arXiv subjects

P. Andreani

Publications and source records attributed to P. Andreani.

At least 55 records · Page 3Linked to original sources

arXiv2015

ALMA imaging of SDP.81 - I. A pixelated reconstruction of the far-infrared continuum emission

We present a sub-50 pc-scale analysis of the gravitational lens system SDP.81 at redshift 3.042 using Atacama Large Millimetre/submillimetre Array (ALMA) science verification data. We model both the mass distribution of the gravitational lensing galaxy and the pixelated surface brightness distribution of the background source using a novel Bayesian technique that fits the data directly in visibility space. We find the 1 and 1.3 mm dust emission to be magnified by a factor of u_tot = 17.6+/-0.4, giving an intrinsic total star-formation rate of 315+/-60 M_sol/yr and a dust mass of 6.4+/-1.5*10^8 M_sol. The reconstructed dust emission is found to be non-uniform, but composed of multiple regions that are heated by both diffuse and strongly clumped star-formation. The highest surface brightness region is a ~1.9*0.7 kpc disk-like structure, whose small extent is consistent with a potential size-bias in gravitationally lensed starbursts. Although surrounded by extended star formation, with a density of 20-30+/-10 M_sol/yr/kpc^2, the disk contains three compact regions with densities that peak between 120-190+/-20 M_sol/yr/kpc^2. Such star-formation rate densities are below what is expected for Eddington-limited star-formation by a radiation pressure supported starburst. There is also a tentative variation in the spectral slope of the different star-forming regions, which is likely due to a change in the dust temperature and/or opacity across the source.

astro-ph.GA↗

arXiv2015

An Overview of the 2014 ALMA Long Baseline Campaign

A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions of tens of milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up to ~15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from September to late November 2014, culminating in end-to-end observations, calibrations, and imaging of selected Science Verification (SV) targets. This paper presents an overview of the campaign and its main results, including an investigation of the short-term coherence properties and systematic phase errors over the long baselines at the ALMA site, a summary of the SV targets and observations, and recommendations for science observing strategies at long baselines. Deep ALMA images of the quasar 3C138 at 97 and 241 GHz are also compared to VLA 43 GHz results, demonstrating an agreement at a level of a few percent. As a result of the extensive program of LBC testing, the highly successful SV imaging at long baselines achieved angular resolutions as fine as 19 mas at ~350 GHz. Observing with ALMA on baselines of up to 15 km is now possible, and opens up new parameter space for submm astronomy.

astro-ph.IM↗

arXiv2015

ALMA Observations of Asteroid 3 Juno at 60 Kilometer Resolution

We present Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum images of the asteroid 3 Juno obtained with an angular resolution of 0.042 arcseconds (60 km at 1.97 AU). The data were obtained over a single 4.4 hr interval, which covers 60% of the 7.2 hr rotation period, approximately centered on local transit. A sequence of ten consecutive images reveals continuous changes in the asteroid's profile and apparent shape, in good agreement with the sky projection of the three-dimensional model of the Database of Asteroid Models from Inversion Techniques. We measure a geometric mean diameter of 259pm4 km, in good agreement with past estimates from a variety of techniques and wavelengths. Due to the viewing angle and inclination of the rotational pole, the southern hemisphere dominates all of the images. The median peak brightness temperature is 215pm13 K, while the median over the whole surface is 197pm15 K. With the unprecedented resolution of ALMA, we find that the brightness temperature varies across the surface with higher values correlated to the subsolar point and afternoon areas, and lower values beyond the evening terminator. The dominance of the subsolar point is accentuated in the final four images, suggesting a reduction in the thermal inertia of the regolith at the corresponding longitudes, which are possibly correlated to the location of the putative large impact crater. These results demonstrate ALMA's potential to resolve thermal emission from the surface of main belt asteroids, and to measure accurately their position, geometric shape, rotational period, and soil characteristics.

