- ID:
- ivo://CDS.VizieR/J/A+A/588/A131
- Title:
- Warm ISM in the Sagittarius A Complex
- Short Name:
- J/A+A/588/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the spatial and spectral distribution of the local standard of rest (LSR) velocity resolved submillimetre emission from the warm (25-90K) gas in the Sgr A Complex, located in the Galactic centre. We present large-scale submillimetre heterodyne observations towards the Sgr A Complex covering ~300-arcmin2. These data were obtained in the frame of the Herschel EXtraGALactic guaranteed time key program (HEXGAL) with the Herschel-HIFI satellite and are complemented with submillimetre observations obtained with the NANTEN2/SMART telescope as part of the NANTEN2/SMART Central Nuclear Zone Survey. The observed species are CO(J=4-3) at 461.0GHz observed with the NANTEN2/SMART telescope, and [CI] 3P1-3P0 at 492.2GHz, [CI] 3P2-3P1 at 809.3GHz, [NII] 3P1-3P0 at 1461.1GHz, and [CII] 2P3/2-2P1/2 at 1900.5GHz observed with the Herschel-HIFI satellite. The observations are presented in a 1km/s spectral resolution and a spatial resolution ranging from 46-arcsec to 28-arcsec. The spectral coverage of the three lower frequency lines is +/-200km/s, while in the two high frequency lines, the upper LSR velocity limit is +94km/s and +145km/s for the [NII] and [CII] lines, respectively. The spatial distribution of the emission in all lines is very widespread. The bulk of the carbon monoxide emission is found towards Galactic latitudes below the Galactic plane, and all the known molecular clouds are identified. Both neutral atomic carbon lines have their brightest emission associated with the +50km/s cloud. Their spatial distribution at this LSR velocity describes a crescent-shape structure, which is probably the result of interaction with the energetic event (one or several supernovae explosions) that gave origin to the non-thermal Sgr A-East source. The [CII] and [NII] emissions have most of their flux associated with the thermal arched-filaments and the H region and bright spots in [CII] emission towards the central nuclear disk (CND) are detected. Warm Gas at very high (|Vlsr|>100km/s) LSR velocities is also detected towards the line of sight to the Sgr A Complex, and it is most probably located outside the region, in the X1 orbits.
« Previous |
171 - 180 of 180
|
Next »
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/255/10
- Title:
- WISE MIR variability in gamma-ray Seyfert 1 gal.
- Short Name:
- J/ApJS/255/10
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- Fermi-LAT's detection of {gamma}-rays from narrow-line Seyfert 1 galaxies (NLS1s) has received increasing attention. Understanding these {gamma}-NLS1s is of interest because they have some properties similar to blazars, which are known to show rapid and large-amplitude variability. Based on the largest sample of {gamma}-NLS1s (25 sources), we carried out a systematic search for rapid mid-infrared (MIR, 3.4 and 4.6{mu}m) variability using the multiepoch data of the Wide-field Infrared Survey Explorer (WISE). We also compared a few variability properties between {gamma}-NLS1s and {gamma}-ray blazars. Our main results are as follows. (1) Thirteen {gamma}-NLS1s showed significant (>3{sigma}) rapid variability in at least one of the two MIR bands. The MIR emission of these sources is dominated by the synchrotron emission of relativistic electrons in the jet. (2) The {gamma}-NLS1s with flat radio spectra are more variable than those not detected in {gamma}-rays. (3) The {gamma}-NLS1s tend to show smaller amplitude of variability as well as lower duty cycle relative to {gamma}-ray blazars. (4) The {gamma}-NLS1s tend to show a trend of bluer-when-brighter on both intraday and long timescales, similar to {gamma}-ray blazars. (5) The {gamma}-NLS1s that are more variable on long timescales have larger amplitudes of variability and higher duty cycles on intraday timescales. (6) In the majority of cases, the {gamma}-NLS1s fall in the WISE Gamma-ray Blazar Strip (WGS). However, we noted migrations outside of the WGS due to significant variability.
- ID:
- ivo://CDS.VizieR/J/AJ/159/245
- Title:
- Xinglong optical spectra of UGC3223 in 4 epochs
- Short Name:
- J/AJ/159/245
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of spectral type transition of active galactic nuclei (AGNs), the so-called "changing-look" (CL) phenomenon, challenges the widely accepted AGN paradigm, not only in the orientation-based unified model, but also in the standard disk model. In past decades, only a couple of nearby repeat changing-look active galactic nuclei (CL-AGNs) have been identified. Here we report spectroscopic observations of UGC3223 over the course of 18yr, from 2001 onwards. Combining the spectrum taken in 1987 by Stirpe, we have witnessed its type transitions from 1.5 to 2.0 to 1.8 over 32yr, and captured a long-lived (at least 10 yr) thorough "turn-off" state with a spectrum typical of a Seyfert 2 galaxy. The long-term thorough turn-off state probably suggests a once-dormant and an awakening central engine in UGC3223. We argue that the (dis)appearance of the broad Balmer emission lines can be explained by the disk-wind broad-line region model given the evolution of the calculated Eddington ratio of accretion of the supermassive black hole.
