Login | Create
Sort by: Relevance Date Users's collections Twitter
Group by: Day Week Month Year All time
Based on the idea and the provided source code of Andrej Karpathy (arxiv-sanity)
Towards a census of high-redshift dusty galaxies with $\mathit{Herschel}$: A selection of "500 $\mu$m-risers" (1709.00942)
D. Donevski, V. Buat, F. Boone, C. Pappalardo, M. Bethermin, C. Schreiber, F. Mazyed, J. Álvarez-Márquez, S. Duivenvoorden
Feb. 1, 2018 astro-ph.GA
$\mathit{Herschel}$ extragalactic surveys offer a unique opportunity to efficiently select a significant number of rare and massive dusty objects, and thus gain insight into the prodigious star-forming activity that takes place in the very distant Universe. To search for $z\geq4$ dusty star-forming galaxies, in this work we consider red SPIRE objects with fluxes rising from 250 $\mu$m to $500\:\mu$m (so-called "500 $\mu$m-risers"). We aim to implement a novel method to obtain a statistical sample of "500 $\mu$m-risers" and fully evaluate our selection inspecting different models of galaxy evolution. We consider one of the largest and deepest ${\it Herschel}$ surveys, the Herschel Virgo Cluster Survey. We develop a novel selection algorithm which links the source extraction and spectral energy distribution fitting. We select 133 "500 $\mu$m-risers" over 55 deg$^{2}$, imposing the criteria: $S_{500}>S_{350}>S_{250}$, $S_{250}>13.2$ mJy and $S_{500}>$30 mJy. Differential number counts are in a fairly good agreement with models, displaying better match than other existing samples. In order to interpret the statistical properties of selected sources, which has been proven as a very challenging task due the complexity of observed artefacts, we make end-to-end simulations including physical clustering and lensing. The estimated fraction of strongly lensed sources is $24^{+6}_{-5}\%$ based on models. We present the faintest known statistical sample of "500 $\mu$m-risers" and show that noise and strong lensing have crucial impact on measured counts and redshift distribution of selected sources. We estimate the flux-corrected star formation rate density at $4<z<5$ with the "500 $\mu$m-risers" and found it close to the total value measured in far-infrared. It indicates that colour selection is not a limiting effect to search for the most massive, dusty $z>4$ sources.
GitHub 0
PHIBSS: Unified Scaling Relations of Gas Depletion Time and Molecular Gas Fractions (1702.01140)
L. J. Tacconi, R. Genzel, A. Saintonge, F. Combes, S. García-Burillo, R. Neri, A. Bolatto, T. Contini, N. M. Förster Schreiber, S. Lilly, D. Lutz, S. Wuyts, G. Accurso, J. Boissier, F. Boone, N. Bouché, F. Bournaud, A. Burkert, M. Carollo, M. Cooper, P. Cox, C. Feruglio, J. Freundlich, R. Herrera-Camus, S. Juneau, M. Lippa, T. Naab, A. Renzini, P. Salome, A. Sternberg, K. Tadaki, H. Übler, F. Walter, B. Weiner, A. Weiss
Jan. 11, 2018 astro-ph.GA
This paper provides an update of our previous scaling relations (Genzel et al.2015) between galaxy integrated molecular gas masses, stellar masses and star formation rates, in the framework of the star formation main-sequence (MS), with the main goal to test for possible systematic effects. For this purpose our new study combines three independent methods of determining molecular gas masses from CO line fluxes, far-infrared dust spectral energy distributions, and ~1mm dust photometry, in a large sample of 1444 star forming galaxies (SFGs) between z=0 and 4. The sample covers the stellar mass range log(M*/M_solar)=9.0-11.8, and star formation rates relative to that on the MS, delta_MS=SFR/SFR(MS), from 10^{-1.3} to 10^{2.2}. Our most important finding is that all data sets, despite the different techniques and analysis methods used, follow the same scaling trends, once method-to-method zero point offsets are minimized and uncertainties are properly taken into account. The molecular gas depletion time t_depl, defined as the ratio of molecular gas mass to star formation rate, scales as (1+z)^{-0.6}x(delta_MS)^{-0.44}, and is only weakly dependent on stellar mass. The ratio of molecular-to-stellar mass mu_gas depends on (1+z)^{2.5}x (delta_MS)^{0.52}x(M*)^{-0.36}, which tracks the evolution of the specific star formation rate. The redshift dependence of mu_gas requires a curvature term, as may the mass-dependences of t_depl and mu_gas. We find no or only weak correlations of t_depl and mu_gas with optical size R or surface density once one removes the above scalings, but we caution that optical sizes may not be appropriate for the high gas and dust columns at high-z.
ALMA reveals metals yet no dust within multiple components in CR7 (1709.06569)
J. Matthee, D. Sobral, F. Boone, H. Röttgering, D. Schaerer, M. Girard, A. Pallottini, L. Vallini, A. Ferrara, B. Darvish, B. Mobasher
Nov. 6, 2017 astro-ph.GA
We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [CII]$_{158 \mu \rm m}$ line-emission at high spatial resolution matched to the HST/WFC3 imaging. CR7 is a luminous Ly$\alpha$ emitting galaxy at $z=6.6$ that consists of three separated UV-continuum components. Our observations reveal several well-separated components of [CII] emission. The two most luminous components in [CII] coincide with the brightest UV components (A and B), blue-shifted by $\approx 150$ km s$^{-1}$ with respect to the peak of Ly$\alpha$ emission. Other [CII] components are observed close to UV clumps B and C and are blue-shifted by $\approx300$ and $\approx80$ km s$^{-1}$ with respect to the systemic redshift. We do not detect FIR continuum emission due to dust with a 3$\sigma$ limiting luminosity L$_{\rm IR} (T_d = 35 \rm \, K) < 3.1\times10^{10}$ L$_{\odot}$. This allows us to mitigate uncertainties in the dust-corrected SFR and derive SFRs for the three UV clumps A, B and C of 28, 5 and 7 M$_{\odot}$ yr$^{-1}$. All clumps have [CII] luminosities consistent within the scatter observed in the local relation between SFR and L$_{\rm [CII]}$, implying that strong Ly$\alpha$ emission does not necessarily anti-correlate with [CII] luminosity. Combining our measurements with the literature, we show that galaxies with blue UV slopes have weaker [CII] emission at fixed SFR, potentially due to their lower metallicities and/or higher photoionisation. Comparison with hydrodynamical simulations suggests that CR7's clumps have metallicities of $0.1<\rm Z/Z_{\odot}<0.2$. The observed ISM structure of CR7 indicates that we are likely witnessing the build up of a central galaxy in the early Universe through complex accretion of satellites.
