412 research outputs found
Co-evolution and Nuclear Structure in the Dwarf Galaxy POX 52 Studied by Multi-wavelength Data From Radio to X-ray
The nearby dwarf galaxy POX 52 at hosts an active galactic
nucleus (AGN) with a black-hole (BH) mass of
and an Eddington ratio of 0.1-1. This object provides the rare
opportunity to study both AGN and host-galaxy properties in a low-mass highly
accreting system. To do so, we collected its multi-wavelength data from X-ray
to radio. First, we construct a spectral energy distribution, and by fitting it
with AGN and host-galaxy components, we constrain AGN-disk and dust-torus
components. Then, while considering the AGN-disk emission, we decompose optical
HST images. As a result, it is found that a classical bulge component is
probably present, and its mass () is consistent with an expected
value from a local relation. Lastly, we analyze new quasi-simultaneous X-ray
(0.2-30 keV) data obtained by NuSTAR and XMM-Newton. The X-ray spectrum can be
reproduced by multi-color blackbody, warm and hot coronae, and disk and torus
reflection components. Based on this, the spin is estimated to be , which could suggest that most of the current BH mass was
achieved by prolonged mass accretion. Given the presence of the bulge, POX 52
would have undergone a galaxy merger, while the -
relation and the inferred prolonged accretion could suggest that AGN feedback
occurred. Regarding the AGN structure, the spectral slope of the hot corona,
its relative strength to the bolometric emission, and the torus structure are
found to be consistent with Eddington-ratio dependencies found for nearby AGNs.Comment: 26 pages, 10 figures, 4 tables, accepted for publication in ApJ. The
data in Table 4 are available from
http://www.kusastro.kyoto-u.ac.jp/~kawamuro/arxiv/SEDplusComponents_u.tx
Naval History by Conspiracy Theory: The British Admiralty before the First World War and the Methodology of Revisionism
Revisionist interpretations of British naval policy in the Fisher era claim that an elaborate smoke screen was created to hide the Royal Navy’s real policies; while documents showing the true goals were systematically destroyed. By asserting this, revisionists are able to dismiss those parts of the documentary record that contradict their theories, while simultaneously excusing the lack of evidence for their theories by claiming it has been destroyed. This article shows that this methodology is misleading and untenable
BASS XXXIX: Swift-BAT AGN with changing-look optical spectra
Changing-look (CL) AGN are unique probes of accretion onto supermassive black
holes (SMBHs), especially when simultaneous observations in complementary
wavebands allow investigations into the properties of their accretion flows. We
present the results of a search for CL behaviour in 412 Swift-BAT detected AGN
with multiple epochs of optical spectroscopy from the BAT AGN Spectroscopic
Survey (BASS). 125 of these AGN also have 14-195 keV ultra-hard X-ray
light-curves from Swift-BAT which are contemporaneous with the epochs of
optical spectroscopy. Eight CL events are presented for the first time, where
the appearance or disappearance of broad Balmer line emission leads to a change
in the observed Seyfert type classification. Combining with known events from
the literature, 21 AGN from BASS are now known to display CL behaviour. Nine CL
events have 14-195 keV data available, and five of these CL events can be
associated with significant changes in their 14-195 keV flux from BAT. The
ultra-hard X-ray flux is less affected by obscuration and so these changes in
the 14-195 keV band suggest that the majority of our CL events are not due to
changes in line-of-sight obscuration. We derive a CL rate of 0.7-6.2 per cent
on 10-25 year time-scales, and show that many transitions happen within at most
a few years. Our results motivate further multi-wavelength observations with
higher cadence to better understand the variability physics of accretion onto
SMBHs.Comment: 14 pages, 7 figures, plus appendix. v2: updated references. Published
in MNRA
The LSST AGN Data Challenge: Selection methods
Development of the Rubin Observatory Legacy Survey of Space and Time (LSST)
includes a series of Data Challenges (DC) arranged by various LSST Scientific
Collaborations (SC) that are taking place during the projects preoperational
phase. The AGN Science Collaboration Data Challenge (AGNSCDC) is a partial
prototype of the expected LSST AGN data, aimed at validating machine learning
approaches for AGN selection and characterization in large surveys like LSST.
