24 research outputs found
Supermassive Black Holes and Their Host Galaxies - I. Bulge luminosities from dedicated near-infrared data
In an effort to secure, refine and supplement the relation between central
Supermassive Black Hole masses (Mbh), and the bulge luminosities of their host
galaxies, (Lbul), we obtained deep, high spatial resolution K-band images of 35
nearby galaxies with securely measured Mbh, using the wide-field WIRCam imager
at the Canada-France-Hawaii-Telescope (CFHT). A dedicated data reduction and
sky subtraction strategy was adopted to estimate the brightness and structure
of the sky, a critical step when tracing the light distribution of extended
objects in the near-infrared. From the final image product, bulge and total
magnitudes were extracted via two-dimensional profile fitting. As a first order
approximation, all galaxies were modeled using a simple Sersic-bulge +
exponential-disk decomposition. However, we found that such models did not
adequately describe the structure that we observe in a large fraction of our
sample galaxies which often include cores, bars, nuclei, inner disks, spiral
arms, rings and envelopes. In such cases, we adopted profile modifications
and/or more complex models with additional components. The derived bulge
magnitudes are very sensitive to the details and number of components used in
the models, although total magnitudes remain almost unaffected. Usually, but
not always, the luminosities and sizes of the bulges are overestimated when a
simple bulge+disk decomposition is adopted in lieu of a more complex model.
Furthermore we found that some spheroids are not well fit when the ellipticity
of the Sersic model is held fixed. This paper presents the details of the image
processing and analysis, while in a companion paper we discuss how
model-induced biases and systematics in bulge magnitudes impact the Mbh-Lbul
relation.Comment: 48 pages, 40 Figures, 5 tables; high-resolution figures and a
corresponding version of the .pdf are available at
https://www.dropbox.com/sh/lx0xqn89wa3y320/2hS-zZ12Y
Supermassive Black Holes and Their Host Galaxies - II. The correlation with near-infrared luminosity revisited
We present an investigation of the scaling relations between Supermassive
Black Hole (SMBH) masses (Mbh), and their host galaxies' K-band bulge (Lbul)
and total (Ltot) luminosities. The wide-field WIRCam imager at the
Canada-France-Hawaii-Telescope (CFHT) was used to obtain the deepest and
highest resolution near infrared images available for a sample of 35 galaxies
with securely measured Mbh, selected irrespective of Hubble type. For each
galaxy, we derive bulge and total magnitudes using a two-dimensional image
decomposition code that allows us to account, if necessary, for large- and
small-scale disks, cores, bars, nuclei, rings, envelopes and spiral arms. We
find that the present-day Mbh-Lbul and Mbh-Ltot relations have consistent
intrinsic scatter, suggesting that Mbh correlates equally well with bulge and
total luminosity of the host. Our analysis provides only mild evidence of a
decreased scatter if the fit is restricted to elliptical galaxies. The
log-slopes of the Mbh-Lbul and Mbh-Ltot relations are 0.75+/-0.10 and
0.92+/-0.14, respectively. However, while the slope of the Mbh-Lbul relation
depends on the detail of the image decomposition, the characterization of
Mbh-Ltot does not. Given the difficulties and ambiguities of decomposing galaxy
images into separate components, our results indicate that Ltot is more
suitable as a tracer of SMBH mass than Lbul, and that the Mbh-Ltot relation
should be used when studying the co-evolution of SMBHs and galaxies.Comment: 19 pages, 3 figures, 7 table
Supermassive Black Holes and their Host Galaxies - Fundamental Scaling Relations
The research presented in this thesis aims at improving the characterization of the scaling relations of
the masses of central Supermassive Black Holes with bulge and total luminosities of their host galaxies.
