- ID:
- ivo://CDS.VizieR/J/MNRAS/446/911
- Title:
- X-ray sources in the AKARI NEP deep field
- Short Name:
- J/MNRAS/446/911
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present data products from the 300ks Chandra survey in the AKARI North Ecliptic Pole (NEP) deep field. This field has a unique set of 9-band infrared photometry covering 2-24 micron from the AKARI Infrared Camera, including mid-infrared (MIR) bands not covered by Spitzer. The survey is one of the deepest ever achieved at ~15 micron, and is by far the widest among those with similar depths in the MIR. This makes this field unique for the MIR-selection of AGN at z~1. We design a source detection procedure, which performs joint Maximum Likelihood PSF fits on all of our 15 mosaicked Chandra pointings covering an area of 0.34 square degree. The procedure has been highly optimized and tested by simulations. We provide a point source catalog with photometry and Bayesian-based 90 per cent confidence upper limits in the 0.5-7, 0.5-2, 2-7, 2-4, and 4-7keV bands. The catalog contains 457 X-ray sources and the spurious fraction is estimated to be ~1.7 per cent. Sensitivity and 90 per cent confidence upper flux limits maps in all bands are provided as well. We search for optical MIR counterparts in the central 0.25 square degree, where deep Subaru Suprime-Cam multiband images exist. Among the 377 X-ray sources detected there, ~80 per cent have optical counterparts and ~60 per cent also have AKARI mid-IR counterparts. We cross-match our X-ray sources with MIR-selected AGN from Hanami et al. Around 30 per cent of all AGN that have MID-IR SEDs purely explainable by AGN activity are strong Compton-thick AGN candidates.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/422/2302
- Title:
- X-ray sources in the Phoenix dwarf galaxy
- Short Name:
- J/MNRAS/422/2302
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the first X-ray images of the Phoenix dwarf galaxy, taken with XMM-Newton in 2009 July. This Local Group dwarf galaxy shares similarities with the Small Magellanic Cloud (SMC) including a burst of star formation ~50Myr ago. The SMC has an abundance of high-mass X-ray binaries (HMXBs) and so we have investigated the possibility of an HMXB population in Phoenix with the intention of furthering the understanding of the HMXB-star formation rate relation. The data from the combined European Photon Imaging Cameras (EPIC) were used to distinguish between different source classes [foreground stars, background galaxies, active galactic nuclei (AGN) and supernova remnants] using EPIC hardness ratios and correlations with optical and radio catalogues.
- ID:
- ivo://CDS.VizieR/J/ApJ/681/1464
- Title:
- X-ray sources near soft gamma repeater in M31
- Short Name:
- J/ApJ/681/1464
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- GRB 070201 was a bright, short-duration, hard-spectrum gamma-ray burst detected by the Interplanetary Network. Its error quadrilateral, which has an area of 0.124deg^2^, intersects some prominent spiral arms of the nearby M31 (Andromeda) galaxy. Given the properties of this GRB, along with the fact that LIGO data argue against a compact binary merger origin in M31, it is an excellent candidate to have been an extragalactic soft gamma-ray repeater (SGR) giant flare, with an energy of 1.4x1045ergs. However, we cannot rule out the possibility that it was a short-duration GRB in the background. Analysis of ROTSE-IIIb visible-light observations of M31, taken 10.6hr after the burst and covering 42% of the GRB error region, does not reveal any optical transient down to a limiting magnitude of 17.1. We inspected archival and proprietary XMM-Newton X-ray observations of the intersection of the GRB error region and M31, obtained about 4 weeks prior to the outburst, in order to look for periodic variable X-ray sources. No SGR or anomalous X-ray pulsar (AXP) candidates (periods in the range 1-20s) were detected. We discuss the possibility of detecting extragalactic SGRs/AXPs by identifying their periodic X-ray light curves. Our simulations suggest that the probability of detecting the periodic X-ray signal of one of the known Galactic SGRs/AXPs, if placed in M31, is about 10% using a 50ks XMM-Newton exposure, increasing to 50% for a 2Ms observation.
- ID:
- ivo://CDS.VizieR/J/ApJ/865/43
- Title:
- X-ray stacking analysis of Chandra-COSMOS gal.