Molecular gas properties of a lensed star-forming galaxy at z~3.6: a case study (1610.08065)
M. Dessauges-Zavadsky, M. Zamojski, W. Rujopakarn, J. Richard, P. Sklias, D. Schaerer, F. Combes, H. Ebeling, T. D. Rawle, E. Egami, F. Boone, B. Clément, J.-P. Kneib, K. Nyland, G. Walth
Aug. 7, 2017 astro-ph.GA
We report on the galaxy MACSJ0032-arc at z=3.6314 discovered during the Herschel Lensing snapshot Survey of massive galaxy clusters, and strongly lensed by the cluster MACSJ0032.1+1808. The successful detections of its rest-frame UV, optical, FIR, millimeter, and radio continua, and of its CO emission enable us to characterize, for the first time at such a high redshift, the stellar, dust, and molecular gas properties of a compact star-forming galaxy with a size smaller than 2.5 kpc, a fairly low stellar mass of 4.8x10^9 Msun, and a moderate IR luminosity of 4.8x10^11 Lsun. We find that the bulk of the molecular gas mass and star formation seems to be spatially decoupled from the rest-frame UV emission. About 90% of the total star formation rate is undetected at rest-frame UV wavelengths because of severe obscuration by dust, but is seen through the thermal FIR dust emission and the radio synchrotron radiation. The observed CO(4-3) and CO(6-5) lines demonstrate that high-J transitions, at least up to J=6, remain excited in this galaxy, whose CO spectral line energy distribution resembles that of high-redshift submm galaxies, even though the IR luminosity of MACSJ0032-arc is ten times lower. This high CO excitation is possibly due to the compactness of the galaxy. We find evidence that this high CO excitation has to be considered in the balance when estimating the CO-to-H2 conversion factor. The inferred depletion time of the molecular gas in MACSJ0032-arc supports the decrease in the gas depletion timescale of galaxies with redshift, although to a lesser degree than predicted by galaxy evolution models. Instead, the measured molecular gas fraction as high as 60-79% in MACSJ0032-arc favors the continued increase in the gas fraction of galaxies with redshift as expected, despite the plateau observed between z~1.5 and z~2.5.
Planck's Dusty GEMS. II. Extended [CII] emission and absorption in the Garnet at z=3.4 seen with ALMA (1610.01169)
N. Nesvadba, R. Kneissl, R. Canameras, F. Boone, E. Falgarone, B. Frye, M. Gerin, S. Koenig, G. Lagache, E. Le Floc'h, S. Malhotra, D. Scott
Oct. 4, 2016 astro-ph.GA
We present spatially resolved ALMA [CII] observations of the bright (flux density S=400 mJy at 350 microns), gravitationally lensed, starburst galaxy PLCK G045.1+61.1 at z=3.427, the "Garnet". This source is part of our set of "Planck's Dusty GEMS", discovered with the Planck's all-sky survey. Two emission-line clouds with a relative velocity offset of ~600 km/s extend towards north-east and south-west, respectively, of a small, intensely star-forming clump with a star-formation intensity of 220 Msun/yr/kpc^2, akin to maximal starbursts. [CII] is also seen in absorption, with a redshift of +350 km/s relative to the brightest CO component. [CII] absorption has previously only been found in the Milky Way along sightlines toward bright high-mass star-forming regions, and this is the first detection in another galaxy. Similar to Galactic environments, the [CII] absorption feature is associated with [CI] emission, implying that this is diffuse gas shielded from the UV radiation of the clump, and likely at large distances from the clump. Since absorption can only be seen in front of a continuum source, the gas in this structure can definitely be attributed to gas flowing towards the clump. The absorber could be part of a cosmic filament or merger debris being accreted onto the galaxy. We discuss our results also in light of the on-going debate of the origin of the [CII] deficit in dusty star-forming galaxies.
Planck's Dusty GEMS: Gravitationally lensed high-redshift galaxies discovered with the Planck survey (1506.01962)
R. Canameras, N. P. H. Nesvadba, D. Guery, T. McKenzie, S. Koenig, G. Petitpas, H. Dole, B. Frye, I. Flores-Cacho, L. Montier, M. Negrello, A. Beelen, F. Boone, D. Dicken, G. Lagache, E. Le Floch, B. Altieri, M. Bethermin, R. Chary, G. De Zotti, M. Giard, R. Kneissl, M. Krips, S. Malhotra, C. Martinache, A. Omont, E. Pointecouteau, J.-L. Puget, D. Scott, G. Soucail, I. Valtchanov, N. Welikala, L. Yan
June 5, 2015 astro-ph.GA
We present an analysis of 11 bright far-IR/submm sources discovered through a combination of the Planck survey and follow-up Herschel-SPIRE imaging. Each source has a redshift z=2.2-3.6 obtained through a blind redshift search with EMIR at the IRAM 30-m telescope. Interferometry obtained at IRAM and the SMA, and optical/near-infrared imaging obtained at the CFHT and the VLT reveal morphologies consistent with strongly gravitationally lensed sources. Additional photometry was obtained with JCMT/SCUBA-2 and IRAM/GISMO at 850 um and 2 mm, respectively. All objects are bright, isolated point sources in the 18 arcsec beam of SPIRE at 250 um, with spectral energy distributions peaking either near the 350 um or the 500 um bands of SPIRE, and with apparent far-infrared luminosities of up to 3x10^14 L_sun. Their morphologies and sizes, CO line widths and luminosities, dust temperatures, and far-infrared luminosities provide additional empirical evidence that these are strongly gravitationally lensed high-redshift galaxies. We discuss their dust masses and temperatures, and use additional WISE 22-um photometry and template fitting to rule out a significant contribution of AGN heating to the total infrared luminosity. Six sources are detected in FIRST at 1.4 GHz. Four have flux densities brighter than expected from the local far-infrared-radio correlation, but in the range previously found for high-z submm galaxies, one has a deficit of FIR emission, and 6 are consistent with the local correlation. The global dust-to-gas ratios and star-formation efficiencies of our sources are predominantly in the range expected from massive, metal-rich, intense, high-redshift starbursts. An extensive multi-wavelength follow-up programme is being carried out to further characterize these sources and the intense star-formation within them.
