1,400 research outputs found
Can galaxy growth be sustained through HI-rich minor mergers?
Local galaxies with specific star-formation rates (star-formation rate per
unit mass; sSFR~0.2-10/Gyr) as high as distant galaxies (z~1-3), are very rich
in HI. Those with low stellar masses, log M_star (M_sun)=8-9, for example, have
M_HI/M_star~5-30. Using continuity arguments of Peng et al. (2014), whereby the
specific merger rate is hypothesized to be proportional to the specific
star-formation rate, and HI gas mass measurements for local galaxies with high
sSFR, we estimate that moderate mass galaxies, log M_star (M_sun)=9-10.5, can
acquire sufficient gas through minor mergers (stellar mass ratios ~4-100) to
sustain their star formation rates at z~2. The relative fraction of the gas
accreted through minor mergers declines with increasing stellar mass and for
the most massive galaxies considered, log M_star (M_sun)=10.5-11, this
accretion rate is insufficient to sustain their star formation. We checked our
minor merger hypothesis at z=0 using the same methodology but now with
relations for local normal galaxies and find that minor mergers cannot account
for their specific growth rates, in agreement with observations of HI-rich
satellites around nearby spirals. We discuss a number of attractive features,
like a natural down-sizing effect, in using minor mergers with extended HI
disks to support star formation at high redshift. The answer to the question
posed by the title, "Can galaxy growth be sustained through \HI-rich minor
mergers?", is maybe, but only for relatively low mass galaxies and at high
redshift.Comment: 6 pages, 3 figures; in final acceptance by A&
Completing HI observations of galaxies II. The Coma Supercluster
High sensitivity 21-cm HI line observations, with an rms noise level of \sim
0.5 mJy, were made of 35 spiral galaxies in the Coma Supercluster, using the
refurbished Arecibo telescope, which resulted in the detection of 25 objects.
These data, combined with the measurements available from the literature,
provide the set of HI data for 94% of all late-type galaxies in the Coma
Supercluster with an apparent photographic magnitude m_p <15.7 mag. We confirm
that the typical scale of HI deficiency around the Coma cluster is 2 Mpc, i.e.
one virial radius. Comparing the HI mass function (HIMF) of cluster with
non-cluster members of the Coma Supercluster we detect a shortage of high HI
mass galaxies among cluster members that can be ascribed to the pattern of HI
deficiency found in rich clusters.Comment: 16 pages, 8 figures, 4 tables. Accepted for publication on A&
The properties of Low Surface Brightness galaxies
A description is given of the samples of Low Surface Brightness galaxies
(LSBs) used for comparison with models of their chemical and
spectro-photometric evolution (Boissier et al., this Volume). These samples
show the large variation and scatter in observed global properties of LSBs,
some of which cannot be modeled without adding starbursts or truncations to
their star formation history.Comment: To appear in the Proceedings of the Euroconference on The Evolution
of Galaxies: III. From simple approaches to self-consistent models (Kluwer).
4 page
Nearby Gas-Rich Low Surface Brightness Galaxies
We examine the Fisher-Tully cz<1000 km/s galaxy sample to determine whether
it is a complete and representative sample of all galaxy types, including low
surface brightness populations, as has been recently claimed. We find that the
sample is progressively more incomplete for galaxies with (1) smaller physical
diameters at a fixed isophote and (2) lower HI masses. This is likely to lead
to a significant undercounting of nearby gas-rich low surface brightness
galaxies. However, through comparisons to other samples we can understand how
the nearby galaxy counts need to be corrected, and we see some indications of
environmental effects that probably result from the local high density of
galaxies.Comment: 12 page, 2 figures, to appear in Ap
Proceedings of the International Workshop on: methods and tools for water-related adaptation to climate change and climate proofing
The workshop fits in the National Water Plan of the Netherlandsâ government of which the international chapter includes the strengthening of cooperation with other delta countries, including Indonesia, Vietnam and Bangladesh and is part of the work plan of the Cooperative Programme on Water and Climate, a Netherlandsâ sponsored programme with the objective to improve knowledge and capacity on the relation between water and climate change especially in developing countries and countries in transition
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