plotted in the figure, after
correction for the distance (50\,kpc) and mean extinction
\citep[$A_V$\,$=$\,2.8\,mag,][]{Testor2006}.

The main sequence is well defined (albeit sparsely populated) down to
$J$\,$\sim$\,18.5\,mag in Fig.~\ref{fig:JJH}. At fainter magnitudes a
number of redder stars are seen and, from comparison with the
isochrones from \citet{Siess2000}, some are probably PMS stars. The
majority of these stars are located redwards of the 3\,Myr isochrone
(after correction for the mean extinction), indicating that the
cluster is unlikely to be older than 3\,Myr.  However, background
sources could also populate this PMS zone. To minimise such
contamination we selected only sources within a radius of 4$''$
(1\,pc) of the central massive stars, where the stellar density is
greatest. These sources are marked with open circles in
Fig.~\ref{fig:JJH}, and most are located between the 0.5 and 3\,Myr
isochrones, confirming the young age of the cluster. From this
spatially-restricted subsample the average age estimated for the
central cluster is 2\,$\pm$\,1\,Myr.

\begin{figure}
\centering
\includegraphics[trim=0cm 0cm 0cm 2cm,width=11.5cm,height=10.5cm]{N159_new_JJH-eps-converted-to.pdf}
\caption{Colour-magnitude diagram of stars in the region of the
  central cluster, with the two central O-type stars indicated by the
  large blue symbols. PMS isochrones from \citet[][for
  $Z$\,$=$\,0.01]{Siess2000} and ages of 0.5, 1, 2, and 3\,Myr (from
  right to left), corrected for a distance of 50\,kpc and average
  extinction of $A_V$\,$=$\,2.8\,mag, are indicated by the solid black
  lines, with the zero-age main sequence from \citet{Marigo2008} shown
  by the blue line.}\label{fig:JJH}
\end{figure}

\subsection{Mass function}

We also investigated the IMF and total mass of the central cluster. We
limited our analysis to the region indicated by the white circle in
Fig.~\ref{fig:threecolor} as it represents a well-bounded sample (in
terms of age, metallicity and distance), and the observed present-day
mass function should then be a fair representation of the underlying
IMF. Here we used the $H$-band photometry, as the number of sources
and photometric accuracy were better cf. the other bands (while also
avoiding potential NIR excesses which might influence the \mbox{$K_{\rm s}$}-band
photometry).

In constructing the luminosity function for the cluster we corrected
for possible field-star contamination using two
approaches\footnote{Note that by adopting a completeness criterion of
  90\% in Sect.~\ref{subsec:comp}, the impact of incompleteness below
  this magnitude limit is negligible.}. The first method used
statistics from the control field, while the second attempted to
disentangle cluster and field stars based on their location in the
$H$\,vs.\,$H-\mbox{$K_{\rm s}$}$ CMD \citep[see][]{Neichel2015a}. Corrections
were done for magnitude bin by subtracting the estimated number
of field stars from the detected source counts. The two methods
gave consistent results, as shown in Fig.~\ref{fig:HLF}, in which
estimated uncertainties are from Poisson statistics (i.e, the square
root of the number of stars). As our sample is limited in size, these
uncertainties are the primary limitation on determination of the
luminosity function.

\begin{figure}
   \centering
 \includegraphics[width=\hsize]{LuminosityF_Hband.pdf}
 \caption{$H$-band luminosity functions for the central cluster
   (dashed line), and the control field (dotted line). The luminosity
   functions are also shown after correction for field-star
   contamination, using the control field (black solid line) and the
   colour-cut selection (red line). Error bars are estimated from
   Poisson statistics, and the (90\%) completeness limit is indicated
   by the vertical solid line ($H$\,$=$\,21.85\,mag).}\label{fig:HLF}
\end{figure}

To construct the present-day mass function of the cluster we converted
the luminosity function using mass-luminosity relations
(Fig.~\ref{fig:MLR}), constructed from isochrones from
\citet{Siess2000} for $M$\,$<$\,6\,\mbox{\rm $M_{\odot}$}, and from \citet{Marigo2008}
for more massive stars, adopting the same distance and average
extinction as before. Given the uncertainty in the exact age of the
cluster, we estimated the mass function using both the 1 and 3\,Myr
relations, and then calculated the average to account for a small
spread of ages. The final mass function, assumed to be representative
of the IMF given the young age, is shown in Fig.~\ref{fig:IMF}.  The
typical uncertainties on the mass estimates are indicated above the
mass function, and the estimated uncertainties on the number in each
bin are again from Poisson statistics.