astro-ph.EP↗

arXiv2015

First Results from High Angular Resolution ALMA Observations Toward the HL Tau Region

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission from the HL Tau region. The continuum images at wavelengths of 2.9, 1.3, and 0.87 mm have unprecedented angular resolutions of 0.075 arcseconds (10 AU) to 0.025 arcseconds (3.5 AU), revealing an astonishing level of detail in the circumstellar disk surrounding the young solar analogue HL Tau, with a pattern of bright and dark rings observed at all wavelengths. By fitting ellipses to the most distinct rings, we measure precise values for the disk inclination (46.72pm0.05 degrees) and position angle (+138.02pm0.07 degrees). We obtain a high-fidelity image of the 1.0 mm spectral index ($α$), which ranges from $α\sim2.0$ in the optically-thick central peak and two brightest rings, increasing to 2.3-3.0 in the dark rings. The dark rings are not devoid of emission, we estimate a grain emissivity index of 0.8 for the innermost dark ring and lower for subsequent dark rings, consistent with some degree of grain growth and evolution. Additional clues that the rings arise from planet formation include an increase in their central offsets with radius and the presence of numerous orbital resonances. At a resolution of 35 AU, we resolve the molecular component of the disk in HCO+ (1-0) which exhibits a pattern over LSR velocities from 2-12 km/s consistent with Keplerian motion around a ~1.3 solar mass star, although complicated by absorption at low blue-shifted velocities. We also serendipitously detect and resolve the nearby protostars XZ Tau (A/B) and LkHa358 at 2.9 mm.

astro-ph.SR↗

arXiv2015

ALMA Long Baseline Observations of the Strongly Lensed Submillimeter Galaxy HATLAS J090311.6+003906 at z=3.042

We present initial results of very high resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the $z$=3.042 gravitationally lensed galaxy HATLAS J090311.6+003906 (SDP.81). These observations were carried out using a very extended configuration as part of Science Verification for the 2014 ALMA Long Baseline Campaign, with baselines of up to 15 km. We present continuum imaging at 151, 236 and 290 GHz, at unprecedented angular resolutions as fine as 23 milliarcseconds (mas), corresponding to an un-magnified spatial scale of ~180 pc at z=3.042. The ALMA images clearly show two main gravitational arc components of an Einstein ring, with emission tracing a radius of ~1.5". We also present imaging of CO(10-9), CO(8-7), CO(5-4) and H2O line emission. The CO emission, at an angular resolution of ~170 mas, is found to broadly trace the gravitational arc structures but with differing morphologies between the CO transitions and compared to the dust continuum. Our detection of H2O line emission, using only the shortest baselines, provides the most resolved detection to date of thermal H2O emission in an extragalactic source. The ALMA continuum and spectral line fluxes are consistent with previous Plateau de Bure Interferometer and Submillimeter Array observations despite the impressive increase in angular resolution. Finally, we detect weak unresolved continuum emission from a position that is spatially coincident with the center of the lens, with a spectral index that is consistent with emission from the core of the foreground lensing galaxy.

astro-ph.GA↗

arXiv2015

Extragalactic sources in Cosmic Microwave Background maps

We discuss the potential of a next generation space-borne CMB experiment for studies of extragalactic sources with reference to COrE+, a project submitted to ESA in response to the M4 call. We consider three possible options for the telescope size: 1m, 1.5m and 2m (although the last option is probably impractical, given the M4 boundary conditions). The proposed instrument will be far more sensitive than Planck and will have a diffraction-limited angular resolution. These properties imply that even the 1m telescope option will perform substantially better than Planck for studies of extragalactic sources. The source detection limits as a function of frequency have been estimated by means of realistic simulations. The most significant improvements over Planck results are presented for each option. COrE+ will provide much larger samples of truly local star-forming galaxies, making possible analyses of the properties of galaxies (luminosity functions, dust mass functions, star formation rate functions, dust temperature distributions, etc.) across the Hubble sequence. Even more interestingly, COrE+ will detect, at |b|> 30 deg, thousands of strongly gravitationally lensed galaxies. Such large samples are of extraordinary astrophysical and cosmological value in many fields. Moreover, COrE+ high frequency maps will be optimally suited to pick up proto-clusters of dusty galaxies, i.e. to investigate the evolution of large scale structure at larger redshifts than can be reached by other means. Thanks to its high sensitivity COrE+ will also yield a spectacular advance in the blind detection of extragalactic sources in polarization. This will open a new window for studies of radio source polarization and of the global properties of magnetic fields in star forming galaxies and of their relationships with SFRs.