ALMA detection of [CII] 158 micron emission from a strongly lensed z=2 star-forming galaxy (1502.03842)
D. Schaerer, F. Boone, T. Jones, M. Dessauges-Zavadsky, P. Sklias, M. Zamojski, A. Cava, J. Richard, R. Ellis, T.D. Rawle, E. Egami, F. Combes
Feb. 12, 2015 astro-ph.GA
Our objectives are to determine the properties of the interstellar medium (ISM) and of star-formation in typical star-forming galaxies at high redshift. Following up on our previous multi-wavelength observations with HST, Spitzer, Herschel, and the Plateau de Bure Interferometer (PdBI), we have studied a strongly lensed z=2.013 galaxy, the arc behind the galaxy cluster MACS J0451+0006, with ALMA to measure the [CII] 158 micron emission line, one of the main coolants of the ISM. [CII] emission from the southern part of this galaxy is detected at 10 $\sigma$. Taking into account strong gravitational lensing, which provides a magnification of $\mu=49$, the intrinsic lensing-corrected [CII]158 micron luminosity is $L(CII)=1.2 \times 10^8 L_\odot$. The observed ratio of [CII]-to-IR emission, $L(CII)/L(FIR) \approx (1.2-2.4) \times 10^{-3}$, is found to be similar to that in nearby galaxies. The same also holds for the observed ratio $L(CII)/L(CO)=2.3 \times 10^3$, which is comparable to that of star-forming galaxies and active galaxy nuclei (AGN) at low redshift. We utilize strong gravitational lensing to extend diagnostic studies of the cold ISM to an order of magnitude lower luminosity ($L(IR) \sim (1.1-1.3) \times 10^{11} L_\odot$) and SFR than previous work at high redshift. While larger samples are needed, our results provide evidence that the cold ISM of typical high redshift galaxies has physical characteristics similar to normal star forming galaxies in the local Universe.
Molecular gas content in strongly-lensed z~1.5-3 star-forming galaxies with low IR luminosities (1408.0816)
M. Dessauges-Zavadsky, M. Zamojski, D. Schaerer, F. Combes, E. Egami, A. M. Swinbank, J. Richard, P. Sklias, T. D. Rawle, M. Rex, J.-P. Kneib, F. Boone, A. Blain
To extend the molecular gas measurements to typical star-forming galaxies (SFGs) with SFR < 40 Msun yr^{-1} and M* < 2.5x10^{10} Msun at z~1.5-3, we have observed CO emission with the IRAM Plateau de Bure Interferometer and 30m telescope for five strongly-lensed galaxies selected from the Herschel Lensing Survey. These observations are combined with a compilation of CO measurements from the literature. We infer the luminosity correction factors r2,1 = 0.81+/-0.20 and r3,1 = 0.57+/-0.15 for the J=2 and J=3 CO transitions, respectively, valid for SFGs at z>1. The combined sample of CO-detected SFGs at z>1 shows a large spread in star formation efficiency (SFE), such that SFE extend beyond the low values of local spirals and overlap the distribution of z>1 sub-mm galaxies. We find that the spread in SFE (or equivalently in molecular gas depletion timescale) is due to primarily the specific star formation rate, but also stellar mass and redshift. Correlations of SFE with the offset from the main-sequence and the compactness of the starburst are less clear. The increase of the molecular gas depletion timescale with M* now revealed by low M* SFGs at z>1 and observed at z=0 is in contrast to the admitted constant molecular gas depletion timescale and the linear Kennicutt-Schmidt relation. We confirm an increase of the molecular gas fraction (fgas) from z~0.2 to z~1.2, followed by a very mild increase toward higher redshifts. At each redshift fgas shows a large dispersion due to the dependence of fgas on M*, producing a gradient of increasing fgas with decreasing M*. We provide the first measure of fgas of z>1 SFGs at the low-M* end (10^{9.4} < M*/Msun < 10^{9.9}), reaching a mean fgas = 0.69+/-0.18, which shows a clear fgas upturn. Finally, we find evidence for a non-universal dust-to-gas ratio among high-redshift SFGs and sub-mm galaxies, local spirals and ULIRGs with near-solar metallicities.
Combined CO & Dust Scaling Relations of Depletion Time and Molecular Gas Fractions with Cosmic Time, Specific Star Formation Rate and Stellar Mass (1409.1171)
R. Genzel, L.J. Tacconi, D. Lutz, A. Saintonge, S. Berta, B. Magnelli, F. Combes, S. García-Burillo, R. Neri, A. Bolatto, T. Contini, S. Lilly, J. Boissier, F. Boone, N. Bouché, F. Bournaud, A. Burkert, M. Carollo, L. Colina, M.C. Cooper, P. Cox, C. Feruglio, N.M. Förster Schreiber, J. Freundlich, J. Gracia-Carpio, S. Juneau, K. Kovac, M. Lippa, T. Naab, P. Salome, A. Renzini, A. Sternberg, F. Walter, B. Weiner, A. Weiss, S. Wuyts
Dec. 5, 2014 astro-ph.GA
We combine molecular gas masses inferred from CO emission in 500 star forming galaxies (SFGs) between z=0 and 3, from the IRAM-COLDGASS, PHIBSS1/2 and other surveys, with gas masses derived from Herschel far-IR dust measurements in 512 galaxy stacks over the same stellar mass/redshift range. We constrain the scaling relations of molecular gas depletion time scale (tdepl) and gas to stellar mass ratio (Mmolgas/M*) of SFGs near the star formation main-sequence with redshift, specific star formation rate (sSFR) and stellar mass (M*). The CO- and dust-based scaling relations agree remarkably well. This suggests that the CO-H2 mass conversion factor varies little within 0.6dex of the main sequence (sSFR(ms,z,M*)), and less than 0.3dex throughout this redshift range. This study builds on and strengthens the results of earlier work. We find that tdepl scales as (1+z)^-0.3 *(sSFR/sSFR(ms,z,M*))^-0.5, with little dependence on M*. The resulting steep redshift dependence of Mmolgas/M* ~(1+z)^3 mirrors that of the sSFR and probably reflects the gas supply rate. The decreasing gas fractions at high M* are driven by the flattening of the SFR-M* relation. Throughout the redshift range probed a larger sSFR at constant M* is due to a combination of an increasing gas fraction and a decreasing depletion time scale. As a result galaxy integrated samples of the Mmolgas-SFR rate relation exhibit a super-linear slope, which increases with the range of sSFR. With these new relations it is now possible to determine Mmolgas with an accuracy of 0.1dex in relative terms, and 0.2dex including systematic uncertainties.