We do not expect significant variations in NIR extinction across the
central cluster, so adopting a mean value in this analysis should have
a limited impact on the estimated masses. To investigate this further
we estimated the $\mbox{$K_{\rm s}$}$-band extinction from the $H-\mbox{$K_{\rm s}$}$ colours
\citep[as described by][]{Gutermuth2005}, finding an average $A_{K\rm
  s}$\,$=$\,0.3\,$\pm$\,0.05\,mag, with peak values between
0.2\,$<$\,$A_{K\rm s}$\,$<$\,0.4\,mag. This is consistent with the
estimated optical extinction ($A_V$\,$=$\,2.15 and 3.54\,mag) toward
the two central massive stars \citep{Testor2006}. Thus, the impact of
variable extinction is minimal compared to the potential age spread.

\begin{figure}
   \centering
 \includegraphics[width=\hsize]{MLR.pdf}
 \caption{Mass-luminosity relation for the
   1\,Myr (black solid) and 3\,Myr (blue dashed)
   isochrones.}\label{fig:MLR}
\end{figure}

The IMF estimated from Fig.~\ref{fig:IMF} spans masses of $\sim$0.5-
10\,\mbox{\rm $M_{\odot}$}, and shows the typical rise in number of stars with
decreasing mass into the subsolar regime. A simple fit over this mass
range gave a power-law slope of $\Gamma$\,$=$\,$-$1.05\,$\pm$\,0.2,
cf. the canonical value of $\Gamma$\,$=$\,$-$1.35
\citep{Salpeter1955}. We experimented with changing the bin sizes and
mass limits of the fit, but the results were consistent with the
quoted uncertainty of $\pm$\,0.2\,dex.

The IMF for the cluster in N159W appears to peak at a mass between 0.5
and 1\,\mbox{\rm $M_{\odot}$}, although we are limited by our uncertainties in the mass
estimates in this range; incompleteness also limits any conclusions
for lower masses ($M$\,$<$\,0.5\,\mbox{\rm $M_{\odot}$}) from our data. Nonetheless, we
note that such a flattening of the IMF at $\sim$0.5\,\mbox{\rm $M_{\odot}$}\/ is
found in Galactic clusters \citep[e.g.][] {Kroupa2001, Kroupa2002,
  Luhman2007, Bastian2010, Dib2014} and in other clusters in the
Magellanic Clouds
\citep[e.g.][]{Dario2009,Andersen2009,Liu2009a,Gouliermis2012}.

Only deep {\em HST} observations can currently investigate the
lower-mass IMF in clusters in the Clouds. The only example to date is
the study of NGC\,1818 (with an age of 20-45\,Myr) by
\citet{Liu2009b}, who investigated the IMF down to 0.15\,\mbox{\rm $M_{\odot}$},
concluding that it was best described by a broken power-law
($\Gamma$\,$=$\,0.46\,$\pm$\,0.10 for 0.15\,$<$\,$M$\,$<$\,0.8\,\mbox{\rm $M_{\odot}$},
and a Salpeter-like slope, $\Gamma$\,$\sim$\,$-$1.35, at higher
masses) and that the estimated turn-over mass was consistent with the
0.5\,\mbox{\rm $M_{\odot}$}\/ from \citet{Kroupa2001} given the uncertainties.

The N159W data discussed here are representative of the limitations of
AO-corrected observations from current 8-10\, class telescopes.
Robust investigation of the low-mass regime of the IMF in the Clouds
requires imaging with both the high sensitivity and angular resolution
provided by, e.g. the MICADO instrument \citep{Davies2010} under
construction for the 39\,m European Extremely Large Telescope.

\begin{figure}
   \centering
 \includegraphics[width=\hsize]{N159_IMF.pdf}
 \caption{Present-day mass function (MF) of the central cluster of N159W.
The solid histogram is the MF computed after correction from field stars
using the control field; the dotted histogram shows the MF corrected
using the CMD analysis (see text for details). Uncertainties in the
mass estimates are shown as horizontal lines above the MF, with the
vertical lines in each bin indicating the Poisson uncertainties.
Fit to the MFs is shown in red, and is consistent with
$\Gamma$\,$=$\,$-$1.05\,$\pm$\,0.2. The 90\% completeness limit
is shown by the dashed vertical line.}\label{fig:IMF}
\end{figure}

When integrating over all the bins of the IMF, down to a mass limit of
0.9\,\mbox{\rm $M_{\odot}$}, we estimated a total mass of 650\,$\pm$\,60\,\mbox{\rm $M_{\odot}$}\/ for
the central cluster. If the cluster IMF indeed follows a canonical
power-law \citep{Kroupa2001,Kroupa2002,Kroupa2013}, we can infer that
around half of its mass is in the subsolar regime, giving a total
mass estimate of $\sim$1300\,\mbox{\rm $M_{\odot}$}.