astro-ph.CO↗

arXiv2014

A Multiwavelength Consensus on the Main Sequence of Star-Forming Galaxies at z~2

We compare various star formation rate (SFR) indicators for star-forming galaxies at $1.4<z<2.5$ in the COSMOS field. The main focus is on the SFRs from the far-IR (PACS-Herschel data) with those from the ultraviolet, for galaxies selected according to the BzK criterion. FIR-selected samples lead to a vastly different slope of the SFR-stellar mass ($M_*$) relation, compared to that of the dominant main sequence population as measured from the UV, since the FIR selection picks predominantly only a minority of outliers. However, there is overall agreement between the main sequences derived with the two SFR indicators, when stacking on the PACS maps the BzK-selected galaxies. The resulting logarithmic slope of the SFR-{$M_*$} relation is $\sim0.8-0.9$, in agreement with that derived from the dust-corrected UV-luminosity. Exploiting deeper 24$μ$m-Spitzer data we have characterized a sub-sample of galaxies with reddening and SFRs poorly constrained, as they are very faint in the $B$ band. The combination of Herschel with Spitzer data have allowed us to largely break the age/reddening degeneracy for these intriguing sources, by distinguishing whether a galaxy is very red in B-z because of being heavily dust reddened, or whether because star formation has been (or is being) quenched. Finally, we have compared our SFR(UV) to the SFRs derived by stacking the radio data and to those derived from the H$α$ luminosity of a sample of star-forming galaxies at $1.4<z<1.7$. The two sets of SFRs are broadly consistent as they are with the SFRs derived from the UV and by stacking the corresponding PACS data in various mass bins.

astro-ph.GA↗

arXiv2014

The bivariate K-band-submillimetre luminosity functions of the local HRS galaxy sample

We study the relationship between the K-band and the sub-millimetre (submm) emissions of nearby galaxies by computing the bivariate K-band-submm luminosity function (BLF) of the Herschel Reference Survey (HRS), a volume-limited sample observed in submm with Hersche/SPIRE. We derive the BLF from the K-band and submm cumulative distributions using a copula method. Using the BLF allows us to derive the relationship between the luminosities on more solid statistical ground. The analysis shows that over the whole HRS sample, no statistically meaningful conclusion can be derived for any relationship between the K-band and the submm luminosity. However, a very tight relationship between these luminosities is highlighted, by restricting our analysis to late-type galaxies. The luminosity function of late-type galaxies computed in the K-band and in the submm are dependent and the dependence is caused by the link, between the stellar mass and the cold dust mass, which has been already observed