- Short Name:
- J/ApJ/865/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an X-ray stacking analysis of ~75000 star-forming galaxies between 0.1<z<5.0 using the Chandra COSMOS-Legacy survey to study the X-ray emission of low-luminosity active galactic nuclei (AGN) and its connection to host galaxy properties. The stacks at z<0.9 have luminosity limits as low as 10^40^-10^41^erg/s, a regime in which X-ray binaries (XRBs) can dominate the X-ray emission. Comparing the measured luminosities to established XRB scaling relations, we find that the redshift evolution of the luminosity per star formation rate (SFR) of XRBs depends sensitively on the assumed obscuration and may be weaker than previously found. The XRB scaling relation based on stacks from the Chandra Deep Field South overestimates the XRB contribution to the COSMOS high specific SFR stacks, possibly due to a bias affecting the CDF-S stacks because of their small galaxy samples. After subtracting the estimated XRB contribution from the stacks, we find that most stacks at z>1.3 exhibit a significant X-ray excess indicating nuclear emission. The AGN emission is strongly correlated with stellar mass but does not exhibit an additional correlation with SFR. The hardness ratios of the high-redshift stacks indicate that the AGN are substantially obscured (N_H_~10^23^cm^-2^). These obscured AGN are not identified by IRAC color selection and have L_X_~10^41^-10^43^erg/s, consistent with accretion at an Eddington rate of ~10^-3^ onto 10^7^-10^8^M_{sun}_ black holes. Combining our results with other X-ray studies suggests that AGN obscuration depends on stellar mass and an additional variable, possibly the Eddington rate.
- ID:
- ivo://CDS.VizieR/J/MNRAS/440/269
- Title:
- X-ray survey of the 2Jy sample. I.
- Short Name:
- J/MNRAS/440/269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carry out a systematic study of the X-ray emission from the active nuclei of the 0.02<z<0.7 2Jy sample, using Chandra and XMM-Newton observations. We combine our results with those from mid-infrared, optical emission-line and radio observations, and add them to those of the 3CRR sources. We show that the low-excitation objects in our samples show signs of radiatively inefficient accretion. We study the effect of the jet-related emission on the various luminosities, confirming that it is the main source of soft X-ray emission for our sources. We also find strong correlations between the accretion-related luminosities, and identify several sources whose optical classification is incompatible with their accretion properties. We derive the bolometric and jet kinetic luminosities for the samples and find a difference in the total Eddington rate between the low- and high-excitation populations, with the former peaking at ~1% and the latter at ~20% Eddington. Our results are consistent with a simple Eddington switch when the effects of environment on radio luminosity and black hole mass calculations are considered. The apparent independence of jet kinetic power and radiative luminosity in the high-excitation population in our plots supports a model in which jet production and radiatively efficient accretion are not strongly correlated in high-excitation objects, though they have a common underlying mechanism.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/48
- Title:
- X-ray through NIR photometry of NGC 2617
- Short Name:
- J/ApJ/788/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- After the All-Sky Automated Survey for SuperNovae discovered a significant brightening of the inner region of NGC 2617, we began a ~70 day photometric and spectroscopic monitoring campaign from the X-ray through near-infrared (NIR) wavelengths. We report that NGC 2617 went through a dramatic outburst, during which its X-ray flux increased by over an order of magnitude followed by an increase of its optical/ultraviolet (UV) continuum flux by almost an order of magnitude. NGC 2617, classified as a Seyfert 1.8 galaxy in 2003, is now a Seyfert 1 due to the appearance of broad optical emission lines and a continuum blue bump. Such "changing look active galactic nuclei (AGNs)" are rare and provide us with important insights about AGN physics. Based on the H{beta} line width and the radius-luminosity relation, we estimate the mass of central black hole (BH) to be (4+/-1)x10^7^ M_{sun}_. When we cross-correlate the light curves, we find that the disk emission lags the X-rays, with the lag becoming longer as we move from the UV (2-3 days) to the NIR (6-9 days). Also, the NIR is more heavily temporally smoothed than the UV. This can largely be explained by a simple model of a thermally emitting thin disk around a BH of the estimated mass that is illuminated by the observed, variable X-ray fluxes.
