- ID:
- ivo://CDS.VizieR/J/ApJS/235/17
- Title:
- NuSTAR Extragalactic Surveys: UDS field
- Short Name:
- J/ApJS/235/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results and the source catalog of the NuSTAR survey in the UKIDSS Ultra Deep Survey (UDS) field, bridging the gap in depth and area between NuSTAR's ECDFS and COSMOS surveys. The survey covers a ~0.6deg^2^ area of the field for a total observing time of ~1.75Ms, to a half-area depth of ~155ks corrected for vignetting at 3-24keV, and reaching sensitivity limits at half-area in the full (3-24keV), soft (3-8keV), and hard (8-24keV) bands of 2.2x10^-14^erg/cm^2^/s, 1.0x10^-14^erg/cm^2^/s, and 2.7x10^-14^erg/cm^2^/s, respectively. A total of 67 sources are detected in at least one of the three bands, 56 of which have a robust optical redshift with a median of <z>~1.1. Through a broadband (0.5-24keV) spectral analysis of the whole sample combined with the NuSTAR hardness ratios, we compute the observed Compton-thick (CT; N_H_>10^24^cm^-2^) fraction. Taking into account the uncertainties on each NH measurement, the final number of CT sources is 6.8+/-1.2. This corresponds to an observed CT fraction of 11.5%+/-2.0%, providing a robust lower limit to the intrinsic fraction of CT active galactic nuclei and placing constraints on cosmic X-ray background synthesis models.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/836/99
- Title:
- NuSTAR serendipitous survey: the 40-month catalog
- Short Name:
- J/ApJ/836/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first full catalog and science results for the Nuclear Spectroscopic Telescope Array (NuSTAR) serendipitous survey. The catalog incorporates data taken during the first 40 months of NuSTAR operation, which provide ~20Ms of effective exposure time over 331 fields, with an areal coverage of 13deg^2^, and 497 sources detected in total over the 3-24keV energy range. There are 276 sources with spectroscopic redshifts and classifications, largely resulting from our extensive campaign of ground-based spectroscopic follow-up. We characterize the overall sample in terms of the X-ray, optical, and infrared source properties. The sample is primarily composed of active galactic nuclei (AGNs), detected over a large range in redshift from z=0.002 to 3.4 (median of <z>=0.56), but also includes 16 spectroscopically confirmed Galactic sources. There is a large range in X-ray flux, from log(f_3-24keV_/erg/s/cm^2^)~-14 to -11, and in rest-frame 10-40keV luminosity, from log(L_10-40keV_/erg/s)~39 to 46, with a median of 44.1. Approximately 79% of the NuSTAR sources have lower-energy (<10keV) X-ray counterparts from XMM-Newton, Chandra, and Swift XRT. The mid-infrared (MIR) analysis, using WISE all-sky survey data, shows that MIR AGN color selections miss a large fraction of the NuSTAR-selected AGN population, from ~15% at the highest luminosities (L_X_>10^44^erg/s) to ~80% at the lowest luminosities (L_X_<10^43^erg/s). Our optical spectroscopic analysis finds that the observed fraction of optically obscured AGNs (i.e., the type 2 fraction) is F_Type2_=53_-15_^+14^% , for a well-defined subset of the 8-24keV selected sample. This is higher, albeit at a low significance level, than the type 2 fraction measured for redshift- and luminosity-matched AGNs selected by <10keV X-ray missions.
- ID:
- ivo://CDS.VizieR/J/ApJ/808/185
- Title:
- NuSTAR surveys: COSMOS catalog
- Short Name:
- J/ApJ/808/185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To provide the census of the sources contributing to the X-ray background peak above 10keV, Nuclear Spectroscopic Telescope Array (NuSTAR) is performing extragalactic surveys using a three-tier "wedding cake" approach. We present the NuSTAR survey of the COSMOS field, the medium sensitivity, and medium area tier, covering 1.7deg^2^ and overlapping with both Chandra and XMM-Newton data. This survey consists of 121 observations for a total exposure of ~3Ms. To fully exploit these data, we developed a new detection strategy, carefully tested through extensive simulations. The survey sensitivity at 20% completeness is 5.9, 2.9, and 6.4x10^-14^erg/cm^2^/s in the 3-24, 3-8, and 8-24keV bands, respectively. By combining detections in 3 bands, we have a sample of 91 NuSTAR sources with 10^42^-10^45.5^erg/cm^2^/s luminosities and redshift z=0.04-2.5. Thirty-two sources are detected in the 8-24keV band with fluxes ~100 times fainter than sources detected by Swift-BAT. Of the 91 detections, all but 4 are associated with a Chandra and/or XMM-Newton point-like counterpart. One source is associated with an extended lower energy X-ray source. We present the X-ray (hardness ratio and luminosity) and optical-to-X-ray properties. The observed fraction of candidate Compton-thick active galactic nuclei measured from the hardness ratio is between 13%-20%. We discuss the spectral properties of NuSTAR J100259+0220.6 (ID 330) at z=0.044, with the highest hardness ratio in the entire sample. The measured column density exceeds 10^24^/cm2, implying the source is Compton-thick. This source was not previously recognized as such without the >10keV data.
