The relative contribution of baryons and dark matter to the inner regions of spiral galaxies provides critical clues to their formation and evolution, but it is generally difficult to determine. For ...spiral galaxies that are strong gravitational lenses, however, the combination of lensing and kinematic observations can be used to break the disc-halo degeneracy. In turn, such data constrain fundamental parameters such as (i) the mass density profile slope and axial ratio of the dark matter halo, and by comparison with dark matter-only numerical simulations the modifications imposed by baryons; (ii) the mass in stars and therefore the overall star formation efficiency, and the amount of feedback; (iii) by comparison with stellar population synthesis models, the normalization of the stellar initial mass function. In this first paper of a series, we present a sample of 16 secure, one probable and six possible strong lensing spiral galaxies, for which multiband high-resolution images and rotation curves were obtained using the Hubble Space Telescope and Keck II telescope as part of the Sloan WFC Edge-on Late-type Lens Survey (SWELLS). The sample includes eight newly discovered secure systems. We characterize the sample of deflector galaxies in terms of their morphologies, structural parameters and stellar masses. We find that the SWELLS sample of secure lenses spans a broad range of morphologies (from lenticular to late-type spiral), spectral types (quantified by Hα emission) and bulge to total stellar mass ratio (0.22-0.85), while being limited to M
* > 1010.5 M⊙. The SWELLS sample is thus well suited for exploring the relationship between dark and luminous matter in a broad range of galaxies. We find that the deflector galaxies obey the same size-mass relation as that of a comparison sample of elongated non-lens galaxies selected from the Sloan Digital Sky Survey. We conclude that the SWELLS sample is consistent with being representative of the overall population of high-mass high-inclination discy galaxies.
Abstract
We have modeled the velocity-resolved reverberation response of the H
β
broad emission line in nine Seyfert 1 galaxies from the Lick Active Galactic Nucleus (AGN) Monitoring Project 2016 ...sample, drawing inferences on the geometry and structure of the low-ionization broad-line region (BLR) and the mass of the central supermassive black hole. Overall, we find that the H
β
BLR is generally a thick disk viewed at low to moderate inclination angles. We combine our sample with prior studies and investigate line-profile shape dependence, such as
log
10
(
FWHM
/
σ
)
, on BLR structure and kinematics and search for any BLR luminosity-dependent trends. We find marginal evidence for an anticorrelation between the profile shape of the broad H
β
emission line and the Eddington ratio, when using the rms spectrum. However, we do not find any luminosity-dependent trends, and conclude that AGNs have diverse BLR structure and kinematics, consistent with the hypothesis of transient AGN/BLR conditions rather than systematic trends.
Abstract
We present the first ever models of a broad line region (BLR) at the peak of active galactic nucleus (AGN) activity using the multiply imaged
z
= 2.805 quasar SDSS J2222+2745. The modeled ...data consist of monthly spectra covering the broad C
iv
emission line over a 5.3 yr baseline. The models suggest a thick disk BLR that is inclined by ∼40° to the observer’s line of sight and with an emissivity weighted median radius of
r
median
=
33.0
−
2.1
+
2.4
light days. The kinematics are dominated by near-circular Keplerian motion with the remainder inflowing. The rest-frame lag one would measure from the models is
τ
median
=
36.4
−
1.8
+
1.8
days, which is consistent with measurements based on cross-correlation. We show a possible geometry and transfer function based on the model fits and find that the model-produced velocity-resolved lags are consistent with those from cross-correlation. We measure a black hole mass of
log
10
(
M
BH
/
M
⊙
)
=
8.31
−
0.06
+
0.07
, which requires a scale factor of
log
10
(
f
mean
,
σ
)
=
0.20
−
0.07
+
0.09
. This is the most precise
M
BH
measurement for any AGN at cosmological distances and it demonstrates that the precision required for BH-host coevolution studies is attainable.