The mass of the most massive star in a cluster is generally found to
be linked to the total cluster mass \citep[see,
e.g.][]{Weidner2010b,Weidner2013,Popescu2014}, although there are
candidates of relatively isolated massive stars which challenge this
as a universal relationship \citep[e.g.][]{Bressert2012}. With the
earliest-type star in the cluster classified as O5-6, and assuming it
is a dwarf given the young age, at LMC metallicity this is expected to
have an initial mass in the range of 37-44\,\mbox{\rm $M_{\odot}$}\/
\citep{Weidner2010a}. Although at the lower end, this is within the
expected range of the maximum mass from the simulations of
\citet{Popescu2014}, i.e. the maximum stellar mass in the N159W
cluster appears consistent with the cluster-mass relation.

\section{Star-formation scenario of the complex}
\label{sec:scenario}

Before investigating star-formation scenarios for the complex, we
investigated the dynamics of the compact clumps and central cluster.
ATCA observations from \citet{Seale2012} of HCO$^{+}$ (J = 1
$\rightarrow$ 0) and HCN (J = 1 $\rightarrow$ 0) revealed five
significant clumps of gas in the GeMS field: nos. 1, 7, 10, 12 and 15
in their Fig.~3 (with mass estimates in the range of
800-33\,000\,\mbox{\rm $M_{\odot}$}), corresponding, respectively, to the C3, C5, C1,
C2, and C4 compact clumps identified here.  The radial velocities for
these clumps are in the range of 230-240\,km\,s$^{-1}$ (Fig.~6 from
\citeauthor{Seale2012}), in good agreement with the velocity of
ionised gas observed in the direction of the N159W cluster
\citep{Paron2016}, and confirming that they are dynamically
associated.

\cite{Seale2012} hypothesised that the massive clumps are sites of
cluster formation, and identified YSOs which appear associated.  Our
high angular-resolution images reveal that the clumps actually
comprise several YSOs, and that young cluster formation is indeed
underway at these locations. In contrast, we note that no HCO$^{+}$ or
HCN dense gas was observed by \cite{Seale2012} in the direction of
central cluster, indicating that star formation there is at a more
advanced stage. Indeed, from the locations of the PMS stars in
Fig.~\ref{fig:JJH}, we argued in Sect.~\ref{sect:age} that the central
cluster formed 1-3\,Myr ago.

Thus, a possible scenario is that the central O-type stars
ionised the region around them which, when expanding, swept-up the ambient
gas and dust into a shell (accounting for the low level of 8\,$\mu$m
emission within the bubble). The distribution of the candidate YSOs in
close vicinity of the bubble suggests they may have been
triggered by its expansion, similar to star formation seen at the
edges of several geometrically-simple Galactic bubbles \citep[see,
e.g.][]{Deharveng2010a, Ohlendorf2013, Samal2014, Dewangan2015,
  Liu2015}. If this is really sequential star-formation in N159W, we
would expect the YSOs to be younger than the stars in the main
cluster.

Unfortunately, from the current data we have no way to estimate the
ages of the embedded YSOs. Nonetheless, we searched for signatures of
the early phases of high-mass star formation such as masers
\citep[e.g. emission from water masers has a characteristic lifetime
of 2.5-4.5\,$\times$\.10$^4$\,yr;][]{vander2005}, UCHII regions
\citep[which typically only last for $\sim$3\,$\times$\,
10$^{5}$\,yr;][]{Mottram2011} and molecular outflows (generally
associated with type 0/I YSOs). The presence of outflows in C2 and C5
\citep{Fukui2015} and UCHII regions in C3 and C5 \citep{Hunt1994},
suggests star formation that is not older than a few
$\times$\,10$^5$\,yr.

If true, this favours an age difference between the central cluster
and the YSOs in the peripheral clumps, pointing to sequential star
formation. This appears particularly plausible for C1, which has an
associated limb-brightened rim in the \mbox{$K_{\rm s}$}-band image (highlighted by
the yellow arc in Fig.~\ref{fig:spatial-loc}), with its apex pointing
toward the massive stars at the centre of the cluster. The morphology
of this structure resembles those from numerical simulations
\citep{Miao2009,Bisbas2011} and observations of bright-rimmed clouds
\citep[e.g.][]{Sugitani2002, Ikeda2008, Panwar2014}. The latter are
thought to arise from the impact of UV photons from nearby massive
stars on pre-existing dense molecular material
\citep{Lefloch1994,Miao2009}, leading to the formation of a new
generation of stars by radiatively-driven implosion. The morphology of
C1 suggests it is strongly influenced by ionising photons from the
central cluster, and the presence of candidate YSOs within the
clump provides support of a triggered scenario in this instance.

