- ID:
- ivo://CDS.VizieR/J/ApJS/180/102
- Title:
- AEGIS-X: Chandra deep survey
- Short Name:
- J/ApJS/180/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the EGIS-X survey, a series of deep Chandra ACIS-I observations of the Extended Groth Strip. The survey comprises pointings at eight separate positions, each with nominal exposure of 200ks, covering a total area of approximately 0.67deg^2^ in a strip of length 2 degrees. We describe in detail an updated version of our data reduction and point-source-detection algorithms used to analyze these data. A total of 1325 band-merged sources have been found to a Poisson probability limit of 4x10^-6^, with limiting fluxes of 5.3x10^-21^W/m2 in the soft (0.5-2keV) band and 3.8x10^-19^W/m2 in the hard (2-10keV) band. We present simulations verifying the validity of our source-detection procedure and showing a very small, <1.5%, contamination rate from spurious sources. Optical/NIR counterparts have been identified from the DEEP2, CFHTLS, and Spitzer/Infrared Array Camera (IRAC) surveys of the same region. Using a likelihood ratio method, we find optical counterparts for 76% of our sources, complete to R_AB_=24.1, and, of the 66% of the sources that have IRAC coverage, 94% have a counterpart to a limit of 0.9uJy at 3.6um (m_AB_=23.8). After accounting for (small) positional offsets in the eight Chandra fields, the astrometric accuracy of Chandra positions is found to be 0"8rms; however, this number depends both on the off-axis angle and the number of detected counts for a given source. All data products described in this paper are made available via a public Web site.
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- ID:
- ivo://CDS.VizieR/J/ApJS/220/10
- Title:
- AEGIS-X Deep survey of EGS (AEGIS-XD)
- Short Name:
- J/ApJS/220/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of deep Chandra imaging of the central region of the Extended Groth Strip, the AEGIS-X Deep (AEGIS-XD) survey. When combined with previous Chandra observations of a wider area of the strip, AEGIS-X Wide (AEGIS-XW), these provide data to a nominal exposure depth of 800ks in the three central ACIS-I fields, a region of approximately 0.29deg^2^. This is currently the third deepest X-ray survey in existence; a factor ~2-3 shallower than the Chandra Deep Fields (CDFs), but over an area ~3 times greater than each CDF. We present a catalog of 937 point sources detected in the deep Chandra observations, along with identifications of our X-ray sources from deep ground-based, Spitzer, GALEX, and Hubble Space Telescope imaging. Using a likelihood ratio analysis, we associate multiband counterparts for 929/937 of our X-ray sources, with an estimated 95% reliability, making the identification completeness approximately 94% in a statistical sense. Reliable spectroscopic redshifts for 353 of our X-ray sources are available predominantly from Keck (DEEP2/3) and MMT Hectospec, so the current spectroscopic completeness is ~38%. For the remainder of the X-ray sources, we compute photometric redshifts based on multiband photometry in up to 35 bands from the UV to mid-IR. Particular attention is given to the fact that the vast majority the X-ray sources are active galactic nuclei and require hybrid templates. Our photometric redshifts have mean accuracy of {sigma}=0.04 and an outlier fraction of approximately 5%, reaching {sigma}=0.03 with less than 4% outliers in the area covered by CANDELS.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/824
- Title:
- Afterglows of short and long-duration GRBs
- Short Name:
- J/ApJ/701/824
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comparative study of the observed properties of the optical and X-ray afterglows of short- and long-duration {gamma}-ray bursts (GRBs). Using a large sample of 37 short and 421 long GRBs, we find a strong correlation between the afterglow brightness measured after 11hr and the observed fluence of the prompt emission. Both the optical (R band) and X-ray flux densities (F_R_ and F_X_) scale with the {gamma}-ray fluence, F_{gamma}_. For bursts with a known redshift, a tight correlation exists between the afterglow flux densities at 11hr (rest frame) and the total isotropic {gamma}-ray energy, E_{gamma},ISO_: F_R,X_{prop.to}E_{gamma},ISO_^{alpha}^, with {alpha}~1.
