68 research outputs found
A Region of Violent Star Formation in the Irr Galaxy IC 10: Structure and Kinematics of Ionized and Neutral Gas
We have used observations of the galaxy IC 10 at the 6-m telescope of the
Special Astrophysical Observatory with the SCORPIO focal reducer in the
Fabry-Perot interferometer mode and with the MPFS spectrograph to study the
structure and kinematics of ionized gas in the central region of current
intense star formation. Archive VLA 21-cm observations are used to analyze the
structure and kinematics of neutral gas in this region. High-velocity wings of
the H-alpha and [SII] emission lines were revealed in the inner cavity of the
nebula HL 111 and in other parts of the complex of violent star formation. We
have discovered local expanding neutral-gas shells around the nebulae HL 111
and HL 106.Comment: 22 pages, 10 figures; accepted in Astronomy Report
Pathway to the Square Kilometre Array - The German White Paper -
The Square Kilometre Array (SKA) is the most ambitious radio telescope ever
planned. With a collecting area of about a square kilometre, the SKA will be
far superior in sensitivity and observing speed to all current radio
facilities. The scientific capability promised by the SKA and its technological
challenges provide an ideal base for interdisciplinary research, technology
transfer, and collaboration between universities, research centres and
industry. The SKA in the radio regime and the European Extreme Large Telescope
(E-ELT) in the optical band are on the roadmap of the European Strategy Forum
for Research Infrastructures (ESFRI) and have been recognised as the essential
facilities for European research in astronomy.
This "White Paper" outlines the German science and R&D interests in the SKA
project and will provide the basis for future funding applications to secure
German involvement in the Square Kilometre Array.Comment: Editors: H. R. Kl\"ockner, M. Kramer, H. Falcke, D.J. Schwarz, A.
Eckart, G. Kauffmann, A. Zensus; 150 pages (low resolution- and colour-scale
images), published in July 2012, language English (including a foreword and
an executive summary in German), the original file is available via the MPIfR
homepag
The far-infrared view of M87 as seen by the Herschel Space Observatory
The origin of the far-infrared emission from the nearby radio galaxy M87
remains a matter of debate. Some studies find evidence of a far-infrared excess
due to thermal dust emission, whereas others propose that the far-infrared
emission can be explained by synchrotron emission without the need for an
additional dust emission component. We observed M87 with PACS and SPIRE as part
of the Herschel Virgo Cluster Survey (HeViCS). We compare the new Herschel data
with a synchrotron model based on infrared, submm and radio data to investigate
the origin of the far-infrared emission. We find that both the integrated SED
and the Herschel surface brightness maps are adequately explained by
synchrotron emission. At odds with previous claims, we find no evidence of a
diffuse dust component in M87.Comment: 4 pages, 2 figures, proceedings IAU Symposium 275 (Jets at all
scales
The Herschel Virgo Cluster Survey: IV. Resolved dust analysis of spiral galaxies
We present a resolved dust analysis of three of the largest angular size
spiral galaxies, NGC 4501 and NGC 4567/8, in the Herschel Virgo Cluster Survey
(HeViCS) Science Demonstration field. Herschel has unprecedented spatial
resolution at far-infrared wavelengths and with the PACS and SPIRE instruments
samples both sides of the peak in the far infrared spectral energy distribution
(SED).We present maps of dust temperature, dust mass, and gas-to-dust ratio,
produced by fitting modified black bodies to the SED for each pixel. We find
that the distribution of dust temperature in both systems is in the range ~19 -
22 K and peaks away from the centres of the galaxies. The distribution of dust
mass in both systems is symmetrical and exhibits a single peak coincident with
the galaxy centres. This Letter provides a first insight into the future
analysis possible with a large sample of resolved galaxies to be observed by
Herschel.Comment: Letter accepted for publication in A&A (Herschel special issue
The LOFAR LBA Sky Survey II. First data release
The Low Frequency Array (LOFAR) is the only existing radio interferometer
able to observe at ultra-low frequencies (<100 MHz) with high resolution (<15")
and high sensitivity (<1 mJy/beam). To exploit these capabilities, the LOFAR
Surveys Key Science Project is using the LOFAR Low Band Antenna (LBA) to carry
out a sensitive wide-area survey at 41-66 MHz named the LOFAR LBA Sky Survey
(LoLSS). LoLSS is covering the whole northern sky above declination 24 deg with
a resolution of 15" and a sensitivity of 1-2 mJy/beam (1 sigma) depending on
declination, field properties, and observing conditions. Here we present the
first data release. An automated pipeline was used to reduce the 95 fields
included in this data release. The data reduction procedures developed for this
project have general application and are currently being used to process LOFAR
LBA interferometric observations. Compared to the preliminary release,
direction-dependent errors have been corrected for during the calibration
process. This results in a typical sensitivity of 1.55 mJy/beam at the target
resolution of 15". The first data release of the LOFAR LBA Sky Survey covers
650 sqdeg in the HETDEX spring field. The resultant data products released to
the community include mosaic images (I and V Stokes) of the region, and a
catalogue of 42463 detected sources and related Gaussian components used to
describe sources' morphologies. Separate catalogues for 6 in-band frequencies
