586 research outputs found
The Arecibo Galaxy Environments survey IV: the NGC7448 region and the HI mass function
In this paper we describe results from the Arecibo Galaxy Environments Survey
(AGES). The survey reaches column densities of ~3x10^18 cm^-2 and masses of
~10^7 M_O, over individual regions of order 10 sq deg in size, out to a maximum
velocity of 18,000 km s^-1. Each surveyed region is centred on a nearby galaxy,
group or cluster, in this instance the NGC7448 group. Galaxy interactions in
the NGC7448 group reveal themselves through the identification of tidal tails
and bridges. We find ~2.5 times more atomic gas in the inter-galactic medium
than in the group galaxies. We identify five new dwarf galaxies, two of which
appear to be members of the NGC7448 group. This is too few, by roughly an order
of magnitude, dwarf galaxies to reconcile observation with theoretical
predictions of galaxy formation models. If they had observed this region of sky
previous wide area blind HI surveys, HIPASS and ALFALFA, would have detected
only 5% and 43% respectively of the galaxies we detect, missing a large
fraction of the atomic gas in this volume. We combine the data from this paper
with that from our other AGES papers (370 galaxies) to derive a HI mass
function with the following Schechter function parameters alpha=-1.52+/-0.05,
M^*=5.1+/-0.3x10^9 h_72^-2 M_O, phi=8.6+/-1.1x10-3 h_72^3 Mpc^-3 dex-1.
Integrating the mass function leads to a cosmic mass density of atomic hydrogen
of Omega_HI=5.3+/-0.8x10^-4 h_72^-1. Our mass function is steeper than that
found by both HIPASS and ALFALFA (alpha=1.37 and 1.33 respectively), while our
cosmic mass density is consistent with ALFALFA, but 1.7 times larger than found
by HIPASS
The Arecibo Galaxy Environment Survey: II. A HI view of the Abell cluster 1367 and its outskirts
We present 21 cm HI line observations of 5x1 square degrees centered on the
local Abell cluster 1367 obtained as part of the Arecibo Galaxy Environment
Survey. One hundred sources are detected (79 new HI measurements and 50 new
redshifts), more than half belonging to the cluster core and its infalling
region. Combining the HI data with SDSS optical imaging we show that our HI
selected sample follows scaling relations similar to the ones usually observed
in optically selected samples. Interestingly all galaxies in our sample appear
to have nearly the same baryon fraction independently of their size, surface
brightness and luminosity. The most striking difference between HI and
optically selected samples resides in their large scale distribution: whereas
optical and X-ray observations trace the cluster core very well, in HI there is
almost no evidence of the presence of the cluster. Some implications on the
determination of the cluster luminosity function and HI distribution for
samples selected at different wavelength are also discussed.Comment: 22 pages, 15 figures, 4 tables. Accepted for publication on MNRAS
Main Journal. High resolution version of this paper can be downloaded at
http://www.astro.cf.ac.uk/pub/Luca.Cortese/papers/ages_a1367.pdf . Datacubes
and catalogs can be downloaded at http://www.naic.edu/~ages/public_data.htm
The brightest OH maser in the sky: a flare of emission in W75 N
A flare of maser radio emission in the OH-line 1665 MHz has been discovered
in the star forming region W75 N in 2003, with the flux density of about 1000
Jy. At the time it was the strongest OH maser detected during the whole history
of observations since the discovery of cosmic masers in 1965. The flare
emission is linearly polarized with a degree of polarization near 100%. A
weaker flare with a flux of 145 Jy was observed in this source in 2000 - 2001,
which was probably a precursor of the powerful flare. Intensity of two other
spectral features has decreased after beginning of the flare. Such variation of
the intensity of maser condensation emission (increasing of one and decreasing
of the other) can be explained by passing of the magneto hydrodynamic shock
across regions of enhanced gas concentration.Comment: 9 pages with 2 figures, accepted for publication in Astronomy Letter
An Imaging Survey of Early-Type Barred Galaxies
This paper presents the results of a high-resolution imaging survey, using
both ground-based and Hubble Space Telescope images, of a complete sample of
nearby barred S0--Sa galaxies in the field, with a particular emphasis on
identifying and measuring central structures within the bars: secondary bars,
inner disks, nuclear rings and spirals, and off-plane dust. A discussion of the
frequency and statistical properties of the various types of inner structures
has already been published. Here, we present the data for the individual
galaxies and measurements of their bars and inner structures. We set out the
methods we use to find and measure these structures, and how we discriminate
between them. In particular, we discuss some of the deficiencies of ellipse
fitting of the isophotes, which by itself cannot always distinguish between
bars, rings, spirals, and dust, and which can produce erroneous measurements of
bar sizes and orientations.Comment: LaTeX, 66 pages (including 42 figures, 36 in color). To appear in The
Astrophysical Journal Supplement. Full-resolution and text-only versions
available at http://www.iac.es/galeria/erwin/research
Citrullinated human and murine MOG<sub>35–55</sub> display distinct biophysical and biochemical behavior
The peptide spanning residues 35 to 55 of the protein myelin oligodendrocyte glycoprotein (MOG) has been studied extensively in its role as a key autoantigen in the neuroinflammatory autoimmune disease multiple sclerosis. Rodents and nonhuman primate species immunized with this peptide develop a neuroinflammatory condition called experimental autoimmune encephalomyelitis, often used as a model for multiple sclerosis. Over the last decade, the role of citrullination of this antigen in the disease onset and progression has come under increased scrutiny. We recently reported on the ability of these citrullinated MOG35–55 peptides to aggregate in an amyloid-like fashion, suggesting a new potential pathogenic mechanism underlying this disease. The immunodominant region of MOG is highly conserved between species, with the only difference between the murine and human protein, a polymorphism on position 42, which is serine in mice and proline for humans. Here, we show that the biophysical and biochemical behavior we previously observed for citrullinated murine MOG35–55 is fundamentally different for human and mouse MOG35–55. The citrullinated human peptides do not show amyloid-like behavior under the conditions where the murine peptides do. Moreover, we tested the ability of these peptides to stimulate lymphocytes derived from MOG immunized marmoset monkeys. While the citrullinated murine peptides did not produce a proliferative response, one of the citrullinated human peptides did. We postulate that this unexpected difference is caused by disparate antigen processing. Taken together, our results suggest that further study on the role of citrullination in MOG-induced experimental autoimmune encephalomyelitis is necessary.</p
'In het model kun je het makkelijker uitbeelden dan het in werkelijkheid is’. Het gebruik van modellen en modelleeractiviteiten bij schei- en natuurkunde.
