5 research outputs found
Early-type galaxies with core collapse supernovae
It is widely accepted that the progenitors of core collapse SNe are young
massive stars and therefore their host galaxies are mostly spiral or irregular
galaxies dominated by a young stellar population. Surprisingly, among
morphologically classified hosts of core collapse SNe, we find 22 cases where
the host has been classified as an Elliptical or S0 galaxy. To clarify this
apparent contradiction, we carry out a detailed morphological study and an
extensive literature search for additional information on the sample objects.
Our results are as follows: 1. Of 22 "early type" objects, 17 are in fact
misclassified spiral galaxies, one is a misclassified irregular, and one is a
misclassified ring galaxy. 2. Of the 3 objects maintaining the early type
classification, one (NGC2768) is a suspected merger remnant, another (NGC4589)
is definitely a merger, and the third (NGC2274) is in close interaction. The
presence of some amount of young stellar population in these galaxies is
therefore not unexpected. These results confirm the presence of a limited, but
significant, number of core collapse SNe in galaxies generally classified of
early type. In all cases, anyway, there are independent indicators of the
presence in host galaxies of recent star formation due to merging or
gravitational interaction.Comment: 12 pages, 1 figure, 1 table, accepted for publication in A&
Ultraluminous Infrared Galaxies
Ever since their discovery in the 1970's, UltraLuminous InfraRed Galaxies
(ULIRGs; classically Lir>10^12Lsun) have fascinated astronomers with their
immense luminosities, and frustrated them due to their singularly opaque
nature, almost in equal measure. Over the last decade, however, comprehensive
observations from the X-ray through to the radio have produced a consensus
picture of local ULIRGs, showing that they are mergers between gas rich
galaxies, where the interaction triggers some combination of dust-enshrouded
starburst and AGN activity, with the starburst usually dominating. Very recent
results have thrown ULIRGs even further to the fore. Originally they were
thought of as little more than a local oddity, but the latest IR surveys have
shown that ULIRGs are vastly more numerous at high redshift, and tantalizing
suggestions of physical differences between high and low redshift ULIRGs hint
at differences in their formation modes and local environment. In this review
we look at recent progress on understanding the physics and evolution of local
ULIRGs, the contribution of high redshift ULIRGs to the cosmic infrared
background and the global history of star formation, and the role of ULIRGs as
diagnostics of the formation of massive galaxies and large-scale structures.Comment: Review article, published in "Astrophysics Update 2 - topical and
timely reviews on astronomy and astrophysics". Ed. John W. Mason.
Springer/Praxis books. ISBN: 3-540-30312-X. 53 pages, 5 figures. Higher
quality figures available on reques
The saturation states of compact and diffuse components of OH megamaser galaxies
A sample of 9 OH megamaser galaxies detected in the soft
X-ray domain was compiled. Using available OH and X-ray data a
striking correlation was found between the X-ray luminosity and
the width of the OH line. This correlation may indicate that the
X-ray heating of a molecular gas may increase the collisional
excitation of the maser emission. However, this result should be
considered as a tentative one because of the insufficient number
of galaxies. An analysis of the saturation states of compact and
diffuse components of OH emission was performed. The results of
the analysis support the assumption that both the compact and
diffuse OH maser emissions in the megamaser galaxies are
saturated. The diffuse component might show unsaturated masing
under certain conditions, such as the appropriate relation between
the intensities of compact and diffuse components and a relevant
number of the IR photons to pump the maser emission
The cold gas properties of Markarian galaxies
A sample of 61 Markarian galaxies
detected in the CO line was compiled. Using available HI,
H2, optical and radio continuum data, the analysis
of the gas kinematics and the star formation properties for this
sample of galaxies was performed.
The main conclusion can be summarized as follows:
(1) The HI and CO line widths are well correlated. Interaction
between galaxies has no influence on the CO line broadening. A
rapidly rotating nuclear disk in the galaxy might lead
to the CO line broadening with less influence on the HI line.
(2) The atomic and molecular gas surface densities are well
correlated with the blue, FIR and radio continuum surface
brightness; however, the correlation for molecular component is
stronger. (3) In general, the galaxies with UV-excess (Markarian
galaxies) do not differ in their star formation properties from
the non-UV galaxies