are also released. The first data release of LoLSS shows that, despite the
influences of the ionosphere, LOFAR can conduct large-scale surveys in the
frequency window 42-66 MHz with unprecedentedly high sensitivity and
resolution. The data can be used to derive unique information on the
low-frequency spectral properties of many thousands of sources with a wide
range of applications in extragalactic and galactic astronomy.Comment: 20 pages, 22 figures, images and catalogues available at
https://www.lofar-surveys.org/lolss.htm
CALIFA, the Calar Alto Legacy Integral Field Area survey: I. Survey presentation
We present here the Calar Alto Legacy Integral Field Area (CALIFA) survey,
which has been designed to provide a first step in this direction.We summarize
the survey goals and design, including sample selection and observational
strategy.We also showcase the data taken during the first observing runs
(June/July 2010) and outline the reduction pipeline, quality control schemes
and general characteristics of the reduced data. This survey is obtaining
spatially resolved spectroscopic information of a diameter selected sample of
galaxies in the Local Universe (0.005< z <0.03). CALIFA has been
designed to allow the building of two-dimensional maps of the following
quantities: (a) stellar populations: ages and metallicities; (b) ionized gas:
distribution, excitation mechanism and chemical abundances; and (c) kinematic
properties: both from stellar and ionized gas components. CALIFA uses the PPAK
Integral Field Unit (IFU), with a hexagonal field-of-view of
\sim1.3\sq\arcmin', with a 100% covering factor by adopting a three-pointing
dithering scheme. The optical wavelength range is covered from 3700 to 7000
{\AA}, using two overlapping setups (V500 and V1200), with different
resolutions: R\sim850 and R\sim1650, respectively. CALIFA is a legacy survey,
intended for the community. The reduced data will be released, once the quality
has been guaranteed. The analyzed data fulfill the expectations of the original
observing proposal, on the basis of a set of quality checks and exploratory
analysis.
We conclude from this first look at the data that CALIFA will be an important
resource for archaeological studies of galaxies in the Local Universe.Comment: 32 pages, 29 figures, Accepted for publishing in Astronomy and
Astrophysic
High-Redshift Galaxy Outflows and the Formation of Dwarf Galaxies
We examine the effects of galaxy outflows on the formation of dwarf galaxies
in numerical simulations of the high-redshift Universe. Using a Smoothed
Particle Hydrodynamic code, we conduct two detailed simulations of a (5.2
Mpc/h)^3 comoving volume of the Universe. In both simulations we implement
simple, well-motivated models of galaxy identification and star formation,
while our second simulation also includes a simple ``blow-out'' model of galaxy
outflows in which supernova driven winds from newly formed disk galaxies
punch-out and shock the intergalactic medium while leaving the host galaxies
intact. A direct comparison between these simulations suggests that there are
two major mechanisms by which outflows affect dwarf formation. Firstly, the
formation of an outflow slows down the further accretion of gas onto a galaxy,
causing an overall decrease of approximately 50% in the total gas mass accreted
by the objects in our simulations. Additionally, our simulations uncover a
significant population of approximately 10^9 solar mass objects whose formation
is suppressed by the mechanism of ``baryonic stripping,'' in which outflows
from early galaxies strip the gas out of nearby overdense regions that would
have otherwise later formed into dwarf galaxies. This mechanism may be
important in explaining the observed discrepancy between the number of dwarf
galaxies predicted and observed in the local group and provide a natural
explanation for the formation of empty halos which may be required by the
existence of the extremely gas-poor extra-galactic High-Velocity Clouds.Comment: 15 pages, 9 figures, accepted to the Astrophysical Journa
Detection of magnetic fields in the circumgalactic medium of nearby galaxies using Faraday rotation
Context. The existence of magnetic fields in the circumgalactic medium (CGM)
is largely unconstrained. Their detection is important as magnetic fields can
have a significant impact on the evolution of the CGM and, in turn, the fields
can serve as tracers for dynamical processes in the CGM. Aims. With Faraday
rotation of polarised background sources, we aim to detect a possible excess of
the rotation measure in the surrounding area of nearby galaxies. Methods. We
use 2,461 residual rotation measures (RRMs) observed with the LOw Frequency
ARray (LOFAR), where the foreground contribution from the Milky Way is
subtracted. The RRMs are then studied around a subset of 183 nearby galaxies
that was selected by apparent -band magnitude. Results. We find that, in
general, the RRMs show no significant excess for small impact parameters (i.e.
the perpendicular distance to the line of sight). However, if we only consider
galaxies at higher inclination angles and sight lines that pass close to the
minor axis of the galaxies, we find significant excess at impact parameters of
less than 100 kpc. The excess in |RRM| is 3.7 with an
uncertainty between and
depending on the statistical properties of the background
(2.8-4.1). With electron densities of ~
this suggests magnetic field strengths of a few tenths of a micro Gauss.
Conclusions. Our results suggest a slow decrease of the magnetic field strength
with distance from the galactic disc such as expected if the CGM is magnetised
by galactic winds and outflows.Comment: 5 pages, 4 figures, accepted as Letter to Astronomy and Astrophysic
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