These scaling relations are significant for our understanding of the evolution of galaxies and the origins
of Supermassive Black Holes. As part of this investigation, 35 galaxies with known central Black Hole
mass were observed at near-infrared wavelengths. The obtained images were subjected to a thorough
photometric analysis, which led to reliable bulge and total luminosities. As a result, it could be shown
that the slope of the correlation between central Black Hole masses and bulge luminosities was previously
overestimated. Further, it was found that the correlation with total luminosity is equally tight as the
correlation with bulge luminosity. A linear regression method was devolped that enables extraction of
more detailed information about the cosmic scatter in the scaling relations. In the last part of this thesis,
a Black Hole mass was determined by means of dynamical modeling. The measured mass far exceeds
the prediction from current scaling relations, thereby putting the universality of the scaling relations in
question and principally opening up opportunities to better understand the physics of galaxy and Black
Hole formation
Balmer filaments in Tycho's supernova remnant: an interplay between cosmic-ray and broad-neutral precursors
We present H spectroscopic observations and detailed modelling of the
Balmer filaments in the supernova remnant Tycho. We used Galaxy H
Fabry-P\'erot Spectrometer on the William Herschel Telescope with a
3.4'3.4' field-of-view, 0.2" pixel scale and \sigma_\rm{instr}=8.1
km/s resolution at 1" seeing for hours, resulting in 82
spatial-spectral bins that resolve the narrow H line in the entire
Tycho's northeastern rim. For the first time, we can mitigate artificial line
broadening from unresolved differential motion, and probe H emission
parameters in varying shock and ambient medium conditions. Broad H line
remains unresolved within spectral coverage of 392 km/s. We employed Bayesian
inference to obtain reliable parameter confidence intervals, and quantify the
evidence for models with multiple line components. The median H
narrow-line full-width at half-maximum of all bins and models is
W_\rm{NL}=(54.8\pm1.8) km/s at the confidence level, varying within
[35, 72] km/s between bins and clearly broadened compared to the intrinsic
(thermal) km/s. Possible line splits are accounted for, significant
in of the filament, and presumably due to remaining projection
effects. We also find wide-spread evidence for intermediate-line emission of a
broad-neutral precursor, with median W_\rm{IL}=(180\pm14) km/s (
confidence). Finally, we present a measurement of the remnant's systemic
velocity, V_\rm{LSR}=-34 km/s, and map differential line-of-sight motions.
Our results confirm the existence and interplay of shock precursors in Tycho's
remnant. In particular, we show that suprathermal narrow-line emission is
near-universal in Tycho and that, in absence of an alternative explanation,
collisionless supernova remnant shocks constitute a viable acceleration source
for Galactic TeV Cosmic-Ray protons.Comment: 36 pages, 17 figures, 5 tables, Paper accepted for publication in the
Astrophysical Journal; References correcte
Balmer-dominated shocks in Tycho's SNR: omnipresence of CRs
We present wide-field, spatially and highly resolved spectroscopic
observations of Balmer filaments in the northeastern rim of Tycho's supernova
remnant in order to investigate the signal of cosmic-ray (CR) acceleration. The
spectra of Balmer-dominated shocks (BDSs) have characteristic narrow (FWHM
10 kms) and broad (FWHM 1000 kms) H
components. CRs affect the H-line parameters: heating the cold neutrals
in the interstellar medium results in broadening of the narrow H-line
width beyond 20 kms, but also in reduction of the broad H-line
width due to energy being removed from the protons in the post-shock region.
For the first time we show that the width of the narrow H line, much
larger than 20 kms, is not a resolution or geometric effect nor a
spurious result of a neglected intermediate (FWHM 100 kms)
component resulting from hydrogen atoms undergoing charge exchange with warm
protons in the broad-neutral precursor. Moreover, we show that a narrow line
width 20 kms extends across the entire NE rim, implying CR
acceleration is ubiquitous, and making it possible to relate its strength to
locally varying shock conditions. Finally, we find several locations along the
rim, where spectra are significantly better explained (based on Bayesian
evidence) by inclusion of the intermediate component, with a width of 180
kms on average.Comment: Proceeding for contributed talk at the IAU Symposium No. 331: "SN
1987A, 30 years later - Cosmic Rays and Nuclei from Supernovae and their
Aftermaths", 2017, La Reunion Island; References correcte
Selection bias in dynamically measured supermassive black hole samples : its consequences and the quest for the most fundamental relation
