arXiv subjects

M. Dessauges-Zavadsky

Publications and source records attributed to M. Dessauges-Zavadsky.

At least 73 records · Page 4Linked to original sources

arXiv2018

Physics of a clumpy lensed galaxy at z=1.6

Observations have shown that massive star-forming clumps are present in the internal structure of high-redshift galaxies. One way to study these clumps in detail with a higher spatial resolution is by exploiting the power of strong gravitational lensing which stretches images on the sky. In this work, we present an analysis of the clumpy galaxy A68-HLS115 at $z=1.5858$, located behind the cluster Abell 68, but strongly lensed by a cluster galaxy member. Resolved observations with SINFONI/VLT in the near-infrared show Ha, Hb, [NII], and [OIII] emission lines. Combined with images covering the B band to the far-infrared and CO(2-1) observations, this makes this galaxy one of the only sources for which such multi-band observations are available and for which it is possible to study the properties of resolved star-forming clumps and to perform a detailed analysis of the integrated properties, kinematics, and metallicity. We obtain a stability of $\upsilon_{rot}/σ_0 = 2.73$ by modeling the kinematics, which means that the galaxy is dominated by rotation, but this ratio also indicates that the disk is marginally stable. We find a high intrinsic velocity dispersion of $80\pm10$ km s$^{-1}$ that could be explained by the high gas fraction of $f_{gas}=0.75\pm0.15$ observed in this galaxy. This high $f_{gas}$ and the observed sSFR of $\rm 3.12 \, Gyr^{-1}$ suggest that the disk turbulence and instabilities are mostly regulated by incoming gas. The direct measure of the Toomre stability criterion of $Q_{crit}=0.70$ could also indicate the presence of a quasi-stable thick disk. Finally, we identify three clumps in the Ha map which have similar velocity dispersions, metallicities, and seem to be embedded in the rotating disk. These three clumps contribute together to $40\%$ on the SFR(Ha) of the galaxy and show a SFR density about $100$ times higher than HII regions in the local Universe.

astro-ph.GA↗

arXiv2018

ALMA observations of a metal-rich damped Lyα absorber at z = 2.5832: evidence for strong galactic winds in a galaxy group

We report on the results of a search for CO(3-2) emission from the galaxy counterpart of a high-metallicity Damped Ly-alpha Absorber (DLA) at z=2.5832 towards the quasar Q0918+1636. We do not detect CO emission from the previously identified DLA galaxy counterpart. The limit we infer on M_gas / M_star is in the low end of the range found for DLA galaxies, but is still consistent with what is found for other star-forming galaxies at similar redshifts. Instead we detect CO(3-2) emission from another intensely star-forming galaxy at an impact parameter of 117 kpc from the line-of-sight to the quasar and 131 km s^-1 redshifted relative to the velocity centroid of the DLA in the quasar spectrum. In the velocity profile of the low- and high-ionisation absorption lines of the DLA there is an absorption component consistent with the redshift of this CO-emitting galaxy. It is plausible that this component is physically associated with a strong outflow in the plane of the sky from the CO-emitting galaxy. If true, this would be further evidence, in addition to what is already known from studies of Lyman-break galaxies, that galactic outflows can be traced beyond 100 kpc from star-forming galaxies. The case of this z=2.583 structure is an illustration of this in a group environment.