- ID:
- ivo://CDS.VizieR/J/A+A/639/A5
- Title:
- X-ray absorption in INTEGRAL AGN
- Short Name:
- J/A+A/639/A5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work the INTEGRAL hard X-ray selected sample of AGN has been used to investigate the possible contribution of absorbing material distributed within the host galaxies to the total amount of NH measured in the X-ray band. We collected all the available axial ratio measurements of the galaxies hosting our AGN together with their morphological information and find that also for our hard X-ray selected sample a deficit of edge-on galaxies hosting type 1 AGN is present. We estimate that in our hard X-ray selected sample there is a deficit of 24% (+/-5%) of type 1 AGN. Possible bias in redshift has been excluded, as we found the same effect in a well determined range of z where the number and the distributions of the two classes are statistically the same. Our findings clearly indicate that material located in the host galaxy on scales of hundreds of parsecs and not aligned with the putative absorbing torus of the AGN can contribute to the total amount of column density. This galactic absorber can be large enough to hide the broad line region of some type 1 AGN causing their classification as type 2 objects and giving rise to the deficiency of type 1 in edge-on galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/896/95
- Title:
- X-ray obs. of narrow- and broad-line Seyfert 1 gal.
- Short Name:
- J/ApJ/896/95
- Date:
- 03 Dec 2021 00:52:46
- Publisher:
- CDS
- Description:
- We present a detailed comparative systematic study using a sample of 221 narrow-line Seyfert 1 (NLSy1) galaxies in comparison to a redshift-matched sample of 154 broad-line Seyfert 1 (BLSy1) galaxies based on their observations using ROSAT and/or XMM-Newton in soft X-ray band (0.1-2.0keV). A homogeneous analysis is carried out to estimate their soft X-ray photon indices ({Gamma}_X_^s^) and its correlations with other parameters of nuclear activities such as Eddington ratios (REdd), bolometric luminosities (Lbol), black hole masses (MBH), and the widths of the broad component of H{beta} lines (FWHM(H{beta})). In our analysis, we found clear evidence of the difference in the {Gamma}_X_^s^ and R_Edd_ distributions among NLSy1 and BLSy1 galaxies, with steeper {Gamma}_X_^s^ and higher R_Edd_ for the former. Such a difference also exists in the spectral index distribution in hard X-ray ({Gamma}_X_^h^), based on the analysis of 53 NLSy1 and 46 BLSy1 galaxies in the 2-10keV energy band. The difference in REdd distributions does exist even after applying the average correction for the difference in the inclination angle of NLSy1 and BLSy1 galaxies. We also estimated R_Edd_, based on SED fitting of 34 NLSy1 and 30 BLSy1 galaxies over the 0.3-10keV energy band, and found that results are still consistent with REdd estimates based on the optical bolometric luminosity. Our analysis suggests that the higher REdd in NLSy1 is responsible for its steeper X-ray spectral slope compared to the BLSy1, consistent with the disk-corona model as proposed for the luminous AGNs.
- ID:
- ivo://CDS.VizieR/VII/181
- Title:
- X-ray of active galaxies and nuclei
- Short Name:
- VII/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/ApJ/713/L11
- Title:
- X-ray properties of Seyfert 1 galaxies
- Short Name:
- J/ApJ/713/L11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use publicly available XMM-Newton data to systematically compare the hard X-ray photon indices, {Gamma}_2-10keV_, and the iron K{alpha} emission lines of narrow- and broad-line Seyfert 1 (NLS1 and BLS1) galaxies. We compile a flux-limited (f_2-10keV_>=1x10^-12^erg/s/cm^2^) sample including 114 radio-quiet objects, with the 2-10keV luminosity ranging from 10^41^ to 10^45^erg/s. 86 out of these 114 AGNs are included in the CAIXA catalogue (Bianchi et al. 2009, Cat. J/A+A/495/421). The redshift range of the present sample is z<0.37, with only seven objects having z>0.2.
- ID:
- ivo://CDS.VizieR/J/A+A/319/18
- Title:
- X-ray sources <1 degree from Seyfert galaxies
- Short Name:
- J/A+A/319/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Archived PSPC observations of 26 Seyfert galaxies have been analyzed for bright X-ray sources out to the full extent of the field (< about 50'). Of all Seyferts known this represents a sample 88% complete to B_T_=10mag, 74% complete to 11mag and 50% complete to 12mag. Using the same reduction algorithm, 14 fields centered on stars at high galactic latitudes have been used as control fields. Excluding the two brightest Seyferts, a subset of 24 Seyferts with corrected apparent magnitude between 8.04<B^o,i^_T_<12.90mag show a minimum excess of 46 bright X-ray sources generally distributed between 10 and 25' from the target galaxy. The significances of association of these sources with the Seyferts in the median brightness range are as high as 7.4-sigma.
- 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.
- 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.