We introduce a general Monte Carlo method based on Nested Sampling (NS), for sampling complex probability distributions and estimating the normalising constant. The method uses one or more particles, ...which explore a mixture of nested probability distributions, each successive distribution occupying ∼
e
−1
times the enclosed prior mass of the previous distribution. While NS technically requires independent generation of particles, Markov Chain Monte Carlo (MCMC) exploration fits naturally into this technique. We illustrate the new method on a test problem and find that it can achieve four times the accuracy of classic MCMC-based Nested Sampling, for the same computational effort; equivalent to a factor of 16 speedup. An additional benefit is that more samples and a more accurate evidence value can be obtained simply by continuing the run for longer, as in standard MCMC.
ABSTRACT The degeneracy among the disc, bulge and halo contributions to galaxy rotation curves prevents an understanding of the distribution of baryons and dark matter in disc galaxies. In an attempt ...to break this degeneracy, we present an analysis of the strong gravitational lens SDSSJ2141-0001, discovered as part of the Sloan Lens ACS survey. The lens galaxy is a high-inclination, disc-dominated system. We present new Hubble Space Telescope multicolour imaging, gas and stellar kinematics data derived from long-slit spectroscopy and K-band laser guide star adaptive optics imaging, both from the Keck telescopes. We model the galaxy as a sum of concentric axisymmetric bulge, disc and halo components and infer the contribution of each component, using information from gravitational lensing and gas kinematics. This analysis yields a best-fitting total (disc plus bulge) stellar mass of log10(M*/M) = 10.99+0.11- 0.25. The photometric data combined with stellar population synthesis models yield log10(M*/M) = 10.97 ± 0.07 and 11.21 ± 0.07 for the Chabrier and Salpeter initial mass functions (IMFs), respectively. Assuming no cold gas, a Salpeter IMF is marginally disfavoured, with a Bayes factor of 2.7. Accounting for the expected gas fraction of 20 per cent reduces the lensing plus kinematics stellar mass by 0.10 ± 0.05dex, resulting in a Bayes factor of 11.9 in favour of a Chabrier IMF. The dark matter halo is roughly spherical, with minor to major axis ratio q3, h= 0.91+0.15- 0.13. The dark matter halo has a maximum circular velocity of Vmax= 276+17- 18kms-1, and a central density parameter of log10ΔV/2= 5.9+0.9- 0.5. This is higher than predicted for uncontracted dark matter haloes in Λ cold dark matter cosmologies, log10ΔV/2= 5.2, suggesting that either the halo has contracted in response to galaxy formation, or that the halo has a higher than average concentration. Larger samples of spiral galaxy strong gravitational lenses are needed in order to distinguish between these two possibilities. At 2.2 disc scalelengths the dark matter fraction is fDM= 0.55+0.20- 0.15, suggesting that SDSSJ2141-0001 is submaximal. PUBLICATION ABSTRACT
What Does the Geometry of the Hβ BLR Depend On? Villafaña, Lizvette; Williams, Peter R.; Treu, Tommaso ...
Astrophysical journal/The Astrophysical journal,
05/2023, Letnik:
948, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
We combine our dynamical modeling black-hole mass measurements from the Lick AGN Monitoring Project 2016 sample with measured cross-correlation time lags and line widths to recover ...individual scale factors,
f
, used in traditional reverberation-mapping analyses. We extend our sample by including prior results from Code for AGN Reverberation and Modeling of Emission Lines (
caramel
) studies that have utilized our methods. Aiming to improve the precision of black-hole mass estimates, as well as uncover any regularities in the behavior of the broad-line region (BLR), we search for correlations between
f
and other AGN/BLR parameters. We find (i) evidence for a correlation between the virial coefficient
log
10
(
f
mean
,
σ
)
and black-hole mass, (ii) marginal evidence for a similar correlation between
log
10
(
f
rms
,
σ
)
and black-hole mass, (iii) marginal evidence for an anticorrelation of BLR disk thickness with
log
10
(
f
mean
,
FWHM
)
and
log
10
(
f
rms
,
FWHM
)
, and (iv) marginal evidence for an anticorrelation of inclination angle with
log
10
(
f
mean
,
FWHM
)
,
log
10
(
f
rms
,
σ
)
, and
log
10
(
f
mean
,
σ
)
. Last, we find marginal evidence for a correlation between line-profile shape, when using the root-mean-square spectrum,
log
10
(
FWHM
/
σ
)
rms
, and the virial coefficient,
log
10
(
f
rms
,
σ
)
, and investigate how BLR properties might be related to line-profile shape using
caramel
models.
