47 research outputs found
Radial Velocity Studies of Close Binary Stars.IV
Radial-velocity measurements and sine-curve fits to the orbital velocity
variations are presented for the fourth set of ten close binary systems: 44
Boo, FI Boo, V2150 Cyg, V899 Her, EX Leo, VZ Lib, SW Lyn, V2377 Oph, Anon Psc
(GSC 8-324), HT Vir. All systems are double-lined spectroscopic binaries with
only two of them not being contact systems (SW Lyn and GSC 8-324) and with five
(FI Boo, V2150 Cyg, V899 Her, EX Leo, V2377 Oph) being the recent photometric
discoveries of the Hipparcos satellite project. Five of the binaries are
triple-lined systems (44 Boo, V899 Her, VZ Lib, SW Lyn, HT Vir). Three (or
possibly four) companions in the triple-lined systems show radial-velocity
changes during the span of our observations suggesting that these are in fact
quadruple systems. Several of the studied systems are prime candidates for
combined light and radial-velocity synthesis solutions.Comment: aastex5.0, 5 figures in PS; submitted to Astron.
Darstellung und Fluoreszenzverhalten von 2,3,4,4a,10a,11,12,13-Octahydro-1,4a,10a,14-tetraazaviolanthron-Derivaten
Laboratory spectra of C60 and related molecular structures
The electronic spectra of fullerene structures in high frequency discharge are studied in the plasma chemistry laboratory of the Faculty of Science of Masaryk University in Brno. The ultraviolet and visual spectra are investigated in order to be compared with the diffuse interstellar bands and interpreted within the theory of quantum mechanics. The preliminary results of the study are presented here in the form of a poster
Globular Cluster and Galaxy Formation: M31, the Milky Way and Implications for Globular Cluster Systems of Spiral Galaxies
The globular cluster (GC) systems of the Milky Way and of our neighboring
spiral galaxy, M31, comprise 2 distinct entities, differing in 3 respects. 1.
M31 has young GCs, ages from ~100 Myr to 5 Gyr old, as well as old globular
clusters. No such young GCs are known in the Milky Way. 2. We confirm that the
oldest M31 GCs have much higher nitrogen abundances than do Galactic GCs at
equivalent metallicities. 3. Morrison et al. found M31 has a subcomponent of
GCs that follow closely the disk rotation curve of M31. Such a GC system in our
own Galaxy has yet to be found. These data are interpreted in terms of the
hierarchical-clustering-merging (HCM) paradigm for galaxy formation. We infer
that M31 has absorbed more of its dwarf systems than has the Milky Way. This
inference has 3 implications: 1. All spiral galaxies likely differ in their GC
properties, depending on how many companions each galaxy has, and when the
parent galaxy absorbs them. The the Milky Way ties down one end of this
spectrum, as almost all of its GCs were absorbed 10-12 Gyr ago. 2. It suggests
that young GCs are preferentially formed in the dwarf companions of parent
galaxies, and then absorbed by the parent galaxy during mergers. 3. Young GCs
seen in tidally-interacting galaxies might come from dwarf companions of these
galaxies, rather than be made a-new in the tidal interaction. There is no ready
explanation for the marked difference in nitrogen abundance for old M31 GCs
relative to the oldest Galactic GCs. The predictions made by Li & Burstein
regarding the origin of nitrogen abundance in globular clusters are consistent
with what is found for the old M31 GCs compared to that for the two 5 Gyr-old
M31 GCs.Comment: to be published in ApJ, Oct 2004; 13 pages of text, 2 tables, 7
postscript figure
Spectral Energy Distributions and Age Estimates of 172 Globular Clusters in M31
In this paper we present CCD multicolor photometry for 172 globular clusters
(GCs), taken from the Bologna catalog (Battistini et al. 1987), in the nearby
spiral galaxy M31. The observations were carried out by using the National
Astronomical Observatories 60/90 cm Schmidt Telescope in 13 intermediate-band
filters, which covered a range of wavelength from 3800 to 10000A. This provides
a multicolor map of M31 in pixels of 1.7"*1.7". By aperture photometry, we
obtain the spectral energy distributions (SEDs) for these GCs. Using the
relationship between the BATC intermediate-band system used for the
observations and the UBVRI broad-band system, the magnitudes in the B and V
bands are derived. The computed V and B-V are in agreement with the values
given by Battistini et al. (1987) and Barmby et al. (2000). Finally, by
comparing the photometry of each GC with theoretical stellar population
synthesis models, we estimate ages of the sample GCs for different
metallicities. The results show that nearly all our sample GCs have ages more
than 10^{9} years, and most of them are around 10^{10} years old. Also, we find
that GCs fitted by the metal-poor model are generally older than ones fitted by
the metal-rich model.Comment: 38 pages, 7 figures will appear in the February 2003 issue of A
Otoacoustic Emissions Simulated in the Time-Domain by a Hydroynamic Model of the Human Cochlea
Time-domain simulations of the response to click of a human ear show that, if the cochlear amplifier gain (CAG) is a smooth function of basilar-membrane (BM) position, the filtering performed by a middle ear with an irregular (non-smooth) transfer function suffices to produce irregular and long-lasting residual BM oscillations at selected frequencies. Feeding back to the middle ear through hydrodynamic coupling, these oscillations are detected as otoacoustic emissions (OAEs) in the ear canal. If, in addition, also the CAG profile is irregular, residual BM oscillations are even more irregular, often ensuing to self-sustaining oscillations at CAG irregularity loci. Correspondingly, transient evoked OAE spectra exhibit sharp peaks. If both the CAG and the middle-ear transfer function are smooth, residual BM oscillations are characterized by regular waveform, extinguish rapidly and do not generate appreciable emission. Simulating localized damage to the cochlear amplifier results in spontaneous emissions and stimulus-frequency OAEs, with typical modulation patterns, for inputs near hearing threshold
