Cosmic star-formation history from a non-parametric inversion of infrared galaxy counts

Lutz

et al. 2010

A&A

Self Cite

112

The constituents of the cosmic IR background (CIB) are studied at its peak wavelengths (100 and 160 μm) by exploiting Herschel/PACS observations of the GOODS-N, Lockman Hole, and COSMOS fields in the PACS evolutionary probe (PEP) guaranteed-time survey. The GOODS-N data reach 3σ depths of ∼3.0 mJy at 100 μm and ∼5.7 mJy at 160 μm. At these levels, source densities are 40 and 18 beams/source, respectively, thus hitting the confusion limit at 160 μm. Differential number counts extend from a few mJy up to 100-200 mJy, and are approximated as a double power law, with the break lying between 5 and 10 mJy. The available ancillary information allows us to split number counts into redshift bins. At z ≤ 0.5 we isolate a class of luminous sources (L IR ∼ 10 11 L ), whose SEDs resemble late-spiral galaxies, peaking at ∼130 μm restframe and significantly colder than what is expected on the basis of pre-Herschel models. By integrating number counts over the whole covered flux range, we obtain a surface brightness of 6.36± 1.67 and 6.58± 1.62 [nW m −2 sr −1 ] at 100 and 160 μm, resolving ∼45% and ∼52% of the CIB, respectively. When stacking 24 μm sources, the inferred CIB lies within 1.1σ and 0.5σ from direct measurements in the two bands, and fractions increase to 50% and 75%. Most of this resolved CIB fraction was radiated at z ≤ 1.0, with 160 μm sources found at higher redshift than 100 μm ones.

Section: Discussionmentioning

confidence: 99%

Dissecting the cosmic infra-red background withHerschel/PEP

Berta

Lutz

et al. 2010

A&A

Self Cite

112

“…We first start from a simulated catalog generated from the model of Le Borgne et al (2009) that best fits number counts of sources at 15, 24, 70, 160, 850 μm. This catalog, which contains all infrared sources that should be observed over a field of 283 arcmin 2 with 0 < z < 5, reproduces the observed infrared LF up to z ∼ 1.3 (e.g., see Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Based on these correlations SED libraries have been developed and extensively used to estimate the total infrared luminosity of galaxies (e.g., Chary & Elbaz 2001;Lagache et al 2003;Dale & Helou 2002, hereafter CE01, LDP, and DH 1 respectively). However, it is not clear that these local templates are suitable to describe the spectral properties of distant galaxies (Papovich et al 2007;Daddi et al 2007b;Le Borgne et al 2009). To study this issue, we decided to characterize the observed 24 μm vs. 70 μm correlation and compare it to the predictions of standard SED libraries.…”

Section: The Total Infrared Bolometric Correctionmentioning

confidence: 99%

Evolution of the dusty infrared luminosity function fromz = 0toz = 2.3using observations fromSpitzer

