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We present first insights into the far-IR properties for a sample of IRAC and MIPS 24 μm detected Lyman break galaxies (LBGs) at z ∼ 3, as derived from observations in the northern field of the Great Observatories Origins Survey (GOODS-N) carried out with the PACS instrument on board the Herschel Space Observatory. Although none of our galaxies are detected by Herschel, we employ a stacking technique to construct, for the first time, the average spectral energy distribution (SED) of infrared luminous LBGs from UV to radio wavelengths. We derive a median IR luminosity of LIR = 1.6 × 1012 L⊙, placing the population in the class of ultra-luminous infrared galaxies (ULIRGs). Complementing our study with existing multi-wavelength data, we put constraints on the dust temperature of the population and find that for their LIR, MIPS-LBGs are warmer than submillimeter-luminous galaxies while they fall in the locus of the L IR-Td relation of the local ULIRGs. This, along with estimates based on the average SED, explains the marginal detection of LBGs in current submillimeter surveys and suggests that these latter studies introduce a bias toward the detection of colder ULIRGs in the high-z universe, while missing high-z ULIRGS with warmer dust. © 2010. The American Astronomical Society. All rights reserved.

Aims. We exploit the deepest existing far-infrared (FIR) data obtained so far by Herschel at 100 and 160 μm in the GOODS-N, as part of the PACS evolutionary probe (PEP) survey, to derive for the first time the evolution of the rest-frame 60-μm, 90-μm, and total IR luminosity functions (LFs) of galaxies and AGNs from z = 0 to unprecedented high redshifts (z ∼ 2-3). Methods. The PEP LFs were computed using the 1/Vmax method. The FIR sources were classified by means of a detailed broad-band SED-fitting analysis and spectral characterisation. Based on the best-fit model results, k-correction and total IR (8-1000 μm) luminosity were obtained for each source. LFs (monochromatic and total) were then derived for various IR populations separately in different redshift bins and compared to backward evolution model predictions. Results. We detect strong evolution in the LF to at least z ∼ 2. Objects with SEDs similar to local spiral galaxies are the major contributors to the star formation density (SFD) at z a 0.3, then, as redshift increases, moderate SF galaxies - most likely containing a low-luminosity AGN - start dominating up to z $\simeq$ 1.5. At z a 1.5 the SFD is dominated by the contributions of starburst galaxies. In agreement with previous findings, the comoving IR LD derived from our data evolves approximately as (1 + z) 3.8±0.3 up to z ∼ 1, there being some evidence of flattening up to z ∼ 2. © 2010 ESO.

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-, 90- and total infrared (IR) luminosity functions (LFs) up to z ~ 4.We detect very strong luminosity evolution for the total IR LF (LIR α (1 + z)3.55 ± 0.10 up to z ~ 2, and α (1 + z)1.62 ± 0.51 at 2 < z 4) combined with a density evolution (α (1 + z)-0.57 ± 0.22 up to z ~ 1 and α (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. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

We study the evolution of the dust temperature of galaxies in the SFR-Mâ̂- plane up to z ~ 2 using far-infrared and submillimetre observations from the Herschel Space Observatory taken as part of the PACS Evolutionary Probe (PEP) and Herschel Multi-tiered Extragalactic Survey (HerMES) guaranteed time key programmes. Starting from a sample of galaxies with reliable star-formation rates (SFRs), stellar masses (M-) and redshift estimates, we grid the SFR-M-parameter space in several redshift ranges and estimate the mean dust temperature (Tdust) of each SFR-M--z bin. Dust temperatures are inferred using the stacked far-infrared flux densities (100-500 μm) of our SFR-M--z bins. At all redshifts, the dust temperature of galaxies smoothly increases with rest-frame infrared luminosities (LIR), specific SFRs (SSFR; i.e., SFR/M-), and distances with respect to the main sequence (MS) of the SFR-M- plane (i.e., Δlog (SSFR)MS = log [SSFR(galaxy)/SSFRMS(M-,z)]). The Tdust-SSFR and Tdust-Δlog (SSFR)MS correlations are statistically much more significant than the Tdust-LIR one. While the slopes of these three correlations are redshift-independent, their normalisations evolve smoothly from z = 0 and z ~ 2. We convert these results into a recipe to derive Tdust from SFR, M- and z, valid out to z ~ 2 and for the stellar mass and SFR range covered by our stacking analysis. The existence of a strong Tdust-Δlog (SSFR)MS correlation provides us with several pieces of information on the dust and gas content of galaxies. Firstly, the slope of the T dust-Δlog (SSFR)MS correlation can be explained by the increase in the star-formation efficiency (SFE; SFR/Mgas) with Δlog (SSFR)MS as found locally by molecular gas studies. Secondly, at fixed Δlog (SSFR)MS, the constant dust temperature observed in galaxies probing wide ranges in SFR and M- can be explained by an increase or decrease in the number of star-forming regions with comparable SFE enclosed in them. And thirdly, at high redshift, the normalisation towards hotter dust temperature of the Tdust-Δlog (SSFR)MS correlation can be explained by the decrease in the metallicities of galaxies or by the increase in the SFE of MS galaxies. All these results support the hypothesis that the conditions prevailing in the star-forming regions of MS and far-above-MS galaxies are different. MS galaxies have star-forming regions with low SFEs and thus cold dust, while galaxies situated far above the MS seem to be in a starbursting phase characterised by star-forming regions with high SFEs and thus hot dust. © 2014 ESO.

