2,840 research outputs found
Aerothermochemical analysis of non-oscillatory and oscillatory characteristics of liquid bipropellant rocket motors - Wave model, droplet heating, and evaporation program computation Third quarterly report no. 65-1
Aerothermochemical analysis of nonoscillatory and oscillatory characteristics of liquid bipropellant rocket motors - wave model, droplet heating, and evaporation computer progra
Aerothermochemical analysis of non-oscillatory and oscillatory characteristics of liquid bipropellant rocket motors - droplet evaporation, wave equations, motor instrumentation, non-oscillatory program computation
Model to determine vaporization rate of liquid fuel drople
Steady state aerothermochemistry for liquid bipropellant rocket motors
Model and theoretical equations describing liquid propellant droplet ballistics and combustion gas behavior in bipropellant rocket motors - aerothermochemistr
An optical spectroscopic survey of the 3CR sample of radio galaxies with z<0.3. III. Completing the sample
We present optical nuclear spectra for nine 3CR radio sources obtained with
the Telescopio Nazionale Galileo, that complete our spectroscopic observations
of the sample up to redshifts 0.3. We measure emission line luminosities
and ratios, and derive a spectroscopic classification for these sources.Comment: Accepted for publication in A&A. We provide as additional material
two tables presenting the main data for the whole sample, combining the
results presented here with those of Paper I and Paper I
The Axis Ratio Distribution of Local and Distant Galaxies
Surface photometry from 16 HST/WFPC2 fields in the I(F814W) filter is used to
derive the distribution of apparent axis ratios for galaxies in progressively
fainter magnitude intervals for I<25. We assess the systematic and accidental
errors in ellipticity measurements as a function of image resolution and
signal-to-noise ratio, and statistically correct for the effect of cosmological
surface brightness dimming on our isophotal measurements. The axis ratio
distribution for the local galaxy population was computed using logR
measurements for 1569 RC3 galaxies with Bt<13 mag. Nonparametric tests are used
to show that our distant samples, in the redshift range 0.1<z<1.5, are not
statistically different from the local sample. We present image montages of
galaxies selected randomly from different axis ratio and apparent magnitude
ranges and discuss the evolutionary consequences of the lack of a strong
difference between the ellipticity distributions in near and far data sets.Comment: LaTex, 35 pages, 8 figures, accepted for Dec97 A
Color--Luminosity Relations for the Resolved Hot Stellar Populations in the Centers of M 31 and M 32
We present Faint Object Camera (FOC) ultraviolet images of the central
14x14'' of Messier 31 and Messier 32. The hot stellar population detected in
the composite UV spectra of these nearby galaxies is partially resolved into
individual stars, and their individual colors and apparent magnitudes are
measured. We detect 433 stars in M 31 and 138 stars in M 32, down to detection
limits of m_F275W = 25.5 mag and m_F175W = 24.5 mag. We investigate the
luminosity functions of the sources, their spatial distribution, their
color-magnitude diagrams, and their total integrated far-UV flux. Although M 32
has a weaker UV upturn than M 31, the luminosity functions and color-magnitude
diagrams of M 31 and M 32 are surprisingly similar, and are inconsistent with a
majority contribution from any of the following: PAGB stars more massive than
0.56 Msun, main sequence stars, or blue stragglers. Both the the luminosity
functions and color-magnitude diagrams are consistent with a dominant
population of stars that have evolved from the extreme horizontal branch (EHB)
along tracks with masses between 0.47 and 0.53 Msun. These stars are well below
the detection limits of our images while on the zero-age EHB, but become
detectable while in the more luminous (but shorter) AGB-Manque' and post-early
asymptotic giant branch (PEAGB) phases. The FOC observations require that only
a only a very small fraction of the main sequence population (2% in M 31 and
0.5% in M 32) in these two galaxies evolve though the EHB and post-EHB phases,
with the remainder evolving through bright PAGB evolution that is so rapid that
few if any stars are expected in the small field of view covered by the FOC.Comment: 35 pages, Latex. 19 figures. To appear in ApJ. Uses emulateapj.sty
and apjfonts.sty (included). Color plates distributed seperatedly: fig1.jpg
and fig2.jp
M Dwarfs from Hubble Space Telescope Star Counts. IV
We study a sample of about 1400 disk M dwarfs that are found in 148 fields
observed with the Wide Field Camera 2 (WFC2) on the Hubble Space Telescope and
162 fields observed with pre-repair Planetary Camera 1 (PC1), of which 95 of
the WFC2 fields are newly analyzed. The method of maximum likelihood is applied
to derive the luminosity function and the Galactic disk parameters. At first,
we use a local color-magnitude relation and a locally determined
mass-luminosity relation in our analysis. The results are consistent with those
of previous work but with considerably reduced statistical errors. These small
statistical errors motivate us to investigate the systematic uncertainties.
Considering the metallicity gradient above the Galactic plane, we introduce a
modified color-magnitude relation that is a function of Galactic height. The
resultant M dwarf luminosity function has a shape similar to that derived using
the local color-magnitude relation but with a higher peak value. The peak
occurs at and the luminosity function drops sharply toward . We then apply a height-dependent mass-luminosity function
interpolated from theoretical models with different metallicities to calculate
the mass function. Unlike the mass function obtained using local relations,
which has a power-law index , the one derived from the
height-dependent relations tends to be flat (). The resultant
local surface density of disk M dwarfs (12.2 +/- 1.6 M_sun pc^{-2}) is somewhat
smaller than the one obtained using local relations (14.3 +/- 1.3 M_sun
pc^{-2}). Our measurement favors a short disk scale length, H = 2.75 +/- 0.16
(statistical) +/- 0.25 (systematic) kpc.Comment: 20 pages, 10 ps figures, accepted for publication in Ap
Hot Populations in M87 Globular Clusters
We have obtained HST/STIS far- and near-UV photometry of globular clusters in
four fields in the gE galaxy M87. To a limit of m(FUV) = 25 we detect a total
of 66 globular clusters (GCs) in common with the deep HST optical-band study of
Kundu et al. (1999). Despite strong overlap in V- and I-band properties, the
M87 GCs have UV/optical properties that are distinct from clusters in the Milky
Way and in M31. M87 clusters, especially metal-poor ones, produce larger hot HB
populations than do Milky Way analogues. Cluster mass is probably not a factor
in these distinctions. The most metal-rich M87 GCs in our sample are near Z_sun
and overlap the local E galaxy sample in estimated Mg_2 line indices.
Nonetheless, the clusters produce much more UV light at a given Mg_2, being up
to 1 mag bluer than any gE galaxy in (FUV-V) color. The M87 GCs do not appear
to represent a transition between Milky Way-type clusters and E galaxies. The
differences are in the correct sense if the clusters are significantly older
than the E galaxies. Comparisons with Galactic open clusters indicate that the
hot stars lie on the extreme horizontal branch, rather than being blue
stragglers, and that the EHB becomes well populated for ages > 5 Gyr. We find
that 43 of our UV detections have no optical-band counterparts. Most appear to
be UV-bright background galaxies, seen through M87. Eleven NUV variable sources
detected at only one epoch in the central field are probably classical novae.
[Abridged]Comment: 70 pages, 25 figures (including 4 jpgs), 7 tables. To appear in AJ.
Full resolution version available at
http://www.astro.virginia.edu/~rwo/m87/m87-hotpops.pd
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