However, it is difficult to conclude such triggering is the only
formation process for the YSOs. Star-forming regions often contain
smaller cores/clumps with high column-densities, as revealed by {\em
  Herschel} observations \citep{Hill2011, Giannini2012, Hennemann2012,
  Schneider2012}, possibly due to density fluctuations present in the
original cloud. Provided the local conditions are close to
gravitationally bound, star formation can occur in these cores/clumps
on a local dynamical timescale. This can result in multiple stellar
groups, possibly in different evolutionary stages, in the same
complex, i.e. spontaneous star-formation can also occur close to a
H\,{\footnotesize II}~ region.

For example, the cluster of YSOs detected in C2 coincides with the
N159W-S clump in the ALMA observations from \cite{Fukui2015}. As noted
earlier, they argued that the clump was formed by the collision of two
parsec-scale filaments.  If this is the case, then expansion of the
H\,{\footnotesize II}~ region is not the prime mechanism in forming the clump, although
it may have brought the energy required to initiate star formation in
a clump formed via the filament collision. To further complicate
things, C2 also sits perfectly on the edge of the (1-2\,Myr old)
larger-scale bubble suggested by \citet{Jones2005} and
\citet{Nakajima2005} to have triggered star formation in N159E and
N159W, so its origins are even more ambiguous.
The C5 clump appears unrelated to the central cluster in N159W, and
may have been triggered by the larger-scale bubble.
As in the case of C2, this may have been a pre-existing molecular
reservoir in which the pressure from expansion of the large-scale
bubble initiated star formation, although the current data to
not allow firm conclusions.

Lastly, given the age of the central cluster (1-3\,Myr) and its
location outside of the larger-scale bubble, its formation is probably
not connected, providing support of the scenario from
\citet{Chen2010a} where star formation in N159W started spontaneously
(or at least, was not triggered by the larger bubble).

\section{Summary}

We have presented deep, high angular-resolution, NIR images of the
N159W region in the LMC. We have used these to explore the stellar
content of the central cluster, as well as the star-formation history
of the region. Based on these observations, via construction of
colour-colour and colour-magnitude diagrams, we have identified 104
candidate YSOs in the observed 90$''$\,$\times$\,90$''$ field
($\sim$22\,$\times$\,22\,pc). These candidates are prominently
distributed at the edges of the N159W H\,{\footnotesize II}~ bubble, and are
concentrated into clumps and subclusters of stars, which are resolved
for the first time by the high angular-resolution of our observations.
These groups are associated with active star-formation processes, as
highlighted by the presence of UCHII regions, outflows, and class 0/I
YSOs -- each of which are indicators of very recent star-formation
events, possibly forming massive stars.

In contrast, the stars located inside the H\,{\footnotesize II}~ bubble appear to be at
a more evolved stage, with an average age of 2\,$\pm$\,1\,Myr. The
central cluster has two massive O-type stars at its centre, which probably
dominate the ionisation of the H\,{\footnotesize II}~ region. From the IMF of the
cluster, we estimate its total mass to be $\sim$1300\,\mbox{\rm $M_{\odot}$}.  This
cluster may have instigated the star-formation events at its edges,
but further observations will be needed to firmly confirm the
presence of sequential star-formation in the N159W region.

\begin{acknowledgements}

  Based on observations obtained at the Gemini Observatory, which is
  operated by the Association of Universities for Research in
  Astronomy, Inc., under a cooperative agreement with the NSF on
  behalf of the Gemini partnership: the National Science Foundation
  (United States), the National Research Council (Canada), CONICYT
  (Chile), the Australian Research Council (Australia), Minist\'erio
  da Ci$\rm{\hat{e}}$ncia, Tecnologia e Inova{\c{c}}$\rm{\tilde{a}}$o
  (Brazil) and Ministerio de Ciencia, Tecnologiaa e Innovaci\'on
  Productiva (Argentine). B.~Neichel and A.~Bernard acknowledge the
  financial support from the French ANR program WASABI to carry out
  this work. H.~Plana thanks the CNPq/CAPES for its financial support
  using the PROCAD project 552236/2011-0. M.~R.~Samal acknowledges
  the financial support provided by the French Space Agency (CNES) for
  his postdoctoral fellowship.
\end{acknowledgements}