The AGNSC-DC took part in 2021 focusing on accuracy, robustness, and
scalability. The training and the blinded datasets were constructed to mimic
the future LSST release catalogs using the data from the Sloan Digital Sky
Survey Stripe 82 region and the XMM-Newton Large Scale Structure Survey region.
Data features were divided into astrometry, photometry, color, morphology,
redshift and class label with the addition of variability features and images.
We present the results of four DC submitted solutions using both classical and
machine learning methods. We systematically test the performance of supervised
(support vector machine, random forest, extreme gradient boosting, artificial
neural network, convolutional neural network) and unsupervised (deep embedding
clustering) models when applied to the problem of classifying/clustering
sources as stars, galaxies or AGNs. We obtained classification accuracy 97.5%
for supervised and clustering accuracy 96.0% for unsupervised models and 95.0%
with a classic approach for a blinded dataset. We find that variability
features significantly improve the accuracy of the trained models and
correlation analysis among different bands enables a fast and inexpensive first
order selection of quasar candidatesComment: Accepted by ApJ. 21 pages, 14 figures, 5 table
A disc wind model for blueshifts in quasar broad emission lines
Blueshifts - or, more accurately, blue asymmetries - in broad emission lines
such as CIV 1550 are common in luminous quasars and correlate with
fundamental properties such as Eddington ratio and broad absorption line (BAL)
characteristics. However, the formation of these blueshifts is still not
understood, and neither is their physical connection to the BAL phenomenon or
accretion disc. In this work, we present Monte Carlo radiative transfer and
photoionization simulations using parametrized biconical disc-wind models. We
take advantage of the azimuthal symmetry of a quasar and show that we can
reproduce CIV blueshifts provided that (i) the disc-midplane is optically thick
out to radii beyond the line formation region, so that the receding wind bicone
is obscured; and (ii) the system is viewed from relatively low (that is, more
face-on) inclinations (). We show that CIV emission line
blueshifts and BALs can form in the same wind structure. The velocity profile
of the wind has a significant impact on the location of the line formation
region and the resulting line profile, suggesting that the shape of the
emission lines can be used as a probe of wind-driving physics. While we are
successful at producing blueshifts/blue asymmetries in outflows, we struggle to
match the detailed shape or skew of the observed emission line profiles. In
addition, our models produce redshifted emission-line asymmetries for certain
viewing angles. We discuss our work in the context of the CIV 1550
emission blueshift versus equivalent-width space and explore the implications
for quasar disc wind physics.Comment: 20 pages, 12 figures + 1 appendix. Supplementary material, simulation
data and plotting scripts available at:
https://github.com/jhmatthews/blueshift
BASS-XL: X-ray variability properties of unobscured active galactic nuclei
We investigate the X-ray variability properties of Seyfert 1 Galaxies belonging to the BAT AGN Spectroscopic Survey (BASS). The sample includes 151 unobscured (N-H < 10(22) cm(-2)) AGNs observed with XMM-Newton for a total exposure time of similar to 27 ms, representing the deepest variability study done so far with high signal-to-noise XMM-Newton observations, almost doubling the number of observations analysed in previous works. We constrain the relation between the normalized excess variance and the 2-10 keV AGN luminosities, black hole masses, and Eddington ratios. We find a highly significant correlation between sigma(2)(NXS) and M-BH, with a scatter of similar to 0.85 dex. For sources with high L2-10 this correlation has a lower normalization, confirming that more luminous (higher mass) AGNs show less variability. We explored the sigma(2)(NXS) versus M-BH relation for the sub-sample of sources with M-BH estimated via the 'reverberation mapping' technique, finding a tighter anticorrelation, with a scatter of similar to 0.65 dex. We examine how the sigma(2)(NXS) changes with energy by studying the relation between the variability in the hard (3-10 keV) and the soft (0.2-1 keV)/medium (1-3 keV) energy bands, finding that the spectral components dominating the hard energy band are more variable than the spectral components dominating in softer energy bands, on time-scales shorter than 10 ks
Probing the Structure and Evolution of BASS AGN through Eddington Ratios
We constrain the intrinsic Eddington ratio (\lamEdd ) distribution function
for local AGN in bins of low and high obscuration (log NH <= 22 and 22 < log NH
< 25), using the Swift-BAT 70-month/BASS DR2 survey. We interpret the fraction
of obscured AGN in terms of circum-nuclear geometry and temporal evolution.
