The observations described here have been taken as part of the Herschel Multi-tiered Extragalactic Survey (HerMES; Oliver et al., 2012MNRAS.424.1614O) under the programme KPGT_soliver 1 whose main objective was to chart the formation and evolution of infrared galaxies throughout cosmic history, measuring the bolometric emission of infrared galaxies and their clustering properties. The catalogues extracted from these maps include over 1,200,000 entries representing over 340,000 galaxies. (11 data files).
We exploit the deep and extended far-IR data sets (at 70, 100 and 160 mu m) of the Herschel Guaranteed Time Observation (GTO) PACS Evolutionary Probe (PEP) Survey, in combination with the Herschel Multi-tiered Extragalactic Survey data at 250, 350 and 500 mu m, to derive the evolution of the rest-frame 35-, 60-, 90-and total infrared (IR) luminosity functions (LFs) up to z similar to 4. We detect very strong luminosity evolution for the total IR LF (L-IR alpha (1 + z)(3.55 +/- 0.10) up to z similar to 2, and. (1 + z) 1.62 similar to 0.51 at 2 < z less than or similar to 4) combined with a density evolution ( (1 + z)-0.57 +/- 0.22 up to z similar to 1 and. (1 + z)-3.92 +/- 0.34 at 1 < z less than or similar to 4). In agreement with previous findings, the IR luminosity density (.IR) increases steeply to z similar to 1, then flattens between z similar to 1 and z similar to 3 to decrease at z similar to 3. Galaxies with different spectral energy distributions, masses and specific star formation rates (SFRs) evolve in very different ways and this large and deep statistical sample is the first one allowing us to separately study the different evolutionary behaviours of the individual IR populations contributing to.IR. Galaxies occupying the well-established SFR-stellar mass main sequence (MS) are found to dominate both the total IR LF and.IR at all redshifts, with the contribution from off-MS sources (= 0.6 dex above MS) being nearly constant (similar to 20 per cent of the total IR) and showing no significant signs of increase with increasing z over the whole 0.8 < z < 2.2 range. Sources with mass in the range 10 = log(M/M-circle dot) = 11 are found to dominate the total IR LF, with more massive galaxies prevailing at the bright end of the high-z (greater than or similar to 2) LF. A two-fold evolutionary scheme for IR galaxies is envisaged: on the one hand, a starburst-dominated phase in which the Super Massive Black Holes (SMBH) grows and is obscured by dust (possibly triggered by a major merging event), is followed by an AGN-dominated phase, then evolving towards a local elliptical. On the other hand, moderately star-forming galaxies containing a low-luminosity AGN have various properties suggesting they are good candidates for systems in a transition phase preceding the formation of steady spiral galaxies.
We exploit the deep and extended far-IR data sets (at 70, 100 and 160 μm) of the Herschel Guaranteed Time Observation (GTO) PACS Evolutionary Probe (PEP) Survey, in combination with the Herschel Multi-tiered Extragalactic Survey data at 250, 350 and 500 μm, to derive the evolution of the rest-frame 35-, 60-, 90and total infrared (IR) luminosity functions (LFs) up to z ∼ 4. We detect very strong luminosity evolution for the total IR LF (LIR ∝ (1 + z)3.55 ± 0.10 up to z ∼ 2, and ∝ (1 + z)1.62 ± 0.51 at 2 < z 4) combined with a density evolution (∝ (1 + z)−0.57 ± 0.22 up to z ∼ 1 and ∝ (1 + z)−3.92 ± 0.34 at 1 < z 4). In agreement with previous findings, the IR luminosity density (ρIR) increases steeply to z ∼ 1, then flattens between z ∼ 1 and z ∼ 3 to decrease at z 3. Galaxies with different spectral energy distributions, masses and specific star formation rates (SFRs) evolve in very different ways and this large and deep statistical sample is the first one allowing us to separately study the different evolutionary behaviours of the individual IR populations contributing to ρIR. Galaxies occupying the well-established SFR–stellar mass main sequence (MS) are found to dominate both the total IR LF and ρIR at all redshifts, with the contribution from off-MS sources (≥0.6 dex above MS) being nearly constant (∼20 per cent of the total ρIR) and showing no significant signs of increase with increasing z over the whole 0.8 < z < 2.2 range. Sources with mass in the range 10 ≤ log(M/M ) ≤ 11 are found to dominate the total IR LF, with more massive galaxies prevailing at the bright end of the high-z ( 2) LF. A two-fold evolutionary scheme for IR galaxies is envisaged: on the one hand, a starburst-dominated phase in which the Super Massive Black Holes (SMBH) grows and is obscured by dust (possibly triggered by a major merging event), is followed by an AGN-dominated phase, then evolving towards a local elliptical. On the other hand, moderately star-forming galaxies containing a low-luminosity AGN have various properties suggesting they are good candidates for systems in a transition phase preceding the formation of steady spiral galaxies.