Age Estimations of M31 Globular Clusters from Their Spectral Energy Distributions
This paper presents accurate spectral energy distributions (SEDs) of 16 M31
globular clusters (GCs) confirmed by spectroscopy and/or high
spatial-resolution imaging, as well as 30 M31 globular cluster candidates
detected by Mochejska et al. Most of these candidates have m_V > 18, deeper
than previous searches, and these candidates have not yet been confirmed to be
globular clusters. The SEDs of these clusters and candidates are obtained as
part of the BATC Multicolor Survey of the Sky, in which the
spectrophotometrically-calibrated CCD images of M31 in 13 intermediate-band
filters from 4000 to 10000 A were observed. These filters are specifically
designed to exclude most of the bright and variable night-sky emission lines
including the OH forest. In comparison to the SEDs of true GCs, we find that
some of the candidate objects are not GCs in M31. SED fits show that
theoretical simple stellar population (SSP) models can fit the true GCs very
well. We estimate the ages of these GCs by comparing with SSP models. We find
that, the M31 clusters range in age from a few ten Myr to a few Gyr old, as
well as old GCs, confirming the conclusion that has been found by Barmby et a,
Williams & Hodge, Beasley et al., Burstein et al. and Puzia et al. in their
investigations of the SEDs of M31 globular clusters.Comment: Accepted for Publication in A&Ap, 13 pages, 6 figure
Wide-Field Survey of Globular Clusters in M31. I. A Catalog of New Clusters
We present the result of a wide-field survey of globular clusters (GCs) in
M31 covering a 3deg x 3deg field c. We have searched for GCs on CCD images
taken with Washington CMT1 filters at the KPNO 0.9 m telescope using steps: (1)
inspection of morphological parameters given by the SExtractor package such as
stellarity, full maximum, and ellipticity; (2) consulting the spectral types
and radial velocities obtained from spectra takena spectrograph at the WIYN 3.5
m telescope; and (3) visual inspection of the images of each object. We have
and GC candidates, of which 605 are newly found GCs and GC candidates and 559
are previously known GCs. Amoects there are 113 genuine GCs, 258 probable GCs,
and 234 possible GCs, according to our classification critee known objects
there are 383 genuine GCs, 109 probable GCs, and 67 possible GCs. In total
there are 496 genprobable GCs and 301 possible GCs. Most of these newly found
GCs have T1 magnitudes of 17.5 - 19.5 mag, [17.9 < V < 19.9 mag assuming (C-T1)
~ 1.5], and (C-T1) colors in the range 1 - 2.Comment: accepted by AJ, using emulateapj.cl
The M31 Globular Cluster Luminosity Function
We combine our compilation of photometry of M31 globular cluster and probable
cluster candidates with new near-infrared photometry for 30 objects. Using
these data we determine the globular cluster luminosity function (GCLF) in
multiple filters for the M31 halo clusters. We find a GCLF peak and dispersion
of V_0^0=16.84 +/-0.11, sigma_t=0.93 +/- 0.13 (Gaussian sigma = 1.20 +/- 0.14),
consistent with previous results. The halo GCLF peak colors (e.g., B^0_0 -
V^0_0) are consistent with the average cluster colors. We also measure V-band
GCLF parameters for several other subsamples of the M31 globular cluster
population. The inner third of the clusters have a GCLF peak significantly
brigher than that of the outer clusters (delta V =~ 0.5mag). Dividing the
sample by both galacticentric distance and metallicity, we find that the GCLF
also varies with metallicity, as the metal-poor clusters are on average 0.36
mag fainter than the metal-rich clusters. Our modeling of the catalog selection
effects suggests that they are not the cause of the measured differences, but a
more complete, less-contaminated M31 cluster catalog is required for
confirmation. Our results imply that dynamical destruction is not the only
factor causing variation in the M31 GCLF: metallicity, age, and cluster initial
mass function may also be important.Comment: AJ, in press. 36 pages, including 7 figure
The Kinematics and Metallicity of the M31 Globular Cluster System
With the ultimate aim of distinguishing between various models describing the
formation of galaxy halos (e.g. radial or multi-phase collapse, random
mergers), we have completed a spectroscopic study of the globular cluster
system of M31. We present the results of deep, intermediate-resolution,
fibre-optic spectroscopy of several hundred of the M31 globular clusters using
the Wide Field Fibre Optic Spectrograph (WYFFOS) at the William Herschel
Telescope in La Palma, Canary Islands. These observations have yielded precise
radial velocities (+/-12 km/s) and metallicities (+/-0.26 dex) for over 200
members of the M31 globular cluster population out to a radius of 1.5 degrees
from the galaxy center. Many of these clusters have no previous published
radial velocity or [Fe/H] estimates, and the remainder typically represent
significant improvements over earlier determinations. We present analyses of
the spatial, kinematic and metal abundance properties of the M31 globular
clusters. We find that the abundance distribution of the cluster system is
consistent with a bimodal distribution with peaks at [Fe/H] = -1.4 and -0.5.
The metal-rich clusters demonstrate a centrally concentrated spatial
distribution with a high rotation amplitude, although this population does not
appear significantly flattened and is consistent with a bulge population. The
metal-poor clusters tend to be less spatially concentrated and are also found
to have a strong rotation signature.Comment: 33 pages, 20 figure