601 research outputs found
Combined color indexes and photometric structure of galaxies NGC 834 and NGC 1134
We present the results of BVRI photometry of two galaxies with active star
formation: NGC 834 and NGC 1134. Combined color index Q_{BVI} was used to
investigate the photometrical structure of the galaxies. Index Q_{BVI} is not
affected by internal extinction and is sensitive to the presence of blue stars.
Ring-like region with active star formation at 15" from the center reveals
itself in the Q_{BVI} map of NGC 834. Three-arm spiral structure is well-seen
on the Q_{BVI} map of NGC 1134.
We propose to use the combined indexes Q_{BVI} and similarly defined indices
as a tracers of Star Formation activity and structure of dusty galaxies.Comment: 3 pages, 4 embedded figures, LaTeX2e, using the EslabStyle.cls file,
presented as a poster in the 33rd ESLAB Symp. "Star formation from the small
to the large scale", Noordwijk, The Netherlands, 2-5 November 1999, (F.
Favata, A.A. Kaas & A. Wilson eds, ESA SP-445
Do Bars Drive Spiral Density Waves?
We present deep near-infrared K_s-band AAT IRIS2 observations of a selected
sample of nearby barred spiral galaxies, including some with the strongest
known bars. The sample covers a range of Hubble types from SB0- to SBc. The
goal is to determine if the torque strengths of the spirals correlate with
those of the bars, which might be expected if the bars actually drive the
spirals as has been predicted by theoretical studies. This issue has
implications for interpreting bar and spiral fractions at high redshift.
Analysis of previous samples suggested that such a correlation exists in the
near-infrared, where effects of extinction and star formation are less
important. However, the earlier samples had only a few excessively strong bars.
Our new sample largely confirms our previous studies, but still any correlation
is relatively weak. We find two galaxies, NGC 7513 and UGC 10862, where there
is a only a weak spiral in the presence of a very strong bar. We suggest that
some spirals probably are driven by their bars at the same pattern speed, but
that this may be only when the bar is growing or if there is abundant gas and
dissipation.Comment: 84 pages, 29 figures, accepted by Astronomical Journa
Grand Design and Flocculent Spirals in the Spitzer Survey of Stellar Structure in Galaxies (S4G)
Spiral arm properties of 46 galaxies in the Spitzer Survey of Stellar
Structure in Galaxies (S4G) were measured at 3.6mu, where extinction is small
and the old stars dominate. The sample includes flocculent, multiple arm, and
grand design types with a wide range of Hubble and bar types. We find that most
optically flocculent galaxies are also flocculent in the mid-IR because of star
formation uncorrelated with stellar density waves, whereas multiple arm and
grand design galaxies have underlying stellar waves. Arm-interarm contrasts
increase from flocculent to multiple arm to grand design galaxies and with
later Hubble types. Structure can be traced further out in the disk than in
previous surveys. Some spirals peak at mid-radius while others continuously
rise or fall, depending on Hubble and bar type. We find evidence for regular
and symmetric modulations of the arm strength in NGC 4321. Bars tend to be
long, high amplitude, and flat-profiled in early type spirals, with arm
contrasts that decrease with radius beyond the end of the bar, and they tend to
be short, low amplitude, and exponential-profiled in late Hubble types, with
arm contrasts that are constant or increase with radius. Longer bars tend to
have larger amplitudes and stronger arms.Comment: 31 pages, 14 figures, ApJ in pres
The Distribution of Maximum Relative Torques in Disk Galaxies
The maximum ratio of the tangential force to the mean background radial force
is a useful quantitative measure of the strength of nonaxisymmetric
perturbations in disk galaxies. Here we consider the distribution of this
ratio, called Qg, for a statistically well-defined sample of 180 spiral
galaxies from the Ohio State University Bright Galaxy Survey and the Two Micron
All-Sky Survey. Qg is derived from gravitational potentials inferred from
near-infrared images under the assumptions of a constant mass-to-light ratio
and an exponential vertical density law. In order to derive the most reliable
maximum relative torques, orientation parameters based on blue-light isophotes
are used to deproject the galaxies, and the more spherical shapes of bulges are
