425 research outputs found
Constrained simulations of the Antennae Galaxies: Comparison with Herschel-PACS observations
We present a set of hydro-dynamical numerical simulations of the Antennae
galaxies in order to understand the origin of the central overlap starburst.
Our dynamical model provides a good match to the observed nuclear and overlap
star formation, especially when using a range of rather inefficient stellar
feedback efficiencies (0.01 < q_EoS < 0.1). In this case a simple conversion of
local star formation to molecular hydrogen surface density motivated by
observations accounts well for the observed distribution of CO. Using radiative
transfer post-processing we model synthetic far-infrared spectral energy
distributions (SEDs) and two-dimensional emission maps for direct comparison
with Herschel-PACS observations. For a gas-to-dust ratio of 62:1 and the best
matching range of stellar feedback efficiencies the synthetic far-infrared SEDs
of the central star forming region peak at values of ~65 - 81 Jy at 99 - 116
um, similar to a three-component modified black body fit to infrared
observations. Also the spatial distribution of the far-infrared emission at 70
um, 100 um, and 160 um compares well with the observations: >50% (> 35%) of the
emission in each band is concentrated in the overlap region while only < 30% (<
15%) is distributed to the combined emission from the two galactic nuclei in
the simulations (observations). As a proof of principle we show that parameter
variations in the feedback model result in unambiguous changes both in the
global and in the spatially resolved observable far-infrared properties of
Antennae galaxy models. Our results strengthen the importance of direct,
spatially resolved comparative studies of matched galaxy merger simulations as
a valuable tool to constrain the fundamental star formation and feedback
physics.Comment: 17 pages, 8 figures, 4 tables, submitted to MNRAS, including
revisions after first referee report, comments welcom
On the Origin of Lyman Blobs at High Redshift: Submillimetric Evidence for a Hyperwind Galaxy at z=3.1
The most remarkable class of high-redshift objects observed so far is
extended Ly emission-line blobs found in an over-density region at
redshift 3.1. They may be either a dust-enshrouded, extreme starburst galaxy
with a large-scale galactic outflow (superwind) or cooling radiation from dark
matter halos. Recently one of these Ly blobs has been detected at
submillimeter wavelengths (450 and 850 m). Here we show that its
rest-frame spectral energy distribution between optical and far-infrared is
quite similar to that of Arp 220, which is a typical ultraluminous
starburst/superwind galaxy in the local universe. This suggests strongly that
the superwind model proposed by Taniguchi & Shioya is applicable to this
Ly blob. Since the blob is more luminous in the infrared by a factor of
30 than Arp 220, it comprises a new population of hyperwind galaxies at high
redshift.Comment: 4 pages, 1 figure. ApJ (Letters), in pres
Far-infrared photometric observations of the outer planets and satellites with Herschel-PACS
We present all Herschel PACS photometer observations of Mars, Saturn, Uranus,
Neptune, Callisto, Ganymede, and Titan. All measurements were carefully
inspected for quality problems, were reduced in a (semi-)standard way, and were
calibrated. The derived flux densities are tied to the standard PACS photometer
response calibration, which is based on repeated measurements of five fiducial
stars. The overall absolute flux uncertainty is dominated by the estimated 5%
model uncertainty of the stellar models in the PACS wavelength range between 60
and 210 micron. A comparison with the corresponding planet and satellite models
shows excellent agreement for Uranus, Neptune, and Titan, well within the
specified 5%. Callisto is brighter than our model predictions by about 4-8%,
Ganymede by about 14-21%. We discuss possible reasons for the model offsets.