\bibliographystyle{aa}

redpajama_set_name: RedPajamaArXiv


text:
Goss: GreenEdge doing a "pretty good job" in first year
By Jane Aubrey 19 March 2012
New team sticking to the game plan
Matthew Harley Goss (GreenEdge Cycling Team) kept his race lead (Image credit: Fotoreporter Sirotti)
Simon Gerrans (GreenEdge) celebrates winning (Image credit: Bettini Photo)
Simon Gerrans takes over the lead with only one stage to go. (Image credit: Mark Gunter)
Matthew Goss enjoys another day in the leader's jersey (Image credit: Bettini Photo)
The GreenEDGE kit. (Image credit: Mark Gunter)
Matt Goss believes that WorldTour neophytes GreenEdge are measuring up to expectations, at least those set by the team, in their first few months.
Gerrans targets Ardennes Classics after Tour Down Under victory
WorldTour rookie Kruopis nabs first international podium for GreenEdge
Cooke steps up to the mark for GreenEdge
Paris-Nice, Tirreno-Adriatico crucial for GreenEdge
Gerrans: I can't deny Cancellara was the strongest
Goss, speaking to Cyclingnews before teammate Simon Gerrans' victory at Milan-San Remo on Saturday afternoon, said that there was little to complain about.
"In the team respect we've done fairly well so far, we've won the national title, Down Under, pretty much everything in Australia," he said. "We've won the team time trial in Tirreno which is a huge thing being a brand new team and having never ridden together, never used this equipment and then to come out and win the way we did and have the jersey there.
"While doing that we've had a team in Paris-Nice with Gerro who just missed out on a stage win and was unlucky to crash on the second opportunity for a stage win for himself," Goss continued. "I think that for a brand new team there's not a lot that people can pick at at the moment. We've been performing well."
Question marks over the performance of GreenEdge followed the outfit from Gerrans' narrow overall win at the Tour Down Under to Qatar and Oman, while the opening WorldTour race raised some eyebrows for the way the ochre jersey was won.
Phil Anderson, the man by and large responsible for Gerrans' love of the bike having lived next door in the town of Mansfield in Victoria, viewed the GreenEdge tactics as being "risky" especially with the stage and then overall result on Willunga Hill so close to not falling in Gerrans' favour.
"Seeing Simon isolated on the circuits at the end was a very dangerous situation and if it was my team I'd be pretty upset about that, but as long as they learn from their mistakes and that it doesn't happen further in the season," Anderson said.
Meantime Gerrans himself admitted to the team still working their way into their groove.
"We haven't all raced in a stage race together before," he said. "Obviously we did the national championships and we've done certain world championships and Olympic Games that sort of thing together but it does take a few days for everyone to really learn their roles in the team."
Lithuanian sprinter Aidis Kruopis took third in Qatar's third stage and Baden Cooke was runner-up on Stage 2 in Oman. When it came to the Belgian semi classics, Het Nieuwsblad and Kuurne-Brussel-Kuurne, the team was labelled as 'anonymous'.
From the outset, GreenEdge said they would target the Australian Road Championships, the classics and smaller stage races in their inaugural year – and three months in, they had delivered, yet opinion remained divided as to their performance.
"There's always going to be people where something's never enough and I think you're going to get that no matter what," Goss admitted to Cyclingnews.
Regardless, the 2011 Milan-SanRemo winner believes that at the end of the day, variety in results only adds to the sport's popularity.
"It's what makes the sport exciting," Goss said. "It's what makes people watch the sport. If they knew who was going to win they wouldn't turn the tv on.
"I'm really happy with how the team's going and we're just sticking to what we said at the start, if we keep going the way we are at the end of the season I don't think there's going to be too much for people to complain about."

redpajama_set_name: RedPajamaCommonCrawl


developers. The goal is to develop webpage that can take a user name + password combination, and fetch contacts from Yahoo, Outlook, Gmail.
They will be displayed as shown in the images. Initially, all will be selected. Someone can deselect the contacts.
There should be a "Mail" button in the listing page. If someone clicks on the mail button then it should send a mail to each of these contacts (which are selected).
You must put the API Key AP secret etc in one place. so that I can replace that with my API key.
You must first deliver the code and explain to me how to integrate it. Only then I will release the money.
I need it in 2-3 days.


text:
Robert Reed Altman (born December 22, 1959) is an American cinematographer. He has served as a camera operator and director of photography on feature films and television series since the 1970s. He is the son of filmmaker Robert Altman and Kathryn Reed.