astro-ph.CO↗

arXiv2014

Relativistic cosmology number densities in void-Lemaitre-Tolman-Bondi models

The goal of this work is to compute the number density of far-IR selected galaxies in the comoving frame and along the past lightcone of observationally constrained LTB models and to compare those results with their standard model counterparts. We derived integral number densities and differential number densities using different cosmological distance definitions in the LTB models. Then, we computed selection functions and consistency functions for the luminosity functions in the combined fields of the Herschel/PACS evolutionary probe (PEP) survey in both standard and void cosmologies, from which we derived the observed values of the above-mentioned densities. We used the Kolmogorov-Smirnov statistics to study both the evolution of the consistency functions and its connection to the evolution of the comoving density of sources. Finally, we fitted the power-law behaviour of the densities along the observer's past lightcone. The analysis of the comoving number density shows that the increased flexibility of the LTB models is not enough to fit the observed redshift evolution of the number counts, if it is specialised to a recent best-fit giant void parametrisation. The results for the power-law fits of the densities along the observer's past lightcone show general agreement across both cosmological models studied here around a slope of -2.5 $\pm$ 0.1 for the integral number density on the luminosity-distance volumes. The differential number densities show much bigger slope discrepancies. We conclude that the differential number densities on the observer's past lightcone were still rendered dependent on the cosmological model by the flux limits of the PEP survey. In addition, we show that an intrinsic evolution of the sources must be assumed to fit the comoving number-density redshift evolution in the giant void parametrisation for the LTB models used in this work.

astro-ph.CO↗

arXiv2014

Karl G. Jansky Very Large Array observations of cold dust and molecular gas in starbursting quasar host galaxies at z~4.5

We present Karl G. Jansky Very Large Array (VLA) observations of 44 GHz continuum and CO J=2-1 line emission in BR1202-0725 at z=4.7 (a starburst galaxy and quasar pair) and BRI1335-0417 at z=4.4 (also hosting a quasar). With the full 8 GHz bandwidth capabilities of the upgraded VLA, we study the (rest-frame) 250 GHz thermal dust continuum emission for the first time along with the cold molecular gas traced by the Low-J CO line emission. The measured CO J=2-1 line luminosities of BR1202-0725 are L'(CO) = (8.7+/-0.8)x10^10 K km/s pc^2 and L'(CO) = (6.0+/-0.5)x10^10 K km/s pc^2 for the submm galaxy (SMG) and quasar, which are equal to previous measurements of the CO J=5-4 line luminosities implying thermalized line emission and we estimate a combined cold molecular gas mass of ~9x10^10 Msun. In BRI1335-0417 we measure L'(CO) = (7.3+/-0.6)x10^10 K km/s pc^2. We detect continuum emission in the SMG BR1202-0725 North (S(44GHz) = 51+/-6 microJy), while the quasar is detected with S(44GHz) = 24+/-6 microJy and in BRI1335-0417 we measure S(44GHz) = 40+/-7 microJy. Combining our continuum observations with previous data at (rest-frame) far-infrared and cm-wavelengths, we fit three component models in order to estimate the star-formation rates. This spectral energy distribution fitting suggests that the dominant contribution to the observed 44~GHz continuum is thermal dust emission, while either thermal free-free or synchrotron emission contributes less than 30%.

astro-ph.GA↗

arXiv2013

The evolution of the dust and gas content in galaxies

We use deep Herschel PACS and SPIRE observations in GOODSS, GOODSN and COSMOS to estimate the average dust mass (Mdust) of galaxies on a redshift-stellar mass (Mstar)-SFR grid. We study the scaling relations between Mdust, Mstar and SFR at z<=2.5. No clear evolution of Mdust is observed at fixed SFR and Mstar. We find a tight correlation between SFR and Mdust, likely a consequence of the Schmidt-Kennicutt (S-K) law. The Mstar-Mdust correlation observed by previous works flattens or sometimes disappears when fixing the SFR. Most of it likely derives from the combination of the Mdust-SFR and Mstar-SFR correlations. We then investigate the gas content as inferred by converting Mdust by assuming that the dust/gas ratio scales linearly with the gas metallicity. All galaxies in the sample follow, within uncertainties, the same SFR-Mgas relation (integrated S-K law), which broadly agrees with CO-based results for the bulk of the population, despite the completely different approaches. The majority of galaxies at z~2 form stars with an efficiency (SFE=SFR/Mgas) ~5 times higher than at z~0. It is not clear what fraction of such variation is an intrinsic redshift evolution and what fraction arises from selection effects. The gas fraction (fgas) decreases with Mstar and increases with SFR, and does not evolve with z at fixed Mstar and SFR. We explain these trends by introducing a universal relation between fgas, Mstar and SFR, non-evolving out to z~2.5. Galaxies move across this relation as their gas content evolves in time. We use the 3D fundamental fgas-Mstar-SFR relation and the redshift evolution of the Main Sequence to estimate the evolution of fgas in the average population of galaxies as a function of z and Mstar, and we find evidence a downsizing scenario.

