- ID:
- ivo://CDS.VizieR/J/MNRAS/448/2900
- Title:
- Emission lines for SDSS Coronal-Line Forest AGNs
- Short Name:
- J/MNRAS/448/2900
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We introduce Coronal-Line Forest active galactic nuclei (CLiF AGN), AGN which have a rich spectrum of forbidden high-ionization lines (FHILs, e.g. [FeVII], [FeX] and [NeV]), as well as relatively strong narrow (~300 km/s) H{alpha} emission when compared to the other Balmer transition lines. We find that the kinematics of the CLiF emitting region are similar to those of the forbidden low-ionization emission-line (FLIL) region. We compare emission line strengths of both FHILs and FLILs to cloudy photoionization results and find that the CLiF emitting region has higher densities (10^4.5^<n_H_<10^7.5^/cm^3^) when compared to the FLIL emitting region (10^3.0^<n_H_<10^4.5^/cm^3^). We use the photoionization results to calculate the CLiF regions radial distances (0.04<R_CLiF_<32.5 pc) and find that they are comparable to the dust grain sublimation distances (0.10<R_SUB_<4.3 pc). As a result, we suggest that the inner torus wall is the most likely location of the CLiF region, and the unusual strength of the FHILs is due to a specific viewing angle giving a maximal view of the far wall of the torus without the continuum being revealed.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/599/886
- Title:
- Emission lines of radio-loud AGN
- Short Name:
- J/ApJ/599/886
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the completion of a survey of radio-loud active galactic nuclei (AGNs) begun in an earlier paper (Eracleous & Halpern, 1994ApJS...90....1E) with the main goal of finding and studying broad, double-peaked Balmer lines. We present H{alpha} spectra of 13 more broad-lined objects, including three with double-peaked H{alpha} profiles. The final sample includes 106 radio-loud AGNs. In our final census 20% of objects have H{alpha} lines with double peaks or twin shoulders (the "double-peaked emitters"), and of these 60% (the disklike emitters) can be fitted quite well with a model attributing the emission to a circular, relativistic, Keplerian disk. In four objects where broad H{beta} and Mg II lines have been observed, we compare the profiles with models of photoionized accretion disks and find them to be in reasonable agreement.
- ID:
- ivo://CDS.VizieR/J/ApJ/825/7
- Title:
- Evolution of ~6Ms CDF-S galaxies
- Short Name:
- J/ApJ/825/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the evolution of normal-galaxy X-ray emission from z~0-7 using local galaxies and galaxy samples in the ~6Ms Chandra Deep Field-South (CDF-S) survey. The majority of the CDF-S galaxies are observed at rest-frame energies above 2keV, where the emission is expected to be dominated by X-ray binary (XRB) populations; however, hot gas is expected to provide small contributions to the observed-frame <~1keV emission at z<~1. We show that a single scaling relation between X-ray luminosity (L_X_) and star-formation rate (SFR) literature, is insufficient for characterizing the average X-ray emission at all redshifts. We establish that scaling relations involving not only SFR, but also stellar mass (M_*_) and redshift, provide significantly improved characterizations of the average X-ray emission from normal galaxy populations at z~0-7. We further provide the first empirical constraints on the redshift evolution of X-ray emission from both low-mass XRB (LMXB) and high-mass XRB (HMXB) populations and their scalings with M_*_ and SFR, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/699/603
- Title:
- Evolution of Swift/BAT blazars
- Short Name:
- J/ApJ/699/603
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use three years of data from the Swift/Burst Alert Telescope (BAT) survey to select a complete sample of X-ray blazars above 15keV. This sample comprises 26 flat-spectrum radio quasars (FSRQs) and 12 BL Lacertae (BL Lac) objects detected over a redshift range of 0.03<z<4.0. We use this sample to determine, for the first time in the 15-55keV band, the evolution of blazars. We find that, contrary to the Seyfert-like active galactic nuclei (AGNs) detected by BAT, the population of blazars shows strong positive evolution. This evolution is comparable to the evolution of luminous optical quasi-stellar objects (QSOs) and luminous X-ray-selected AGNs. We also find evidence for an epoch dependence of the evolution as determined previously for radio-quiet AGNs. We interpret both these findings as a strong link between accretion and jet activity. In our sample, the FSRQs evolve strongly, while our best fit shows that BL Lac objects might not evolve at all. The blazar population accounts for 10%-20% (depending on the evolution of the BL Lac objects) of the cosmic X-ray background (CXB) in the 15-55keV band. We find that FSRQs can explain the entire CXB emission for energies above 500 keV solving the mystery of the generation of the MeV background. The evolution of luminous FSRQs shows a peak in redshift (z_c_=4.3+/-0.5) which is larger than the one observed in QSOs and X-ray-selected AGNs. We argue that FSRQs can be used as tracers of massive elliptical galaxies in the early universe.
