Astrophysical and Cosmological Information from Large-scale sub-mm Surveys of Extragalactic Sources

We present a quantitative analysis of the astrophysical and cosmological information that can be extracted from the many important wide-area, shallow surveys that will be carried out in the next few years. Our calculations combine the predictions of the physical model by Granato et al. (2004) for the formation and evolution of spheroidal galaxies with up-to-date phenomenological models for the evolution of starburst and normal late-type galaxies and of radio sources. We compute the expected number counts and the redshift distributions of these source populations separately and then focus on proto-spheroidal galaxies. For the latter objects we predict the counts and redshift distributions of strongly lensed sources at 250, 350, 500, and 850 micron, the angular correlation function of sources detected in the surveys considered, the angular power spectra due to clustering of sources below the detection limit in Herschel and Planck surveys. An optimal survey for selecting strongly lensed proto-spheroidal galaxies is described, and it is shown how they can be easily distinguished from the other source populations. We also discuss the detectability of the imprints of the 1-halo and 2-halo regimes on angular correlation functions and clustering power spectra, as well as the constraints on cosmological parameters that can be obtained from the determinations of these quantities. The novel data relevant to derive the first sub-millimeter estimates of the local luminosity functions of starburst and late-type galaxies, and the constraints on the properties of rare source populations, such as blazars, are also briefly described.Comment: 16 pages, 10 figures. Accepted for publication on MNRA

Simulating the infrared sky with a S PRITZ

Aims. Current hydrodynamical and semi-empirical simulations of galaxy formation and evolution have difficulties in reproducing the number densities of infrared-detected galaxies. Therefore, a phenomenological simulation tool that is new and versatile is necessary to reproduce current and predict future observations at infrared (IR) wavelengths. Methods. In this work we generate simulated catalogues starting from the Herschel IR luminosity functions of different galaxy populations to consider different populations of galaxies and active galactic nuclei (AGN) in a consistent way. We associated a spectral energy distribution and physical properties, such as stellar mass, star formation rate, and AGN contribution, with each simulated galaxy using a broad set of empirical relations. We compared the resulting simulated galaxies, extracted up to z = 10, with a broad set of observational relations. Results. Spectro-Photometric Realisations of IR-Selected Targets at all-z (SPRITZ) simulations allow us to obtain, in a fully consistent way, simulated observations for a broad set of current and future facilities with photometric capabilities as well as low-resolution IR spectroscopy, such as the James Webb Space Telescope (JWST) or the Origin Space Telescope (OST). The derived simulated catalogue contains galaxies and AGN that by construction reproduce the observed IR galaxy number density, but this catalogue also agrees with the observed number counts from UV to far-IR wavelengths, the observed stellar mass function, the star formation rate versus stellar mass plane, and the luminosity function from the radio to X-ray wavelengths. The proposed simulation is therefore ideal to make predictions for current and future facilities, in particular, but not limited to, those operating at IR wavelengths

Simulating the infrared sky with a Spritz

Current hydrodynamical and semi-empirical simulations of galaxy formation and evolution have difficulties in reproducing the number densities of IR-detected galaxies. Therefore, a versatile, phenomenological new simulation tool is necessary to reproduce current and predict future observations at IR wavelengths. In this work we generate simulated catalogues starting from the Herschel infrared luminosity functions of different galaxy populations, in order to consider in a consistent way different populations of galaxies and active galactic nuclei. We associated a spectral energy distribution and physical properties, such as stellar mass, star-formation-rate and AGN contribution, to each simulated galaxy using a broad set of empirical relations. We compare the resulting simulated galaxies, extracted up to z$=$10, with a broad set of observational relations. The Spectro-Photometric Realisations of Infrared-selected Targets at all-z (SPRITZ) simulation will allow us to obtain in a fully consistent way simulated observations for a broad set of current and future facilities with photometric capabilities as well as low-resolution IR spectroscopy, like the James Webb Space Telescope (JWST) or the Origin Space Telescope (OST). The derived simulated catalogue contains galaxies and active galactic nuclei that by construction reproduce the observed IR galaxy number density, but it is also in agreement with the observed number counts from UV to far-IR wavelengths, the observed stellar mass function, the star-formation-rate vs. stellar mass plane and the luminosity function from the radio to the X-ray. The proposed simulation is therefore ideal to make predictions for current and future facilities, in particular, but not limited to, those operating at IR wavelengths. The SPRITZ simulation will be publicly available.Comment: Accepted for publication in A&A, 32 pages, 30 figure

