314 research outputs found
The Herschel Space Observatory view of dust in M81
We use Herschel Space Observatory data to place observational constraints on the peak and Rayleigh-Jeans slope of dust emission observed at 70−500 μm in the nearby spiral galaxy M81. We find that the ratios of wave bands between 160 and 500 μm are primarily dependent on radius but that the ratio of 70 to 160 μm emission shows no clear dependence on surface brightness or radius. These
results along with analyses of the spectral energy distributions imply that the 160−500 μm emission traces 15−30 K dust heated by evolved stars in the bulge and disc whereas the 70 μm emission includes dust heated by the active galactic nucleus and young stars in star forming regions
Tests of star formation metrics in the low metallicity galaxy NGC 5253 using ALMA observations of H30 line emission
We use Atacama Large Millimeter/submillimeter Array (ALMA) observations of
H30 (231.90 GHz) emission from the low metallicity dwarf galaxy NGC
5253 to measure the star formation rate (SFR) within the galaxy and to test the
reliability of SFRs derived from other commonly-used metrics. The H30
emission, which originates mainly from the central starburst, yields a
photoionizing photon production rate of (1.90.3)10 s
and an SFR of 0.0870.013 M yr based on conversions that
account for the low metallicity of the galaxy and for stellar rotation. Among
the other star formation metrics we examined, the SFR calculated from the total
infrared flux was statistically equivalent to the values from the H30
data. The SFR based on previously-published versions of the H flux that
were extinction corrected using Pa and Pa lines were lower than
but also statistically similar to the H30 value. The mid-infrared (22
m) flux density and the composite star formation tracer based on H
and mid-infrared emission give SFRs that were significantly higher because the
dust emission appears unusually hot compared to typical spiral galaxies.
Conversely, the 70 and 160 m flux densities yielded SFR lower than the
H30 value, although the SFRs from the 70 m and H30 data
were within 1-2 of each other. While further analysis on a broader
range of galaxies are needed, these results are instructive of the best and
worst methods to use when measuring SFR in low metallicity dwarf galaxies like
NGC 5253.Comment: 14 pages, 5 figures, accepted for publication in MNRA
ALMA observations of 99 GHz free-free and H40 line emission from star formation in the centre of NGC 253
We present Atacama Large Millimeter/submillimeter Array observations of 99.02
GHz free-free and H40 emission from the centre of the nearby starburst
galaxy NGC 253. We calculate electron temperatures of 3700-4500 K for the
photoionized gas, which agrees with previous measurements. We measure a
photoionizing photon production rate of s and
a star formation rate of M yr within the central
2010 arcsec, which fall within the broad range of measurements from
previous millimetre and radio observations but which are better constrained. We
also demonstrate that the dust opacities are ~3 dex higher than inferred from
previous near-infrared data, which illustrates the benefits of using millimetre
star formation tracers in very dusty sources.Comment: 5 pages, 3 figures, accepted for publication in MNRAS Letter
Total Infrared Luminosity Estimation of Resolved and Unresolved Galaxies
The total infrared (TIR) luminosity from galaxies can be used to examine both
star formation and dust physics. We provide here new relations to estimate the
TIR luminosity from various Spitzer bands, in particular from the 8 micron and
24 micron bands. To do so, we use 45" subregions within a subsample of nearby
face-on spiral galaxies from the Spitzer Infrared Nearby Galaxies Survey
(SINGS) that have known oxygen abundances as well as integrated galaxy data
from the SINGS, the Local Volume Legacy Survey (LVL) and Engelbracht et al.
(2008) samples. Taking into account the oxygen abundances of the subregions,
the star formation rate intensity, and the relative emission of the polycyclic
aromatic hydrocarbons at 8 micron, the warm dust at 24 micron and the cold dust
at 70 micron and 160 micron we derive new relations to estimate the TIR
luminosity from just one or two of the Spitzer bands. We also show that the
metallicity and the star formation intensity must be taken into account when
estimating the TIR luminosity from two wave bands, especially when data
longward of 24 micron are not available.Comment: 11 pages, 10 figures, accepted for publication in Ap
Diffuse far-infrared and ultraviolet emission in the NGC4435/4438 system: tidal stream or Galactic cirrus?