New constraints on dust emission and UV attenuation of z=6.5-7.5 galaxies from millimeter observations (1407.5793)
D. Schaerer, F. Boone, M. Zamojski, J. Staguhn, M. Dessauges-Zavadsky, S. Finkelstein, F. Combes
We have targeted two recently discovered Lyman break galaxies (LBGs) to search for dust continuum and [CII] 158 micron line emission. The strongly lensed z~6.8 LBG A1703-zD1 behind the galaxy cluster Abell 1703, and the spectroscopically confirmed z=7.508 LBG z8-GND-5296 in the GOODS-N field have been observed with the Plateau de Bure interferometer (PdBI) at 1.2mm. These observations have been combined with those of three z>6.5 Lya emitters (named HCM6A, Himiko, and IOK-1), for which deep measurements were recently obtained with the PdBI and ALMA. [CII] is undetected in both galaxies, providing a deep upper limit for Abell1703-zD1, comparable to recent ALMA non-detections. Dust continuum emission from Abell1703-zD1 and z8-GND-5296 is not detected with an rms of 0.12 and 0.16 mJy/beam. From these non-detections we derive upper limits on their IR luminosity and star formation rate, dust mass, and UV attenuation. Thanks to strong gravitational lensing the limit for Abell1703-zD1 is probing the sub-LIRG regime ($L_{IR} <8.1 \times 10^{10}$ Lsun) and very low dust masses ($M_d<1.6 \times 10^7$ Msun). We find that all five galaxies are compatible with the Calzetti IRX-$\beta$ relation, their UV attenuation is compatible with several indirect estimates from other methods (the UV slope, extrapolation of the attenuation measured from the IR/UV ratio at lower redshift, and SED fits), and the dust-to-stellar mass ratio is not incompatible with that of galaxies from z=0 to 3. For their stellar mass the high-z galaxies studied here have an attenuation below the one expected from the mean relation of low redshift (z<1.5) galaxies. More and deeper (sub)-mm data are clearly needed to directly determine the UV attenuation and dust content of the dominant population of high-z star-forming galaxies and to establish more firmly their dependence on stellar mass, redshift, and other properties.
Molecular line emission in NGC1068 imaged with ALMA: II. The chemistry of the dense molecular gas (1407.4940)
S. Viti, S. García-Burillo, A. Fuente, L. K. Hunt, A. Usero, C. Henkel, A. Eckart, S. Martin, M. Spaans, S. Muller, F. Combes, M. Krips, E. Schinnerer, V. Casasola, F. Costagliola, I. Marquez, P. Planesas, P. P. van der Werf, S. Aalto, A. J. Baker, F. Boone, L. J. Tacconi
July 18, 2014 astro-ph.GA
We present a detailed analysis of ALMA Bands 7 and 9 data of CO, HCO+, HCN and CS, augmented with Plateau de Bure Interferometer (PdBI) data of the ~ 200 pc circumnuclear disk (CND) and the ~ 1.3 kpc starburst ring (SB ring) of NGC~1068, a nearby (D = 14 Mpc) Seyfert 2 barred galaxy. We aim at determining the physical characteristics of the dense gas present in the CND and whether the different line intensity ratios we find within the CND as well as between the CND and the SB ring are due to excitation effects (gas density and temperature differences) or to a different chemistry. We estimate the column densities of each species in Local Thermodynamic Equilibrium (LTE). We then compute large one-dimensional non-LTE radiative transfer grids (using RADEX) by using first only the CO transitions, and then all the available molecules in order to constrain the densities, temperatures and column densities within the CND. We finally present a preliminary set of chemical models to determine the origin of the gas. We find that in general the gas in the CND is very dense (> 10^5 cm^-3) and hot (T> 150K), with differences especially in the temperature across the CND. The AGN position has the lowest CO/HCO+, CO/HCN and CO/CS column density ratios. RADEX analyses seem to indicate that there is chemical differentiation across the CND. We also find differences between the chemistry of the SB ring and some regions of the CND; the SB ring is also much colder and less dense than the CND. Chemical modelling does not succeed in reproducing all the molecular ratios with one model per region, suggesting the presence of multi-gas phase components. The LTE, RADEX and chemical analyses all indicate that more than one gas-phase component is necessary to uniquely fit all the available molecular ratios within the CND.
Future mmVLBI Research with ALMA: A European vision (1406.4650)
R.P.J. Tilanus, T.P. Krichbaum, J.A. Zensus, A. Baudry, M. Bremer, H. Falcke, G. Giovannini, R. Laing, H. J. van Langevelde, W. Vlemmings, Z. Abraham, J. Afonso, I. Agudo, A. Alberdi, J. Alcolea, D. Altamirano, S. Asadi, K. Assaf, P. Augusto, A-K. Baczko, M. Boeck, T. Boller, M. Bondi, F. Boone, G. Bourda, R. Brajsa, J. Brand, S. Britzen, V. Bujarrabal, S. Cales, C. Casadio, V. Casasola, P. Castangia, J. Cernicharo, P. Charlot, L. Chemin, Y. Clenet, F. Colomer, F. Combes, J. Cordes, M. Coriat, N. Cross, F. D'Ammando, D. Dallacasa, J-F. Desmurs, R. Eatough, A. Eckart, D. Eisenacher, S. Etoka, M. Felix, R. Fender, M. Ferreira, E. Freeland, S. Frey, C. Fromm, L. Fuhrmann, K. Gabanyi, R. Galvan-Madrid, M. Giroletti, C. Goddi, J. Gomez, E. Gourgoulhon, M. Gray, I. di Gregorio, R. Greimel, N. Grosso, J. Guirado, K. Hada, A. Hanslmeier, C. Henkel, F. Herpin, P. Hess, J. Hodgson, D. Horns, E. Humphreys, B. Hutawarakorn Kramer, V. Ilyushin, V. Impellizzeri, V. Ivanov, M. Julião, M. Kadler, E. Kerins, P. Klaassen, K. van 't Klooster, E. Kording, M. Kozlov, M. Kramer, A. Kreikenbohm, O. Kurtanidze, J. Lazio, A. Leite, M. Leitzinger, J. Lepine, S. Levshakov, R. Lico, M. Lindqvist, E. Liuzzo, A. Lobanov, P. Lucas, K. Mannheim, J. Marcaide, S. Markoff, I. Martí-Vidal, C. Martins, N. Masetti, M. Massardi, K. Menten, H. Messias, S. Migliari, A. Mignano, J. Miller-Jones, D. Minniti, P. Molaro, S. Molina, A. Monteiro, L. Moscadelli, C. Mueller, A. Müller, S. Muller, F. Niederhofer, P. Odert, H. Olofsson, M. Orienti, R. Paladino, F. Panessa, Z. Paragi, T. Paumard, P. Pedrosa, M. Pérez-Torres, G. Perrin, M. Perucho, D. Porquet, I. Prandoni, S. Ransom, D. Reimers, M. Rejkuba, L. Rezzolla, A. Richards, E. Ros, A. Roy, A. Rushton, T. Savolainen, R. Schulz, M. Silva, G. Sivakoff, R. Soria-Ruiz, R. Soria, M. Spaans, R. Spencer, B. Stappers, G. Surcis, A. Tarchi, M. Temmer, M. Thompson, J. Torrelles, J. Truestedt, V. Tudose, T. Venturi, J. Verbiest, J. Vieira, P. Vielzeuf, F. Vincent, N. Wex, K. Wiik, T. Wiklind, J. Wilms, E. Zackrisson, H. Zechlin