astro-ph.CO↗

arXiv2013

The evolution of the dust temperatures of galaxies in the SFR$-M_{\ast}$ plane up to $z$$\,\thicksim\,$$2$

[Abridged] We study the evolution of the dust temperatures of galaxies in the SFR-M* plane up to z~2 using observations from the Herschel Space Observatory. 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 Tdust of each SFR-M*-z bin. Dust temperatures are inferred using the stacked far-infrared flux densities of our SFR-M*-z bins. At all redshifts, Tdust increases with 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., D_SSFR_MS=log[SSFR(galaxy)/SSFR_MS(M*,z)]). The Tdust-SSFR and Tdust-D_SSFR_MS correlations are statistically more significant than the Tdust-LIR one. While the slopes of these three correlations are redshift-independent, their normalizations evolve from z=0 and z~2. We convert these results into a recipe to derive Tdust from SFR, M* and z. The existence of a strong Tdust-D_SSFR_MS correlation provides us with information on the dust and gas content of galaxies. (i) The slope of the Tdust-D__SSFR_MS correlation can be explained by the increase of the star-formation efficiency (SFE; SFR/Mgas) with D_SSFR_MS as found locally by molecular gas studies. (ii) At fixed D_SSFR_MS, the constant Tdust observed in galaxies probing large ranges in SFR and M* can be explained by an increase or decrease of the number of star-forming regions with comparable SFE enclosed in them. (iii) At high redshift, the normalization towards hotter temperature of the Tdust-D_SSFR_MS correlation can be explained by the decrease of the metallicities of galaxies or by the increase of 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.

astro-ph.CO↗

arXiv2013

Cosmological model dependence of the galaxy luminosity function: far-infrared results in the Lemaitre-Tolman-Bondi model

This is the first paper of a series aiming at investigating galaxy formation and evolution in the giant-void class of the Lemaitre-Tolman-Bondi (LTB) models that best fits current cosmological observations. Here we investigate the Luminosity Function (LF) methodology, and how its estimates would be affected by a change on the cosmological model assumed in its computation. Are the current observational constraints on the allowed Cosmology enough to yield robust LF results? We use the far-infrared source catalogues built on the observations performed with the Herschel/PACS instrument, and selected as part of the PACS evolutionary probe (PEP) survey. Schechter profiles are obtained in redshift bins up to z approximately 4, assuming comoving volumes in both the standard model, that is, Friedmann-Lemaitre-Robertson-Walker metric with a perfect fluid energy-momentum tensor, and non-homogeneous LTB dust models, parametrized to fit the current combination of results stemming from the observations of supernovae Ia, the cosmic microwave background, and baryonic acoustic oscillations. We find that the luminosity functions computed assuming both the standard model and LTB void models show in general good agreement. However, the faint-end slope in the void models shows a significant departure from the standard model up to redshift 0.4. We demonstrate that this result is not artificially caused by the used LF estimator which turns out to be robust under the differences in matter-energy density profiles of the models. The differences found in the LF slopes at the faint end are due to variation in the luminosities of the sources, which depend on the geometrical part of the model. It follows that either the standard model is over-estimating the number density of faint sources or the void models are under-estimating it.

astro-ph.CO↗

arXiv2013

The Herschel PEP/HerMES Luminosity Function. I: Probing the Evolution of PACS selected Galaxies to z~4