Recent work has suggested that the stellar initial mass function (IMF) is not universal, but rather is correlated with galaxy stellar mass, stellar velocity dispersion or morphological type. In this ...paper, we investigate variations of the IMF within individual galaxies. For this purpose, we use strong lensing and gas kinematics to measure independently the normalization of the IMF of the bulge and disc components of a sample of five massive spiral galaxies with substantial bulge components taken from the Sloan WFC Edge-on Late-type Lens Survey (SWELLS). We find that the stellar masses of the bulges are tightly constrained by the lensing and kinematic data. A comparison with masses based on stellar population synthesis models fitted to optical and near-infrared photometry favours a Salpeter-like normalization of the IMF. Conversely, the disc masses are less well constrained due to degeneracies with the dark matter halo, but are consistent with Milky Way-type IMFs in agreement with previous studies. The discs are submaximal at 2.2 disc scale lengths, but due to the contribution of the bulges, the galaxies are baryon dominated at 2.2 disc scale lengths. Globally, our inferred IMF normalization is consistent with that found for early-type galaxies of comparable stellar mass (>1011 M). Our results suggest a non-universal IMF within the different components of spiral galaxies, adding to the well-known differences in stellar populations between discs and bulges.
Abstract
We present a novel Bayesian method, referred to as blobby3d, to infer gas kinematics that mitigates the effects of beam smearing for observations using integral field spectroscopy. The ...method is robust for regularly rotating galaxies despite substructure in the gas distribution. Modelling the gas substructure within the disc is achieved by using a hierarchical Gaussian mixture model. To account for beam smearing effects, we construct a modelled cube that is then convolved per wavelength slice by the seeing, before calculating the likelihood function. We show that our method can model complex gas substructure including clumps and spiral arms. We also show that kinematic asymmetries can be observed after beam smearing for regularly rotating galaxies with asymmetries only introduced in the spatial distribution of the gas. We present findings for our method applied to a sample of 20 star-forming galaxies from the SAMI Galaxy Survey. We estimate the global H α gas velocity dispersion for our sample to be in the range $\bar{\sigma }_v \sim$7, 30 km s−1. The relative difference between our approach and estimates using the single Gaussian component fits per spaxel is $\Delta \bar{\sigma }_v / \bar{\sigma }_v = - 0.29 \pm 0.18$ for the H α flux-weighted mean velocity dispersion.
In Spring 2011, the Lick AGN Monitoring Project observed a sample of 15 bright, nearby Seyfert 1 galaxies in the V band as part of a reverberation mapping campaign. The observations were taken at six ...ground-based telescopes, including the West Mountain Observatory 0.91 m telescope, the 0.76 m Katzman Automatic Imaging Telescope, 0.6 m Super-LOTIS at Kitt Peak, the Palomar 60 inch telescope, and the 2 m Faulkes telescopes North and South. The V-band light curves measure the continuum variability of our sample of Seyferts on an almost daily cadence for 2-3 months. We use image-subtraction software to isolate the variability of the Seyfert nucleus from the constant V-band flux of the host galaxy for the most promising targets, and we adopt standard aperture photometry techniques for the targets with smaller levels of variability. These V-band light curves will be used, with measurements of the broad emission line flux, to measure supermassive black hole masses and to constrain the geometry and dynamics of the broad-line region through dynamical modeling techniques.
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