astro-ph.GA↗

arXiv2018

Massive, Absorption-selected Galaxies at Intermediate Redshifts

The nature of absorption-selected galaxies and their connection to the general galaxy population have been open issues for more than three decades, with little information available on their gas properties. Here we show, using detections of carbon monoxide (CO) emission with the Atacama Large Millimeter/submillimeter Array (ALMA), that five of seven high-metallicity, absorption-selected galaxies at intermediate redshifts, $z \approx 0.5-0.8$, have large molecular gas masses, $M_{\rm Mol} \approx (0.6 - 8.2) \times 10^{10} \: {\rm M}_\odot$ and high molecular gas fractions ($f_{\rm Mol} \equiv \: M_{\rm Mol}/(M_\ast + M_{\rm Mol}) \approx 0.29-0.87)$. Their modest star formation rates (SFRs), $\approx (0.3-9.5) \: {\rm M}_\odot$ yr$^{-1}$, then imply long gas depletion timescales, $\approx (3 - 120)$ Gyr. The high-metallicity absorption-selected galaxies at $z \approx 0.5-0.8$ appear distinct from populations of star-forming galaxies at both $z \approx 1.3-2.5$, during the peak of star formation activity in the Universe, and lower redshifts, $z \lesssim 0.05$. Their relatively low SFRs, despite the large molecular gas reservoirs, may indicate a transition in the nature of star formation at intermediate redshifts, $z \approx 0.7$.

astro-ph.GA↗

arXiv2018

KMOS LENsing Survey (KLENS) : morpho-kinematic analysis of star-forming galaxies at $z \sim 2$

We present results from the KMOS lensing survey-KLENS which is exploiting gravitational lensing to study the kinematics of 24 star forming galaxies at $1.4 10$). We derive a $\rm M_\star-σ_0$ relation, using the Tully-Fisher relation, which highlights that a different evolution of the velocity dispersion is expected depending on the stellar mass, with lower velocity dispersions for lower masses, and an increase for higher masses, stronger at higher redshift. The observed velocity dispersions from this work and from comparison samples spanning $0 2$), where we observe higher velocity dispersions for low masses ($\rm log(M_\star/M_\odot)\sim 9.6$) and lower velocity dispersions for high masses ($\rm log(M_\star/M_\odot)\sim 10.9$) than expected. This discrepancy could, for instance, suggest that galaxies at high-$z$ do not satisfy the stability criterion, or that the adopted parametrisation of the specific star formation rate and molecular properties fail at high redshift.

astro-ph.GA↗

arXiv2017

ALMA view of RX J1131-1231: Sub-kpc CO (2-1) mapping of a molecular disk in a lensed star-forming quasar host galaxy

We present ALMA 2-mm continuum and CO (2-1) spectral line imaging of the gravitationally lensed z=0.654 star-forming/quasar composite RX J1131-1231 at 240-400 mas angular resolution. The continuum emission is found to be compact and coincident with the optical emission, whereas the molecular gas forms a complete Einstein ring, which shows strong differential magnification. The de-lensed source structure is determined on 400-pc resolution using a visibility-fitting lens modelling technique. The reconstructed molecular gas velocity-field is consistent with a rotating disk with a maximum rotational velocity of 280 km/s. From dynamical model fitting we find an enclosed mass M(r<5 kpc)=(1.46+/-0.31)*10^11 M_sol. The molecular gas distribution is highly structured, with clumps that are co-incident with higher gas velocity dispersion regions 40-50 km/s and with the intensity peaks in the optical emission, which are associated with sites of on-going turbulent star-formation. The peak in the CO (2-1) distribution is not co-incident with the AGN, where there is a paucity of molecular gas emission, possibly due to radiative feedback from the central engine. The intrinsic molecular gas luminosity is L'_CO=(1.2+/-0.3)*10^10 K km/s pc^2 and the inferred gas mass is M(H2)=(8.3+/-3.0)*10^10 M_sol, which given its dynamical mass is consistent with a CO-H2 conversion factor of alpha = 5.5+/-2.0 M_solar(K km/s pc^2)^-1. This suggests that the star-formation efficiency is dependent on the host galaxy morphology as opposed to the nature of the AGN. The far-infrared continuum spectral energy distribution shows evidence for heated dust, equivalent to an obscured star-formation rate of SFR=69^(+41)_(-25)*(7.3/u_IR)M_sol/yr, which demonstrates the composite star-forming/AGN nature of this system. RX J1131-1231

astro-ph.GA↗

arXiv2017

ALMA + VLT observations of a Damped Lyman-α absorbing galaxy: Massive, wide CO emission, gas-rich but with very low SFR