Observations at submillimetre and X-ray wavelengths show that rapid star formation was common in the host galaxies of active galactic nuclei when the Universe was 2–6 Gyr old, but that the most vigorous star formation is not observed around powerful black holes, thereby confirming a key prediction of models in which an active galactic nucleus expels the interstellar medium of its host galaxy. Radiation from active galactic nuclei (AGNs) outshines that produced by star formation at most wavelengths, but in the far-infrared to millimetre waveband AGNs emit comparatively little radiation in comparison with strongly star-forming galaxies. A combination of deep X-ray observations from the Chandra catalogue and submillimetre observations from the SPIRE instrument on the Herschel Space Observatory shows that rapid star formation was common in the host galaxies of AGNs when the Universe was between two billion and six billion years old, but that vigorous star formation is not seen around the more luminous black holes. This suppression of star formation in galaxies that host a powerful AGN is a key prediction of models in which the AGN expels the interstellar medium of its host galaxy when it becomes sufficiently powerful. The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight correlation between the mass of the black hole and the mass of the stellar bulge1 results from the AGN quenching the surrounding star formation as it approaches its peak luminosity2,3,4. X-rays trace emission from AGN unambiguously5, whereas powerful star-forming galaxies are usually dust-obscured and are brightest at infrared and submillimetre wavelengths6. Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2–6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 1044 ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow7,8,9, expelling the interstellar medium of its host and transforming the galaxy’s properties in a brief period of cosmic time.
ABRIGED Herschel/SPIRE has provided confusion limited maps of deep fields at 250, 350, and 500um, as part of the HerMES survey. Due to confusion, only a small fraction of the Cosmic Infrared Background can be resolved into individually-detected sources. Our goal is to produce deep galaxy number counts and redshift distributions below the confusion limit, which we then use to place strong constraints on the origins of the cosmic infrared background and on models of galaxy evolution. We individually extracted the bright SPIRE with a method using the positions, the flux densities, and the redshifts of the 24um sources as a prior, and derived the number counts and redshift distributions of the bright SPIRE sources. For fainter SPIRE sources, we reconstructed the number counts and the redshift distribution below the confusion limit using the deep 24um catalogs associated with photometric redshift and information provided by the stacking of these sources into the deep SPIRE maps. Finally, by integrating all these counts, we studied the contribution of the galaxies to the CIB as a function of their flux density and redshift. Through stacking, we managed to reconstruct the source counts per redshift slice down to 2 mJy in the three SPIRE bands, which lies about a factor 10 below the 5sigma confusion limit. None of the pre-existing population models are able to reproduce our results at better than 3sigma. Finally, we extrapolate our counts to zero flux density in order to derive an estimate of the total contribution of galaxies to the CIB, finding 10.1, 6.5, and 2.8 nW/m2/sr at 250, 350, and 500um, respectively. These values agree well with FIRAS absolute measurements, suggesting our number counts and their extrapolation are sufficient to explain the CIB. Finally, combining our results with other works, we estimate the energy budget contained in the CIB between 8 and 1000um: 26 nW/m2/sr.
We describe the generation of single-band point source catalogues from submillimetre Herschel-SPIRE observations taken as part of the Science Demonstration Phase of the Herschel Multi-tiered Extragalactic Survey (HerMES). Flux densities are found by means of peak finding and the fitting of a Gaussian point-response function. With highly confused images, careful checks must be made on the completeness and flux-density accuracy of the detected sources. This is done by injecting artificial sources into the images and analysing the resulting catalogues. Measured flux densities at which 50 per cent of injected sources result in good detections at (250, 350 and 500) mu m range from (11.6, 13.2 and 13.1) to (25.7, 27.1 and 35.8) mJy, depending on the depth of the observation (where a good detection is taken to be one with positional offset less than one full-width half-maximum of the point-response function, and with the measured flux density within a factor of 2 of the flux density of the injected source). This paper acts as a reference for the 2010 July HerMES public data release.