Aims. We exploit the deepest existing far-infrared (FIR) data obtained so far by Herschel at 100 and 160 μm in the GOODS-N, as part of the PACS evolutionary probe (PEP) survey, to derive for the first time the evolution of the rest-frame 60-μm, 90-μm, and total IR luminosity functions (LFs) of galaxies and AGNs from z = 0 to unprecedented high redshifts (z ∼ 2-3). Methods. The PEP LFs were computed using the 1/Vmax method. The FIR sources were classified by means of a detailed broad-band SED-fitting analysis and spectral characterisation. Based on the best-fit model results, k-correction and total IR (8-1000 μm) luminosity were obtained for each source. LFs (monochromatic and total) were then derived for various IR populations separately in different redshift bins and compared to backward evolution model predictions. Results. We detect strong evolution in the LF to at least z ∼ 2. Objects with SEDs similar to local spiral galaxies are the major contributors to the star formation density (SFD) at z ≲ 0.3, then, as redshift increases, moderate SF galaxies-most likely containing a low-luminosity AGN-start dominating up to z 1.5. At z ≳ 1.5 the SFD is dominated by the contributions of starburst galaxies. In agreement with previous findings, the comoving IR LD derived from our data evolves approximately as (1 + z) 3.8±0.3 up to z ∼ 1, there being some evidence of flattening up to z ∼ 2. © 2010 ESO.

We present a study of the far-infrared (IR) properties of a stellar mass selected sample of 1.5 < z < 3 galaxies with log(M */M ⊙) > 9.5 drawn from the Great Observatories Origins Deep Survey (GOODS) Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Survey (GNS), the deepest H-band Hubble Space Telescope survey of its type prior to the installation of Wide Field Camera 3 (WFC3). We use far-IR and submm data from the Photoconductor Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging Receiver (SPIRE) instruments on-board Herschel, taken from the PACS Evolutionary Probe (PEP) and Herschel Multi-Tiered Extragalactic Survey (HerMES) key projects, respectively. We find a total of 22 GNS galaxies, with median log(M */M ⊙) = 10.8 and z = 2.0, associated with 250μm sources detected with signal-to-noise ratio (SNR) > 3. We derive mean total IR luminosity logL IR(L ⊙) = 12.36 ± 0.05 and corresponding star formation rate (SFR) IR + UV = (280 ± 40)M ⊙yr -1 for these objects, and find them to have mean dust temperature T dust ≈ 35K. We find that the SFR derived from the far-IR photometry combined with ultraviolet (UV)-based estimates of unobscured SFR for these galaxies is on average more than a factor of 2 higher than the SFR derived from extinction-corrected UV emission alone, although we note that the IR-based estimate is subject to substantial Malmquist bias. To mitigate the effect of this bias and extend our study to fainter fluxes, we perform a stacking analysis to measure the mean SFR in bins of stellar mass. We obtain detections at the 2-4σ level at SPIRE wavelengths for samples with log(M */M ⊙) > 10. In contrast to the Herschel detected GNS galaxies, we find that estimates of SFR IR + UV for the stacked samples are comparable to those derived from extinction-corrected UV emission, although the uncertainties are large. We find evidence for an increasing fraction of dust obscured star formation with stellar mass, finding SFR IR / SFR UV ∝M*0.7±0.2, which is likely a consequence of the mass-metallicity relation. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