We report the discovery of diffuse far-infrared and far-ultraviolet emission
projected near the interacting pair NGC4435/4438, in the Virgo cluster. This
feature spatially coincides with a well known low surface-brightness optical
plume, usually interpreted as tidal debris. If extragalactic, this stream would
represent not only one of the clearest examples of intracluster dust, but also
a rare case of intracluster molecular hydrogen and large-scale intracluster
star formation. However, the ultraviolet, far-infrared, HI and CO emission as
well as the dynamics of this feature are extremely unusual for tidal streams
but are typical of Galactic cirrus clouds. In support to the cirrus scenario,
we show that a strong spatial correlation between far-infrared and
far-ultraviolet cirrus emission is observed across the center of the Virgo
cluster, over a scale of several degrees. This study demonstrates how dramatic
Galactic cirrus contamination can be, even at optical and ultraviolet
wavelengths and at high galactic latitudes. If ignored, the presence of diffuse
light scattered by Galactic dust clouds could significantly bias our
interpretation of low surface-brightness features and diffuse light observed
around galaxies and in clusters of galaxies.Comment: 6 pages, 4 figures. Accepted for publication in MNRAS Letter
Detection of serum anti-B/B' UsnRNP antibodies in patients with connective tissue diseases by immunoblotting
Objective: To investigate the reliability of the immunoblot method in the detection of serum immunoreactivity towards the B/B' polypeptides of U small nuclear ribonucleoproteins (UsnRNP) and to assess the significance of these antibodies in connective tissue disease (CTD) patients. Methods: We tested the sera of 348 patients with CTD (101 SLE, 51 systemic sclerosis, 53 primary Sjogren's syndrome, 27 poly/dermatomyositis, 15 rheumatoid arthritis and 101 overlap CTD), of 31 matched healthy subjects and 13 patients with primary Epstein-Barr virus (EBV) infection with high titre IgG anti-EBV antibodies. IgG anti-UsnRNP antibodies were determined by immunoblotting on nuclear extract from Raji cells (an EBV-immortalised human B lymphoid cell line) and Jurkat cells (a human T lymphoid cell line). Anti-dsDNA antibodies were detected by indirect immunofluorescence on Crithidia luciliae and anti-ENA by counterimmunoelectrophoresis. Anti-dsDNA activity and avidity were measured in SLE sera by ELISA with Scatchard analysis. Results were statistically analysed by chi-square and Mann-Whitney tests. Results: A high frequency of anti-B/B' antibodies was found in the sera of CTD patients, confined to SLE (54.4%) and overlap CTD with SLE features (55,2%). Anti-B/B' immune reactivity was closely associated with other anti-UsnRNP specificities, gel precipitating anti-nRNP and anti-P antibodies. Nine out of 15 (60%) anti-B/B' positive/anti-ENA negative lupus sera on Raji blots were confirmed to be positive also on Jurkat blots. The sera from patients with EBV infection provided, on Raji blots, completely different band patterns from those obtained with auto-immune sera. Conclusions. The Sm B/B' proteins are the predominant or, at least, the most frequently targeted antigens of the UsnRNP auto-immune response in SLE and "lupus-like" overlap CTD. Moreover, anti-B/B' is diagnostically specific for CTD with SLE features. Immunoblotting on human B lymphoid cells is a reliable method, in terms of sensitivity and specificity, for the detection of anti-Sm B/B' antibodies
The Herschel Virgo Cluster Survey: X.The relationship between cold dust and molecular gas content in Virgo spirals
Using the far-infrared emission, as observed by the Herschel Virgo Cluster
Survey (HeViCS), and the integrated HI and CO brightness, we infer the dust and
total gas mass for a magnitude limited sample of 35 metal rich spiral galaxies
in Virgo. The CO flux correlates tightly and linearly with far-infrared fluxes
observed by Herschel. Molecules in these galaxies are more closely related to
cold dust rather than to dust heated by star formation or to optical/NIR
brightness. We show that dust mass establishes a stronger correlation with the
total gas mass than with the atomic or molecular component alone. The
dust-to-gas ratio increases as the HI deficiency increases, but in highly HI
deficient galaxies it stays constant. Dust is in fact less affected than atomic
gas by weak cluster interactions, which remove most of the HI gas from outer
and high latitudes regions. Highly disturbed galaxies, in a dense cluster
environment, can instead loose a considerable fraction of gas and dust from the
inner regions of the disk keeping constant the dust-to-gas ratio. There is
evidence that the molecular phase is also quenched. This quencing becomes
evident by considering the molecular gas mass per unit stellar mass. Its
amplitude, if confirmed by future studies, highlights that molecules are
