- ID:
- ivo://CDS.VizieR/J/ApJ/690/295
- Title:
- Chandra observations of J1604+4314 supercluster
- Short Name:
- J/ApJ/690/295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of Chandra observations of the Cl1604 supercluster at z~0.9. The system is the largest structure mapped at redshifts approaching unity, containing at least eight spectroscopically confirmed galaxy clusters and groups. Using two 50ks ACIS-I pointings we examine both the X-ray point-source population and the diffuse emission from individual clusters in the system. Over an area encompassing the entire supercluster (~0.154deg^2^), we find a 2.5{sigma} excess of point sources detected in the hard band (2-10keV) relative to the number of sources found in blank fields observed by Chandra. No such excess is observed in the soft band (0.5-2keV). The hard-band source density is 1.47 times greater than that of a blank field, in agreement with the previously reported correlation between overdensity amplitude and cluster redshift. Using a maximum likelihood technique, we have matched 112 of the 161 detected X-ray point sources to optical counterparts and found 15 sources that are associated with the supercluster. All 15 sources have rest-frame luminosities consistent with emission from active galactic nuclei (AGNs).
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/681/1017
- Title:
- Chandra observations of lens groups
- Short Name:
- J/ApJ/681/1017
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a systematic investigation of the X-ray properties of a sample of moderate-redshift (0.3<z<0.6) galaxy groups. These groups were selected not by traditional X-ray or optical search methods, but rather by an association, either physical or along the line of sight, with a strong gravitational lens. We calculate the properties of seven galaxy groups in the fields of six lens systems. Diffuse X-ray emission from the intragroup medium is detected in four of the groups. All of the detected groups have X-ray luminosities greater than 10^42^h^-2^ergs/s and lie on the L_X_^-{sigma}_v_^ relations defined by local groups and clusters. The upper limits for the nondetections are also consistent with the local L_X_^-{sigma}_v_^ relationships. Although the sample size is small and deeper optical and X-ray data are needed, these results suggest that lens-selected groups are similar to X-ray-selected samples and thus are more massive than the typical poor-group environments of local galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/735/26
- Title:
- Chandra observations of M81
- Short Name:
- J/ApJ/735/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of 15 Chandra observations of the nearby spiral galaxy M81 taken over the course of six weeks in 2005 May-July. Each observation reaches a sensitivity of ~10^37^erg/s. With these observations and one previous deeper Chandra observation, we compile a master source list of 265 point sources, extract and fit their spectra, and differentiate basic populations of sources through their colors. We also carry out variability analyses of individual point sources and of X-ray luminosity functions (XLFs) in multiple regions of M81 on timescales of days, months, and years. We find that, despite measuring significant variability in a considerable fraction of sources, snapshot observations provide a consistent determination of the XLF of M81. We also fit the XLFs for multiple regions of M81 and, using common parameterizations, compare these luminosity functions to those of two other spiral galaxies, M31 and the Milky Way.
- ID:
- ivo://CDS.VizieR/J/PASJ/55/635
- Title:
- Chandra observations of Monoceros R2
- Short Name:
- J/PASJ/55/635
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the results of the Chandra ACIS-I observation on the central region of the Monoceros R2 cloud (Mon R2), a high-mass star-forming region (SFR) at a distance of 830pc. With a deep exposure of ~100ks, we detected 368 X-ray sources, ~80% of which were identified with the near-infrared (NIR) counterparts. We systematically analyzed the spectra and time variability of most of the X-ray emitting sources and provided a comprehensive X-ray source catalog for the first time. Using the J-, H- and K-bands magnitudes of the NIR counterparts, we estimated the evolutionary phase (classical T Tauri stars and weak-lined T Tauri stars) and the mass of the X-ray emitting sources, and analyzed the X-ray properties as a function of the age and mass.
- ID:
- ivo://CDS.VizieR/J/ApJ/675/464
- Title:
- Chandra observations of NGC 2244
- Short Name:
- J/ApJ/675/464
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first high spatial resolution X-ray study of NGC 2244, the 2Myr old stellar cluster in the Rosette Nebula, using Chandra. Over 900 X-ray sources are detected; 77% have optical or FLAMINGOS NIR stellar counterparts and are mostly previously uncataloged young cluster members.
