3,386 research outputs found
Rotation curves and metallicity gradients from HII regions in spiral galaxies
In this paper we study long slit spectra in the region of H emission
line of a sample of 111 spiral galaxies with recognizable and well defined
spiral morphology and with a well determined environmental status, ranging from
isolation to non-disruptive interaction with satellites or companions. The form
and properties of the rotation curves are considered as a function of the
isolation degree, morphological type and luminosity. The line ratios are used
to estimate the metallicity of all the detected HII regions, thus producing a
composite metallicity profile for different types of spirals. We have found
that isolated galaxies tend to be of later types and lower luminosity than the
interacting galaxies. The outer parts of the rotation curves of isolated
galaxies tend to be flatter than in interacting galaxies, but they show similar
relations between global parameters. The scatter of the Tully-Fisher relation
defined by isolated galaxies is significantly lower than that of interacting
galaxies. The [NII]/H ratios, used as metallicity indicator, show a
clear trend between Z and morphological type, t, with earlier spirals showing
larger ratios; this trend is tighter when instead of t the gradient of the
inner rotation curve, G, is used; no trend is found with the interaction
status. The Z-gradient of the disks depends on the type, being almost flat for
early spirals, and increasing for later types. The [NII]/H ratios
measured for disk HII regions of interacting galaxies are higher than for
normal/isolated objects, even if all the galaxy families present similar
distributions of H Equivalent Width.Comment: accepted for publication in A&A (tables for HII region parameters
incomplete, contact [email protected] for the whole set of tables
Diffuse Gas and LMXBs in the Chandra Observation of the S0 Galaxy NGC 1553
We have spatially and spectrally resolved the sources of X-ray emission from
the X-ray faint S0 galaxy NGC 1553 using an observation from the Chandra X-ray
Observatory. The majority (70%) of the emission in the 0.3 - 10.0 keV band is
diffuse, and the remaining 30% is resolved into 49 discrete sources. Most of
the discrete sources associated with the galaxy appear to be low mass X-ray
binaries (LMXBs). The luminosity function of the LMXB sources is well-fit by a
broken power-law with a break luminosity comparable to the Eddington luminosity
for a 1.4 solar mass neutron star. It is likely that those sources with
luminosities above the break are accreting black holes and those below are
mostly neutron stars in binary systems. Spectra were extracted for the total
emission, diffuse emission, and sum of the resolved sources; the spectral fits
for all require a model including both a soft and hard component. The diffuse
emission is predominately soft while the emission from the sources is mostly
hard. Approximately 24% of the diffuse emission arises from unresolved LMXBs,
with the remainder resulting from thermal emission from hot gas. There is a
very bright source at the projected position of the nucleus of the galaxy. The
spectrum and luminosity derived from this central source are consistent with it
being an AGN; the galaxy also is a weak radio source. Finally, the diffuse
emission exhibits significant substructure with an intriguing spiral feature
passing through the center of the galaxy. The X-ray spectrum and surface
brightness of the spiral feature are consistent with adiabatic or shock
compression of ambient gas, but not with cooling. This feature may be due to
compression of the hot interstellar gas by radio lobes or jets associated with
the AGN.Comment: 23 pages using emulateapj.sty; ApJ, in press; revised version
includes correction to error in the L_X,src/L_B ratio as well as other
revision
Dalle Province all’area vasta: un’incoerenza italiana
La storia della delimitazione regionale in Italia ci aiuta a capire quanto artificiale possa essere la rappresentazione che di esse hanno i diversi governi regionali. In questo capitolo si procede a una comparazione con quella provinciale, ben più antica, che ci permetta anche di mostrarne il ruolo nella programmazione attuale.The history of regional borders in Italy cans show the artificial representation that their governments propose. For this reason the comparison with the provincial delimitations, older than the first, can help to explain why it is important a deeper reflection about the question to renounce to this institutional level
Scaling relations of cluster elliptical galaxies at z~1.3. Distinguishing luminosity and structural evolution
[Abridged] We studied the size-surface brightness and the size-mass relations
of a sample of 16 cluster elliptical galaxies in the mass range
10^{10}-2x10^{11} M_sun which were morphologically selected in the cluster RDCS
J0848+4453 at z=1.27. Our aim is to assess whether they have completed their
mass growth at their redshift or significant mass and/or size growth can or
must take place until z=0 in order to understand whether elliptical galaxies of
clusters follow the observed size evolution of passive galaxies. To compare our
data with the local universe we considered the Kormendy relation derived from
the early-type galaxies of a local Coma Cluster reference sample and the WINGS
survey sample. The comparison with the local Kormendy relation shows that the
luminosity evolution due to the aging of the stellar content already assembled
at z=1.27 brings them on the local relation. Moreover, this stellar content
places them on the size-mass relation of the local cluster ellipticals. These
results imply that for a given mass, the stellar mass at z~1.3 is distributed
within these ellipticals according to the same stellar mass profile of local
ellipticals. We find that a pure size evolution, even mild, is ruled out for
our galaxies since it would lead them away from both the Kormendy and the
size-mass relation. If an evolution of the effective radius takes place, this
must be compensated by an increase in the luminosity, hence of the stellar mass
of the galaxies, to keep them on the local relations. We show that to follow
the Kormendy relation, the stellar mass must increase as the effective radius.