H-alpha Kinematics of the SINGS Nearby Galaxies Survey. II
This is the second part of an H-alpha kinematics follow-up survey of the
Spitzer Infrared Nearby Galaxies Survey (SINGS) sample. The aim of this program
is to shed new light on the role of baryons and their kinematics and on the
dark/luminous matter relation in the star forming regions of galaxies, in
relation with studies at other wavelengths. The data for 37 galaxies are
presented. The observations were made using Fabry-Perot interferometry with the
photon-counting camera FaNTOmM on 4 different telescopes, namely the
Canada-France-Hawaii 3.6m, the ESO La Silla 3.6m, the William Herschel 4.2m,
and the Observatoire du mont Megantic 1.6m telescopes. The velocity fields are
computed using custom IDL routines designed for an optimal use of the data. The
kinematical parameters and rotation curves are derived using the GIPSY
software. It is shown that non-circular motions associated with galactic bars
affect the kinematical parameters fitting and the velocity gradient of the
rotation curves. This leads to incorrect determinations of the baryonic and
dark matter distributions in the mass models derived from those rotation
curves.Comment: 18 pages, 5 figures, 4 tables. Accepted for publication in MNRAS. All
high-res. figures are available at
http://www.astro.umontreal.ca/fantomm/singsII
Fluorescent labeling of nascent RNA reveals transcription by RNA polymerase II in domains scattered throughout the nucleus
The Arecibo Galaxy Environment Survey III: Observations Toward the Galaxy Pair NGC 7332/7339 and the Isolated Galaxy NGC 1156
Two 5 square degree regions around the NGC 7332/9 galaxy pair and the
isolated galaxy NGC 1156 have been mapped in the 21-cm line of neutral hydrogen
(HI) with the Arecibo L-band Feed Array out to a redshift of ~0.065
km/s) as part of the Arecibo Galaxy Environment Survey. One of the aims of this
survey is to investigate the environment of galaxies by identifying dwarf
companions and interaction remnants; both of these areas provide the potential
for such discoveries. The neutral hydrogen observations were complemented by
optical and radio follow-up observations with a number of telescopes. A total
of 87 galaxies were found, of which 39 (45 per cent) were previously cataloged
and 15 (17 per cent) have prior redshifts. Two dwarf galaxies have been
discovered in the NGC 7332 group and a single dwarf galaxy in the vicinity NGC
1156 . A parallel optical search of the area revealed one further possible
dwarf galaxy near NGC 7332.Comment: 18 pages, 17 figures, uses emulateap
The Extraordinary `Superthin' Spiral Galaxy UGC7321. I. Disk Color Gradients and Global Properties from Multiwavelength Observations
We present B- and R-band imaging and photometry, H-alpha narrow-band imaging,
NIR H-band imaging, and HI 21-cm spectroscopy of the nearby Sd spiral galaxy
UGC7321. UGC7321 exhibits a remarkably thin stellar disk with no bulge
component. The galaxy has a very diffuse, low surface brightness disk, which
appears to suffer little internal extinction in spite of its edge-on geometry.
The UGC7321 disk shows significant B-R color gradients in both the radial and
vertical directions. These color gradients cannot be explained solely by dust
and are indicative of changes in the mix of stellar ages and/or metallicity as
a function of both radius and height above the galaxy plane. The outer regions
of the UGC7321 disk are too blue to be explained by low metallicity alone
(B-R<0.6), and must be relatively young. However, the galaxy also contains
stellar populations with B-R>1.1, indicating it is not a young or
recently-formed galaxy. The disk of UGC7321 is not a simple exponential, but
exhibits a light excess at small radii, as well as distinct surface brightness
zones. Together the properties of UGC7321 imply that it is an under-evolved
galaxy in both a dynamical and in a star-formation sense. (Abridged)Comment: Accepted to the Astronomical Journal; 28 pages, 1 table and 21
figures (GIF and postscript
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