- ID:
- ivo://CDS.VizieR/J/ApJ/884/11
- Title:
- Exploring 6 AGN dusty torus models. II.
- Short Name:
- J/ApJ/884/11
- Date:
- 04 Dec 2021
- Publisher:
- CDS
- Description:
- This is the second in a series of papers devoted to exploring a set of six dusty models of active galactic nuclei (AGN) with available spectral energy distributions. These models are the smooth torus by Fritz+ (2006MNRAS.366..767F), the clumpy torus by Nenkova+ (2008ApJ...685..147N and 2008ApJ...685..160N), the clumpy torus by Honig & Kishimoto (2010A&A...523A..27H), the two-phase torus by Siebenmorgen+ (2015A&A...583A.120S), the two-phase torus by Stalevski+ (2012MNRAS.420.2756S and 2016MNRAS.458.2288S), and the wind model by Honig & Kishimoto (2017ApJ...838L..20H). The first paper explores discrimination among models and the parameter restriction using synthetic spectra. Here we perform spectral fitting of a sample of 110 AGN drawn from the Swift/BAT survey with Spitzer/IRS spectroscopic data. The aim is to explore which is the model that describes better the data and the resulting parameters. The clumpy wind-disk model by Honig & Kishimoto provides good fits for ~50% of the sample, and the clumpy torus model by Nenkova+ is good at describing ~30% of the objects. The wind-disk model by Honig & Kishimoto is better for reproducing the mid-infrared spectra of type 1 Seyferts (with 60% of the type 1 Seyferts well reproduced by this model compared to the 10% well represented by the clumpy torus model by Nenkova+), while type 2 Seyferts are equally fitted by both models (roughly 40% of the type 2 Seyferts). Large residuals are found irrespective of the model used, indicating that the AGN dust continuum emission is more complex than predicted by the models or that the parameter space is not well sampled. We found that all the resulting parameters for our AGN sample are roughly constrained to 10%-20% of the parameter space. Contrary to what is generally assumed, the derived outer radius of the torus is smaller (reaching up to a factor of ~5 smaller for 10pc tori) for the smooth torus by Fritz+ and the two-phase torus by Stalevski+ than the one derived from the clumpy torus by Nenkova+ Covering factors and line-of-sight viewing angles strongly depend on the model used. The total dust mass is the most robust derived quantity, giving equivalent results for four of these models.
- ID:
- ivo://CDS.VizieR/J/ApJS/161/21
- Title:
- Extended Chandra Deep Field-South survey
- Short Name:
- J/ApJS/161/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Chandra point-source catalogs for the Extended Chandra Deep Field-South (E-CDF-S) survey. The E-CDF-S consists of four contiguous 250ks Chandra observations covering an approximately square region of total solid angle ~0.3{deg}^2^, which flank the existing ~1Ms Chandra Deep Field-South (CDF-S). The survey reaches sensitivity limits of ~1.1x10^-16^ and ~6.7x10^-16^ergs/cm^2^/s for the 0.5-2.0 and 2-8keV bands, respectively. We detect 762 distinct X-ray point sources within the E-CDF-S exposure; 589 of these sources are new (i.e., not previously detected in the ~1Ms CDF-S). This brings the total number of X-ray point sources detected in the E-CDF-S region to 915 (via the E-CDF-S and ~1Ms CDF-S observations). Source positions are determined using matched-filter and centroiding techniques; the median positional uncertainty is ~0.35". In addition to our main Chandra catalog, we constructed a supplementary source catalog containing 33 lower significance X-ray point sources that have bright optical counterparts (R<23).