We compare the set of local galaxies having dynamically measured black holes with a large, unbiased sample of galaxies extracted from the Sloan Digital Sky Survey. We confirm earlier work showing that the majority of black hole hosts have significantly higher velocity dispersions sigma than local galaxies of similar stellar mass. We use Monte Carlo simulations to illustrate the effect on black hole scaling relations if this bias arises from the requirement that the black hole sphere of influence must be resolved to measure black hole masses with spatially resolved kinematics. We find that this selection effect artificially increases the normalization of the M-bh-sigma relation by a factor of at least similar to 3; the bias for the M-bh-M-star relation is even larger. Our Monte Carlo simulations and analysis of the residuals from scaling relations both indicate that sigma is more fundamental than M-star or effective radius. In particular, the M-bh-M-star relation is mostly a consequence of the M-bh-sigma and sigma-M-star relations, and is heavily biased by up to a factor of 50 at small masses. This helps resolve the discrepancy between dynamically based black hole-galaxy scaling relations versus those of active galaxies. Our simulations also disfavour broad distributions of black hole masses at fixed sigma. Correcting for this bias suggests that the calibration factor used to estimate black hole masses in active galaxies should be reduced to values of f(vir) similar to 1. Black hole mass densities should also be proportionally smaller, perhaps implying significantly higher radiative efficiencies/black hole spins. Reducing black hole masses also reduces the gravitational wave signal expected from black hole mergers.Peer reviewe
Towards a new classification of galaxies: principal component analysis of CALIFA circular velocity curves
We present a galaxy classification system for 238 (E1-Sdm) CALIFA (Calar Alto
Legacy Integral Field Area) galaxies based on the shapes and amplitudes of
their circular velocity curves (CVCs). We infer the CVCs from the de-projected
surface brightness of the galaxies, after scaling by a constant mass-to-light
ratio based on stellar dynamics - solving axisymmetric Jeans equations via
fitting the second velocity moment of
the stellar kinematics. We use principal component analysis (PCA) applied to
the CVC shapes to find characteristic features and use a -means classifier
to separate circular curves into classes. This objective classification method
identifies four different classes, which we name slow-rising (SR), flat (FL),
round-peaked (RP) and sharp-peaked (SP) circular curves.
SR are typical for low-mass, late-type (Sb-Sdm), young, faint, metal-poor and
disc-dominated galaxies. SP are typical for high-mass, early-type (E1-E7), old,
bright, metal-rich and bulge-dominated galaxies. FL and RP appear presented by
galaxies with intermediate mass, age, luminosity, metallicity, bulge-to-disk
ratio and morphologies (E4-S0a, Sa-Sbc). The discrepancy mass factor,
, have the largest value for SR and SP classes ( 74
per cent and 71 per cent, respectively) in contrast to the FL and RP
classes (with 59 per cent and 61 per cent, respectively).
Circular curve classification presents an alternative to typical morphological
classification and appears more tightly linked to galaxy evolution.Comment: Accepted for publication in MNRAS (Minor changes), 123 pages, 19
figures, 87 Tables (containing the basic properties of the 238 E1-Sdm
galaxies; the five main Principal Component Eigenvectors; the five main
Principal Components - PC_i; the Multi-Gaussian Expansion models - MGEs; the
circular velocity curve models and their uncertainties
The Next Generation Virgo Cluster Survey - Infrared (NGVS-IR): I. A new Near-UV/Optical/Near-IR Globular Cluster selection tool
The NGVS-IR project (Next Generation Virgo Survey - Infrared) is a contiguous
near-infrared imaging survey of the Virgo cluster of galaxies. It complements
the optical wide-field survey of Virgo (NGVS). The current state of NGVS-IR
consists of Ks-band imaging of 4 deg^2 centered on M87, and J and Ks-band
imaging of 16 deg^2 covering the region between M49 and M87. In this paper, we
present the observations of the central 4 deg^2 centered on Virgo's core
region. The data were acquired with WIRCam on the Canada-France-Hawaii
Telescope and the total integration time was 41 hours distributed in 34
contiguous tiles. A survey-specific strategy was designed to account for
extended galaxies while still measuring accurate sky brightness within the
survey area. The average 5\sigma limiting magnitude is Ks=24.4 AB mag and the
50% completeness limit is Ks=23.75 AB mag for point source detections, when
using only images with better than 0.7" seeing (median seeing 0.54"). Star
clusters are marginally resolved in these image stacks, and Virgo galaxies with
\mu_Ks=24.4 AB mag arcsec^-2 are detected. Combining the Ks data with optical
and ultraviolet data, we build the uiK color-color diagram which allows a very
clean color-based selection of globular clusters in Virgo. This diagnostic plot
will provide reliable globular cluster candidates for spectroscopic follow-up
campaigns needed to continue the exploration of Virgo's photometric and
kinematic sub-structures, and will help the design of future searches for
globular clusters in extragalactic systems. Equipped with this powerful new
tool, future NGVS-IR investigations based on the uiK diagram will address the
mapping and analysis of extended structures and compact stellar systems in and
around Virgo galaxies.Comment: 23 pages, 18 figures. Accepted for publication in ApJ