- ID:
- ivo://CDS.VizieR/J/ApJ/808/184
- Title:
- NuSTAR surveys: ECDF-S catalog
- Short Name:
- J/ApJ/808/184
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the initial results and the source catalog from the Nuclear Spectroscopic Telescope Array (NuSTAR) survey of the Extended Chandra Deep Field South (hereafter, ECDFS) --currently the deepest contiguous component of the NuSTAR extragalactic survey program. The survey covers the full ~30'x30' area of this field to a maximum depth of ~360ks (~220ks when corrected for vignetting at 3-24keV), reaching sensitivity limits of ~1.3x10^-14^erg/s/cm^2^ (3-8keV), ~3.4x10^-14^erg/s/cm^2^ (8-24keV), and ~3.0x10^-14^erg/s/cm^2^ (3-24keV). A total of 54 sources are detected over the full field, although five of these are found to lie below our significance threshold once contaminating flux from neighboring (i.e., blended) sources is taken into account. Of the remaining 49 that are significant, 19 are detected in the 8-24keV band. The 8-24 to 3-8keV band ratios of the 12 sources that are detected in both bands span the range 0.39-1.7, corresponding to a photon index range of {Gamma}~0.5-2.3, with a median photon index of {Gamma}{bar}=1.70+/-0.52. The redshifts of the 49 sources in our main sample span the range z=0.21-2.7, and their rest-frame 10-40keV luminosities (derived from the observed 8-24keV fluxes) span the range L_10-40keV_~(0.7-300)x10^43^erg/s, sampling below the "knee" of the X-ray luminosity function out to z~0.8-1. Finally, we identify one NuSTAR source that has neither a Chandra nor an XMM-Newton counterpart, but that shows evidence of nuclear activity at infrared wavelengths and thus may represent a genuine, new X-ray source detected by NuSTAR in the ECDFS.
- ID:
- ivo://CDS.VizieR/J/AJ/132/2014
- Title:
- NUV sources in CDF-S and HDF-N GOODS fields
- Short Name:
- J/AJ/132/2014
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an ultraviolet-selected sample of 268 objects in the two fields of the Great Observatories Origins Deep Survey (GOODS). We used the parallel observations taken with the Wide Field Planetary Camera 2 in the U band (F300W), which covered 88% of the GOODS fields, to identify sources and selected only objects with GOODS Advanced Camera for Surveys counterparts. Spectroscopic redshifts for 95 of these sources are available, and we have used the multiwavelength GOODS data to estimate photometric redshifts for the others. Most of the objects have redshifts 0.2<z<0.8. We used the spectral types obtained by photometric redshift fitting to identify starburst galaxies. We have also visually checked all objects and looked for tidal effects and nearby companions.
- ID:
- ivo://CDS.VizieR/J/AJ/138/598
- Title:
- NUV sources in Hubble Ultra Deep Field
- Short Name:
- J/AJ/138/598
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog from the first high-resolution U-band image of the Hubble Ultra Deep Field, taken with Hubble's Wide-Field Planetary Camera 2 through the F300W filter, is presented. We detect 96 U-band objects and compare and combine this catalog with a Great Observatories Origins Deep Survey B-selected catalog that provides B, V, i, and z photometry, spectral types, and photometric redshifts. We have also obtained far-ultraviolet (FUV, 1614{AA}) data with Hubble's Advanced Camera for Surveys Solar Blind Channel (ACS/SBC) and with GALEX. We detected 31 sources with ACS/SBC, 28 with GALEX/FUV, and 45 with GALEX/NUV. The methods of observations, image processing, object identification, catalog preparation, and catalog matching are presented.