Career
Altman began his career serving as focus puller and second assistant camera on the films such as: Nashville (1975), Buffalo Bill and the Indians (1976), A Wedding (1978), Popeye (1980), Health (1982), Come Back to the Five and Dime, Jimmy Dean, Jimmy Dean (1982), Streamers (1983), and Fool for Love (1985).

Altman shifted gears and gravitated to television where he served as camera operator on the TV series Alien Nation (1989), Tales of the City (1993), Melrose Place (1992), and Robert Altman's Gun (1997). Altman also served as second unit director of photography on the hit TV series, The Wonder Years.

In 2004, Altman served as director of Photography on director Robert Altman and writer/cartoonist Garry Trudeau's Tanner on Tanner. Premiering at the Sundance Film Festival, the film was a follow-up to their documentary-style Emmy-winning film, Tanner '88. The new "Tanner", a four-part series following the new adventures of fictional presidential nominee Tanner, was filmed to coincide with the Bush-Kerry elections.

In between his work for television, Altman continues to return to feature filmmaking as a camera operator or cinematographer. Credits include Looking for Trouble for Roger Corman; several projects directed by Robert Altman, Kansas City (1996), The Gingerbread Man (1998), Cookie's Fortune (1999) and Dr. T & the Women (2000), as well as Jay and Silent Bob Strike Back (2001) directed by Kevin Smith, and The Scorpion King (2002) starring The Rock.

Altman last worked with his father on A Prairie Home Companion.

Altman has worked on the network shows Boston Legal, The O.C., Bones and Lost.

Personal life
Altman is married to Barbara Ann Altman and has one daughter, Cora Kathryn Ann Altman.

References

External links

1959 births
Living people
American cinematographers
People from Los Angeles

redpajama_set_name: RedPajamaWikipedia


Virgin Media named fastest broadband UK provider – but who is the slowest?
It's a sad-but-true fact – superfast broadband is a necessity for the majority of people in today's technology-driven world. Without it, how would we binge-watch our favourite Netflix series? Or what if we wanted to ask Alexa for a weather update instead of simply looking out a window?
So imagine the stress and annoyance of having to constantly call your broadband provider's customer service team because your download speeds are slower than a sloth – it's not pleasant.
But, if you're a household who chose Virgin Media as your supplier, then you're much smarter than those who didn't. Because they've been named the fastest broadband provider in the UK for the seventh year in a row!
Analysis from UK broadband comparison website Broadband Genie, who analysed more than 12,000 speed tests across the UK up until December 2018, recorded an average download of 71.5Mb for Virgin Media customers – almost three times faster than its nearest challenger.
'We're on a mission to make Britain faster and build connections that really matter so we're thrilled that for the seventh year in a row we've been crowned the UK's fastest broadband provider by Broadband Genie,' says Richard Sinclair MBE, Executive Director for Connectivity at Virgin Media.
Vodafone came second in the poll, with average download speeds of 24.9Mb. However, the telecommunications conglomerate hit the top spot when it came to upload speeds, averaging 10.1Mb compared to runner-up Virgin Media's 7.7Mb.
'We're really pleased to have been recognised as the fastest broadband provider for uploading for the second year running,' Scott Petty, Chief Technology Officer at Vodafone UK, said.
But it may come as a shock to some – or not, they're bottom of the list for a reason – that Sky failed to impress with both its download and upload speeds.
Related:Do you use one (or all) of the internet's favourite cleaning products in your home?
Landing bottom of the leaderboard, Sky only managed 17.1Mb average download speeds and just 5.2Mb average upload speeds.
Other worthy mentions goes to EE and BT, who averaged download speeds of 23.5Mb and 22.3Mb respectively.
Will you be changing your broadband provider?


On Sunday, March 6, the English department hosted a live reading of the epic poem Paradise Lost, by John Milton.
Volunteers sat around the big oval table in the Fager Lounge and read the more than 10,000 lines from 12 books.
"The Miltonathon, which began last year, is a tribute to my late friend and colleague Professor George Hudson, who taught Milton at Colgate for over forty years," said Professor Deborah Knuth Kleck, who now teaches the Milton course at Colgate, and started this event.
Marathon readings of Paradise Lost at other colleges exist, but Kunth Kleck has never heard of one that has the reader play parts. Participants at Colgate divided up roles as they read, so sometimes the narrator had only a couple of words — like "she said" — before a speech resumed. "Professor Judith Oliver, emerita professor of art and art history, for example, got to be God!" reported Kunth Kleck.
The day included a snake cake (pictured above, designed and executed by local baker Sharon Stevens) and live tweeting on Colgate's Twitter feed. Every tweet was written by English major Emily Daniel '18.