The Herschel Multi-tiered Extragalactic Survey, HerMES, is a legacy program designed to map a set of nested fields totalling 380 deg^2. Fields range in size from 0.01 to 20 deg^2, using Herschel-SPIRE (at 250, 350 and 500 μm), and Herschel-PACS (at 100 and 160 μm), with an additional wider component of 270 deg^2 with SPIRE alone. These bands cover the peak of the redshifted thermal spectral energy distribution from interstellar dust and thus capture the re-processed optical and ultra-violet radiation from star formation that has been absorbed by dust, and are critical for forming a complete multi-wavelength understanding of galaxy formation and evolution. The survey will detect of order 100,000 galaxies at 5σin some of the best studied fields in the sky. Additionally, HerMES is closely coordinated with the PACS Evolutionary Probe survey. Making maximum use of the full spectrum of ancillary data, from radio to X-ray wavelengths, it is designed to: facilitate redshift determination; rapidly identify unusual objects; and understand the relationships between thermal emission from dust and other processes. Scientific questions HerMES will be used to answer include: the total infrared emission of galaxies; the evolution of the luminosity function; the clustering properties of dusty galaxies; and the properties of populations of galaxies which lie below the confusion limit through lensing and statistical techniques. This paper defines the survey observations and data products, outlines the primary scientific goals of the HerMES team, and reviews some of the early results.
We report the detection of CO(J = 5 -> 4), CO(J = 3 -> 2), and CO(J = 1 -> 0) emission in the strongly lensed, Herschel/SPIRE-selected submillimeter galaxy (SMG) HERMES J105751.1+573027 at z = 2.9574 +/- 0.0001, using the Plateau de Bure Interferometer, the Combined Array for Research in Millimeter-wave Astronomy, and the Green Bank Telescope. The observations spatially resolve the molecular gas into four lensed images with a maximum separation of similar to 9 '' and reveal the internal gas dynamics in this system. We derive lensing-corrected CO line luminosities of L'(CO(1-0)) = (4.17 +/- 0.41), L'(CO(3-2)) = (3.96 +/- 0.20), and L'(CO(5-4)) = (3.45 +/- 0.20) x 10(10) (mu(L)/10.9)(-1) K km s(-1) pc(2), corresponding to luminosity ratios of r(31) = 0.95 +/- 0.10, r(53) = 0.87 +/- 0.06, and r(51) = 0.83 +/- 0.09. This suggests a total molecular gas mass of M-gas = 3.3 x 10(10) (alpha(CO)/0.8) (mu(L)/10.9)(-1) M-circle dot. The gas mass, gas mass fraction, gas depletion timescale, star formation efficiency, and specific star formation rate are typical for an SMG. The velocity structure of the gas reservoir suggests that the brightest two lensed images are dynamically resolved projections of the same dust-obscured region in the galaxy that are kinematically offset from the unresolved fainter images. The resolved kinematics appear consistent with the complex velocity structure observed in major, "wet" (i.e., gas-rich) mergers. Major mergers are commonly observed in SMGs and are likely to be responsible for fueling their intense starbursts at high gas consumption rates. This study demonstrates the level of detail to which galaxies in the early universe can be studied by utilizing the increase in effective spatial resolution and sensitivity provided by gravitational lensing.
We present the results of a gravitational lensing analysis of the bright z(s) = 2.957 submillimeter galaxy (SMG) HERMES found in the Herschel/SPIRE science demonstration phase data from the Herschel Multi-tiered Extragalactic Survey (HerMES) project. The high-resolution imaging available in optical and near-IR channels, along with CO emission obtained with the Plateau de Bure Interferometer, allows us to precisely estimate the intrinsic source extension and hence estimate the total lensing magnification to be mu = 10.9 +/- 0.7. We measure the half-light radius R-eff of the source in the rest-frame near-UV and V bands that characterize the unobscured light coming from stars and find R-eff,R-* = [2.0 +/- 0.1] kpc, in good agreement with recent studies on the SMG population. This lens model is also used to estimate the size of the gas distribution (R-eff,R-gas = [1.1 +/- 0.5] kpc) by mapping back in the source plane the CO (J = 5 -> 4) transition line emission. The lens modeling yields a relatively large Einstein radius R-Ein = 4 ''.10 +/- 0 ''.02, corresponding to a deflector velocity dispersion of [483 +/- 16] km s(-1). This shows that HERMES is lensed by a galaxy group-size dark matter halo at redshift z(l) similar to 0.6. The projected dark matter contribution largely dominates the mass budget within the Einstein radius with f(dm)(<R-Ein) similar to 80%. This fraction reduces to f(dm)(< R-eff,R-G1 similar or equal to 4.5 kpc) similar to 47% within the effective radius of the main deflecting galaxy of stellar mass M-*,M-G1 = [8.5 +/- 1.6] x 10(11) M-circle dot. At this smaller scale the dark matter fraction is consistent with results already found for massive lensing ellipticals at z similar to 0.2 from the Sloan Lens ACS Survey.