July 1, 2014 astro-ph.IM
Very long baseline interferometry at millimetre/submillimetre wavelengths (mmVLBI) offers the highest achievable spatial resolution at any wavelength in astronomy. The anticipated inclusion of ALMA as a phased array into a global VLBI network will bring unprecedented sensitivity and a transformational leap in capabilities for mmVLBI. Building on years of pioneering efforts in the US and Europe the ongoing ALMA Phasing Project (APP), a US-led international collaboration with MPIfR-led European contributions, is expected to deliver a beamformer and VLBI capability to ALMA by the end of 2014 (APP: Fish et al. 2013, arXiv:1309.3519). This report focuses on the future use of mmVLBI by the international users community from a European viewpoint. Firstly, it highlights the intense science interest in Europe in future mmVLBI observations as compiled from the responses to a general call to the European community for future research projects. A wide range of research is presented that includes, amongst others: - Imaging the event horizon of the black hole at the centre of the Galaxy - Testing the theory of General Relativity an/or searching for alternative theories - Studying the origin of AGN jets and jet formation - Cosmological evolution of galaxies and BHs, AGN feedback - Masers in the Milky Way (in stars and star-forming regions) - Extragalactic emission lines and astro-chemistry - Redshifted absorption lines in distant galaxies and study of the ISM and circumnuclear gas - Pulsars, neutron stars, X-ray binaries - Testing cosmology - Testing fundamental physical constants
The first Frontier Fields cluster: 4.5{\mu}m excess in a z~8 galaxy candidate in Abell 2744 (1401.8263)
N. Laporte, A. Streblyanska, B. Clement, I. Perez-Fournon, D. Schaerer, H. Atek, F. Boone, J.-P. Kneib, E. Egami, P. Martinez-Navajas, R. Marques-Chaves, R. Pello, J. Richard
Feb. 3, 2014 astro-ph.CO, astro-ph.GA
We present in this letter the first analysis of a z~8 galaxy candidate found in the Hubble and Spitzer imaging data of Abell 2744, as part of the Hubble Frontier Fields legacy program. We applied the most commonly-used methods to select exceptionally high-z galaxies by combining non-detection and color-criteria using seven HST bands. We used GALFIT on IRAC images for fitting and subtracting contamination of bright nearby sources. The physical properties have been inferred from SED-fitting using templates with and without nebular emission. This letter is focussed on the brightest candidate we found (m$_{F160W}$=26.2) over the 4.9 arcmin$^2$ field of view covered by the WFC3. It shows a non-detection in the ACS bands and at 3.6{\mu}m whereas it is clearly detected at 4.5{\mu}m with rather similar depths. This break in the IRAC data could be explained by strong [OIII]+H{\beta} lines at z~8 which contribute to the 4.5{\mu}m photometry. The best photo-z is found at z~8.0$^{+0.2}_{-0.5}$, although solutions at low-redshift (z~1.9) cannot be completely excluded, but they are strongly disfavoured by the SED-fitting work. The amplification factor is relatively small at {\mu}=1.49$\pm$0.02. The Star Formation Rate in this object is ranging from 8 to 60 Mo/yr, the stellar mass is in the order of M$_{\star}$=(2.5-10) x 10$^{9}$Mo and the size is r~0.35$\pm$0.15 kpc. This object is one of the first z~8 LBG candidates showing a clear break between 3.6{\mu}m and 4.5{\mu}m which is consistent with the IRAC properties of the first spectroscopically confirmed galaxy at a similar redshift. Due to its brightness, the redshift of this object could potentially be confirmed by near infrared spectroscopy with current 8-10m telescopes. The nature of this candidate will be revealed in the coming months with the arrival of new ACS and Spitzer data, increasing the depth at optical and near-IR wavelengths.
Star formation histories, extinction, and dust properties of strongly lensed z~1.5-3 star-forming galaxies from the Herschel Lensing Survey (1310.2655)
P. Sklias, M. Zamojski, D. Schaerer, M. Dessauges-Zavadsky, E. Egami, M. Rex, T. Rawle, J. Richard, F. Boone, J.M. Simpson, I. Smail, P. van der Werf, B. Altieri, J.P. Kneib
Oct. 25, 2013 astro-ph.CO
Multi-wavelength, optical to IR/sub-mm observations of 5 strongly lensed galaxies identified by the Herschel Lensing Survey, plus two well-studied lensed galaxies, MS1512-cB58 and the Cosmic Eye, for which we also provide updated Herschel measurements, are used to determine the physical properties of z~1.5-3 star-forming galaxies close to or below the detection limits of blank fields. We constrain their stellar and dust content, determine star formation rates and histories, dust attenuation and extinction laws, and other related properties. We perform SED-fits of the full photometry of each object as well for the optical and infrared parts separately, exploring various parameters, including nebular emission. The IR observations and emission line measurements, where available, are used a posteriori constraints on the models. Besides the various stellar population models we explore, we use the observed IR/UV ratio to estimate the extinction and create "energy conserving models", that constrain most accurately the physical properties of our sources. Our sample has a median lensing-corrected IR luminosity ~ 3e11 Lsun, stellar masses between 2e9 and 2e11 Msun, and IR/UV luminosity ratios spanning a wide range. The dust masses of our galaxies are in the range 2 to 17e7 Msun, extending previous studies at the same redshift down to lower masses. We do not find any particular trend of the dust temperature Tdust with IR luminosity, suggesting an overall warmer dust regime at our redshift regardless of luminosity. Lensing enables us to study the detailed physical properties of individual IR-detected z~1.5-3 galaxies up to a factor ~10 fainter than achieved with deep blank field observations. We demonstrate that multi-wavelength observations combining stellar and dust emission can constrain star formation histories and extinction laws of star-forming galaxies.