- ID:
- ivo://CDS.VizieR/J/ApJS/177/465
- Title:
- X-ray variability in NGC 6946, NGC 4485/90
- Short Name:
- J/ApJS/177/465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze data from five Chandra observations of the spiral galaxy NGC 6946 and from three Chandra observations of the irregular/spiral interacting galaxy pair NGC 4485/4490, with an emphasis on investigating the long-term variability exhibited by the source populations. We detect 90 point sources coincident with NGC 6946 down to luminosities of a few times 10^36^ergs/s, and 38 sources coincident with NGC 4485/90 down to a luminosity of ~1x10^37^ergs/s. Twenty-five (15) sources in NGC 6946 (NGC 4485/90) exhibit long-term (i.e., weeks to years) variability in luminosity; 11 (4) are transient candidates. The single ultraluminous X-ray source (ULX) in NGC 6946 and all but one of the eight ULXs in NGC 4485/90 exhibit long-term flux variability. Two of the ULXs in NGC 4485/90 have not been identified before as ultraluminous sources. The widespread variability in both systems is indicative of the populations being dominated by X-ray binaries, and this is supported by the X-ray colors of the sources. The distribution of colors among the sources indicates a large fraction of high-mass X-ray binaries in both systems. The shapes of the X-ray luminosity functions of the galaxies do not change significantly between observations and can be described by power laws with cumulative slopes ~0.6-0.7 (NGC 6946) and ~0.4 (NGC 4485/90).
- ID:
- ivo://CDS.VizieR/J/AJ/139/1066
- Title:
- X-ray view of NGC 2403 central region
- Short Name:
- J/AJ/139/1066
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Archival Chandra observations are used to study the X-ray emission associated with star formation in the central region of the nearby SAB(s)cd galaxy NGC 2403. The distribution of X-ray emission is compared to the morphology visible at other wavelengths using complementary Spitzer, Galaxy Evolution Explorer, and ground-based H{alpha} imagery.
- ID:
- ivo://CDS.VizieR/J/ApJS/245/17
- Title:
- X-shaped radio galaxies from FIRST
- Short Name:
- J/ApJS/245/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 290 "winged" or X-shaped radio galaxies (XRGs) extracted from the latest (2014 December 17) data release of the "Very Large Array Faint Images of the Radio Sky at Twenty centimeter". We have combined these radio images with their counterparts in the TIFR GMRT sky survey at 150MHz, in an attempt to identify any low surface brightness radio emission present in these sources. This has enabled us to assemble a sample of 106 "strong" XRG candidates and 184 "probable" XRG candidates whose XRG designation needs to be verified by further observations. The present sample of 290 XRG candidates is almost twice as large as the number of XRGs currently known. Twenty-five of our 290 XRG candidates (9 "strong" and 16 "probable") are identified as quasars. Double-peaked narrow emission lines are seen in the optical spectra of three of the XRG candidates (two "strong" and one "probable"). Nearly 90% of the sample is located in the FR II domain of the Owen-Ledlow diagram. A few of the strong XRG candidates have a rather flat radio spectrum (spectral index {alpha} flatter than -0.3) between 150MHz and 1.4GHz, or between 1.4 and 5GHz. Since this is not expected for lobe-dominated extragalactic radio sources (like nearly all known XRGs), these sources are particularly suited for follow-up radio imaging and near-simultaneous measurement of the radio spectrum.
- ID:
- ivo://CDS.VizieR/J/ApJS/181/548
- Title:
- X-shaped radio sources. II. New redshifts
- Short Name:
- J/ApJS/181/548
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We reported optical spectroscopic observations of X-shaped radio sources with the Hobby-Eberly Telescope and Multiple-Mirror Telescope, focused on the sample of candidates from the FIRST survey presented in Paper I (Cheung, 2007, Cat. <J/AJ/133/2097>). A total of 27 redshifts were successfully obtained, 21 of which are new, including a newly identified candidate source of this type which is presented here. With these observations, the sample of candidates from the previous paper is over 50% spectroscopically identified. Two new broad emission-lined X-shaped radio sources are revealed, while no emission lines were detected in about one-third of the observed sources; a detailed study of the line properties is deferred to a future paper. Finally, to explore their relation to the Fanaroff-Riley division, the radio luminosities and host galaxy absolute magnitudes of a spectroscopically identified sample of 50 X-shaped radio galaxies are calculated to determine their placement in the Owen-Ledlow plane.