We examine the rest-frame far-infrared emission from powerful radio sources with 1.4-GHz luminosity densities of 25 < log(L-1.4/W Hz-1) < 26.5 in the extragalactic Spitzer First Look Survey field. We combine Herschel/SPIRE flux densities with Spitzer/Infrared Array Camera and Multiband Imaging Photometer for Spitzer infrared data to obtain total (8 -1000 mu m ) infrared luminosities for these radio sources. We separate our sources into a moderate, 0.4 < z < 0.9, and a high, 1.2 < z < 3.0, redshift sub-sample and we use Spitzer observations of a z < 0.1 3CRR sample as a local comparison. By comparison to numbers from the Square Kilometre Array (SKA) Simulated Skies, we find that our moderate-redshift sample is complete and our high-redshift sample is 14 per cent complete. We constrain the ranges of mean star formation rates (SFRs) to be 3.4-4.2, 18-41 and 80-581 M-circle dot yr-1 for the local, moderate- and high-redshift samples, respectively. Hence, we observe an increase in the mean SFR with increasing redshift which we can parametrize as similar to(1 + z)Q, where Q = 4.2 +/- 0.8. However, we observe no trends of mean SFR with radio luminosity within the moderate- or high-redshift bins. We estimate that radio-loud active galactic nuclei (AGN) in the high-redshift sample contribute 0.1-0.5 per cent to the total SFR density at that epoch. Hence, if all luminous starbursts host radio-loud AGN we infer a radio-loud phase duty cycle of 0.001-0.005.
ABSTRACT We report the discovery of a bright ( f (250 μm)>400 mJy), multiply lensed submillimeter galaxy HERMES J105751.1+573027 in Herschel /SPIRE Science Demonstration Phase data from the HerMES project. Interferometric 880 μm Submillimeter Array observations resolve at least four images with a large separation of ∼9″. A high-resolution adaptive optics K p image with Keck/NIRC2 clearly shows strong lensing arcs. Follow-up spectroscopy gives a redshift of z = 2.9575, and the lensing model gives a total magnification of μ ∼ 11 ± 1. The large image separation allows us to study the multi-wavelength spectral energy distribution (SED) of the lensed source unobscured by the central lensing mass. The far-IR/millimeter-wave SED is well described by a modified blackbody fit with an unusually warm dust temperature, 88 ± 3 K. We derive a lensing-corrected total IR luminosity of (1.43 ± 0.09) × 10 13 L ☉ , implying a star formation rate of ∼2500 M ☉ yr −1 . However, models primarily developed from brighter galaxies selected at longer wavelengths are a poor fit to the full optical-to-millimeter SED. A number of other strongly lensed systems have already been discovered in early Herschel data, and many more are expected as additional data are collected.
We report on the redshift measurement and CO line excitation of HERMES J105751.1+573027 (HLSW-01), a strongly lensed submillimeter galaxy discovered in Herschel/SPIRE observations as part of the Herschel Multi-tiered Extragalactic Survey (HerMES). HLSW-01 is an ultra-luminous galaxy with an intrinsic far-infrared luminosity of L-FIR = 1.4 x 10(13) L-circle dot, and is lensed by a massive group of galaxies into at least four images with a total magnification of mu = 10.9 +/- 0.7. With the 100 GHz instantaneous bandwidth of the Z-Spec instrument on the Caltech Submillimeter Observatory, we robustly identify a redshift of z = 2.958 +/- 0.007 for this source, using the simultaneous detection of four CO emission lines (J = 7 -> 6, J = 8 -> 7, J = 9 -> 8, and J = 10 -> 9). Combining the measured line fluxes for these high-J transitions with the J = 1 -> 0, J = 3 -> 2, and J = 5 -> 4 line fluxes measured with the Green Bank Telescope, the Combined Array for Research in Millimeter Astronomy, and the Plateau de Bure Interferometer, respectively, we model the physical properties of the molecular gas in this galaxy. We find that the full CO spectral line energy distribution is described well by warm, moderate-density gas with T-kin = 86-235 K and n(H2) = (1.1-3.5) x 10(3) cm(-3). However, it is possible that the highest-J transitions are tracing a small fraction of very dense gas in molecular cloud cores, and two-component models that include a warm/dense molecular gas phase with T-kin similar to 200 K, n(H2) similar to 10(5) cm(-3) are also consistent with these data. Higher signal-to-noise measurements of the J(up) >= 7 transitions with high spectral resolution, combined with high spatial resolution CO maps, are needed to improve our understanding of the gas excitation, morphology, and dynamics of this interesting high-redshift galaxy.