We use Herschel-PACS far-infrared (IR) data, combined with previous multiband information and mid-IR spectra, to properly account for the presence of an active nucleus and constrain its energetic contribution in luminous IR sources at z˜ 2. The sample is composed of 24 sources in the GOODS-South field, with typical IR luminosity of 10^12 L⊙. Data from the 4 Ms Chandra X-ray imaging in this field are also used to identify and characterize active galactic nucleus (AGN) emission. We reproduce the observed spectral energy distribution (SED), decomposed into a host-galaxy and an AGN component. A smooth-torus model for circumnuclear dust is used to account for the direct and reprocessed contribution from the AGN. We confirm that galaxies with typical L(8-1000 micron) at z˜ 2 are powered predominantly by star formation. An AGN component is present in nine objects (˜35 per cent of the sample) at the 3σ confidence level, but its contribution to the 8-1000 micron emission accounts for only ˜5 per cent of the energy budget. The AGN contribution rises to ˜23 per cent over the 5-30 micron range (in agreement with Spitzer IRS results) and to ˜60 per cent over the narrow 2-6 micron range. The presence of an AGN is confirmed by X-ray data for three (out of nine) sources, with X-ray spectral analysis indicating the presence of significant absorption, i.e. NH˜ 10^23-10^24 cm-2. An additional source shows indications of obscured AGN emission from X-ray data. The comparison between the mid-IR-derived X-ray luminosities and those obtained from X-ray data suggests that obscuration is likely present also in the remaining six sources that harbour an AGN according to the SED-fitting analysis.

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We present first insights into the far-IR properties for a sample of IRAC and MIPS 24 μm detected Lyman break galaxies (LBGs) at z ∼ 3, as derived from observations in the northern field of the Great Observatories Origins Survey (GOODS-N) carried out with the PACS instrument on board the Herschel Space Observatory. Although none of our galaxies are detected by Herschel, we employ a stacking technique to construct, for the first time, the average spectral energy distribution (SED) of infrared luminous LBGs from UV to radio wavelengths. We derive a median IR luminosity of LIR = 1.6 × 1012 L⊙, placing the population in the class of ultra-luminous infrared galaxies (ULIRGs). Complementing our study with existing multi-wavelength data, we put constraints on the dust temperature of the population and find that for their LIR, MIPS-LBGs are warmer than submillimeter-luminous galaxies while they fall in the locus of the L IR-Td relation of the local ULIRGs. This, along with estimates based on the average SED, explains the marginal detection of LBGs in current submillimeter surveys and suggests that these latter studies introduce a bias toward the detection of colder ULIRGs in the high-z universe, while missing high-z ULIRGS with warmer dust. © 2010. The American Astronomical Society. All rights reserved.

We study the evolution of the radio spectral index and far-infrared/radio correlation (FRC) across the star-formation rate – stellar masse (i.e. SFR–M_∗) plane up to z ~ 2. We start from a stellar-mass-selected sample of galaxies with reliable SFR and redshift estimates. We then grid the SFR–M_∗ plane in several redshift ranges and measure the infrared luminosity, radio luminosity, radio spectral index, and ultimately the FRC index (i.e. q_(FIR)) of each SFR–M_∗–z bin. The infrared luminosities of our SFR–M_∗–z bins are estimated using their stacked far-infrared flux densities inferred from observations obtained with the Herschel Space Observatory. Their radio luminosities and radio spectral indices (i.e. α, where S_ν ∝ ν^(−α)) are estimated using their stacked 1.4 GHz and 610 MHz flux densities from the Very Large Array and Giant Metre-wave Radio Telescope, respectively. Our far-infrared and radio observations include the most widely studied blank extragalactic fields – GOODS-N, GOODS-S, ECDFS, and COSMOS – covering a total sky area of ~2.0 deg^2. Using this methodology, we constrain the radio spectral index and FRC index of star-forming galaxies with M_∗ > 10^(10) M_⊙ and 0

International audience; We study the evolution of the radio spectral index and far-infrared/radio correlation (FRC) across the star-formation rate – stellar masse (i.e. SFR–$M_\ast$) plane up to $z$ ~ 2. We start from a stellar-mass-selected sample of galaxies with reliable SFR and redshift estimates. We then grid the SFR–$M_\ast$ plane in several redshift ranges and measure the infrared luminosity, radio luminosity, radio spectral index, and ultimately the FRC index (i.e. $q_{FIR}$) of each SFR–$M_\ast$–$z$ bin. The infrared luminosities of our SFR–$M_\ast$–$z$ bins are estimated using their stacked far-infrared flux densities inferred from observations obtained with the Herschel Space Observatory. Their radio luminosities and radio spectral indices (i.e. $\alpha$, where $S_ν$ ∝ $ν^{−α}$) are estimated using their stacked 1.4 GHz and 610 MHz flux densities from the Very Large Array and Giant Metre-wave Radio Telescope, respectively. Our far-infrared and radio observations include the most widely studied blank extragalactic fields – GOODS-N, GOODS-S, ECDFS, and COSMOS – covering a total sky area of ~2.0 deg$^2$. Using this methodology, we constrain the radio spectral index and FRC index of star-forming galaxies with $M_\ast$ > 10$^{10}$ $M_⊙$ and 0

