44 research outputs found
BASS. XXVIII : Near-infrared Data Release 2 : high-ionization and broad lines in active galactic nuclei
We present the BAT AGN Spectroscopic Survey (BASS) Near-infrared Data Release 2 (DR2), a study of 168 nearby (z¯= 0.04, z 100 eV). Comparing the emission of the [Si vi] λ1.9640 CL with the X-ray emission for the DR2 AGN, we find a significantly tighter correlation, with a lower scatter (0.37 dex) than that for the optical [O iii] λ5007 line (0.71 dex). We do not find any correlation between CL emission and the X-ray photon index Γ. We find a clear trend of line blueshifts with increasing ionization potential in several CLs, such as [Si vi] λ1.9640, [Si x] λ1.4300, [S viii] λ0.9915, and [S ix] λ1.2520, indicating the radial structure of the CL region. Finally, we find a strong underestimation bias in black hole mass measurements of Sy 1.9 using broad Hα due to the presence of significant dust obscuration. In contrast, the broad Paα and Paβ emission lines are in agreement with the M–σ relation. Based on the combined DR1 and DR2 X-shooter sample, the NIR BASS sample now comprises 266 AGN with rest-frame NIR spectroscopic observations, the largest set assembled to date
Spectral Stacking of Radio-Interferometric Data
Mapping molecular line emission beyond the bright low-J CO transitions is
still challenging in extragalactic studies, even with the latest generation of
(sub-)mm interferometers, such as ALMA and NOEMA. We summarise and test a
spectral stacking method that has been used in the literature to recover
low-intensity molecular line emission, such as HCN(1-0), HCO+(1-0), and even
fainter lines in external galaxies. The goal is to study the capabilities and
limitations of the stacking technique when applied to imaged interferometric
observations. The core idea of spectral stacking is to align spectra of the low
S/N spectral lines to a known velocity field calculated from a higher S/N line
expected to share the kinematics of the fainter line, e.g., CO(1-0) or 21-cm
emission. Then these aligned spectra can be coherently averaged to produce
potentially high S/N spectral stacks. Here, we use imaged simulated
interferometric and total power observations at different signal-to-noise
levels, based on real CO observations. For the combined interferometric and
total power data, we find that the spectral stacking technique is capable of
recovering the integrated intensities even at low S/N levels across most of the
region where the high S/N prior is detected. However, when stacking
interferometer-only data for low S/N emission, the stacks can miss up to 50% of
the emission from the fainter line. A key result of this analysis is that the
spectral stacking method is able to recover the true mean line intensities in
low S/N cubes and to accurately measure the statistical significance of the
recovered lines. To facilitate the application of this technique we provide a
public Python package, called PyStacker.Comment: 10 pages, 10 figures, accepted for pub in A&A, Apr 28, 202
BASS. XXIV : the BASS DR2 spectroscopic line measurements and AGN demographics
We present the second catalog and data release of optical spectral line measurements and active galactic nucleus (AGN) demographics of the BAT AGN Spectroscopic Survey, which focuses on the Swift-BAT hard X-ray detected AGNs. We use spectra from dedicated campaigns and publicly available archives to investigate spectral properties of most of the AGNs listed in the 70 month Swift-BAT all-sky catalog; specifically, 743 of the 746 unbeamed and unlensed AGNs (99.6%). We find a good correspondence between the optical emission line widths and the hydrogen column density distributions using the X-ray spectra, with a clear dichotomy of AGN types for NH = 1022 cm−2. Based on optical emission-line diagnostics, we show that 48%–75% of BAT AGNs are classified as Seyfert, depending on the choice of emission lines used in the diagnostics. The fraction of objects with upper limits on line emission varies from 6% to 20%. Roughly 4% of the BAT AGNs have lines too weak to be placed on the most commonly used diagnostic diagram, [O iii]λ5007/Hβ versus [N ii]λ6584/Hα, despite the high signal-to-noise ratio of their spectra. This value increases to 35% in the [O iii]λ5007/[O ii]λ3727 diagram, owing to difficulties in line detection. Compared to optically selected narrow-line AGNs in the Sloan Digital Sky Survey, the BAT narrow-line AGNs have a higher rate of reddening/extinction, with Hα/Hβ > 5 (∼36%), indicating that hard X-ray selection more effectively detects obscured AGNs from the underlying AGN population. Finally, we present a subpopulation of AGNs that feature complex broad lines (34%, 250/743) or double-peaked narrow emission lines (2%, 17/743)