Specifically, at low Eddington ratios (log lamEdd < -2), obscured AGN outnumber
unobscured ones by a factor of ~4, reflecting the covering factor of the
circum-nuclear material (0.8, or a torus opening angle of ~ 34 degrees). At
high Eddington ratios (\log lamEdd > -1), the trend is reversed, with < 30% of
AGN having log NH > 22, which we suggest is mainly due to the small fraction of
time spent in a highly obscured state. Considering the Eddington ratio
distribution function of narrow-line and broad-line AGN from our prior work, we
see a qualitatively similar picture. To disentangle temporal and geometric
effects at high lamEdd, we explore plausible clearing scenarios such that the
time-weighted covering factors agree with the observed population ratio. We
find that the low fraction of obscured AGN at high lamEdd is primarily due to
the fact that the covering factor drops very rapidly, with more than half the
time is spent with < 10% covering factor. We also find that nearly all obscured
AGN at high-lamEdd exhibit some broad-lines. We suggest that this is because
the height of the depleted torus falls below the height of the broad-line
region, making the latter visible from all lines of sight.Comment: Accepted by ApJ
BASS XXXIV: A Catalog of the Nuclear Mm-wave Continuum Emission Properties of AGNs Constrained on Scales 100--200 pc
We present a catalog of the millimeter-wave (mm-wave) continuum properties of
98 nearby ( 0.05) active galactic nuclei (AGNs) selected from the 70-month
Swift/BAT hard X-ray catalog that have precisely determined X-ray spectral
properties and subarcsec-resolution ALMA Band-6 (211--275 GHz) observations as
of 2021 April. Due to the hard-X-ray ( 10 keV) selection, the sample is
nearly unbiased for obscured systems at least up to Compton-thick-level
obscuration, and provides the largest number of AGNs with high physical
resolution mm-wave data ( 100--200 pc). Our catalog reports emission
peak coordinates, spectral indices, and peak fluxes and luminosities at 1.3 mm
(230 GHz). Additionally, high-resolution mm-wave images are provided. Using the
images and creating radial surface brightness profiles of mm-wave emission, we
identify emission extending from the central source and isolated blob-like
emission. Flags indicating the presence of these emission features are
tabulated. Among 90 AGNs with significant detections of nuclear emission, 37
AGNs ( 41%) appear to have both or one of extended or blob-like
components. We, in particular, investigate AGNs that show well-resolved mm-wave
components and find that these seem to have a variety of origins (i.e., a jet,
radio lobes, a secondary AGN, stellar clusters, a narrow line region, galaxy
disk, active star-formation regions, and AGN-driven outflows), and some
components have currently unclear origins.Comment: 49 pages, 7 figures, 3 tables, accepted for publication in ApJ
The SDSS-V Black Hole Mapper Reverberation Mapping Project: Unusual Broad-Line Variability in a Luminous Quasar
We present a high-cadence multi-epoch analysis of dramatic variability of
three broad emission lines (MgII, H, and H) in the spectra of
the luminous quasar ((5100\r{A}) =
erg s) SDSS J141041.25+531849.0 at with 127 spectroscopic
epochs over 9 years of monitoring (2013-2022). We observe anti-correlations
between the broad emission-line widths and flux in all three emission lines,
indicating that all three broad emission lines "breathe" in response to
stochastic continuum variations. We also observe dramatic radial velocity
shifts in all three broad emission lines, ranging from 400 km
s to 800 km s, that vary over the course of the monitoring
period. Our preferred explanation for the broad-line variability is complex
kinematics in the broad-line region gas. We suggest a model for the broad-line
variability that includes a combination of gas inflow with a radial gradient,
an azimuthal asymmetry (e.g., a hot spot), superimposed on the stochastic
flux-driven changes to the optimal emission region ("line breathing"). Similar
instances of line-profile variability due to complex gas kinematics around
quasars are likely to represent an important source of false positives in
radial velocity searches for binary black holes, which typically lack the kind
of high-cadence data we analyze here. The long-duration, wide-field, and
many-epoch spectroscopic monitoring of SDSS-V BHM-RM provides an excellent
opportunity for identifying and characterizing broad emission-line variability,
and the inferred nature of the inner gas environment, of luminous quasars
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