An extended Herschel drop-out source in the center of AS1063, a 'normal' dusty galaxy at z=6.1 or SZ substructures? (1308.6707)
F. Boone, B. Clément, J. Richard, D. Schaerer, D. Lutz, A. Weiß, M. Zemcov, E. Egami, T. D. Rawle, G. L. Walth, J.-P. Kneib, F. Combes, I. Smail, A. M. Swinbank, B. Altieri, A. W. Blain, S. Chapman, M. Dessauges-Zavadsky, R. J. Ivison, K. K. Knudsen, A. Omont, R. Pello, P. G. Pérez-González, I. Valtchanov, P. van der Werf, M. Zamojski
Oct. 3, 2013 astro-ph.CO
In the course of our 870um APEX/LABOCA follow up of the Herschel Lensing Survey we have detected a source in AS1063 (RXC J2248.7-4431), that has no counterparts in any of the Herschel PACS/SPIRE bands, it is a Herschel 'drop-out' with S_870/S_500>0.5. The 870um emission is extended and centered on the brightest cluster galaxy suggesting either a multiply imaged background source or substructure in the Sunyaev-Zel'dovich (SZ) increment due to inhomogeneities in the hot cluster gas of this merging cluster. We discuss both interpretations with emphasis on the putative lensed source. Based on the observed properties and on our lens model we find that this source could be the first SMG with a moderate far infrared luminosity (L_FIR<10^12 L_sol) detected so far at z>4. In deep HST observations we identified a multiply imaged z~6 source and we measured its spectroscopic redshift z=6.107 with VLT/FORS. This source could be associated with the putative SMG but it is most likely offset spatially by 10-30kpc and they could be interacting galaxies. With a FIR luminosity in the range [5-15]x10^{11} L_sol corresponding to a star formation rate in the range [80-260]M_sol/yr, this SMG would be more representative than the extreme starbursts usually detected at z>4. With a total magnification of ~25 it would open a unique window to the 'normal' dusty galaxies at the end of the epoch of reionization.
Resolving the molecular gas around the lensed quasar RXJ0911.4+0551 (1303.6110)
P. T. Anh, F. Boone, D. T. Hoai, P. T. Nhung, A. Weiß, J.-P. Kneib, A. Beelen, P. Salomé
March 27, 2013 astro-ph.CO
We report on high angular resolution observations of the CO(7-6) line and millimeter continuum in the host galaxy of the gravitationally lensed (z~2.8) quasar RXJ0911.4+0551 using the Plateau de Bure Interferometer. Our CO observations resolve the molecular disk of the source. Using a lens model based on HST observations we fit source models to the observed visibilities. We estimate a molecular disk radius of 1$\pm$0.2 kpc and an inclination of 69$\pm$6\deg, the continuum is more compact and is only marginally resolved by our observations. The relatively low molecular gas mass, $Mgas=(2.3\pm 0.5)\times 10^{9}$ Msolar, and far infrared luminosity, $LFIR=(7.2\pm 1.5) \times 10^{11}$ Lsolar, of this quasar could be explained by its relatively low dynamical mass, $Mdyn=(3.9\pm 0.9)\times 10^9$ Msolar. It would be a scaled-down version the QSOs usually found at high-z. The FIR and CO luminosities lie on the correlation found for QSOs from low to high redshifts and the gas-to-dust ratio ($45\pm 17$) is similar to the one measured in the z=6.4 QSO, SDSS J1148+5251. Differential magnification affects the continuum-to-line luminosity ratio, the line profile and possibly the spectral energy distribution.
Gravitationally lensed extended sources: the case of QSO RXJ0911 (1303.3707)
D.T. Hoai, P.T. Nhung, P.T. Anh, F. Boone, P. Darriulat, P.N. Diep, P.N. Dong, N.V. Hiep, N.T. Thao
March 15, 2013 astro-ph.GA
After a brief reminder of the mechanism of gravitational lensing of extended sources, the particular case of the host galaxy of QSO RXJ0911, a high redshift (z~2.8) quadruply imaged quasar, is explored. The non linearity of the problem, together with the proximity of the source to a cusp of the lens inner caustic, have important consequences on the dependence of the image appearance on the size and shape of the source. Their expected main features and their interpretation in terms of source extension and shape are investigated in a spirit of simplicity and in preparation for the analysis of high sensitivity and spatial resolution images that will soon be within reach with the completion of the Atacama Large Millimeter/submillimeter Array (ALMA). In particular, the information on source size carried by relative image brightness is discussed. Extension of the results to other types of quadruply imaged quasars is briefly considered.
The bright-end of the luminosity function at z~9 (1205.4187)
N. Laporte, R. Pello, M. Hayes, D. Schaerer, F. Boone, J. Richard, J.F. Le Borgne, J.P. Kneib, F. Combes
May 18, 2012 astro-ph.CO
We report new constraints on the galaxy luminosity function at z~9 based on observations carried out with ESO/VLT FORS2, HAWK-I and X-Shooter around the lensing cluster A2667, as part of our project aimed at selecting z~7-10 candidates accessible to spectroscopy. Only one J-dropout source was selected in this field fulfilling the color and magnitude criteria. This source was recently confirmed as a mid-z interloper based on X-Shooter spectroscopy. The depth and the area covered by our survey are well suited to set strong constraints on the bright-end of the galaxy luminosity function and hence on the star formation history at very high redshift. The non-detection of reliable J-dropout sources over the ~36arcmin2 field of view towards A2667 was used to carefully determine the lens-corrected effective volume and the corresponding upper-limit on the density of sources. The strongest limit is obtained for Phi(M_{1500}=-21.4+/-0.50)<6.70x10^{-6}Mpc^{-3}mag^{-1} at z~9. A maximum-likelihood fit of the luminosity function using all available data points including the present new result yields M*>-19.7 with fixed alpha=-1.74 and Phi*=1.10x10^{-3}Mpc^{-3}. The corresponding star formation rate density should be rho_{SFR}<5.97x10^{-3}M_{solar}/yr/Mpc^{3} at z~9. These results are in good agreement with the most recent estimates already published in this range of redshift and for this luminosity domain. This new result confirms the decrease in the density of luminous galaxies at very high-redshift, hence providing strong constraints for the design of future surveys aiming to explore the very high-redshift Universe.