We are undertaking an ALMA survey of molecular gas in galaxies selected for their strong HI absorption, so-called DLA/sub-DLA galaxies. Here we report CO(2-1) detection from a DLA galaxy at z = 0.716. We also present optical and near-infrared spectra of the galaxy revealing [OII], Hα and [NII] emission lines shifted by ~170 km/s relative to the DLA, and providing an oxygen abundance 3.2 times solar, similar to the absorption metallicity. We report low unobscured SFR ~1 Msun/yr given the large reservoir of molecular gas, and also modest obscured SFR=4.5(+4.4,-2.6) Msun/yr based on far-IR and sub-mm data. We determine mass components of the galaxy: log[M*/Msun] = 10.80(+0.07,-0.14), log[M mol-gas/Msun] = 10.37 +/-0.04, and log[M dust/Msun] = 8.45(+0.10,-0.30). Surprisingly, this HI absorption-selected galaxy has no equivalent objects in CO surveys of flux-selected samples. The galaxy falls off current scaling relations for the SFR to molecular gas mass and CO Tully-Fisher relation. Detailed comparison of kinematical components of the absorbing, ionized and molecular gas, combined with their spatial distribution, suggests that part of the CO gas is both kinematically and spatially de-coupled from the main galaxy. It is thus possible that a major star burst in the past could explain the wide CO profile as well as the low SFR. Support for this also comes from the SED favouring an instantaneous burst of age ~0.5 Gyr. Our survey will establish whether flux-selected surveys of molecular gas are missing a key stage in the evolution of galaxies and their conversion of gas to stars.

astro-ph.GA↗

arXiv2017

Molecular gas properties of a lensed star-forming galaxy at z~3.6: a case study

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.

astro-ph.GA↗

arXiv2016

XQ-100: A legacy survey of one hundred 3.5 < z < 4.5 quasars observed with VLT/XSHOOTER

We describe the execution and data reduction of the European Southern Observatory Large Programme "Quasars and their absorption lines: a legacy survey of the high-redshift universe with VLT/XSHOOTER" (hereafter `XQ-100'). XQ-100 has produced and made publicly available an homogeneous and high-quality sample of echelle spectra of 100 QSOs at redshifts z~3.5-4.5 observed with full spectral coverage from 315 to 2500 nm at a resolving power ranging from R~4000 to 7000, depending on wavelength. The median signal-to-noise ratios are 33, 25 and 43, as measured at rest-frame wavelengths 1700, 3000 and 3600 Angstrom, respectively. This paper provides future users of XQ-100 data with the basic statistics of the survey, along with details of target selection, data acquisition and data reduction. The paper accompanies the public release of all data products, including 100 reduced spectra. XQ-100 is the largest spectroscopic survey to date of high-redshift QSOs with simultaneous rest-frame UV/optical coverage, and as such enables a wide range of extragalactic research, from cosmology and galaxy evolution to AGN astrophysics.

astro-ph.GA↗

arXiv2016

A complete census of Herschel-detected infrared sources within the HST Frontier Fields

We present a complete census of all Herschel-detected sources within the six massive lensing clusters of the HST Frontier Fields (HFF). We provide a robust legacy catalogue of 263 sources with Herschel fluxes, primarily based on imaging from the Herschel Lensing Survey (HLS) and PEP/HerMES Key Programmes. We optimally combine Herschel, Spitzer and WISE infrared (IR) photometry with data from HST, VLA and ground-based observatories, identifying counterparts to gain source redshifts. For each Herschel-detected source we also present magnification factor (mu), intrinsic IR luminosity and characteristic dust temperature, providing a comprehensive view of dust-obscured star formation within the HFF. We demonstrate the utility of our catalogues through an exploratory overview of the magnified population, including more than 20 background sub-LIRGs unreachable by Herschel without the assistance gravitational lensing.

astro-ph.GA↗

arXiv2016

First Connection between Cold Gas in Emission and Absorption: CO Emission from a Galaxy-Quasar Pair