Radio Observations of Star Forming Galaxies in the SKA era

We have combined determinations of the epoch-dependent star formation rate (SFR) function with relationships between SFR and radio (synchrotron and free-free) emission to work out detailed predictions for the counts and the redshift distributions of star-forming galaxies detected by planned Square Kilometer Array (SKA) surveys. The evolving SFR function comes from recent models fitting the far-infrared (FIR) to millimeter-wave luminosity functions and the ultraviolet (UV) luminosity functions up to z=10, extended to take into account additional UV survey data. We used very deep 1.4 GHz number counts from the literature to check the relationship between SFR and synchrotron emission, and the 95 GHz South Pole Telescope (SPT) counts of dusty galaxies to test the relationship between SFR and free-free emission. We show that the SKA will allow us to investigate the SFRs of galaxies down to few Msun/yr up to z=10, thus extending by more than two orders of magnitude the high-z SFR functions derived from Herschel surveys. SKA1-MID surveys, down to microJy levels, will detect hundreds of strongly lensed galaxies per square degree; a substantial fraction of them will show at least two images above the detection limits

Predictions for surveys with the SPICA Mid-infrared Instrument

We present predictions for number counts and redshift distributions of galaxies detectable in continuum and in emission lines with the Mid-infrared (MIR) Instrument (SMI) proposed for the Space Infrared Telescope for Cosmology and Astrophysics. We have considered 24 MIR fine-structure lines, four polycyclic aromatic hydrocarbon bands (at 6.2, 7.7, 8.6 and 11.3 mu m) and two silicate bands (in emission and in absorption) at 9.7 and 18.0 mu m. Six of these lines are primarily associated with active galactic nuclei (AGNs), the others with star formation. A survey with the SMI spectrometers of 1-h integration per field of view (FoV) over an area of 1 deg(2) will yield 5 sigma detections of similar or equal to 140 AGN lines and of similar or equal to 5.2 x 10(4) star-forming galaxies, similar or equal to 1.6 x 10(4) of which will be detected in at least two lines. The combination of a shallow (20.0 deg(2), 1.4 x 10(-1) h integration per FoV) and a deep survey (6.9 x 10(-3) deg(2), 635 h integration time), with the SMI camera, for a total of similar to 1000 h, will accurately determine the MIR number counts of galaxies and of AGNs over five orders of magnitude in flux density, reaching values more than one order of magnitude fainter than the deepest Spitzer 24 mu m surveys. This will allow us to determine the cosmic star formation rate (SFR) function down to SFRs more than 100 times fainter than reached by the Herschel Observatory

Extragalactic source contributions to arcminute-scale Cosmic Microwave Background anisotropies

The possible contributions of the various classes of extragalactic sources (including, in addition to the canonical radio sources, GHz Peaked Spectrum sources, advection-dominated sources, starburst galaxies, high-redshift proto-spheroidal galaxies) to the arcminute scale fluctuations measured by the CBI, BIMA, and ACBAR experiments are discussed. At 30 GHz, fluctuations due to radio sources undetected by ancillary low-frequency surveys may be higher than estimated by the CBI and BIMA groups. High-redshift dusty galaxies, whose fluctuations may be strongly enhanced by the effect of clustering, could contribute to the BIMA excess signal, and dominate at 150 GHz (the ACBAR frequency). Moreover, in the present data situation, the dust emission of these high-redshift sources set an unavoidable limit to the detection of primordial CMB anisotropies at high multipoles, even at frequencies as low as $\simeq 30$ GHz. It is concluded that the possibility that the excess power at high multipoles is dominated by unsubtracted extragalactic sources cannot be ruled out. On the other hand, there is room for a contribution from the Sunyaev-Zeldovich effect within clusters of galaxies, with a density fluctuation amplitude parameter $\sigma_8$ consistent with the values preferred by current data.Comment: 7 pages, 3 figures, A&A in pres

Forecasts on the contamination induced by unresolved point sources in primordial non-Gaussianity beyond Planck