We exploit the deep and extended far infrared data sets (at 70, 100 and 160 um) of the Herschel GTO PACS Evolutionary Probe (PEP) Survey, in combination with the HERschel Multi tiered Extragalactic Survey (HerMES) data at 250, 350 and 500 um, to derive the evolution of the restframe 35 um, 60 um, 90 um, and total infrared (IR) luminosity functions (LFs) up to z~4. We detect very strong luminosity evolution for the total IR LF combined with a density evolution. In agreement with previous findings, the IR luminosity density increases steeply to z~1, then flattens between z~1 and z~3 to decrease at z greater than 3. Galaxies with different SEDs, masses and sSFRs 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 the IR luminosity density. Galaxies occupying the well established SFR/stellar mass main sequence (MS) are found to dominate both the total IR LF and luminosity density at all redshifts, with the contribution from off MS sources (0.6 dex above MS) being nearly constant (~20% of the total IR luminosity density) and showing no significant signs of increase with increasing z over the whole 0.8<z<2.2 range. Sources with mass in the 10< log(M/Msun) <11 range are found to dominate the total IR LF, with more massive galaxies prevailing at the bright end of the high-z LF. A two-fold evolutionary scheme for IR galaxies is envisaged: on the one hand, a starburst-dominated phase in which the SMBH grows and is obscured by dust, is followed by an AGN dominated phase, then evolving toward a local elliptical. On the other hand, moderately starforming 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.

astro-ph.CO↗

arXiv2013

Lyman break and UV-selected galaxies at z ~ 1: II. PACS-100um/160um FIR detections

We report the PACS-100um/160um detections of a sample of 42 GALEX-selected and FIR-detected Lyman break galaxies (LBGs) at z ~ 1 located in the COSMOS field and analyze their ultra-violet (UV) to far-infrared (FIR) properties. The detection of these LBGs in the FIR indicates that they have a dust content high enough so that its emission can be directly detected. According to a spectral energy distribution (SED) fitting with stellar population templates to their UV-to-near-IR observed photometry, PACS-detected LBGs tend to be bigger, more massive, dustier, redder in the UV continuum, and UV-brighter than PACS-undetected LBGs. PACS-detected LBGs at z ~ 1 are mostly disk-like galaxies and are located over the green-valley and red sequence of the color-magnitude diagram of galaxies at their redshift. By using their UV and IR emission, we find that PACS-detected LBGs tend to be less dusty and have slightly higher total star-formation rates (SFRs) than other PACS-detected UV-selected galaxies within their same redshift range. As a consequence of the selection effect due to the depth of the FIR observations employed, all our PACS-detected LBGs are LIRGs. However, none of them are in the ULIRG regime, where the FIR observations are complete. The finding of ULIRGs-LBGs at higher redshifts suggests an evolution of the FIR emission of LBGs with cosmic time. In an IRX-$β$ diagram, PACS-detected LBGs at z ~ 1 tend to be located around the relation for local starburst similarly to other UV-selected PACS-detected galaxies at their same redshift. Consequently, the dust-correction factors obtained with their UV continuum slope allow to determine their total SFR, unlike at higher redshifts. However, the dust attenuation derived from UV to NIR SED fitting overestimates the total SFR for most of our PACS-detected LBGs in age-dependent way: the overestimation factor is higher in younger galaxies.

astro-ph.CO↗

arXiv2013

An approach for the detection of point-sources in very high resolution microwave maps

This paper deals with the detection problem of extragalactic point-sources in multi-frequency, microwave sky maps that will be obtainable in future cosmic microwave background radiation (CMB) experiments with instruments capable of very high spatial resolution. With spatial resolutions that can be of order of 0.1-1.0 arcsec or better, the extragalactic point-sources will appear isolated. The same holds also for the compact structures due to the Sunyaev-Zeldovich (SZ) effect (both thermal and kinetic). This situation is different from the maps obtainable with instruments as WMAP or PLANCK where, because of the smaller spatial resolution (approximately 5-30 arcmin), the point-sources and the compact structures due to the SZ effect form a uniform noisy background (the "confusion noise"). Hence, the point-source detection techniques developed in the past are based on the assumption that all the emissions that contribute to the microwave background can be modeled with homogeneous and isotropic (often Gaussian) random fields and make use of the corresponding spatial power-spectra. In the case of very high resolution observations such an assumption cannot be adopted since it still holds only for the CMB. Here, we propose an approach based on the assumption that the diffuse emissions that contribute to the microwave background can be locally approximated by two-dimensional low order polynomials. In particular, two sets of numerical techniques are presented containing two different algorithms each. The performance of the algorithms is tested with numerical experiments that mimic the physical scenario expected for high Galactic latitude observations with the Atacama Large Millimeter/Submillimeter Array (ALMA).