- ID:
- ivo://CDS.VizieR/J/AJ/131/2373
- Title:
- Extended Chandra Deep Field-South survey
- Short Name:
- J/AJ/131/2373
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Extended Chandra Deep Field-South (ECDFS) survey consists of four Chandra X-Ray Observatory ACIS-I pointings and covers ~1100arcmin^2^ (~0.3{deg}^2^) centered on the original CDF-S field to a depth of approximately 228ks. This is the largest Chandra survey ever conducted at such depth, and only one XMM-Newton survey reaches a lower flux limit in the hard 2.0-8.0keV band. We detect 651 unique sources: 587 using a conservative source-detection threshold and 64 using a lower source-detection threshold. These are presented as two separate catalogs. Of the 651 total sources, 561 are detected in the full 0.5-8.0keV band, 529 in the soft 0.5-2.0keV band, and 335 in the hard 2.0-8.0keV band. For point sources near the aim point, the limiting fluxes are approximately 1.7x10^-16^ and 3.9x10^-16^ergs/cm^2^/s in the 0.5-2.0 and 2.0-8.0keV bands, respectively. Using simulations, we determine the catalog completeness as a function of flux and assess uncertainties in the derived fluxes due to incomplete spectral information. We present the differential and cumulative flux distributions, which are in good agreement with the number counts from previous deep X-ray surveys and with the predictions from an active galactic nucleus (AGN) population synthesis model that can explain the X-ray background. In general, fainter sources have harder X-ray spectra, consistent with the hypothesis that these sources are mainly obscured AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJ/710/764
- Title:
- Extended radio emission in MOJAVE blazars
- Short Name:
- J/ApJ/710/764
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a study on the kiloparsec-scale radio emission in the complete flux density limited MOJAVE sample, comprising 135 radio-loud active galactic nuclei. New 1.4GHz Very Large Array (VLA) radio images of six quasars and previously unpublished images of 21 blazars are presented, along with an analysis of the high-resolution (VLA A-array) 1.4GHz emission for the entire sample. While extended emission is detected in the majority of the sources, about 7% of the sources exhibit only radio core emission. We expect more sensitive radio observations, however, to detect faint emission in these sources, as we have detected in the erstwhile "core-only" source, 1548+056. The kiloparsec-scale radio morphology varies widely across the sample. Many BL Lac objects exhibit extended radio power and kiloparsec-scale morphology typical of powerful FRII jets, while a substantial number of quasars possess radio powers intermediate between FRIs and FRIIs.
- ID:
- ivo://CDS.VizieR/J/ApJ/679/156
- Title:
- Extra central light in galactic nuclei. I.
- Short Name:
- J/ApJ/679/156
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the origin and properties of "extra" or "excess" central light in the surface brightness profiles of remnants of gas-rich mergers. By combining a large set of hydrodynamical simulations with data on observed mergers that span a broad range of profiles at various masses and degrees of relaxation, we show how to robustly separate the physically meaningful extra light (i.e., the stellar population formed in a compact central starburst during a gas-rich merger) from the outer profile established by violent relaxation acting on stars already present in the progenitor galaxies prior to the final stages of the merger. This separation is sensitive to the treatment of the profile, and we demonstrate that certain fitting procedures can yield physically misleading results. We show that our method reliably recovers the younger starburst population, and examine how the properties and mass of this component scale with the mass, gas content, and other aspects of the progenitors. We consider the time evolution of the profiles in different bands, and estimate the biases introduced by observational studies at different phases and wavelengths. We show that, when appropriately quantified, extra light is ubiquitous in both observed and simulated gas-rich merger remnants, with sufficient mass (~3%-30% of the stellar mass) to explain the apparent discrepancy in the maximum phase-space densities of ellipticals and their progenitor spirals.
- ID:
- ivo://CDS.VizieR/J/ApJ/678/96
- Title:
- Extragalactic H2O masers
- Short Name:
- J/ApJ/678/96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Green Bank Telescope, we conducted a "snapshot" survey for water maser emission toward the nuclei of 611 galaxies and detected eight new sources. The sample consisted of nearby (v<5000km/s) and luminous (M_B_<-19.5) galaxies, some with known nuclear activity but most not previously known to host AGNs. Our detections include both megamasers associated with AGNs and relatively low luminosity masers probably associated with star formation. The detection in UGC 3789 is particularly intriguing because the spectrum shows both systemic and high-velocity lines indicative of emission from an AGN accretion disk seen edge-on. Based on 6 months of monitoring, we detected accelerations among the systemic features ranging from 2 to 8km/s/yr, the larger values belonging to the most redshifted systemic components. High-velocity maser lines in UGC 3789 show no detectable drift over the same period. Although UGC 3789 was not known to be an AGN prior to this survey, the presence of a disk maser is strong evidence for nuclear activity, and an optical spectrum obtained later has confirmed it. With follow-up observations, it may be possible to measure a geometric distance to UGC 3789.