Surveying the Whirlpool at Arcseconds with NOEMA (SWAN)- I. Mapping the HCN and NH 3mm lines
We present the first results from "Surveying the Whirlpool at Arcseconds with
NOEMA" (SWAN), an IRAM Northern Extended Millimetre Array (NOEMA)+30m large
program that maps emission from several molecular lines at 90 and 110 GHz in
the iconic nearby grand-design spiral galaxy M~51 at cloud-scale resolution
(3\arcsec=125\,pc). As part of this work, we have obtained the first
sensitive cloud-scale map of NH(1-0) of the inner kpc of a normal star-forming galaxy, which we compare to HCN(1-0) and
CO(1-0) emission to test their ability in tracing dense, star-forming gas. The
average NH-to-HCN line ratio of our total FoV is , with
strong regional variations of a factor of throughout the disk,
including the south-western spiral arm and the center. The central kpc
exhibits elevated HCN emission compared to NH, probably caused by
AGN-driven excitation effects. We find that HCN and NH are strongly
super-linearily correlated in intensity (), with an
average scatter of dex over a span of dex in
intensity. When excluding the central region, the data is best described by a
power-law of exponent , indicating that there is more NH per unit
HCN in brighter regions. Our observations demonstrate that the HCN-to-CO line
ratio is a sensitive tracer of gas density in agreement with findings of recent
Galactic studies which utilize NH. The peculiar line ratios present
near the AGN and the scatter of the power-law fit in the disk suggest that in
addition to a first-order correlation with gas density, second-order physics
(such as optical depth, gas temperature) or chemistry (abundance variations)
are encoded in the NH/CO, HCN/CO and NH/HCN ratios.Comment: Accepted for publication in A&A. 6 pages, 3 figures (+ Appendix 4
pages, 2 figures
Wide-field CO isotopologue emission and the CO-to-H factor across the nearby spiral galaxy M101
Carbon monoxide (CO) emission is the most widely used tracer of the bulk
molecular gas in the interstellar medium (ISM) in extragalactic studies. The
CO-to-H conversion factor, , links the observed CO
emission to the total molecular gas mass. However, no single prescription
perfectly describes the variation of across all environments
across galaxies as a function of metallicity, molecular gas opacity, line
excitation, and other factors. Using resolved spectral line observations of CO
and its isotopologues, we can constrain the molecular gas conditions and link
them to a variation in the conversion factor. We present new IRAM 30-m 1mm and
3mm line observations of CO, CO, and CO} across the nearby
galaxy M101. Based on the CO isotopologue line ratios, we find that selective
nucleosynthesis and opacity changes are the main drivers of the variation in
the line emission across the galaxy. Furthermore, we estimated using different approaches, including (i) the dust mass surface
density derived from far-IR emission as an independent tracer of the total gas
surface density and (ii) LTE-based measurements using the optically thin
CO(1-0) intensity. We find an average value of across the galaxy,
with a decrease by a factor of 10 toward the 2 kpc central region. In contrast,
we find LTE-based values are lower by a factor of 2-3 across the disk relative
to the dust-based result. Accounting for variations, we found
significantly reduced molecular gas depletion time by a factor 10 in the
galaxy's center. In conclusion, our result suggests implications for commonly
derived scaling relations, such as an underestimation of the slope of the
Kennicutt Schmidt law, if variations are not accounted for.Comment: Accepted for publication in A&A, 25 pages, 15 figure
BASS. XXV. DR2 Broad-line-based Black Hole Mass Estimates and Biases from Obscuration