An upper limit to the variation in the fundamental constants at redshift z = 5.2 (1203.3649)
S. A. Levshakov, F. Combes, F. Boone, I. I. Agafonova, D. Reimers, M. G. Kozlov
Aims. We constrain a hypothetical variation in the fundamental physical constants over the course of cosmic time. Methods. We use unique observations of the CO(7-6) rotational line and the [CI] 3P_2 - 3P_1 fine-structure line towards a lensed galaxy at redshift z = 5.2 to constrain temporal variations in the constant F = alpha^2/mu, where mu is the electron-to-proton mass ratio and alpha is the fine-structure constant. The relative change in F between z = 0 and z = 5.2, dFF = (F_obs - F_lab)/F_lab, is estimated from the radial velocity offset, dV = V_rot - V_fs, between the rotational transitions in carbon monoxide and the fine-structure transition in atomic carbon. Results. We find a conservative value dV = 1 +/- 5 km/s (1sigma C.L.), which when interpreted in terms of dFF gives dFF < 2x10^-5. Independent methods restrict the mu-variations at the level of dmm < 1x10^-7 at z = 0.7 (look-back time t_z0.7 = 6.4 Gyr). Assuming that temporal variations in mu, if any, are linear, this leads to an upper limit on dmm < 2x10^-7 at z = 5.2 (t_z5.2 = 12.9 Gyr). From both constraints on dFF and dmm, one obtains for the relative change in alpha the estimate daa < 8x10^-6, which is at present the tightest limit on daa at early cosmological epochs.
Far infrared constraints on the contamination by dust obscured galaxies of high-z dropout searches (1108.2406)
F. Boone, D. Schaerer, R. Pello, D. Lutz, A. Weiss, E. Egami, I. Smail, M. Rex, T. Rawle, R. Ivison, N. Laporte, A. Beelen, F. Combes, A. W. Blain, J. Richard, J.-P. Kneib, M. Zamojski, M. Dessauges-Zavadsky, B. Altieri, P. van der Werf, M. Swinbank, P. G. Perez-Gonzalez, B. Clement, R. Nordon, B. Magnelli, K. M. Menten
Aug. 11, 2011 astro-ph.CO
The spectral energy distributions (SED) of dusty galaxies at intermediate redshift may look similar to very high redshift galaxies in the optical/near infrared (NIR) domain. This can lead to the contamination of high redshift galaxy searches based on broad band optical/NIR photometry by lower redshift dusty galaxies as both kind of galaxies cannot be distinguished. The contamination rate could be as high as 50%. {This work shows how the far infrared (FIR) domain can help to recognize likely low-z interlopers in an optical/NIR search for high-z galaxies.} We analyse the FIR SEDs of two galaxies proposed as very high redshift ($z>7$) dropout candidates based on deep Hawk-I/VLT observations. The FIR SEDs are sampled with PACS/Herschel at 100 and 160\,$\mu$m, with SPIRE/Herschel at 250, 350 and 500\,$\mu$m and with LABOCA/APEX at 870\,$\mu$m. We find that redshifts $>7$ would imply extreme FIR SEDs (with dust temperatures $>100$\,K and FIR luminosities $>10^{13}$\,$L_{\odot}$). At z$\sim$2, instead, the SEDs of both sources would be compatible with that of typical ULIRGs/SMGs. Considering all the data available for these sources from visible to FIR we re-estimate the redshifts and we find $z\sim$1.6--2.5. Due to the strong spectral breaks observed in these galaxies, standard templates from the literature fail to reproduce the visible-near IR part of the SEDs even when additional extinction is included. These sources resemble strongly dust obscured galaxies selected in Spitzer observations with extreme visible-to-FIR colors, and the galaxy GN10 at $z=4$. Galaxies with similar SEDs could contaminate other high redshift surveys.
Molecular gas in NUclei of GAlaxies (NUGA) XV. Molecular gas kinematics in the inner 3kpc of NGC6951 (1102.5104)
T.P.R. van der Laan, E. Schinnerer, F. Boone, S. Garcia-Burillo, F. Combes, S. Haan, S. Leon, L. Hunt, A.J. Baker
Within the NUclei of GAlaxies project we have obtained IRAM PdBI and 30m 12CO(1-0) and 12CO(2-1) observations of the spiral galaxy NGC 6951. Previous work shows that there is indirect evidence of gas inflow from 3 kpc down to small radii: a large-scale stellar bar, a prominent starburst ring (r~580 pc) and a LINER/Seyfert 2 nucleus. In this paper we study the gas kinematics as traced by the CO line emission in detail. We quantify the influence of the large-scale stellar bar by constructing an analytical model of the evolution of gas particles in a barred potential. From this model gravitational torques and mass accumulation rates are computed. We compare our model-based gravitational torque results with previous observationally-based ones. The model also shows that the large-scale stellar bar is indeed the dominant force for driving the gas inward, to the starburst ring. Inside the ring itself a nuclear stellar oval might play an important role. Detailed analysis of the CO gas kinematics there shows that emission arises from two co-spatial, but kinematically distinct components at several locations. The main emission component can always be related to the overall bar-driven gas kinematics. The second component exhibits velocities that are larger than expected for gas on stable orbits, has a molecular gas mass of 1.8x10^6Msun, is very likely connected to the nuclear stellar oval, and is consistent with inflowing motion towards the very center. This may form the last link in the chain of gas inflow towards the active galactic nucleus in NGC 6951.
High-resolution mapping of the physical conditions in two nearby active galaxies based on 12CO(1-0), (2-1) and (3-2) lines (1010.2270)
F. Boone, S. Garcia-Burillo, F. Combes, J. Lim, P. Ho, A. J. Baker, S. Matsushita, M. Krips, Dinh-van-Trung, E. Schinnerer
Oct. 12, 2010 astro-ph.GA
We present a detailed analysis of high resolution observations of the three lowest CO transitions in two nearby active galaxies, NGC4569 and NGC4826. The CO(1-0) and (2-1) lines were observed with the Plateau de Bure Interferometer and the CO(3-2) line with the Submillimeter Array. Combining these data allows us to compare the emission in the three lines and to map the line ratios, R21=I_{CO(2-1)}/I_{CO(1-0)} and R32=I_{CO(3-2)}/I_{CO(1-0)} at a resolution of ~2", i.e., a linear resolution of 160 pc for NGC4569 and 40 pc for NGC4826. In both galaxies the emission in the three lines is similarly distributed spatially and in velocity, and CO is less excited (R32<0.6) than in the Galactic Center or the centers of other active galaxies studied so far. According to a pseudo-LTE model the molecular gas in NGC4569 is cold and mainly optically thick in the CO(1-0) and (2-1) lines; less than 50% of the gas is optically thin in the CO(3-2) line. LVG modeling suggests the presence of an elongated ring of cold and dense gas coinciding with the ILR of the stellar bar. More excited gas is resolved in the circumnuclear disk of NGC4826. According to our pseudo-LTE model this corresponds to warmer gas with a ~50% of the CO(3-2) emission being optically thin. LVG modeling indicates the presence of a semicircular arc of dense and cold gas centered on the dynamical center and ~70 pc in radius. The gas temperature increases and its density decreases toward the center. A near side/far side asymmetry noticeable in the CO, R32 and Pa-alpha maps suggests that opacity effects play a role. Examining published CO maps of nearby active galaxies we find similar asymmetries suggesting that this could be a common phenomenon in active galaxies. These mainly qualitative results open new perspectives for the study of active galaxies with the future Atacama Large Millimeter/submillimeter Array.