Elbaz

Chary

et al. 2011

A&A

Self Cite

352

422

Aims. We derive the evolution of the infrared luminosity function (LF) over the last 4/5ths of cosmic time using deep 24 and 70 μm imaging of the GOODS North and South fields. Methods. We use an extraction technique based on prior source positions at shorter wavelengths to build the 24 and 70 μm source catalogs. The majority (93%) of the sources have a spectroscopic (39%) or a photometric redshift (54%) and, in our redshift range of interest (i.e., 1.3 < z < 2.3) ∼20% of the sources have a spectroscopic redshift. To extend our study to lower 70 μm luminosities we perform a stacking analysis and we characterize the observed L 24/(1+z) vs. L 70/(1+z) correlation. Using spectral energy distribution (SED) templates which best fit this correlation, we derive the infrared luminosity of individual sources from their 24 and 70 μm luminosities. We then compute the infrared LF at z ∼ 1.55 ± 0.25 and z ∼ 2.05 ± 0.25. Results. We observe the break in the infrared LF up to z ∼ 2.3. The redshift evolution of the infrared LF from z = 1.3 to z = 2.3 is consistent with a luminosity evolution proportional to (1 + z) 1.0±0.9 combined with a density evolution proportional to (1 + z) −1.1±1.5 . At z ∼ 2, luminous infrared galaxies (LIRGs: 10 11 L < L IR < 10 12 L ) are still the main contributors to the total comoving infrared luminosity density of the Universe. At z ∼ 2, LIRGs and ultra-luminous infrared galaxies (ULIRGs: 10 12 L < L IR ) account for ∼49% and ∼17% respectively of the total comoving infrared luminosity density of the Universe. Combined with previous results using the same strategy for galaxies at z < 1.3 and assuming a constant conversion between the infrared luminosity and star-formation rate (SFR) of a galaxy, we study the evolution of the SFR density of the Universe from z = 0 to z = 2.3. We find that the SFR density of the Universe strongly increased with redshift from z = 0 to z = 1.3, but is nearly constant at higher redshift out to z = 2.3. As part of the online material accompanying this article, we present source catalogs at 24 μm and 70 μm for both the GOODS-North and -South fields.

“…95.6% of them either have a spectroscopic (67.2%, Cohen et al 2000;Wirth et al 2004;Barger et al 2008) or photometric (28.3%, from Le Borgne et al 2009) redshift. Herschel detects a third of them (493 galaxies) in at least one of the PACS or SPIRE passbands.…”

Section: Sample and Methodsmentioning

confidence: 99%

Herschelunveils a puzzling uniformity of distant dusty galaxies

Elbaz¹,

Hwang²,

et al. 2010

A&A

Self Cite

193

150

The Herschel Space Observatory enables us to accurately measure the bolometric output of starburst galaxies and active galactic nuclei (AGN) by directly sampling the peak of their far-infrared (IR) emission. Here we examine whether the spectral energy distribution (SED) and dust temperature of galaxies have strongly evolved over the last 80% of the age of the Universe. We discuss possible consequences for the determination of starformation rates (SFR) and any evidence for a major change in their star-formation properties. We use Herschel deep extragalactic surveys from 100 to 500 μm to compute total IR luminosities in galaxies down to the faintest levels, using PACS and SPIRE in the GOODS-North field (PEP and HerMES key programs). An extension to fainter luminosities is done by stacking images on 24 μm prior positions. We show that measurements in the SPIRE bands can be used below the statistical confusion limit if information at higher spatial resolution is used, e.g. at 24 μm, to identify "isolated" galaxies whose flux is not boosted by bright neighbors. Below z ∼ 1.5, mid-IR extrapolations are correct for star-forming galaxies with a dispersion of only 40% (0.15 dex), therefore similar to z ∼ 0 galaxies, over three decades in luminosity below the regime of ultra-luminous IR galaxies (ULIRGs, L IR ≥ 10 12 L ). This narrow distribution is puzzling when considering the range of physical processes that could have affected the SED of these galaxies. Extrapolations from only one of the 160 μm, 250 μm or 350 μm bands alone tend to overestimate the total IR luminosity. This may be explained by the lack of far-IR constraints around and above ∼150 μm (rest-frame) before Herschel on those templates. We also note that the dust temperature of luminous IR galaxies (LIRGs, L IR ≥ 10 11 L ) around z ∼ 1 is mildly colder by 10-15% than their local analogs and up to 20% for ULIRGs at z ∼ 1.6 (using a single modified blackbody-fit to the peak far-IR emission with an emissivity index of β = 1.5). Above z = 1.5, distant galaxies are found to exhibit a substantially larger mid-over far-IR ratio, which could either result from stronger broad emission lines or warm dust continuum heated by a hidden AGN. Two thirds of the AGNs identified in the field with a measured redshift exhibit the same behavior as purely star-forming galaxies. Hence a large fraction of AGNs harbor coeval star formation at very high SFR and in conditions similar to purely star-forming galaxies.