We present measurements of broad emission lines and virial estimates of supermassive black hole masses (M BH) for a large sample of ultrahard X-ray-selected active galactic nuclei (AGNs) as part of the second data release of the BAT AGN Spectroscopic Survey (BASS/DR2). Our catalog includes M BH estimates for a total of 689 AGNs, determined from the Hα, Hβ, Mg ii λ2798, and/or C iv λ1549 broad emission lines. The core sample includes a total of 512 AGNs drawn from the 70 month Swift/BAT all-sky catalog. We also provide measurements for 177 additional AGNs that are drawn from deeper Swift/BAT survey data. We study the links between M BH estimates and line-of-sight obscuration measured from X-ray spectral analysis. We find that broad Hα emission lines in obscured AGNs ( log(NH/cm−2)>22.0 ) are on average a factor of 8.0−2.4+4.1 weaker relative to ultrahard X-ray emission and about 35−12+7 % narrower than those in unobscured sources (i.e., log(NH/cm−2)1 dex) masses for Type 1.9 sources (AGNs with broad Hα but no broad Hβ) and/or sources with log(NH/cm−2)≳22.0 . We provide simple multiplicative corrections for the observed luminosity and width of the broad Hα component (L[bHα] and FWHM[bHα]) in such sources to account for this effect and to (partially) remedy M BH estimates for Type 1.9 objects. As a key ingredient of BASS/DR2, our work provides the community with the data needed to further study powerful AGNs in the low-redshift universe
Gaia GraL: Gaia DR2 Gravitational Lens Systems. VII. XMM-Newton Observations of Lensed Quasars
© 2022. The Author(s). Published by the American Astronomical Society. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.3847/1538-4357/ac4476We present XMM-Newton X-ray observations of nine confirmed lensed quasars at 1 ≲ z ≲ 3 identified by the Gaia Gravitational Lens program. Eight systems are strongly detected, with 0.3-8.0 keV fluxes F 0.3-8.0 ≳ 5 ×10-14 erg cm-2 s-1. Modeling the X-ray spectra with an absorbed power law, we derive power-law photon indices and 2-10 keV luminosities for the eight detected quasars. In addition to presenting sample properties for larger quasar population studies and for use in planning for future caustic-crossing events, we also identify three quasars of interest: a quasar that shows evidence of flux variability from previous ROSAT observations, the most closely separated individual lensed sources resolved by XMM-Newton, and one of the X-ray brightest quasars known at z > 3. These sources represent the tip of the discoveries that will be enabled by SRG/eROSITA.Peer reviewe
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
Gaia GraL: Gaia DR2 gravitational lens systems – VIII. A radio census of lensed systems
© 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/We present radio observations of 24 confirmed and candidate strongly lensed quasars identified by the Gaia Gravitational Lenses working group. We detect radio emission from eight systems in 5.5 and 9 GHz observations with the Australia Telescope Compact Array (ATCA), and 12 systems in 6 GHz observations with the Karl G. Jansky Very Large Array (VLA). The resolution of our ATCA observations is insufficient to resolve the radio emission into multiple lensed images, but we do detect multiple images from 11 VLA targets. We have analysed these systems using our observations in conjunction with existing optical measurements, including measuring offsets between the radio and optical positions for each image and building updated lens models. These observations significantly expand the existing sample of lensed radio quasars, suggest that most lensed systems are detectable at radio wavelengths with targeted observations, and demonstrate the feasibility of population studies with high-resolution radio imaging.Peer reviewe
Gaia GraL: Gaia DR2 Gravitational Lens Systems. VIII. A radio census of lensed systems
We present radio observations of 24 confirmed and candidate strongly lensed
quasars identified by the Gaia Gravitational Lenses (GraL) working group. We
detect radio emission from 8 systems in 5.5 and 9 GHz observations with the
Australia Telescope Compact Array (ATCA), and 12 systems in 6 GHz observations
with the Karl G. Jansky Very Large Array (VLA). The resolution of our ATCA
observations is insufficient to resolve the radio emission into multiple lensed
images, but we do detect multiple images from 11 VLA targets. We have analysed
these systems using our observations in conjunction with existing optical
measurements, including measuring offsets between the radio and optical
positions, for each image and building updated lens models. These observations
significantly expand the existing sample of lensed radio quasars, suggest that
most lensed systems are detectable at radio wavelengths with targeted
observations, and demonstrate the feasibility of population studies with high
resolution radio imaging