There's a lot of discussion amongst mothers of all generations about what's best for a child. Most mothers will gladly tell another mother to not spoil the child as it will only make things so much more excruciating in the parenting department. A spoiled child = an ill-behaved child, or so the equation goes. Instilling good behavior in your child at an early age only proves to be beneficial to him or her as they get older. Unfortunately, NOT spoiling my child is a lot more difficult than spoiling him.
My Davey will be 8 weeks old tomorrow. He is my golden child, the apple of my eye, a complete Mama's boy and I'm very proud of that. I've showered him with love, support, adoration and encouragement each day of his so short life. When he's cried, I've fed him, I've held him, I've changed his diaper and he's come to expect someone to pick him up when he cries. Unfortunately, I don't think my husband really agrees with my incessant desire to immediately soothe and comfort our child. He believes (or so I think) that Davey is taking advantage of me, something I believe he's much too young to do. The poor baby just wants his mother's love and comfort around him, I inform my husband.
This past Sunday morning was our first day back to church since Davey's birth. I must admit that I was nervous and anxious at the thought of introducing him into an environment that he may disrupt with his crying. I feared the dreaded evil eyes of so many people as they got frustrated with not hearing the preacher's sermon because my "spoiled" child wanted to make his presence known. So, my husband and I decided to leave Davey in his car seat while in church. Most days he will fall asleep on the car ride and sleep easily another hour after we've reached our destination. This was my hope on Sunday, but alas my son was going to have no part in this.
Within a few minutes of our arrival and all the oohing and aahing of the ladies within our congregation, Davey's chin began to tremble. He looked up at me and I watched painfully as he conveyed to me his fear and insecurity. I wasted no time with immediately releasing him from the confines of his baby carrier and quickly wrapping him in my arms. I can't be sure, but I think we received a roll of the eyes from my husband at how quickly I was willing to hold him.
My mother tells me that I should let him cry it out sometimes, but I just can't. It's sheer torture to hear the cries of my child. At such an early stage in his life, this is his only way to communicate with me and to watch him lie in his crib, desperately seeking my affection, while I pitter patter along with whatever task I have before me, just makes me so heartsick. I can't let him go. I can't NOT hold him.
At dinner, we usually put him in his pack and play so that we can eat. I quickly scarf down my dinner, getting indigestion in the process just so I won't have to listen to the torturous sounds of his cries. My husband tries to soothe me and our son at the same time. He tells me Davey is fine and that there is no need to pick him up. On the occasion that I don't immediately hold him, he will eventually calm down within minutes, but listening to him feels like a lifetime of agony. After all, what is my son thinking about me as a mother and my parenting skills? I'm leaving him to his misery, forcing him to suffer only because he can't tell me exactly what's wrong or because I'm trying to play a game of "Hard Love". I can only imagine how much of a push-over and schmuck I'll be as he gets older. But right now, I can't help but "spoil" him and hold him.


