1,486 research outputs found
The Multi-Wavelength Tully-Fisher relation with spatially resolved HI kinematics
In this paper we investigate the statistical properties of the Tully-Fisher
relation for a sample of 32 galaxies with measured distances from the Cepheid
period-luminosity relation and/or TRGB stars.
We take advantage of panchromatic photometry in 12 bands (from FUV to 4.5
m) and of spatially resolved HI kinematics. We use these data together
with three kinematic measures (, and )
extracted from the global HI profiles or HI rotation curves, so as to construct
36 correlations allowing us to select the one with the least scatter. We
introduce a tightness parameter of the TFr, in order to obtain
a slope-independent measure of the goodness of fit. We find that the tightest
correlation occurs when we select the 3.6 m photometric band together with
the parameter extracted from the HI rotation curve.Comment: 16 pages, 16 figures, accepted for publication in MNRAS, minor
changes due to proof correction
Circumnuclear Gas in Seyfert 1 Galaxies: Morphology, Kinematics, and Direct Measurement of Black Hole Masses
(Abridged) The two-dimensional distribution and kinematics of the molecular,
ionized, and highly ionized gas in the nuclear regions of Seyfert 1 galaxies
have been measured using high spatial resolution (~0''.09) near-infrared
spectroscopy from NIRSPEC with adaptive optics on the Keck telescope. Molecular
hydrogen, H2, is detected in all nine Seyfert 1 galaxies and, in the majority
of galaxies, has a spatially resolved flux distribution. In contrast, the
narrow component of the BrG emission has a distribution consistent with that of
the K-band continuum. In general, the kinematics of H2 are consistent with thin
disk rotation, with a velocity gradient of over 100 km/s measured across the
central 0''.5 in three galaxies, and across the central 1''.5 in two galaxies.
The kinematics of BrG are in agreement with the H2 rotation, except in all four
cases the central 0''.5 is either blue- or redshifted by more than 75 km/s. The
highly ionized gas, measured with the [Ca VIII] and [Si VII] coronal lines, is
spatially and kinematically consistent with BrG in the central 0''.5. Dynamical
models have been fitted to the two-dimensional H2 kinematics, taking into
account the stellar mass distribution, the emission line flux distribution, and
the point spread function. For NGC 3227 the modeling indicates a black hole
mass of Mbh = 2.0{+1.0/-0.4} x 10^7 Msun, and for NGC 4151 Mbh =
3.0{+0.75/-2.2} x 10^7 Msun. In NGC 7469 the best fit model gives Mbh < 5.0 x
10^7 Msun. In all three galaxies, modeling suggests a near face-on disk
inclination angle, which is consistent with the unification theory of active
galaxies. The direct black hole mass estimates verify that masses determined
from the technique of reverberation mapping are accurate to within a factor of
three with no additional systematic errors.Comment: 43 pages, including 47 figures; Accepted for publication in ApJ. All
2-D maps (in high resolution) are available at
http://www.astro.ucla.edu/~ehicks . Minor changes to the text and updated
reverberation mapped black hole mass estimates; the conclusions are unchange
The SKA view of the Neutral Interstellar Medium in Galaxies
Two major questions in galaxy evolution are how star-formation on small
scales leads to global scaling laws and how galaxies acquire sufficient gas to
sustain their star formation rates. HI observations with high angular
resolution and with sensitivity to very low column densities are some of the
important observational ingredients that are currently still missing. Answers
to these questions are necessary for a correct interpretation of observations
of galaxy evolution in the high-redshift universe and will provide crucial
input for the sub-grid physics in hydrodynamical simulations of galaxy
evolutions. In this chapter we discuss the progress that will be made with the
SKA using targeted observations of nearby individual disk and dwarf galaxies.Comment: 22 pages, 4 figures, to appear as part of 'Neutral Hydrogen' in
Proceedings 'Advancing Astrophysics with the SKA (AASKA14)', PoS(AASKA14)12
Encoding points on hyperelliptic curves over finite fields in deterministic polynomial time
We present families of (hyper)elliptic curve which admit an efficient
deterministic encoding function
Hamming weights and Betti numbers of Stanley-Reisner rings associated to matroids
To each linear code over a finite field we associate the matroid of its
parity check matrix. We show to what extent one can determine the generalized
Hamming weights of the code (or defined for a matroid in general) from various
sets of Betti numbers of Stanley-Reisner rings of simplicial complexes
associated to the matroid
Halo Geometry and Dark Matter Annihilation Signal
We study the impact of the halo shape and geometry on the expected weakly
interacting massive particle (WIMP) dark matter annihilation signal from the
galactic center. As the halo profile in the innermost region is still poorly
constrained, we consider different density behaviors like flat cores, cusps and
spikes, as well as geometrical distortions. We show that asphericity has a
strong impact on the annihilation signal when the halo profile near the
galactic center is flat, but becomes gradually less significant for cuspy
profiles, and negligible in the presence of a central spike. However, the
astrophysical factor is strongly dependent on the WIMP mass and annihilation
cross-section in the latter case.Comment: 5 pages, 4 figures, PR
Setting the normalcy level of HI properties in isolated galaxies
Studying the atomic gas (HI) properties of the most isolated galaxies is
essential to quantify the effect that the environment exerts on this sensitive
component of the interstellar medium. We observed and compiled HI data for a
well defined sample of ~ 800 galaxies in the Catalog of Isolated Galaxies, as
part of the AMIGA project (Analysis of the ISM in Isolated GAlaxies,
http://amiga.iaa.es), which enlarges considerably previous samples used to
quantify the HI deficiency in galaxies located in denser environments. By
studying the shape of 182 HI profiles, we revisited the usually accepted result
that, independently of the environment, more than half of the galaxies present
a perturbed HI disk. In isolated galaxies this would certainly be a striking
result if these are supposed to be the most relaxed systems, and has
implications in the relaxation time scales of HI disks and the nature of the
most frequent perturbing mechanisms in galaxies. Our sample likely exhibits the
lowest HI asymmetry level in the local Universe. We found that other field
samples present an excess of ~ 20% more asymmetric HI profiles than that in
CIG. Still a small percentage of galaxies in our sample present large
asymmetries. Follow-up high resolution VLA maps give insight into the origin of
such asymmetries.Comment: 4 pages, 2 figures, Conference 'Galaxies in Isolation: Exploring
Nature vs. Nurture', Granada, 12-15 May 2009. To be published in the ASP
Conference Serie
Antimatter cosmic rays from dark matter annihilation: First results from an N-body experiment
[Abridged]. We take advantage of the galaxy-like 3D dark matter map extracted
from the HORIZON Project results to calculate the positron and antiproton
fluxes from dark matter annihilation, in a model-independent approach as well
as for dark matter particle benchmarks relevant at the LHC scale (from
supersymmetric and extra-dimensional theories). Such a study is dedicated to a
better estimate of the theoretical uncertainties affecting predictions, while
the PAMELA and GLAST satellites are currently taking data which will soon
provide better observational constraints. We discuss the predictions of the
antiproton and positron fluxes, and of the positron fraction as well, as
compared to the current data. We finally discuss the limits of the Nbody
framework in describing the dark matter halo of our Galaxy.Comment: 19 pages, 9 figures. Backgrounds included and additional comments and
figures on the positron fraction. Accepted for publication in PR
- …