10 research outputs found
Dissecting Galaxies: Separating Star Formation, Shock Excitation and AGN Activity in the Central Region of NGC 613
The most rapidly evolving regions of galaxies often display complex optical
spectra with emission lines excited by massive stars, shocks and accretion onto
supermassive black holes. Standard calibrations (such as for the star formation
rate) cannot be applied to such mixed spectra. In this paper we isolate the
contributions of star formation, shock excitation and active galactic nucleus
(AGN) activity to the emission line luminosities of individual spatially
resolved regions across the central 3 3 kpc region of the active
barred spiral galaxy NGC613. The star formation rate and AGN luminosity
calculated from the decomposed emission line maps are in close agreement with
independent estimates from data at other wavelengths. The star formation
component traces the B-band stellar continuum emission, and the AGN component
forms an ionization cone which is aligned with the nuclear radio jet. The
optical line emission associated with shock excitation is cospatial with strong
and [Fe II] emission and with regions of high ionized gas velocity
dispersion ( km s). The shock component also traces the
outer boundary of the AGN ionization cone and may therefore be produced by
outflowing material interacting with the surrounding interstellar medium. Our
decomposition method makes it possible to determine the properties of star
formation, shock excitation and AGN activity from optical spectra, without
contamination from other ionization mechanisms.Comment: 16 pages, 12 figures. Accepted for publication in MNRA
Shedding New Light on Weak Emission-Line Quasars in the C-H Parameter Space
Weak emission-line quasars (WLQs) are a subset of Type 1 quasars that exhibit
extremely weak LyN V 1240 and/or C IV 1549 emission
lines. We investigate the relationship between emission-line properties and
accretion rate for a sample of 230 `ordinary' Type 1 quasars and 18 WLQs at and that have rest-frame ultraviolet and optical
spectral measurements. We apply a correction to the H-based black-hole
mass () estimates of these quasars using the strength of the
optical Fe II emission. We confirm previous findings that WLQs'
values are overestimated by up to an order of magnitude using the traditional
broad emission-line region size-luminosity relation. With this
correction, we find a significant correlation between H-based Eddington
luminosity ratios and a combination of the rest-frame C IV equivalent width and
C IV blueshift with respect to the systemic redshift. This correlation holds
for both ordinary quasars and WLQs, which suggests that the two-dimensional C
IV parameter space can serve as an indicator of accretion rate in all Type 1
quasars across a wide range of spectral properties.Comment: 17 pages (AASTeX 6.3.1), 5 figures, accepted for publication in Ap
Broad-line region in NGC 4151 monitored by two decades of reverberation mapping campaigns. I. Evolution of structure and kinematics
We report the results of long-term reverberation mapping (RM) campaigns of
the nearby active galactic nuclei (AGN) NGC 4151, spanning from 1994 to 2022,
based on archived observations of the FAST Spectrograph Publicly Archived
Programs and our new observations with the 2.3m telescope at the Wyoming
Infrared Observatory. We reduce and calibrate all the spectra in a consistent
way, and derive light curves of the broad H line and 5100\,{\AA}
continuum. Continuum light curves are also constructed using public archival
photometric data to increase sampling cadences. We subtract the host galaxy
contamination using {\it HST} imaging to correct fluxes of the calibrated light
curves. Utilizing the long-term archival photometric data, we complete the
absolute flux-calibration of the AGN continuum. We find that the H time
delays are correlated with the 5100\,{\AA} luminosities as . This is remarkably consistent with
Bentz et al. (2013)'s global size-luminosity relationship of AGNs. Moreover,
the data sets for five of the seasons allow us to obtain the velocity-resolved
delays of the H line, showing diverse structures (outflows, inflows and
disks). Combining our results with previous independent measurements, we find
the measured dynamics of the H broad-line region (BLR) are possibly
related to the long-term trend of the luminosity. There is also a possible
additional 1.86 years time lag between the variation in BLR radius and
luminosity. These results suggest that dynamical changes in the BLR may be
driven by the effects of radiation pressure.Comment: Accepted for publication in MNRAS; comments welcome
Systematically smaller single-epoch quasar black hole masses using a radius-luminosity relationship corrected for spectral bias
Determining black hole masses and accretion rates with better accuracy and
precision is crucial for understanding quasars as a population. These are
fundamental physical properties that underpin models of active galactic nuclei.
A primary technique to measure the black hole mass employs the reverberation
mapping of low-redshift quasars, which is then extended via the
radius-luminosity relationship for the broad-line region to estimate masses
based on single-epoch spectra. An updated radius-luminosity relationship
incorporates the flux ratio of optical Fe ii to H () to correct for a bias in which more highly accreting
systems have smaller line-emitting regions than previously realized. In this
current work, we demonstrate and quantify the effect of using this Fe-corrected
radius-luminosity relationship on mass estimation by employing archival data
sets possessing rest-frame optical spectra over a wide range of redshifts. We
find that failure to use a Fe-corrected radius predictor results in
overestimated single-epoch black hole masses for the most highly accreting
quasars. Their accretion rate measures ( and
), are similarly underestimated. The strongest Fe-emitting
quasars belong to two classes: high-z quasars with rest-frame optical spectra,
which given their extremely high luminosities, require high accretion rates,
and their low-z analogs, which given their low black holes masses, must have
high accretion rates to meet survey flux limits. These classes have mass
corrections downward of about a factor of two, on average. These results
strengthen the association of the dominant Eigenvector 1 parameter
with the accretion process.Comment: Accepted by MNRAS, 16 pages. All figures are included in the source
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