Eva Schinnerer

THE CHANDRA COSMOS LEGACY SURVEY: OPTICAL/IR IDENTIFICATIONS

We present the catalog of optical and infrared counterparts of the Chandra COSMOS-Legacy Survey, a 4.6 Ms Chandra program on the 2.2 deg2 of the COSMOS field, combination of 56 new overlapping observations obtained in Cycle 14 with the previous C-COSMOS survey. In this Paper we report the i, K, and 3.6 μm identifications of the 2273 X-ray point sources detected in the new Cycle 14 observations. We use the likelihood ratio technique to derive the association of optical/infrared (IR) counterparts for 97% of the X-ray sources. We also update the information for the 1743 sources detected in C-COSMOS, using new K and 3.6 μm information not available when the C-COSMOS analysis was performed. The final catalog contains 4016 X-ray sources, 97% of which have an optical/IR counterpart and a photometric redshift, while sime54% of the sources have a spectroscopic redshift. The full catalog, including spectroscopic and photometric redshifts and optical and X-ray properties described here in detail, is available online. We study several X-ray to optical (X/O) properties: with our large statistics we put better constraints on the X/O flux ratio locus, finding a shift toward faint optical magnitudes in both soft and hard X-ray band. We confirm the existence of a correlation between X/O and the the 2–10 keV luminosity for Type 2 sources. We extend to low luminosities the analysis of the correlation between the fraction of obscured AGNs and the hard band luminosity, finding a different behavior between the optically and X-ray classified obscured fraction.

The Host Galaxies of Optically Bright Quasi-stellar Objects: Molecular Gas in [CLC][ITAL]z[/ITAL][/CLC] ≤ 0.1 Palomar-Green Quasi-stellar Objects

We present results of a CO (1-0) line survey in a complete sample of 12 low-redshift (z ≤ 0.1), optically bright Palomar-Green quasi-stellar objects (PG QSOs with MB ≤ -23 mag). Six new CO detections are reported here at levels exceeding ICO 2 Jy km s-1. Combined with three previously reported detections, we find that nine of the 12 QSOs have abundant, dense interstellar medium (ISM) characteristic of late-type galaxies. In all nine of the detected QSOs, the derived molecular gas masses are M ≥ 1.0 × 109 M☉, with the most massive being 1010 M☉ (PG 0050+124; I Zw 1). In the three sources not yet detected in CO, the upper limits on the gas masses are ~109 M☉, and thus we cannot rule out abundant ISMs even in these objects. Since our sample was chosen entirely on the basis of low redshift and optical luminosity (and not selected for strong infrared emission), we conclude that the majority of luminous, low-redshift QSOs have gas-rich host galaxies and therefore cannot be normal elliptical galaxies.We present results of a CO(1-0) line survey in a complete sample of 12 low redshift (Z 1.0e9 M_solar, with the most massive being 1e10 M_solar ~(PG 0050+124 -- I Zw 1). In the three sources not yet detected in CO, the upper limits on the gas masses are ~ 1e9 M_solar and thus we cannot rule out abundant ISMs even in these objects. Since our sample was chosen entirely on the basis of low redshift and optical luminosity (and not selected for strong infrared emission), we conclude that the majority of luminous, low redshift QSOs have gas-rich host galaxies and therefore can not be normal elliptical galaxies.

The faint radio sky: VLBA observations of the COSMOS field

We study the faint radio population using wide-field very long baseline interferometry (VLBI) observations of 2865 known radio sources in the Cosmic Evolution Survey (COSMOS) field. The main objective of the project was to determine where active galactic nuclei (AGN) are present. The combination of number of sources, sensitivity, angular resolution and area covered by this project are unprecedented. We have detected 468 radio sources, expected to be AGNs, with the Very Long Baseline Array (VLBA) at 1.4 GHz. This is, to date, the largest sample assembled of VLBI detected sources in the sub-mJy regime. The input sample was taken from previous observations with the Very Large Array (VLA). We present the catalogue with additional multiwavelength information. We find a detection fraction of 20%, considering only those sources from the input catalogue which were in principle detectable with the VLBA (2361). As a function of redshift, we see no evolution of the detection fraction over the redshift range 0.5 1.5 we find that spiral galaxies become the most prevalent (48%). We demonstrate that wide-field VLBI observations, together with new calibration methods such as multi-source self-calibration and mosaicing, result in information which is difficult or impossible to obtain otherwise.