We present the first detection of molecular emission from a galaxy selected to be near a projected background quasar using the Atacama Large Millimeter/submillimeter Array (ALMA). The ALMA detection of CO(1$-$0) emission from the $z=0.101$ galaxy toward quasar PKS 0439-433 is coincident with its stellar disk and yields a molecular gas mass of $M_{\rm mol} \approx 4.2 \times 10^9 M_\odot$ (for a Galactic CO-to-H$_2$ conversion factor), larger than the upper limit on its atomic gas mass. We resolve the CO velocity field, obtaining a rotational velocity of $134 \pm 11$ km s$^{-1}$, and a resultant dynamical mass of $\geq 4 \times 10^{10} M_\odot$. Despite its high metallicity and large molecular mass, the $z=0.101$ galaxy has a low star formation rate, implying a large gas consumption timescale, larger than that typical of late-type galaxies. Most of the molecular gas is hence likely to be in a diffuse extended phase, rather than in dense molecular clouds. By combining the results of emission and absorption studies, we find that the strongest molecular absorption component toward the quasar cannot arise from the molecular disk, but is likely to arise from diffuse gas in the galaxy's circumgalactic medium. Our results emphasize the potential of combining molecular and stellar emission line studies with optical absorption line studies to achieve a more complete picture of the gas within and surrounding high-redshift galaxies.

astro-ph.GA↗

arXiv2015

Early Science with the Large Millimeter Telescope: Observations of dust continuum and CO emission lines of cluster-lensed submillimetre galaxies at z=2.0-4.7

We present Early Science observations with the Large Millimeter Telescope, AzTEC 1.1 mm continuum images and wide bandwidth spectra (73-111 GHz) acquired with the Redshift Search Receiver, towards four bright lensed submillimetre galaxies identified through the Herschel Lensing Survey-snapshot and the SCUBA-2 Cluster Snapshot Survey. This pilot project studies the star formation history and the physical properties of the molecular gas and dust content of the highest redshift galaxies identified through the benefits of gravitational magnification. We robustly detect dust continuum emission for the full sample and CO emission lines for three of the targets. We find that one source shows spectroscopic multiplicity and is a blend of three galaxies at different redshifts (z=2.040, 3.252 and 4.680), reminiscent of previous high-resolution imaging follow-up of unlensed submillimetre galaxies, but with a completely different search method, that confirm recent theoretical predictions of physically unassociated blended galaxies. Identifying the detected lines as 12CO (J_up=2-5) we derive spectroscopic redshifts, molecular gas masses, and dust masses from the continuum emission. The mean H_2 gas mass of the full sample is (2.0 +- 0.2) x 10^11 M_sun/μ, and the mean dust mass is (2.0+-0.2) x 10^9 M_sun/μ, where μ=2-5 is the expected lens amplification. Using these independent estimations we infer a gas-to-dust ratio of δ_GDR=55-75, in agreement with other measurements of submillimetre galaxies. Our magnified high-luminosity galaxies fall on the same locus as other high-redshift submillimetre galaxies, extending the L'_CO - L_FIR correlation observed for local luminous and ultraluminous infrared galaxies to higher FIR and CO luminosities.

astro-ph.GA↗

arXiv2015

ALMA detection of [CII] 158 micron emission from a strongly lensed z=2 star-forming galaxy

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 $σ$. Taking into account strong gravitational lensing, which provides a magnification of $μ=49$, 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.

astro-ph.GA↗

arXiv2015

Molecular gas content in strongly-lensed z~1.5-3 star-forming galaxies with low IR luminosities

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.

astro-ph.GA↗

arXiv2014

New constraints on dust emission and UV attenuation of z=6.5-7.5 galaxies from millimeter observations

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-$β$ 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.