taken into account using two-dimensional decompositions which allow for
analytical fits to bulges, disks, and bars. Also, vertical scaleheights hz are
derived by scaling the radial scalelengths hR from the two-dimensional
decompositions allowing for the type dependence of hR/hz indicated by optical
and near-infrared studies of edge-on spiral galaxies. The impact of dark matter
is assessed using a "universal rotation curve" parametrization, and is found to
be relatively insignificant for our sample. In agreement with a previous study
by Block et al. (2002), the distribution of maximum relative gravitational
torques is asymmetric towards large values and shows a deficiency of low Qg
galaxies. However, due to the above refinements, our distribution shows more
low Qg galaxies than Block et al. We also find a significant type-dependence in
maximum relative gravitational torques, in the sense that Qg is lower on
average in early-type spirals compared to late-type spirals.Comment: Accepted for publication in the Astronomical Journal, January 2004
issue (Latex, 39 pages + 17 figures, uses aastex.cls
The Kinematically Measured Pattern Speeds of NGC 2523 and NGC 4245
We have applied the Tremaine-Weinberg continuity equation method to derive
the bar pattern speed in the SB(r)b galaxy NGC 2523 and the SB(r)0/a galaxy NGC
4245 using the Calcium Triplet absorption lines. These galaxies were selected
because they have strong inner rings which can be used as independent tracers
of the pattern speed. The pattern speed of NGC 2523 is 26.4 6.1 km
s kpc, assuming an inclination of 49.7 and a distance
of 51.0 Mpc. The pattern speed of NGC 4245 is 75.5 31.3 km s
kpc, assuming an inclination of 35.4 and a distance of 12.6
Mpc. The ratio of the corotation radius to the bar radius of NGC 2523 and NGC
4245 is 1.4 0.3 and 1.1 0.5, respectively. These values place the
bright inner rings near and slightly inside the corotation radius, as predicted
by barred galaxy theory. Within the uncertainties, both galaxies are found to
have fast bars that likely indicate dark halos of low central concentration.
The photometric properties, bar strengths, and disk stabilities of both
galaxies are also discussed.Comment: Accepted for publication in The Astronomical Journal, 11 figures, 2
table
The Distribution of Dark Matter in a Ringed Galaxy
Outer rings are located at the greatest distance from the galaxy center of
any feature resonant with a bar. Because of their large scale, their morphology
is sensitive to the distribution of the dark matter in the galaxy. We introduce
here how study of these rings can constrain the mass-to-light ratio of the bar,
and so the percentage of dark matter in the center of these galaxies. We
compare periodic orbits integrated in the ringed galaxy NGC 6782 near the outer
Lindblad resonance to the shape of the outer ring. The non-axisymmetric
component of the potential resulting from the bar is derived from a
near-infrared image of the galaxy. The axisymmetric component is derived
assuming a flat rotation curve. We find that the pinched non-self-intersecting
periodic orbits are more elongated for higher bar mass-to-light ratios and
faster bars. The inferred mass-to-light ratio of the bar depends on the assumed
inclination of the galaxy. With an assumed galaxy inclination of i=41 degrees,
for the orbits to be consistent with the observed ring morphology the
mass-to-light ratio of the bar must be high, greater than 70% of a maximal disk
value. For i=45 degrees, the mass-to-light ratio of the bar is of
the maximal disk value. Since the velocity field of these rings can be used to
constrain the galaxy inclination as well as which periodic orbit is represented
in the ring, further study will yield tighter constraints on the mass-to-light
ratio of the bar. If a near maximal disk value for the bar is required, then
either there would be little dark matter within the bar, or the dark matter
contained in the disk of the galaxy would be non-axisymmetric and would rotate
with the bar.Comment: AAS Latex + jpg Figures, Accepted for publication in Ap
Quantifying Bar Strength: Morphology Meets Methodology
A set of objective bar-classification methods have been applied to the Ohio
State Bright Spiral Galaxy Survey (Eskridge et al. 2002). Bivariate comparisons
between methods show that all methods agree in a statistical sense. Thus the
distribution of bar strengths in a sample of galaxies can be robustly
determined. There are very substantial outliers in all bivariate comparisons.