He left the Soviet Union in 1973 as Temur Sepiashvili, a 26-year-old Russian who ended up driving a taxicab in Manhattan to make ends meet. His life soon became the stuff of American dreams. He changed his last name to Sapir and built a real estate business in New York that gave him a net worth of $2 billion at the height of the 2007 real estate market boom. In the ultimate acknowledgment of making it, this kid from Tbilisi in the Republic of Georgia, now 63, scaled The Forbes 400 list four years running.
Today Tamir Sapir's circumstances are far less exalted. A host of creditors are suing him for repayment of loans totaling some $340 million, and real estate brokers are claiming he brazenly stiffed them on commissions. In January SL Green Realty Corp. foreclosed on a Sapir-owned 1-million-square-foot building in Manhattan's financial district after he had defaulted on loans of at least $85 million. He's even accused of not paying for things like a custom mat by the American Paper Towel Corp., which claims in a suit that the Sapir Organization owes $23,298.64 plus interest for goods sold for the foreclosed building at 100 Church Street.
By our estimate, Sapir's net worth has fallen to around $700 million, still wealthy indeed but not nearly enough to make this year's rich list.
A tough, unloved landlord, a pariah to many brokers, Sapir looks like yet another credit-starved developer fallen prey to endless refinancing at the wrong time. Yet in a strange twist, his lawyers in one lawsuit are offering a surprising explanation for his troubles. They claim in court that Sapir has, according to a 2008 medical examination, suffered from a "deteriorating mental condition" since at least 1998 that left him vulnerable to shrewd bankers and lawyers out to take advantage of him.
This particular suit, filed in May, claims Sapir hasn't repaid a $66 million loan he took out in 2006 to develop a 47-story residential condominium in Manhattan's financial district. Sapir personally guaranteed the loan, from a Blackstone-controlled fund, at 18% interest, and later revised it to an even steeper interest rate of 20%. Why would he do that? His lawyer, Stephen B. Meister, said in court in August that Sapir's attorney gave him bad advice because he stood to gain $15 million to $16 million from the deal--and Sapir lacked the mental capacity to understand the loan's conditions. "He had not written anything other than signing his name for ten years," Meister told the court. A recent examination, Meister tells FORBES, confirms Sapir is suffering from an incurable degenerative brain illness.
This defense astonished the lender, GSO Re Onshore, which claimed in a letter to the judge that Sapir had never before raised the issue. Sapir's previous lawyer, Robert J. Ivanhoe, has denied the allegation that he misled his client.
Sapir has also tossed accountability over to his 31-year-old son, Alex, who has been running the Sapir Organization since 2006. In a 2009 videotaped deposition involving a pending suit in Las Vegas, Sapir is asked about a $21 million development deal he is accused of reneging on. "My son is doing the business," Sapir answers. "'Papa, give me money,' and that's it." Sapir says he has no knowledge of the property's price or its appraisal, explaining: "My son--I speak little English. My son is in the business. I am the money man, and that's it. Why am I expected to know so much?"
The two Sapirs declined to speak to FORBES. In court papers filed July 30, 2009 in the Las Vegas suit, Alex pleaded poverty for the Sapir Group. He said that the "defendant is more than $250 million in debt, its assets are not liquid and are not readily saleable, and it currently has only approximately $4,000 in cash and cash equivalents."
Over the years his dad has certainly spoiled himself. He's enjoyed a $5 million Trump Tower apartment and a penthouse overlooking Acapulco Bay, not to mention the Versace-accented 150-foot yacht called Mystere. (This was the yacht that he used to illegally import rare animal carcasses into the U.S., which resulted in a $150,000 fine last year and his guilty plea for violating the Endangered Species Act.) He has developed a penchant for jet-setting and wearing expensive fashion labels. A long way from Tbilisi.
After driving a cab when he came to New York and famously borrowing $10,000 against his medallion, he opened an electronics store on Fifth Avenue. The store became a hot spot for Soviet dignitaries and trade delegations, according to Sapir's official bio, and eventually he became a key foreign partner for the emerging oil industry in Russia.
Then he struck real estate gold. In the mid-1990s 2 Broadway was a 32-story building near Wall Street that, originally built in 1959, was badly in need of renovation. Sapir snatched it for $20 million. "As far as grand slams in Manhattan real estate go, that's way up there with [Donald] Trump's purchase of 40 Wall Street," says Dan Fasulo, head of research for Real Capital Analytics, a real estate research firm. "That's really what made him." In 1998 the Metropolitan Transportation Authority agreed to sign a 49-year lease for 2 Broadway, for which it today pays $23.1 million a year.
Just two years later that relationship soured in a barrage of lawsuits involving maintenance and renovation of the building. The MTA later announced that investigators concluded that both parties were victims of fraud and criminality "at the hands of certain third parties."
Sapir, meanwhile, refinanced the valuable building a couple of times, eventually for $440 million, and apparently used the proceeds to buy other properties--some of which he in turn refinanced before the real estate bust. In 2003 Sapir bought 11 Madison Avenue, a prized building near Madison Square Park that now houses tenant royalty, including Credit Suisse . The building cost him and a partner $675 million. Then in 2006 Sapir refinanced the building for $806 million. Sapir also owns two residential apartment buildings in downtown Manhattan, a 950,000-square-foot commercial building in midtown and another, eight-story commercial building nearby on Fifth Avenue that serves as the company headquarters.
Sapir isn't likely to win any Landlord of the Year awards. Three brokers--including one involved in the recent $44 million sale of his Fifth Avenue mansion to Carlos Slim Helú--allege in suits this year that Sapir stiffed them on commissions ranging from $164,076 to $880,000.
Sapir's latest project, the new hotel-condo Trump SoHo in Tribeca, is also embroiled in a lawsuit. Trump SoHo had a highly publicized opening in April, but so far it's been a dud: 15 buyers filed suit in August seeking $1.75 million in deposit refunds and damages, alleging they'd been misled regarding how many units had been sold.
Will Sapir be able to untangle himself from this legal mess? It wouldn't be his first time. In his 2001 divorce proceedings a judge ordered Sapir not to gamble large sums of cash prior to a settlement. Sapir did gamble--and won $1.1 million. "No harm, no foul," he told the judge, who let it slip.