- ID:
- ivo://CDS.VizieR/J/ApJ/787/108
- Title:
- Age estimates for massive SFR stellar populations
- Short Name:
- J/ApJ/787/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A major impediment to understanding star formation in massive star-forming regions (MSFRs) is the absence of a reliable stellar chronometer to unravel their complex star formation histories. We present a new estimation of stellar ages using a new method that employs near-infrared (NIR) and X-ray photometry, Age_JX_. Stellar masses are derived from X-ray luminosities using the L_X_-M relation from the Taurus cloud. J-band luminosities are compared to mass-dependent pre-main-sequence (PMS) evolutionary models to estimate ages. Age_JX_ is sensitive to a wide range of evolutionary stages, from disk-bearing stars embedded in a cloud to widely dispersed older PMS stars. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) project characterizes 20 OB-dominated MSFRs using X-ray, mid-infrared, and NIR catalogs. The Age_JX_ method has been applied to 5525 out of 31784 MYStIX Probable Complex Members. We provide a homogeneous set of median ages for over 100 subclusters in 15 MSFRs; median subcluster ages range between 0.5 Myr and 5 Myr. The important science result is the discovery of age gradients across MYStIX regions. The wide MSFR age distribution appears as spatially segregated structures with different ages. The Age_JX_ ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed populations. The NIR color index J-H, a surrogate measure of extinction, can serve as an approximate age predictor for young embedded clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/787/109
- Title:
- Age estimates for NGC 2024 and ONC stars
- Short Name:
- J/ApJ/787/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze age distributions of two nearby rich stellar clusters, the NGC 2024 (Flame Nebula) and Orion Nebula cluster (ONC) in the Orion molecular cloud complex. Our analysis is based on samples from the MYStIX survey and a new estimator of pre-main sequence (PMS) stellar ages, Age_JX_, derived from X-ray and near-infrared photometric data. To overcome the problem of uncertain individual ages and large spreads of age distributions for entire clusters, we compute median ages and their confidence intervals of stellar samples within annular subregions of the clusters. We find core-halo age gradients in both the NGC 2024 cluster and ONC: PMS stars in cluster cores appear younger and thus were formed later than PMS stars in cluster peripheries. These findings are further supported by the spatial gradients in the disk fraction and K-band excess frequency. Our age analysis is based on Age_JX_ estimates for PMS stars and is independent of any consideration of OB stars. The result has important implications for the formation of young stellar clusters. One basic implication is that clusters form slowly and the apparent age spreads in young stellar clusters, which are often controversial, are (at least in part) real. The result further implies that simple models where clusters form inside-out are incorrect and more complex models are needed. We provide several star formation scenarios that alone or in combination may lead to the observed core-halo age gradients.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A33
- Title:
- AGILE Mini-Calorimeter {gamma}-ray burst catalog
- Short Name:
- J/A+A/553/A33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Mini-Calorimeter of the AGILE satellite can observe the high-energy part of gamma-ray bursts with good timing capability. We present the data of the 85 hard gamma-ray bursts observed by the Mini-Calorimeter since the launch (April 2007) until October 2009. We report the timing data for 84 and spectral data for 21 bursts.
- ID:
- ivo://CDS.VizieR/J/MNRAS/407/2399
- Title:
- AGN activity and black hole mass
- Short Name:
- J/MNRAS/407/2399
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the role of host galaxy classification and black hole mass (MBH) in a heterogeneous sample of 276 mostly nearby (z<0.1) X-ray and IR-selected active galactic nuclei (AGN).
- ID:
- ivo://CDS.VizieR/J/ApJ/751/52
- Title:
- AGN candidates from the WISE, 2MASS, RASS (W2R)
- Short Name:
- J/ApJ/751/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have developed the "S_IX_" statistic to identify bright, highly likely active galactic nucleus (AGN) candidates solely on the basis of Wide-field Infrared Survey Explorer (WISE), Two Micron All-Sky Survey (2MASS), and ROSAT all-sky survey (RASS) data. This statistic was optimized with data from the preliminary WISE survey and the Sloan Digital Sky Survey, and tested with Lick 3m Kast spectroscopy. We find that sources with S_IX_<0 have a >~95% likelihood of being an AGN (defined in this paper as a Seyfert 1, quasar, or blazar). This statistic was then applied to the full WISE/2MASS/RASS dataset, including the final WISE data release, to yield the "W2R" sample of 4316 sources with S_IX_<0. Only 2209 of these sources are currently in the Veron-Cetty and Veron (VCV) catalog of spectroscopically confirmed AGNs, indicating that the W2R sample contains nearly 2000 new, relatively bright (J<~16) AGNs. We utilize the W2R sample to quantify biases and incompleteness in the VCV catalog. We find that it is highly complete for bright (J<14), northern AGNs, but the completeness drops below 50% for fainter, southern samples and for sources near the Galactic plane. This approach also led to the spectroscopic identification of 10 new AGNs in the Kepler field, more than doubling the number of AGNs being monitored by Kepler. The W2R sample contains better than 1 bright AGN every 10 deg^2^, permitting construction of AGN samples in any sufficiently large region of sky.
- ID:
- ivo://CDS.VizieR/J/AJ/133/313
- Title:
- AGN from RASS and SDSS DR5
- Short Name:
- J/AJ/133/313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe further results of a program aimed at yielding ~104 fully characterized optical identifications of ROSAT X-ray sources. Our program employs X-ray data from the ROSAT All Sky Survey (RASS) and both optical imaging and spectroscopic data from the Sloan Digital Sky Survey (SDSS). RASS/SDSS data from 5740deg^2^ of sky spectroscopically covered in SDSS Data Release 5 provide an expanded catalog of 7000 confirmed quasars and other active galactic nuclei (AGNs) that are probable RASS identifications. Again, in our expanded catalog the identifications as X-ray sources are statistically secure, with only a few percent of the SDSS AGNs likely to be randomly superposed on unrelated RASS X-ray sources.
- ID:
- ivo://CDS.VizieR/J/A+AS/110/469
- Title:
- AGN from the RASS
- Short Name:
- J/A+AS/110/469
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents long slit CCD spectroscopy and X-ray data of 283 AGN detected in the ROSAT-All Sky Survey (RASS). Basis of the sample is the pre-identification of 4651 RASS sources on 134 sky fields (covering in total ~3500sq.deg.). The 283 presented AGN were selected from 1253 AGN candidates resulting from the pre-identification work.