10 research outputs found
Herschel*-ATLAS: correlations between dust and gas in local submm-selected galaxies
We present an analysis of CO molecular gas tracers in a sample of 500
μ
m-selected
Herschel
-ATLAS galaxies at
z <
0
.
05 (
cz <
14990 km s
−
1
). Using 22
−
500
μ
m photom-
etry from
WISE
,
IRAS
and
Herschel
, with H
i
data from the literature, we investigate
correlations between warm and cold dust, and tracers of the gas in
different phases.
The correlation between global CO(3–2) line fluxes and FIR–submm fl
uxes weakens
with increasing IR wavelength (
λ
&
60
μ
m), as a result of colder dust being less
strongly associated with dense gas. Conversely, CO(2–1) and H
i
line fluxes both ap-
pear to be better correlated with longer wavelengths, suggesting
that cold dust is more
strongly associated with diffuse atomic and molecular gas phases, co
nsistent with it
being at least partially heated by radiation from old stellar populations
. The increased
scatter at long wavelengths implies that sub-millimetre fluxes are a po
orer tracer of
SFR. Fluxes at 22 and 60
μ
m are also better correlated with diffuse gas tracers than
dense CO(3–2), probably due to very-small-grain emission in the diffu
se interstellar
medium, which is not correlated with SFR. The FIR/CO luminosity ratio a
nd the
dust mass/CO luminosity ratio both decrease with increasing luminosit
y, as a result
of either correlations between mass and metallicity (changing CO/H
2
) or between CO
luminosity and excitation [changing CO(3–2)/CO(1–0)].Web of Scienc
The torsion of a finite quasigroup quandle is annihilated by its order
We prove that if Q is a finite quasigroup quandle, then |Q| annihilates the
torsion of its homology. It is a classical result in reduced homology of finite
groups that the order of a group annihilates its homology. From the very
beginning of the rack homology (between 1990 and 1995) the analogous result was
suspected. The first general results in this direction were obtained
independently about 2001 by R.A.Litherland and S.Nelson, and P.Etingof and
M.Grana. In Litherland-Nelson paper it is proven that if (Q;*) is a finite
homogeneous rack (this includes quasigroup racks) then the torsion of homology
is annihilated by |Q|^n. In Etingof-Grana paper it is proven that if (X;A) is a
finite rack and N=|G^0_Q| is the order of a group of inner automorphisms of Q,
then only primes which can appear in the torsion of homology are those dividing
N (the case of connected Alexander quandles was proven before by T.Mochizuki).
The result of Litherland-Nelson is generalized by Niebrzydowski and Przytycki
and in particular, they prove that the torsion part of the homology of the
dihedral quandle R_3 is annihilated by 3. In Niebrzydowski-Przytycki paper it
is conjectured that for a finite quasigroup quandle, torsion of its homology is
annihilated by the order of the quandle. The conjecture is proved by T.Nosaka
for finite Alexander quasigroup quandles. In this paper we prove the conjecture
in full generality. For this version, we rewrote the Section 3 totally and
introduced the concept of the precubic homotopy. In Section 2, the main
addition is Corollary 2.2 which summarizes identities observed in the proof of
the main theorem as we use it later in Section 3.Comment: 13 pages, 1 figure; accepted for publication in Journal of Pure and
Applied Algebr
Fitting the integrated Spectral Energy Distributions of Galaxies
Fitting the spectral energy distributions (SEDs) of galaxies is an almost
universally used technique that has matured significantly in the last decade.
Model predictions and fitting procedures have improved significantly over this
time, attempting to keep up with the vastly increased volume and quality of
available data. We review here the field of SED fitting, describing the
modelling of ultraviolet to infrared galaxy SEDs, the creation of
multiwavelength data sets, and the methods used to fit model SEDs to observed
galaxy data sets. We touch upon the achievements and challenges in the major
ingredients of SED fitting, with a special emphasis on describing the interplay
between the quality of the available data, the quality of the available models,
and the best fitting technique to use in order to obtain a realistic
measurement as well as realistic uncertainties. We conclude that SED fitting
can be used effectively to derive a range of physical properties of galaxies,
such as redshift, stellar masses, star formation rates, dust masses, and
metallicities, with care taken not to over-interpret the available data. Yet
there still exist many issues such as estimating the age of the oldest stars in
a galaxy, finer details ofdust properties and dust-star geometry, and the
influences of poorly understood, luminous stellar types and phases. The
challenge for the coming years will be to improve both the models and the
observational data sets to resolve these uncertainties. The present review will
be made available on an interactive, moderated web page (sedfitting.org), where
the community can access and change the text. The intention is to expand the
text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics &
Space Scienc
HELGA VI. Giant molecular cloud associations in M31
VizieR online Data Catalogue associated with article published in journal Astronomical Journal (AAS) with title 'The Herschel Exploitation of Local Galaxy Andromeda (HELGA). VI. The distribution and properties of molecular cloud associations in M31.' (bibcode: 2015ApJ...798...58K
The Complex Interplay of Dust and Star Light in Spiral Galaxy Discs
Interstellar dust grains efficiently absorb and scatter UV and optical
radiation in galaxies, and therefore can significantly affect the apparent
structure of spiral galaxies. We discuss the effect of dust attenuation on the
observed structural properties of bulges and discs. We also present some first
results on modelling the dust content of edge-on spiral galaxies using both
optical and Herschel far-infrared data. Both of these results demonstrate the
complex interplay of dust and star light in spiral galaxies.Comment: 6 pages, 2 figures, to appear in "Galaxies and their Masks", eds. D.
L. Block, K. C. Freeman & I. Puerari, Springer (New York
The Herschel ATLAS
The Herschel ATLAS is the largest open-time key project that will be carried out on the Herschel Space Observatory. It will survey 570 deg2 of the extragalactic sky, 4 times larger than all the other Herschel extragalactic surveys combined, in five far-infrared and submillimeter bands. We describe the survey, the complementary multiwavelength data sets that will be combined with the Herschel data, and the six major science programs we are undertaking. Using new models based on a previous submillimeter survey of galaxies, we present predictions of the properties of the ATLAS sources in other wave bands