673 research outputs found
Red Supergiants in the Disk of M81: Tracing the Spatial Distribution of Star Formation 25 Million Years in the Past
Near-infrared images are used to investigate the brightest red stars in the
disk of the nearby spiral galaxy M81. Red supergiants (RSGs) form a
well-defined sequence on the color-magnitude diagrams (CMDs) that peaks near
M_K = -11.5; RSGs with this peak brightness are seen throughout all fields that
were studied, indicating that star formation occured over a large part of the
M81 disk only ~ 10 Myr in the past. The number of RSGs per unit integrated
K-band light is compared at various locations in the disk. We conclude that
star-forming activity in M81 during the past 10 - 25 Myr (1) was distributed
over a larger fraction of the disk than it is at the present day, and (2) was
not restricted to a given radial interval, but was distributed in a manner that
closely followed the stellar mass profile. Star counts indicate that the mean
SFR of M81 between 10 and 25 Myr in the past was ~ 0.1 solar masses per year,
which is not greatly different from the present day SFR estimated from Halpha
and FUV emission.Comment: 21 pages of text and 7 postscript figures; to appear in the PAS
Peripheral arterial tonometry: a new method for improving the diagnosis of exercise-induced myocardial ischemia
The Disk and Extraplanar Environment of NGC 247
The stellar content of the spiral galaxy NGC 247 is investigated. The main
sequence turn-off (MSTO) in the inner 12 kpc of the disk corresponds to an age
of 6 Myr. A mean star formation rate (SFR) of 0.1 solar masses per year during
the past 16 Myr is computed from star counts. The color of the red supergiant
plume does not change with radius, suggesting that the mean metallicity of
young stars does not vary by more than 0.1 dex. The number of bright main
sequence stars per local stellar mass density climbs towards larger radii out
to a distance of 12 kpc; the scale lengths that characterize the radial
distributions of young and old stars in the disk thus differ. The density of
bright main sequence stars with respect to projected HI mass gradually drops
with increasing radius. The population of very young stars disappears in the
outer disk; the MSTO at galactocentric radii between 12 and 15 kpc corresponds
to 16 Myr, while between 15 and 18 kpc the age is > 40 Myr. Red giant branch
(RGB) stars are resolved at a projected minor axis galactocentric distance of
12 kpc. There is a broad spread in metallicity among the RGB stars, with a mean
[M/H] = -1.2. The RGB-tip occurs at i' = 24.5 +/- 0.1, indicating that the
distance modulus is 27.9 +/- 0.1. Luminous AGB stars with an age 3 Gyr are also
seen in this field.Comment: Includes 16 eps figures; to appear in the Astrophysical Journa
Bio-psychosocial determinants of cardiovascular disease in a rural population on Crete, Greece: formulating a hypothesis and designing the SPILI-III study
Background: In 1988, the SPILI project was established in order to evaluate the cardiovascular disease (CVD) risk
profile of the inhabitants of Spili, in rural Crete, Greece. The first reports from this project revealed that against the unfavourable risk factors’ profile observed, only a few men with a previous myocardial infarction were encountered. A follow-up study (SPILI II) was performed twelve years after the initial examination, and the unfavourable cardiovascular risk profile was re-confirmed.
Presentation of the Hypothesis: This paper presents a hypothesis formulated on the basis of previous research to
investigate if dynamic psycho-social determinants, including social coherence of the local community, religiosity and spirituality, are protective against the development of coronary heart disease in a well-defined population. Testing the Hypothesis: A follow-up examination of this Cretan cohort is currently being performed to assess the link between psychosocial factors and CVD. Psychosocial factors including sense of control, religiosity and spirituality are assessed in together with conventional CVD risk factors. Smoking and alcohol consumption, as well as dietary habits and activity levels are recorded. Oxidative stress and inflammatory markers, as well as ultrasound measurement of carotid intima media thickness, a preclinical marker of atherosclerosis, will also be measured. Implications of the hypothesis tested: The issue of the cardio-protective effect of psycho-social factors would be revisited based on the results of this Cretan cohort; nevertheless, further research is needed across different subpopulations in order to establish a definite relationship. A comprehensive approach based on the aspects of biosocial life may result in more accurate CVD risk management
Galaxy Flow in the Canes Venatici I Cloud
We present an analysis of Hubble Space Telescope/WFPC2 images of eighteen
galaxies in the Canes Venatici I cloud.
We derive their distances from the luminosity of the tip of the red giant
branch stars with a typical accuracy of ~12 %. The resulting distances are 3.9
Mpc (UGC 6541), 4.9 Mpc (NGC 3738), 3.0 Mpc (NGC 3741), 4.5 Mpc (KK 109), >6.3
Mpc (NGC 4150), 4.2 Mpc (UGC 7298), 4.5 Mpc (NGC 4244), 4.6 Mpc (NGC 4395), 4.9
Mpc (UGC 7559), 4.2 Mpc (NGC 4449), 4.4 Mpc (UGC 7605), 4.6 Mpc (IC 3687), 4.7
Mpc (KK 166), 4.7 Mpc (NGC 4736), 4.2 Mpc (UGC 8308), 4.3 Mpc (UGC 8320), 4.6
Mpc (NGC 5204), and 3.2 Mpc (UGC 8833). The CVn I cloud has a mean radial
velocity of 286 +- 9 km/s, a mean distance of 4.1 +- 0.2 Mpc, a radial velocity
dispersion of 50 km/s, a mean projected radius of 760 kpc, and a total blue
luminosity of 2.2 * 10^{10} L_{\sun}. Assuming virial or closed orbital motions
for the galaxies, we estimated their virial and their orbital
mass-to-luminosity ratio to be 176 and 88 M_{\sun}/L_{\sun}, respectively.
However, the CVn I cloud is characterized by a crossing time of 15 Gyr, and is
thus far from a state of dynamical equilibrium. The large crossing time for the
cloud, its low content of dSph galaxies ( %), and the almost
``primordial'' shape of its luminosity function show that the CVn I complex is
in a transient dynamical state, driven rather by the free Hubble expansion than
by galaxy interactions.Comment: 23 pages, 6 figures, A&A in preparation. The version does not include
Figure 2. High resolution figures 1 and 2 (11311k) are available at
http://luna.sao.ru/~sme/figsCVn.tar.g
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