missing in Virgo HI deficient spirals, but to a somewhat lesser extent than
dust.Comment: 11 pages, 8 figures. Accepted for publication in A&
Dust in dwarf galaxies: The case of NGC 4214
We have carried out a detailed modelling of the dust heating and emission in
the nearby, starbursting dwarf galaxy NGC 4214. Due to its proximity and the
great wealth of data from the UV to the millimeter range (from GALEX, HST, {\it
Spitzer}, Herschel, Planck and IRAM) it is possible to separately model the
emission from HII regions and their associated photodissociation regions (PDRs)
and the emission from diffuse dust. Furthermore, most model parameters can be
directly determined from the data leaving very few free parameters. We can fit
both the emission from HII+PDR regions and the diffuse emission in NGC 4214
with these models with "normal" dust properties and realistic parameters.Comment: 4pages, 3 figures. To appear in 'The Spectral Energy Distribution of
Galaxies' Proceedings IAU Symposium No 284, 201
Cold dust in a selected sample of nearby galaxies. I. The interacting galaxy NGC4631
We have observed the continuum emission of the interacting galaxy NGC4631 at
0.87 and 1.23mm using the Heinrich-Hertz-Telescope on Mt. Graham and the IRAM
30-m telescope on Pico Veleta. We have obtained fully sampled maps which cover
the optical emission out to a radius of about 7' at both wavelengths. For a
detailed analysis, we carefully subtracted the line contributions and
synchrotron and free-free emission from the data, which added up to 6% at
1.23mm and 10% at 0.87mm. We combined the flux densities with FIR data to
obtain dust spectra and calculate dust temperatures, absorption cross sections,
and masses. Assuming a ``standard'' dust model, which consists of two
populations of big grains at moderate and warm temperatures, we obtained
temperatures of 18K and 50K for the both components. However, such a model
suffers from an excess of the radiation at 1.23mm, and the dust absorption
cross section seems to be enhanced by a factor 3 compared to previous results
and theoretical expectations. At large galactocentric radii, where the galaxy
shows disturbances as a result of gravitational interaction, this effect seems
to be even stronger. Some possibilities to resolve these problems are
discussed. The data could be explained by a very cold dust component at a
temperature of 4-6K, an increased abundance of very small grains, or a
component of grains with unusual optical properties. We favour the latter
possibility, since the first two lead to inconsistencies.Comment: 12 pages, 6 figures, accepted for publication in Astronomy &
Astrophysics. Updated version with minor errors corrected (typos, LaTeX
formatting, missing citation
[Myositis specific and myositis associated autoantibodies in idiopathic inflammatory myopathies: a serologic study of 46 patients]
Objective. To characterize serum autoantibody profiles of patients with idiopathic inflammatory myopathies (IIM) by searching for myositis-specific (MSA) and myositis-associated (MAA) antibodies with sensitive and specific laboratory tests. Methods. We tested the sera from 46 Caucasian patients diagnosed as affected with IIM at the Division of Rheumatology of Padova University (21 polimyositis, PM; 22 dermatomyositis, DM; 3 myositis overlap syndrome). All patients had definite IIM according to the criteria of Bohan-Peter. MSA including anti-tRNA synthetase (anti-Jo-1 and others) and anti-Mi-2 were determined by RNA immunoprecipitation and a modified immunoblot test, respectively. MAA (-U1RNP, -U2RNP, RoRNP, PM/Scl, Ku) were detected by counterimmunoelectrophoresis and immunoblot. Results. Serum MSA and/or MAA were found in 30/46 (65%) patients with IIM. Twenty-three patients (50%) were positive for at least one MSA: anti-Jo-1 in 15 (33%), anti-Mi-2 in 6 (13%), and other anti-tRNA synthetase in 3 (6%).One patient was anti-Jo-1/Mi-2 positive. Moreover, 18 patients (39%) were positive for at least one MAA: anti-Ro/SSA in 13 (28%), anti-U1RNP in 4 (9%), anti-PM/Scl in 1 (2%) and anti-Ku in 1 (2%). Coexisting MSA and MAA were observed in 8 patients (17%), anti-Jo-1/SSA positive in most cases. Anti-Jo-1 was predominantly associated with PM (57% in PM vs 14% in DM), whereas anti-Mi-2 was exclusively found in DM patients (27%). Anti-synthetase antibodies were closely associated with interstitial lung disease and polyarthritis; anti-Mi-2 positive DM patients did not have lung involvement. Notably, anti-Ro/SSA antibody was frequently observed and almost equally detected in either PM or DM (about 30%): in more than 50% of cases the antibody was associated with one MSA. Conclusions. By means of analytically reliable methods, MSA was detected in 50% of our IIM patients. Searching for MSA in patients with IIM is recommended because of its diagnostic and prognostic value
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