However, this mass growth is not sufficient to keep the galaxies on the
size-mass relation for the same variation in effective radius. Thus, if we want
to preserve the Kormendy relation, we fail to satisfy the size-mass relation
and vice versa.Comment: Accepted for publication in A&A, updated to match final journal
versio
Dark matter in the inner parts of barred galaxies: The data
This paper presents surface photometry (B,V, I, J, H, K) and H_alpha rotation
curves of 27 isolated spiral galaxies. The final goal is to obtain the mass
distribution of a sample of isolated spiral galaxies in order to model their
gas kinematics. This is then compared to the observed rotation curve, to
determine the necessity of a dark halo in the inner parts (Perez et al. 2004).
The azimuthally averaged radial surface brightness profiles and the integrated
magnitudes obtained from ellipse fitting are given for each of the sample
galaxies. The ellipse fitting technique applied to the light distribution also
allowed us to obtain the size of the bar, and the inclination and position
angle of the outer isophotes that allow the galaxy deprojection. Using these
profiles, 1-D disk-bulge decomposition was performed to obtain the disk
scale-length and the bulge effective radius for the different bands. Through
the fitting of a parametric function to the observed rotation curve, the
maximum rotational velocity and the corresponding radius was obtained. The
correlation between the bulge and disk parameters is in agreement with previous
studies (de Jong 1996a; Marquez & Moles 1999; Baggett et al. 1998). Regarding
the Kormendy relation (Kormendy 1977), in agreement with de Jong, no
correlation between the bulge effective radius and its surface brightness is
found, possibly due to the small range of bulge magnitudes covered. We find a
smaller scatter in the structural relations when compared to non-isolated
samples in agreement with Marquez & Moles (1999). Finally, a correlation
between the disk scale-length and the bar size is observed, possibly reflecting
the rapid growth of a bar.Comment: A&A accepted. Fig. 11 and Tables 3-8 can be downloaded at:
http://www.astro.rug.nl/~isa (they will also be available at
http://www.edpsciences.org
A renormalization group invariant scalar glueball operator in the (Refined) Gribov-Zwanziger framework
This paper presents a complete algebraic analysis of the renormalizability of
the operator in the Gribov-Zwanziger (GZ) formalism as
well as in the Refined Gribov-Zwanziger (RGZ) version. The GZ formalism offers
a way to deal with gauge copies in the Landau gauge. We explicitly show that
mixes with other gauge variant operators, and we determine
the mixing matrix to all orders, thereby only using algebraic arguments.
The mixing matrix allows us to uncover a renormalization group invariant
including the operator . With this renormalization group
invariant, we have paved the way for the study of the lightest scalar glueball
in the GZ formalism. We discuss how the soft breaking of the BRST symmetry of
the GZ action can influence the glueball correlation function. We expect
non-trivial mass scales, inherent to the GZ approach, to enter the pole
structure of this correlation function.Comment: 27 page
Discovery of a Boxy Peanut Shaped Bulge in the Near Infrared
We report on the discovery of a boxy/peanut shaped bulge in the highly
inclined barred Seyfert 2 galaxy NGC~7582. The peanut shape is clearly evident
in near infrared images but obscured by extinction from dust in visible
images. This suggests that near infrared imaging surveys will discover a
larger number of boxy/peanut morphologies than visible surveys, particularly in
galaxies with heavy extinction such as NGC~7582. The bulge in NGC~7582 exhibits
strong boxiness compared to other boxy/peanut shaped bulges. If the starburst
was mediated by the bar, then it is likely that the bar formed in less than a
few bar rotation periods or a few years ago. If the bar also
caused the peanut, then the peanut would have formed quickly; on a timescale of
a few bar rotation periods.Comment: AAS Latex and Postcript Figures, accepted for publication in Ap
Lenticular galaxies with UV-rings
By using the public UV imaging data obtained by the GALEX (Galaxy Ultraviolet
Explorer) for nearby galaxies, we have compiled a list of lenticular galaxies
possessing ultraviolet rings - starforming regions tightly confined to
particular radial distances from galactic centers. We have studied large-scale
structure of these galaxies in the optical bands by using the data of the SDSS
(Sloan Digital Sky Survey): we have decomposed the galactic images into
large-scale disks and bulges, have measured the ring optical colours from the
residual images after subtracting model disks and bulges, and have compared the
sizes of the rings in the optical light and in the UV-band. The probable origin
of the outer starforming ring appearances in unbarred galaxies demonstrating
otherwise the regular structure and homogeneously old stellar population beyond
the rings is discussed.Comment: 9 pages plus one big colour figure in the Appendix; the slightly
expanded version of the paper accepted to Astronomy Letter
A model to explain angular distributions of and decays into and
BESIII data show a particular angular distribution for the decay of the
and mesons into the hyperons
and . More in details the angular distribution of
the decay exhibits an opposite trend
with respect to that of the other three channels: , and
. We define a model to explain the
origin of this phenomenon.Comment: 6 pages, 7 figures, to be published in Chinese Physics
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