astro-ph.GA↗

arXiv2014

CO map and steep Kennicutt-Schmidt relation in the extended UV disk of M63

Results from the UV satellite GALEX revealed large extensions of disks in some nearby spiral galaxies, extending out to 3 to 4 times the isophotal radius, r25. M63 is a remarkable example of a spiral galaxy with one of the most extended UV disks, so it offers the opportunity to search for the molecular gas and characterize the star formation in outer disk regions as revealed by the UV emission. We obtained deep CO(1-0) and CO(2-1) observations on the IRAM 30 m telescope along the major axis of the M63 disk from the center out to the galactocentric radius rgal = 1.6 r25 and over a bright UV region at rgal = 1.36 r25. CO(1-0) is detected all along the M63 major axis out to r25, and CO(2-1) is confined to rgal = 0.68 r25, which may betray lower excitation temperatures in the outer disk. CO(1-0) is also detected in the external bright UV region of M63. The radial profiles of the CO emission and of the Halpha, 24 micron, NUV and FUV star formation tracers and HI taken from the literature show a severe drop with the galactocentric radius, such that beyond r25 they are all absent with the exception of a faint UV emission and HI. The CO emission detection in the external UV region, where the UV flux is higher than the UV flux observed beyond r25, highlights a tight correlation between the CO and UV fluxes, namely the amount of molecular gas and the intensity of star formation. This external UV region is dominated by the atomic gas, suggesting that HI is more likely the precursor of H2 rather than the product of UV photodissociation. A broken power law needs to be invoked to describe the Kennicutt-Schmidt (K-S) relation of M63 from the center of the galaxy out to rgal = 1.36 r25. While all along the major axis out to r25 the K-S relation is almost linear, in the external UV region the SFR regime is highly nonlinear and characterized by a steep K-S relation and very low star formation efficiency.

astro-ph.GA↗

arXiv2014

[CII] and 12CO(1-0) Emission Maps in HLSJ091828.6+514223: A Strongly Lensed Interacting System at z=5.24

We present Submillimeter Array (SMA) [CII] 158um and Jansky Very Large Array (JVLA) $^{12}$CO(1-0) line emission maps for the bright, lensed, submillimeter source at $z=5.2430$ behind Abell 773: HLSJ091828.6+514223 (HLS0918). We combine these measurements with previously reported line profiles, including multiple $^{12}$CO rotational transitions, [CI], water and [NII], providing some of the best constraints on the properties of the interstellar medium (ISM) in a galaxy at $z>5$. HLS0918 has a total far-infrared (FIR) luminosity L_FIR(8-1000um) = (1.6$\pm$0.1)x10^14 L_sun/mu, where the total magnification mu_total = 8.9$\pm$1.9, via a new lens model from the [CII] and continuum maps. Despite a HyLIRG luminosity, the FIR continuum shape resembles that of a local LIRG. We simultaneously fit all of the observed spectral line profiles, finding four components which correspond cleanly to discrete spatial structures identified in the maps. The two most redshifted spectral components occupy the nucleus of a massive galaxy, with a source plane separation <1 kpc. The reddest dominates the continuum map (de-magnified L_FIR = (1.1$\pm$0.2)x10^13 L_sun), and excites strong water emission in both nuclear components via a powerful FIR radiation field from the intense star formation. A third star-forming component is most likely a region of a merging companion (dV ~ 500 km/s) exhibiting generally similar gas properties. The bluest component originates from a spatially distinct region, and photo-dissociation region (PDR) analysis suggests that it is lower density, cooler and forming stars less vigorously than the other components. Strikingly, it has very strong [NII] emission which may suggest an ionized, molecular outflow. This comprehensive view of gas properties and morphology in HLS0918 previews the science possible for a large sample of high-redshift galaxies once ALMA attains full sensitivity.

astro-ph.CO↗

arXiv2013

Star formation histories, extinction, and dust properties of strongly lensed z~1.5-3 star-forming galaxies from the Herschel Lensing Survey

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.

astro-ph.CO↗

arXiv2013

An extended Herschel drop-out source in the center of AS1063, a 'normal' dusty galaxy at z=6.1 or SZ substructures?

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.

astro-ph.CO↗