Examination of the outliers reveals that the scatter in the bivariate
comparisons correlates with galaxy morphology. Thus multiple measures of bar
strength provide a means of studying the range of physical properties of galaxy
bars in an objective statistical sense.Comment: LaTeX with Kluwer style file, 5 pages with 3 embedded figures. edited
by Block, D.L., Freeman, K.C., Puerari, I., & Groess,
Oценка первичной медицинской службы муниципия Кишинэу через призму качества оказанных медицинских услуг
Ministry of Health, Department of Analysis, monitoring and politics evaluation, Department of Economy, Management and Psychopedagogy in Medicine, Congresul III al Medicilor de Familie din Republica Moldova, 17–18 mai, 2012, Chişinău, Republica Moldova, Conferinţa Naţională „Maladii bronhoobstructive la copii”, consacrată profesorului universitar, doctor habilitat Victor Gheţeul, 27 aprilie, Chişinău, Republica MoldovaThis paper presents the results obtained in the performance of the thesis. Patients were studied opinion on the organization of primary care services
and quality of services provided. Proportion of patients dissatisfied with the quality of medical care is high. However, multivariate analysis revealed that
the main factors shaping discontent in cases not related to organizational issues, and on the personal relationships between family doctors and patients.В данной работе представлены результаты, полученные при выполнении диссертационной работы. Было изучено мнение пациентов
об организации первичной медицинской службы и качестве оказываемых услуг. Доля недовольных пациентов качеством медицинского
обслуживания высокая. Однако, в многофакторном анализе выявлено что основные факторы формирующие недовольство в большинстве
случаев связана не с организационными вопросами, а с межличностными отношениями между семейными врачами и пациентами
Density Waves Inside Inner Lindblad Resonance: Nuclear Spirals in Disk Galaxies
We analyze formation of grand-design two-arm spiral structure in the nuclear
regions of disk galaxies. Such morphology has been recently detected in a
number of objects using high-resolution near-infrared observations. Motivated
by the observed (1) continuity between the nuclear and kpc-scale spiral
structures, and by (2) low arm-interarm contrast, we apply the density wave
theory to explain the basic properties of the spiral nuclear morphology. In
particular, we address the mechanism for the formation, maintenance and the
detailed shape of nuclear spirals. We find, that the latter depends mostly on
the shape of the underlying gravitational potential and the sound speed in the
gas. Detection of nuclear spiral arms provides diagnostics of mass distribution
within the central kpc of disk galaxies. Our results are supported by 2D
numerical simulations of gas response to the background gravitational potential
of a barred stellar disk. We investigate the parameter space allowed for the
formation of nuclear spirals using a new method for constructing a
gravitational potential in a barred galaxy, where positions of resonances are
prescribed.Comment: 18 pages, 9 figures, higher resolution available at
http://www.pa.uky.edu/~ppe/papers/nucsp.ps.g
The Upper Asymptotic Giant Branch of the Elliptical Galaxy Maffei 1, and Comparisons with M32 and NGC 5128
Deep near-infrared images obtained with adaptive optics systems on the Gemini
North and Canada-France-Hawaii telescopes are used to investigate the bright
stellar content and central regions of the nearby elliptical galaxy Maffei 1.
Stars evolving on the upper asymptotic giant branch (AGB) are resolved in a
field 3 arcmin from the center of the galaxy. The locus of bright giants on the
(K, H-K) color-magnitude diagram is consistent with a population of stars like
those in Baade's Window reddened by E(H-K) = 0.28 +/- 0.05 mag. This
corresponds to A_V = 4.5 +/- 0.8 mag, and is consistent with previous estimates
of the line of sight extinction computed from the integrated properties of
Maffei 1. The AGB-tip occurs at K = 20.0, which correponds to M_K = -8.7;
hence, the AGB-tip brightness in Maffei 1 is comparable to that in M32, NGC
5128, and the bulges of M31 and the Milky-Way. The near-infrared luminosity
functions (LFs) of bright AGB stars in Maffei 1, M32, and NGC 5128 are also in
excellent agreement, both in terms of overall shape and the relative density of
infrared-bright stars with respect to the fainter stars that dominate the light
at visible and red wavelengths. It is concluded that the brightest AGB stars in
Maffei 1, NGC 5128, M32, and the bulge of M31 trace an old, metal-rich
population, rather than an intermediate age population. It is also demonstrated
that Maffei 1 contains a distinct red nucleus, and this is likely the optical
signature of low-level nuclear activity and/or a distinct central stellar
population. Finally, there is an absence of globular clusters brighter than the
peak of the globular cluster LF in the central 700 x 700 parsecs of Maffei 1.Comment: 22 pages of text and 9 postscript figures; to appear in the
Astronomical Journa
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