著者人数: 33名, Accepted: 2014-03-14, 資料番号: SA1140080000

International audience; We study the evolution of the dust temperature of galaxies in the SFR− M∗ plane up to z ~ 2 using far-infrared and submillimetre observations from the Herschel Space Observatory taken as part of the PACS Evolutionary Probe (PEP) and Herschel Multi-tiered Extragalactic Survey (HerMES) guaranteed time key programmes. Starting from a sample of galaxies with reliable star-formation rates (SFRs), stellar masses (M∗) and redshift estimates, we grid the SFR− M∗parameter space in several redshift ranges and estimate the mean dust temperature (Tdust) of each SFR–M∗ − z bin. Dust temperatures are inferred using the stacked far-infrared flux densities (100–500 μm) of our SFR–M∗ − z bins. At all redshifts, the dust temperature of galaxies smoothly increases with rest-frame infrared luminosities (LIR), specific SFRs (SSFR; i.e., SFR/M∗), and distances with respect to the main sequence (MS) of the SFR− M∗ plane (i.e., Δlog (SSFR)MS = log [SSFR(galaxy)/SSFRMS(M∗,z)]). The Tdust − SSFR and Tdust − Δlog (SSFR)MS correlations are statistically much more significant than the Tdust − LIR one. While the slopes of these three correlations are redshift-independent, their normalisations evolve smoothly from z = 0 and z ~ 2. We convert these results into a recipe to derive Tdust from SFR, M∗ and z, valid out to z ~ 2 and for the stellar mass and SFR range covered by our stacking analysis. The existence of a strong Tdust − Δlog (SSFR)MS correlation provides us with several pieces of information on the dust and gas content of galaxies. Firstly, the slope of the Tdust − Δlog (SSFR)MS correlation can be explained by the increase in the star-formation efficiency (SFE; SFR/Mgas) with Δlog (SSFR)MS as found locally by molecular gas studies. Secondly, at fixed Δlog (SSFR)MS, the constant dust temperature observed in galaxies probing wide ranges in SFR and M∗ can be explained by an increase or decrease in the number of star-forming regions with comparable SFE enclosed in them. And thirdly, at high redshift, the normalisation towards hotter dust temperature of the Tdust − Δlog (SSFR)MS correlation can be explained by the decrease in the metallicities of galaxies or by the increase in the SFE of MS galaxies. All these results support the hypothesis that the conditions prevailing in the star-forming regions of MS and far-above-MS galaxies are different. MS galaxies have star-forming regions with low SFEs and thus cold dust, while galaxies situated far above the MS seem to be in a starbursting phase characterised by star-forming regions with high SFEs and thus hot dust.

International audience; We empirically MD test the relation between the SFR(LIR) derived from the infrared luminosity, LIR, and the SFR(Ha) derived from the Ha emission line luminosity using simple conversion relations. We use a sample of 474 galaxies at z = 0.060.46 with both Ha detection [from 20k redshift Cosmological Evolution (zCOSMOS) survey] and new far-IR Herschel data (100 and 160 mu m). We derive SFR(Ha) from the Ha extinction corrected emission line luminosity. We find a very clear trend between E(B - V) and LIR that allows us to estimate extinction values for each galaxy even if the H beta emission line measurement is not reliable. We calculate the LIR by integrating from 8 up to 1000 mu m the spectral energy distribution (SED) that is best fitting our data. We compare the SFR(Ha) with the SFR(LIR). We find a very good agreement between the two star formation rate (SFR) estimates, with a slope of m = 1.01 +/- 0.03 in the log SFR(LIR) versus log SFR(Ha) diagram, a normalization constant of a = -0.08 +/- 0.03 and a dispersion of s = 0.28 dex. We study the effect of some intrinsic properties of the galaxies in the SFR(LIR)SFR(Ha) relation, such as the redshift, the mass, the specific star formation rate (SSFR) or the metallicity. The metallicity is the parameter that affects most the SFR comparison. The mean ratio of the two SFR estimators log[SFR(LIR)/SFR(Ha)] varies by similar to 0.6 dex from metal-poor to metal-rich galaxies [8.1 \textless log?(O/H) + 12 \textless 9.2]. This effect is consistent with the prediction of a theoretical model for the dust evolution in spiral galaxies. Considering different morphological types, we find a very good agreement between the two SFR indicators for the Sa, Sb and Sc morphologically classified galaxies, both in slope and in normalization. For the Sd, irregular sample (Sd/Irr), the formal best-fitting slope becomes much steeper (m = 1.62 +/- 0.43), but it is still consistent with 1 at the 1.5s level, because of the reduced statistics of this sub-sample.