The Herschel Lensing Survey (HLS): overview (1005.3820)
E. Egami, M. Rex, T. D. Rawle, P. G. Pérez-González, J. Richard, J.-P. Kneib, D. Schaerer, B. Altieri, I. Valtchanov, A. W. Blain, D. Fadda, M. Zemcov, J. J.Bock, F. Boone, C. R. Bridge, B. Clement, F. Combes, C. D. Dowell, M. Dessauges-Zavadsky, O. Ilbert, R. J. Ivison, M. Jauzac, D. Lutz, L. Metcalfe, A. Omont, R. Pelló, M. J. Pereira, G. H. Rieke, G. Rodighiero, I. Smail, G. P. Smith, G. Tramoy, G. L. Walth, P. van der Werf, M. W. Werner
The Herschel Lensing Survey (HLS) will conduct deep PACS and SPIRE imaging of ~40 massive clusters of galaxies. The strong gravitational lensing power of these clusters will enable us to penetrate through the confusion noise, which sets the ultimate limit on our ability to probe the Universe with Herschel. Here, we present an overview of our survey and a summary of the major results from our Science Demonstration Phase (SDP) observations of the Bullet Cluster (z=0.297). The SDP data are rich, allowing us to study not only the background high-redshift galaxies (e.g., strongly lensed and distorted galaxies at z=2.8 and 3.2) but also the properties of cluster-member galaxies. Our preliminary analysis shows a great diversity of far-infrared/submillimeter spectral energy distributions (SEDs), indicating that we have much to learn with Herschel about the properties of galaxy SEDs. We have also detected the Sunyaev-Zel'dovich (SZ) effect increment with the SPIRE data. The success of this SDP program demonstrates the great potential of the Herschel Lensing Survey to produce exciting results in a variety of science areas.
The far-infrared/submillimeter properties of galaxies located behind the Bullet cluster (1005.3821)
M. Rex, T. D. Rawle, E. Egami, P.G. Pérez-González, M. Zemcov, I. Aretxaga, S. M. Chung, D. Fadda, A. H. Gonzalez, D. H. Hughes, C. Horellou, D. Johansson, J.-P. Kneib, J. Richard, B. Altieri, A. K. Fiedler, M. J. Pereira, G. H. Rieke, I. Smail, I. Valtchanov, A. W. Blain, J. J. Bock, F. Boone, C. R. Bridge, B. Clement, F. Combes, C. D. Dowell, M. Dessauges-Zavadsky, O. Ilbert, R. J. Ivison, M. Jauzac, D. Lutz, A. Omont, R. Pelló, G. Rodighiero, D. Schaerer, G. P. Smith, G. L. Walth, P. van der Werf, M. W. Werner, J. E. Austermann, H. Ezawa, R. Kawabe, K. Kohno, T. A. Perera, K. S. Scott, G. W. Wilson, M. S. Yun
The Herschel Lensing Survey (HLS) takes advantage of gravitational lensing by massive galaxy clusters to sample a population of high-redshift galaxies which are too faint to be detected above the confusion limit of current far-infrared/submillimeter telescopes. Measurements from 100-500 micron bracket the peaks of the far-infrared spectral energy distributions of these galaxies, characterizing their infrared luminosities and star formation rates. We introduce initial results from our science demonstration phase observations, directed toward the Bullet cluster (1E0657-56). By combining our observations with LABOCA 870 micron and AzTEC 1.1 mm data we fully constrain the spectral energy distributions of 19 MIPS 24 micron selected galaxies which are located behind the cluster. We find that their colors are best fit using templates based on local galaxies with systematically lower infrared luminosities.This suggests that our sources are not like local ultra-luminous infrared galaxies in which vigorous star formation is contained in a compact highly dust-obscured region. Instead, they appear to be scaled up versions of lower luminosity local galaxies with star formation occurring on larger physical scales.
Deep Herschel view of obscured star formation in the Bullet cluster (1005.3822)
T.D. Rawle, S.M. Chung, D. Fadda, M. Rex, E. Egami, P.G. Pérez-González, B. Altieri, A.W. Blain, C.R. Bridge, A.K. Fiedler, A.H. Gonzalez, M.J. Pereira, J. Richard, I. Smail, I. Valtchanov, M. Zemcov, P.N. Appleton, J.J. Bock, F. Boone, B. Clement, F. Combes, C.D. Dowell, M. Dessauges-Zavadsky, O. Ilbert, R.J. Ivison, M. Jauzac, J.-P. Kneib, D. Lutz, R. Pelló, G.H. Rieke, G. Rodighiero, D. Schaerer, G.P. Smith, G.L. Walth, P. van der Werf, M.W. Werner
We use deep, five band (100-500um) data from the Herschel Lensing Survey (HLS) to fully constrain the obscured star formation rate, SFR_FIR, of galaxies in the Bullet cluster (z=0.296), and a smaller background system (z=0.35) in the same field. Herschel detects 23 Bullet cluster members with a total SFR_FIR = 144 +/- 14 M_sun yr^-1. On average, the background system contains brighter far-infrared (FIR) galaxies, with ~50% higher SFR_FIR (21 galaxies; 207 +/- 9 M_sun yr^-1). SFRs extrapolated from 24um flux via recent templates (SFR_24) agree well with SFR_FIR for ~60% of the cluster galaxies. In the remaining ~40%, SFR_24 underestimates SFR_FIR due to a significant excess in observed S_100/S_24 (rest frame S_75/S_18) compared to templates of the same FIR luminosity.