We present the first study of the far-infrared (FIR) properties of high-redshift, radio-selected ultraluminous infrared galaxies (ULIRGs) using deep observations obtained with the Spectral and Photometric Imaging Receiver (SPIRE) from the Herschel Multi-tiered Extragalactic Survey (HerMES). These galaxies span a large range of 850-um fluxes from submillimetre-luminous ~10mJy sources (SCUBA galaxies) to ~1.5mJy from stacked SCUBA non-detections, thus likely representing a complete distribution of ULIRG spectral energy distributions (SEDs). From Keck spectroscopic surveys in the Lockman-North field we identified a sample of 31 submillimetre galaxies (SMGs) and 37 submillimetre-faint, optically faint radio galaxies (OFRGs), all with radio-inferred IR luminosities >1012^L ȯ . These galaxies were cross-identified with SPIRE 250-, 350- and 500-um catalogues based on fluxes extracted at 24-um positions in the SWIRE survey, yielding a sample of more than half of the galaxies well detected in at least two of the SPIRE bandpasses. (1 data file).
We present the results of a gravitational lensing analysis of the bright $\zs=2.957$ sub-millimeter galaxy (SMG), HERMES J105751.1+573027 found in {\it Herschel}/SPIRE Science Demonstration Phase data from the Herschel Multi-tiered Extragalactic Survey (HerMES) project. The high resolution imaging available in optical and Near-IR channels, along with CO emission obtained with the Plateau de Bure Interferometer, allow us to precisely estimate the intrinsic source extension and hence estimate the total lensing magnification to be $\mu=10.9\pm 0.7$. We measure the half-light radius $R_{\rm eff}$ of the source in the rest-frame Near-UV and $V$ bands that characterize the unobscured light coming from stars and find $R_{\rm eff,*}= [2.0 \pm 0.1]$ kpc, in good agreement with recent studies on the Submillimeter Galaxy population. This lens model is also used to estimate the size of the gas distribution ($R_{\rm eff,gas}= [1.1\pm0.5]$) kpc by mapping back in the source plane the CO (J=5-4) transition line emission. The lens modeling yields a relatively large Einstein radius $R_{\rm Ein}= 4\farcs10 \pm 0\farcs02$, corresponding to a deflector velocity dispersion of [$483\pm 16] \,\kms$. This shows that HERMES J105751.1+573027 is lensed by a {\it galaxy group-size} dark matter halo at redshift $\zl\sim 0.6$. The projected dark matter contribution largely dominates the mass budget within the Einstein radius with $f_{\rm dm}(<R_{\rm Ein})\sim 80%$. This fraction reduces to $f_{\rm dm}(<R_{\rm eff,G1}\simeq 4.5\kpc)\sim 47%$ within the effective radius of the main deflecting galaxy of stellar mass $M_{\rm *,G1}=[8.5\pm 1.6] \times 10^{11}\msun$. At this smaller scale the dark matter fraction is consistent with results already found for massive lensing ellipticals at $z\sim0.2$ from the SLACS survey.
For the first time, we investigate the X-ray/infrared (IR) correlation for star-forming galaxies (SFGs) at z similar to 1, using SPIRE submm data from the recently launched Herschel Space Observatory and deep X-ray data from the 2-Ms Chandra Deep Field-North survey. We examine the X-ray/IR correlation in the soft X-ray (SX; 0.5-2 keV) and hard X-ray (HX; 2-10 keV) bands by comparing our z similar to 1 SPIRE-detected SFGs to equivalently IR-luminous (L-IR > 10(10) L-circle dot) samples in the local/low-redshift Universe. Our results suggest that the X-ray/IR properties of the SPIRE SFGs are on average similar to those of their local counterparts, as we find no evidence for evolution in the L-SX/L-IR and L-HX/L-IR ratios with redshift. We note, however, that at all redshifts, both L-SX/L-IR and L-HX/L-IR are strongly dependent on IR luminosity, with luminous and ultraluminous IR galaxies (LIRGs and ULIRGs; L-IR > 10(11) L-circle dot) having up to an order of magnitude lower values than normal IR galaxies (L-IR < 10(11) L-circle dot). We derive a L-SX-L-IR relation and confirm the applicability of an existing L-HX-L-IR relation for both local and distant LIRGs and ULIRGs, consistent with a scenario where X-ray luminosity is correlated with the star formation rate.