- ID:
- ivo://CDS.VizieR/J/A+AS/102/251
- Title:
- Objective-prism survey of em. objects in M31
- Short Name:
- J/A+AS/102/251
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using GRENS plates taken at the Canada-France-Hawaii telescope, we have searched almost the whole extent of M31 for small-diameter objects with strong emission lines. Most are planetary nebulae candidates, but there are also many Wolf-Rayet star candidates and small HII regions or compact parts of large HII regions. A catalogue is presented with a cross-identification with previous catalogues. Many new planetary nebulae and Wolf-Rayet candidates are found. Their distribution is compared with those of other tracers in M31. In particular the distribution of planetary nebulae candidates is compared with that of the integrated blue light and we confirm the result obtained by Jacoby ( 1980ApJS...42....1J) and Ciardullo et al. (1989ApJ...339...53C): the number of planetary nebulae per unit total luminosity is a constant throughout the disk of M31. The Wolf- Rayet star candidates are concentrated in the well-known ring of star formation; their total number is estimated as 300 within the limit of detection of the deepest existing surveys, but this may still be an underestimate of the true number.
- ID:
- ivo://CDS.VizieR/J/ApJ/814/11
- Title:
- Obscured AGNs from XMM-Newton and AKARI
- Short Name:
- J/ApJ/814/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a new sample of obscured active galactic nuclei (AGNs) selected from the XMM-Newton serendipitous source and AKARI point-source catalogs. We match X-ray sources with infrared (18 and 90{mu}m) sources located at |b|>10{deg} to create a sample consisting of 173 objects. Their optical classifications and absorption column densities measured by X-ray spectra are compiled and study efficient selection criteria to find obscured AGNs. We apply the criteria (1) X-ray hardness ratio defined by using the 2-4.5keV and 4.5-12keV bands >-0.1 and (2) EPIC-PN count rate (CR) in the 0.2-12keV to infrared flux ratio CR/F_90_<0.1 or CR/F_18_<1 where F_18_ and F_90_ are infrared fluxes at 18 and 90{mu}m in Jy, respectively, to search for obscured AGNs. X-ray spectra of 48 candidates, for which no X-ray results have been published, are analyzed and X-ray evidence for the presence of obscured AGNs such as a convex shape X-ray spectrum indicative of absorption of N_H_~10^22-24^/cm2, a very flat continuum, or a strong Fe-K emission line with an equivalent width of >700eV is found in 26 objects. Six of them are classified as Compton-thick AGNs, and four are represented by either Compton-thin or Compton-thick spectral models. The success rate of finding obscured AGNs combining our analysis and the literature is 92% if the 18{mu}m condition is used. Of the 26 objects, 4 are optically classified as an HII nucleus and are new "elusive AGNs" in which star formation activity likely overwhelms AGN emission in the optical and infrared bands.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A114
- Title:
- Obscured AGNs in XMM deep survey in CDF-S
- Short Name:
- J/A+A/556/A114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accretion onto supermassive black holes is believed to occur mostly in obscured active galactic nuclei (AGN). Such objects are proving rather elusive in surveys of distant galaxies, including those at X-ray energies. Our main goal is to determine whether the revised IRAC criteria of Donley et al. (2012ApJ...748..142D; objects with an infrared (IR) power-law spectral shape), are effective at selecting X-ray type-2 AGN (i.e., absorbed N_H_>10^22^cm^-2^). We present the results from the X-ray spectral analysis of 147 AGN selected by cross-correlating the highest spectral quality ultra-deep XMM-Newton and the Spitzer/IRAC catalogues in the Chandra Deep Field South. Consequently it is biased towards sources with high S/N X-ray spectra. In order to measure the amount of intrinsic absorption in these sources, we adopt a simple X-ray spectral model that includes a power-law modified by intrinsic absorption at the redshift of each source and a possible soft X-ray component.
- ID:
- ivo://CDS.VizieR/J/ApJS/194/29
- Title:
- Observations of blazars at 15GHz
- Short Name:
- J/ApJS/194/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope provides an unprecedented opportunity to study gamma-ray blazars. To capitalize on this opportunity, beginning in late 2007, about a year before the start of LAT science operations, we began a large-scale, fast-cadence 15GHz radio monitoring program with the 40m telescope at the Owens Valley Radio Observatory (OVRO). This program began with the 1158 northern ({delta}>-20{deg}) sources from the Candidate Gamma-ray Blazar Survey and now encompasses over 1500 sources, each observed twice per week with about 4mJy (minimum) and 3% (typical) uncertainty. Here, we describe this monitoring program and our methods, and present radio light curves from the first two years (2008 and 2009). As a first application, we combine these data with a novel measure of light curve variability amplitude, the intrinsic modulation index, through a likelihood analysis to examine the variability properties of subpopulations of our sample.