Variation in the dust spectral index across M33

Using the Herschel PACS and SPIRE FIR/submm data, we investigate variations in the dust spectral index β in the nearby spiral galaxy M33 at a linear resolution of 160 pc. We use an iteration method in two different approaches, single and two-component modified black body models. In both approaches, β is higher in the central disk than in the outer disk similar to the dust temperature. There is a positive correlation between β and Hα as well as with the molecular gas traced by CO(2-1). A Monte-Carlo simulation shows that the physical parameters are better constrained when using the two-component model.

The Spitzer Legacy Survey of the HST-ACS 2 sq. deg. COSMOS Field: survey strategy and first analysis

The Spitzer-COSMOS survey (S-COSMOS) is a Legacy program (Cycles 2+3) designed to carry out a uniform deep survey of the full 2 sq deg COSMOS field in all seven Spitzer bands (3.6, 4.5, 5.6, 8.0, 24.0, 70.0, 160.0 u). This paper describes the survey parameters, mapping strategy, data reduction procedures, achieved sensitivities to date, and the complete data set for future reference. We show that the observed infrared backgrounds in the S-COSMOS field are within 10% of the predicted background levels. The fluctuations in the background at 24u have been measured and do not show any significant contribution from cirrus, as expected. In addition, we report on the number of asteroid detections in the low galactic latitude COSMOS field. We use the Cycle 2 S-COSMOS data to determine preliminary number counts, and compare our results with those from previous Spitzer Legacy surveys (e.g. SWIRE, GOODS). The results from this first analysis confirm that the S-COSMOS survey will have sufficient sensitivity with IRAC to detect ~ L* disks and spheroids out to z ~ 3, and with MIPS to detect ultraluminous starbursts and AGN out to z ~3 at 24u and out to z ~1.5-2 at 70u and 160u.

Constraints on submicrojansky radio number counts based on evolving VLA-COSMOS luminosity functions

We present an investigation of radio luminosity functions (LFs) and number counts based on the Karl G. Jansky Very Large Array-COSMOS 3 GHz Large Project. The radio-selected sample of 7826 galaxies with robust optical/near-infrared counterparts with excellent photometric coverage allows us to construct the total radio LF since z~5.7. Using the Markov chain Monte Carlo algorithm, we fit the redshift dependent pure luminosity evolution model to the data and compare it with previously published VLA-COSMOS LFs obtained on individual populations of radio-selected star-forming galaxies and galaxies hosting active galactic nuclei classified on the basis of presence or absence of a radio excess with respect to the star-formation rates derived from the infrared emission. We find they are in excellent agreement, thus showing the reliability of the radio excess method in selecting these two galaxy populations at radio wavelengths. We study radio number counts down to submicrojansky levels drawn from different models of evolving LFs. We show that our evolving LFs are able to reproduce the observed radio sky brightness, even though we rely on extrapolations toward the faint end. Our results also imply that no new radio-emitting galaxy population is present below 1 ujy. Our work suggests that selecting galaxies with radio flux densities between 0.1 and 10 ujy will yield a star-forming galaxy in 90-95 % of the cases with a high percentage of these galaxies existing around a redshift of z~2, thus providing useful constraints for planned surveys with the Square Kilometer Array and its precursors.

VLBA+GBT observations of the COSMOS field and radio source counts at 1.4 GHz

We present very long baseline interferometry (VLBI) observations of 179 radio sources in the COSMOS field with extremely high sensitivity using the Green Bank Telescope (GBT) together with the Very Long Baseline Array (VLBA) (VLBA+GBT) at 1.4 GHz, to explore the faint radio population in the flux density regime of tens of

Probing star formation and ISM properties using galaxy disk inclination II: testing typical FUV attenuation corrections out to z~0.7

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Star-forming galaxies versus low- and high-excitation radio AGN in the VLA-COSMOS 3GHz Large Project

Jy. Here, the identification of active galactic nuclei (AGN) is based on the VLBI detection of the source, i.e., it is independent of X-ray or infrared properties. The milli-arcsecond resolution provided by the VLBI technique implies that the detected sources must be compact and have large brightness temperatures, and therefore they are most likely AGN (when the host galaxy is located at z

The VLA‐COSMOS 3 GHz Large Project: Cosmic star formation history since z similar to 5

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