In this paper we present forecasts of the contamination on different shapes of the primordial non-Gaussianity fnl parameter \u2013 detectable on future Cosmic Microwave Background (CMB) high\u2013resolution anisotropy maps \u2013 produced by unresolved ex- tragalactic point sources at frequencies of cosmological interest (45\u2013375 GHz). We consider two scenarios: an ideal (noiseless) mission and a possible future space-borne satellite, with instrumental characteristics similar to the ones proposed for the Cos- mic Origins Explorer (COrE). The local, equilateral, orthogonal and flat shapes are considered in both temperature (intensity) and polarized emission data. The angular power spectrum and bispectrum of extragalactic point sources are estimated by state- of-the-art models of source number counts. The impact of all the most relevant (far\u2013IR and radio selected) source populations on these shapes at COrE frequencies is studied. The results of this analysis show that unresolved extragalactic point sources should not induce a very relevant non-Gaussian signal in the frequency range 100\u2013200GHz, thus not preventing a correct estimate of the CMB primordial fnl parameter. Polariza- tion information allows one to significantly reduce the error\u2013bars in the fnl parameter and the bias induced by unresolved sources and, hence, to widen the range of frequen- cies for fnl studies. On the contrary, at \u3bd 225GHz, important non-Gaussian deviations in CMB anisotropy maps are expected due to unresolved extragalactic sources

Chandra and ALMA observations of the nuclear activity in two strongly lensed star-forming galaxies

Aim. According to coevolutionary scenarios, nuclear activity and star formation play relevant roles in the early stages of galaxy formation. We aim at identifying them in high-redshift galaxies by exploiting high-resolution and high-sensitivity X-ray and millimeter-wavelength data to confirm the presence or absence of star formation and nuclear activity and describe their relative roles in shaping the spectral energy distributions and in contributing to the energy budgets of the galaxies. Methods. We present the data, model, and analysis in the X-ray and millimeter (mm) bands for two strongly lensed galaxies, SDP.9 (HATLAS J090740.0-004200) and SDP.11 (HATLAS J091043.1-000322), which we selected in the Herschel-ATLAS catalogs for their excess emission in the mid-IR regime at redshift b3 1.5. This emission suggests nuclear activity in the early stages of galaxy formation. We observed both of them with Chandra ACIS-S in the X-ray regime and analyzed the high-resolution mm data that are available in the ALMA Science Archive for SDP.9. By combining the information available in mm, optical, and X-ray bands, we reconstructed the source morphology. Results. Both targets were detected in the X-ray, which strongly indicates highly obscured nuclear activity. ALMA observations for SDP.9 for the continuum and CO(6-5) spectral line with high resolution (0.02 arcsec corresponding to 3c65 pc at the distance of the galaxy) allowed us to estimate the lensed galaxy redshift to a better accuracy than pre-ALMA estimates (1.5753 \ub1 0.0003) and to model the emission of the optical, millimetric, and X-ray band for this galaxy. We demonstrate that the X-ray emission is generated in the nuclear environment, which strongly supports that this object has nuclear activity. On the basis of the X-ray data, we attempt an estimate of the black hole properties in these galaxies. Conclusions. By taking advantage of the lensing magnification, we identify weak nuclear activity associated with high-z galaxies with high star formation rates. This is useful to extend the investigation of the relationship between star formation and nuclear activity to two intrinsically less luminous high-z star-forming galaxies than was possible so far. Given our results for only two objects, they alone cannot constrain the evolutionary models, but provide us with interesting hints and set an observational path toward addressing the role of star formation and nuclear activity in forming galaxies

The far-infrared/radio correlation for a sample of strongly lensed dusty star-forming galaxies detected by Herschel

We investigate the radio/far-infrared (FIR) correlation for a sample of 28 bright high-redshift (1 z 4) star-forming galaxies selected in the FIR from the Herschel -ATLAS fields as candidates to be strongly gravitationally lensed. The radio information comes either from high sensitivity dedicated Australia Telescope Compact Array observations at 2.1 GHz or from cross-matches with the FIRST surv e y at 1.4 GHz. By taking advantage of source brightness possibly enhanced by lensing magnification, we identify a weak evolution with redshift out to z 4 of the FIR-to-radio luminosity ratio q FIR . We also find that the q FIR parameter as a function of the radio power L 1 . 4 GHz displays a clear decreasing trend, similarly to what is observed for optically/radio- selected lensed quasars found in literature, yet co v ering a complementary region in the q FIR –L 1 . 4 GHz diagram. We interpret such a behaviour in the framework of an in situ galaxy formation scenario, as a result of the transition from an early dust-obscured star-forming phase (mainly pinpointed by our FIR selection) to a late radio-loud quasar phase (preferentially sampled by the optical/radio selection)