- ID:
- ivo://CDS.VizieR/J/AJ/127/2659
- Title:
- CHANDRA observations of NGC 2264
- Short Name:
- J/AJ/127/2659
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a Chandra observation of a field in NGC 2264. The observations were taken with the ACIS-I camera with an exposure time of 48.1ks. We present a catalog of 263 sources, which includes X-ray luminosity, optical and infrared photometry, and X-ray variability information. We found 41 variable sources, 14 of which have a flarelike light curve, and two of which have a pattern of a steady increase or decrease over a 10-hr period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being premain-sequence stars with ages younger than 3Myr.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/105
- Title:
- Chandra observations of NGC2903 central regions
- Short Name:
- J/ApJ/758/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep Chandra observation of the central regions of the late-type barred spiral galaxy NGC 2903. The Chandra data reveal soft (kT_e_~0.2-0.5keV) diffuse emission in the nuclear starburst region and extending ~2' (~5kpc) to the north and west of the nucleus. Much of this soft hot gas is likely to be from local active star-forming regions; however, besides the nuclear region, the morphology of hot gas does not strongly correlate with the bar or other known sites of active star formation. The central ~650pc radius starburst zone exhibits much higher surface brightness diffuse emission than the surrounding regions and a harder spectral component in addition to a soft component similar to the surrounding zones. We interpret the hard component as also being of thermal origin with kT_e_~3.6keV and to be directly associated with a wind fluid produced by supernovae and massive star winds similar to the hard diffuse emission seen in the starburst galaxy M82. The inferred terminal velocity for this hard component, ~1100km/s, exceeds the local galaxy escape velocity suggesting a potential outflow into the halo and possibly escape from the galaxy gravitational potential. Morphologically, the softer extended emission from nearby regions does not display an obvious outflow geometry. However, the column density through which the X-rays are transmitted is lower in the zone to the west of the nucleus compared to that from the east and the surface brightness is relatively higher suggesting some of the soft hot gas originates from above the disk: viewed directly from the western zone but through the intervening disk of the host galaxy along sight lines from the eastern zone. There are several point-like sources embedded in the strong diffuse nuclear emission zone. Their X-ray spectra show them to likely be compact binaries. None of these detected point sources are coincident with the mass center of the galaxy and we place an upper limit luminosity from any point-like nuclear source to be <2x10^38^erg/s in the 0.5-8.0keV band, which indicates that NGC 2903 lacks an active galactic nucleus. Heating from the nuclear starburst and a galactic wind may be responsible for preventing cold gas from accreting onto the galactic center.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/171
- Title:
- Chandra observations of NuSTAR sources
- Short Name:
- J/ApJ/869/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Nuclear Spectroscopic Telescope Array (NuSTAR) serendipitous survey has already uncovered a large number of active galactic nuclei (AGNs), providing new information about the composition of the cosmic X-ray background. For AGNs off the Galactic plane, it has been possible to use existing X-ray archival data to improve source localizations, identify optical counterparts, and classify the AGNs with optical spectroscopy. However, near the Galactic plane, better X-ray positions are necessary to achieve optical or near-IR identifications due to the higher levels of source crowding. Thus, we have used observations with the Chandra X-ray Observatory to obtain the best possible X-ray positions. With eight observations, we have obtained coverage for 19 NuSTAR serendips within 12{deg} of the plane. One or two Chandra sources are detected within the error circle of 15 of the serendips, and we report on these sources and search for optical counterparts. For one source (NuSTAR J202421+3350.9), we obtained a new optical spectrum and detected the presence of hydrogen emission lines. The source is Galactic, and we argue that it is likely a cataclysmic variable. For the other sources, the Chandra positions will enable future classifications in order to place limits on faint Galactic populations, including high-mass X-ray binaries and magnetars.
- ID:
- ivo://CDS.VizieR/J/ApJ/549/441
- Title:
- Chandra observations of Orion Trapezium
- Short Name:
- J/ApJ/549/441
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the High-Energy Transmission Grating Spectrometer on board the Chandra X-Ray Observatory to perform two observations, separated by 3 weeks, of the Orion Trapezium region. The zeroth-order images on the Advanced CCD Imaging Spectrometer provide spatial resolution of 0.5" and moderate energy resolution. Within a 160"x140" region around the Orion Trapezium, we resolve 111 X-ray sources with luminosities between 7x10^28^ and 2x10^32^ergs/s. We do not detect any diffuse emission. All but six sources are identified.
- ID:
- ivo://CDS.VizieR/J/MNRAS/492/719
- Title:
- Chandra observations of 2106 radio-quiet QSOs
- Short Name:
- J/MNRAS/492/719
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Chandra observations of 2106 radio-quiet quasars in the redshift range 1.7<=z<=2.7 from the Sloan Digital Sky Survey (SDSS), through data release fourteen (DR14, 2018ApJS..235...42A), that do not contain broad absorption lines (BAL) in their rest-frame UV spectra. This sample adds over a decade worth of SDSS and Chandra observations to our previously published sample of 139 quasars from SDSS DR5 which is still used to correlate X-ray and optical/UV emission in typical quasars. We fit the SDSS spectra for 753 of the quasars in our sample that have high-quality (large exposure time and small off-axis observation angle) X-ray observations, and analyze their X-ray properties (aox and daox) with respect to the measured CIV and MgII emission-line rest-frame equivalent width (EW) and the CIV emission-line blueshift. We find significant correlations (at the >=99.99% level) between aox and these emission-line parameters, as well as between daox and CIV EW. Slight correlations are found between daox and CIV blueshift, MgII EW, and the ratio of CIV EW to MgII EW. The best-fit trend in each parameter space is used to compare the X-ray weakness (daox) and optical/UV emission properties of typical quasars and weak-line quasars (WLQs). The WLQs clearly deviate from the expectation for every relationship, typically exhibiting much weaker X-ray emission than predicted by the typical quasar relationships. The best-fit relationships for our typical quasars are consistent with predictions from the disk-wind quasar model. The behavior of the WLQs with respect to our typical quasars can be explained by an X-ray shielding model.