astro-ph.IM↗

arXiv2013

The Herschel-PEP survey: evidence for downsizing in the hosts of dusty star-forming systems

By making use of Herschel-PEP observations of the COSMOS and Extended Groth Strip fields, we have estimated the dependence of the clustering properties of FIR-selected sources on their 100um fluxes. Our analysis shows a tendency for the clustering strength to decrease with limiting fluxes: r0(S100um >8 mJy)~4.3 Mpc and r0(S100um >5 mJy)~5.8 Mpc. These values convert into minimum halo masses Mmin~10^{11.6} Msun for sources brighter than 8 mJy and Mmin~10^{12.4} Msun for S100um > 5 mJy galaxies. We show such an increase of the clustering strength to be due to an intervening population of z~2 sources, which are very strongly clustered and whose relative contribution, equal to about 10% of the total counts at S100um > 2 mJy, rapidly decreases for brighter flux cuts. By removing such a contribution, we find that z <~ 1 FIR galaxies have approximately the same clustering properties, irrespective of their flux level. The above results were then used to investigate the intrinsic dependence on cosmic epoch of the clustering strength of dusty star-forming galaxies between z~0 and z~2.5. In order to remove any bias in the selection process, the adopted sample only includes galaxies observed at the same rest-frame wavelength, lambda~60 um, which have comparable luminosities and therefore star-formation rates (SFR>~100 Msun/yr). Our analysis shows that the same amount of (intense) star forming activity takes place in extremely different environments at the different cosmological epochs. For z<~1 the hosts of such star forming systems are small, Mmin~10^{11} Msun, isolated galaxies. High (z~2) redshift star formation instead seems to uniquely take place in extremely massive/cluster-like halos, Mmin~10^{13.5} Msun, which are associated with the highest peaks of the density fluctuation field at those epochs. (abridged)

astro-ph.CO↗

arXiv2013

The deepest Herschel-PACS far-infrared survey: number counts and infrared luminosity functions from combined PEP/GOODS-H observations

We present results from the deepest Herschel-PACS (Photodetector Array Camera and Spectrometer) far-infrared blank field extragalactic survey, obtained by combining observations of the GOODS (Great Observatories Origins Deep Survey) fields from the PACS Evolutionary Probe (PEP) and GOODS-Herschel key programmes. We describe data reduction and the construction of images and catalogues. In the deepest parts of the GOODS-S field, the catalogues reach 3-sigma depths of 0.9, 0.6 and 1.3 mJy at 70, 100 and 160 um, respectively, and resolve ~75% of the cosmic infrared background at 100um and 160um into individually detected sources. We use these data to estimate the PACS confusion noise, to derive the PACS number counts down to unprecedented depths and to determine the infrared luminosity function of galaxies down to LIR=10^11 Lsun at z~1 and LIR=10^12 Lsun at z~2, respectively. For the infrared luminosity function of galaxies, our deep Herschel far-infrared observations are fundamental because they provide more accurate infrared luminosity estimates than those previously obtained from mid-infrared observations. Maps and source catalogues (>3-sigma) are now publicly released. Combined with the large wealth of multi-wavelength data available for the GOODS fields, these data provide a powerful new tool for studying galaxy evolution over a broad range of redshifts.

astro-ph.CO↗