9,185 research outputs found
Molecular Gas Content of HI Monsters and Implications to Cold Gas Content Evolution in Galaxies
We present 12CO (J=1-0) observations of a sample of local galaxies
(0.04<z<0.08) with a large neutral hydrogen reservoir, or "HI monsters". The
data were obtained using the Redshift Search Receiver on the FCRAO 14 m
telescope. The sample consists of 20 HI-massive galaxies with M(HI)>3e10Msun
from the ALFALFA survey and 8 LSBs with a comparable M(HI) (>1.5e10Msun). Our
sample selection is purely based on the amount of neutral hydrogen, thereby
providing a chance to study how atomic and molecular gas relate to each other
in these HI-massive systems. We have detected CO in 15 out of 20 ALFALFA
selected galaxies and 4 out of 8 LSBs with molecular gas mass M(H2) of
(1-11)e9Msun. Their total cold gas masses of (2-7e10Msun make them some of the
most gas-massive galaxies identified to date in the Local Universe. Observed
trends associated with HI, H2, and stellar properties of the HI massive
galaxies and the field comparison sample are analyzed in the context of
theoretical models of galaxy cold gas content and evolution, and the importance
of total gas content and improved recipes for handling spatially differentiated
behaviors of disk and halo gas are identified as potential areas of improvement
for the modeling.Comment: 18 pages, 11 figures, 2 tables; Accepted for publication in MNRA
Magnetic reconnection and stochastic plasmoid chains in high-Lundquist-number plasmas
A numerical study of magnetic reconnection in the large-Lundquist-number
(), plasmoid-dominated regime is carried out for up to . The
theoretical model of Uzdensky {\it et al.} [Phys. Rev. Lett. {\bf 105}, 235002
(2010)] is confirmed and partially amended. The normalized reconnection rate is
\normEeff\sim 0.02 independently of for . The plasmoid flux
() and half-width () distribution functions scale as and . The joint distribution of and
shows that plasmoids populate a triangular region ,
where is the reconnecting field. It is argued that this feature is due to
plasmoid coalescence. Macroscopic "monster" plasmoids with % of the
system size are shown to emerge in just a few Alfv\'en times, independently of
, suggesting that large disruptive events are an inevitable feature of
large- reconnection.Comment: 5 pages, 6 figures, submitted for publicatio
Personality and phobias in adolescence: age and gender in psychopathological expressions
Background: Although the understanding of adolescent phobias is important, this phenomenon has thus far not been adequately researched. This report, based on clinical experience, highlights prevalent phobic phenomena linked to personality characteristics. Methods: A sample of 241 adolescents from High School and the University of Messina, Italy was evaluated for phobic responses using the SAFA Scales. Personality types and aspects were assessed by the Myers-Briggs Type Indicator F Form. Results: The results were consistent with the reported literature and revealed that psychopathological phenomena such as anxiety, obsession, eating disorders and phobias decreased with aging; however, depression remained constant over time. Significant differences emerged regarding gender, with the presence of higher scores on all scales except obsession for the female group. Personality analysis revealed aspects linked to the relations between psychopathological variables, introversion/ extraversion (such as polar dimensions), and rational/ irrational functions. Conclusion: This research indicates that phobic phenomena may be underestimated in adolescents and links personality types and symptoms with phobic phenomena, indicating the potential need for interventions in adolescents
From First Galaxies to QSOs: feeding the baby monsters
We present a physical model for the coevolution of massive spheroidal
galaxies and active nuclei at their centers. Supernova heating is increasingly
effective in slowing down the star formation and in driving gas outflows in
smaller and smaller dark matter halos. Thus the more massive protogalaxies
virializing at early times are the sites of faster star formation. The
correspondingly higher radiation drag causes a faster angular momentum loss by
the gas and induces a larger accretion rate onto the central black hole. In
turn, the kinetic energy of the outflows powered by the active nuclei can
unbind the residual gas in a time shorter for larger halos. The model accounts
for a broad variety of dynamical, photometric and metallicity properties of
early-type galaxies, for the M_BH -- \sigma relation and for the local
supermassive black-hole mass function.Comment: 6 pages, contributed paper to Proceedings of the Conference on
"Growing Black Holes" held in Garching, Germany, on June 21-25, 2004, edited
by A. Merloni, S. Nayakshin and R. Sunyaev, Springer-Verlag series of "ESO
Astrophysics Symposia
On the relation between mathematical and numerical relativity
The large scale binary black hole effort in numerical relativity has led to
an increasing distinction between numerical and mathematical relativity. This
note discusses this situation and gives some examples of succesful interactions
between numerical and mathematical methods is general relativity.Comment: 12 page
Chaos at Fifty
In 1963 Edward Lorenz revealed deterministic predictability to be an illusion
and gave birth to a field that still thrives. This Feature Article discusses
Lorenz's discovery and developments that followed from it.Comment: For an animated visualization of the Lorenz attractor, click here
http://www.youtube.com/watch?v=iu4RdmBVdp
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