The measurements of these very bright point-like sources, together with
observations of stars and asteroids, show the high reliability of the PACS
photometer observations and the linear behavior of the PACS bolometer source
fluxes over more than four orders of magnitude (from mJy levels up to more than
1000 Jy). Our results show the great potential of using the observed solar
system targets for cross-calibration purposes with other ground-based,
airborne, and space-based instruments and projects. At the same time, the PACS
results will lead to improved model solutions for future calibration
applications.Comment: 25 pages, 11 figures, 11 table
ВИНОРОБСТВО І ВИНОГРАДАРСТВО У
Простежено розвиток і проаналізовано чинники, що на нього впливали, виноградарської і
виноробної галузі сільського господарства Буджаку (Південної Бессарабії) наприкінці ХІХ -
на початку ХХ ст. на документах фонду Аккерманської повітової земської управи Ізмаїльського
архіву.There are investigated and analysed factors of development of vine branch of the agriculture of
Budchack (South Bessarabia) at the end of XIX – beginning of XX cent. based on the documents of
Accerman zemskoy upravy of Ismail archive
Far-Infrared Emission from Intracluster Dust in Abell Clusters
The ISOPHOT instrument aboard ISO has been used to observe extended FIR
emission of six Abell clusters. The raw profiles of the I_(120 um) / I_(180 um)
surface brightness ratio including zodiacal light show a bump towards Abell
1656 (Coma), dips towards Abell 262 and Abell 2670, and are without clear
structure towards Abell 400, Abell 496, and Abell 4038. After subtraction of
the zodiacal light, the bump towards Abell 1656 is still present, while the
dips towards Abell 262 and Abell 2670 are no longer noticable. This indicates a
localized excess of emitting material outside the Galaxy towards Abell 1656,
while the behavior in Abell 262 and Abell 2670 can be reconciled with galactic
cirrus structures localized on the line-of-sight to these clusters. The excess
towards Abell 1656 (Coma) is interpreted as thermal emission from intracluster
dust distributed in the hot X-ray emitting intracluster medium. The absence of
any signature for intracluster dust in five clusters and the rather low
inferred dust mass in Abell 1656 indicates that intracluster dust is likely not
responsible for the excess X-ray absorption seen in cooling flow clusters.
These observations thereby represent a further unsuccessful attempt in
detecting the presumed final stage of the cooling flow material, in accord with
quite a number of previous studies in other wavelengths regions. Finally, the
observed dimming of the high-redshift supernovae is unlikely be attributable to
extinction caused by dust in the intracluster or even a presumed intercluster
medium.Comment: 16 pages, 32 figures, accepted for publication in Astronomy &
Astrophysic
Tracing the sites of obscured star formation in the Antennae galaxies with Herschel-PACS
FIR imaging of interacting galaxies allows locating even hidden sites of star
formation and measuring of the relative strength of nuclear and extra-nuclear
star formation. We want to resolve the star-forming sites in the nearby system
of the Antennae. Thanks to the unprecedented sharpness and depth of the PACS
camera onboard ESA's Herschel Space Observatory, it is possible for the first
time to achieve a complete assessment of individual star-forming knots in the
FIR with scan maps at 70, 100, and 160 um. We used clump extraction photometry
and SED diagnostics to derive the properties related to star-forming activity.
The PACS 70, 100, and 160 um maps trace the knotty structure of the most recent
star formation along an arc between the two nuclei in the overlap area. The
resolution of the starburst knots and additional multi-wavelength data allow
their individual star formation history and state to be analysed. In
particular, the brightest knot in the mid-infrared (K1), east of the southern
nucleus, exhibits the highest activity by far in terms of dust heating and star
formation rate, efficiency, and density. With only 2 kpc in diameter, this area
has a 10-1000 um luminosity, which is as high as that of our Milky Way. It
shows the highest deficiency in radio emission in the radio-to-FIR luminosity
ratio and a lack of X-ray emission, classifying it as a very young complex. The
brightest 100 and 160 um emission region (K2), which is close to the collision
front and consists of 3 knots, also shows a high star formation density and
efficiency and lack of X-ray emission in its most obscured part, but an excess
in the radio-to-FIR luminosity ratio. This suggests a young stage, too, but
different conditions in its interstellar medium. Our results provide important
checkpoints for numerical simulations of interacting galaxies when modelling
the star formation and stellar feedback.Comment: 4 pages, 4 figures, 2 tables (A&A Herschel special issue
Deep far infrared ISOPHOT survey in "Selected Area 57", I. Observations and source counts
We present here the results of a deep survey in a 0.4 sq.deg. blank field in
Selected Area 57 conducted with the ISOPHOT instrument aboard ESAs Infrared
Space Observatory (ISO) at both 60 um and 90 um. The resulting sky maps have a
spatial resolution of 15 x 23 sq.arcsec. per pixel which is much higher than
the 90 x 90 sq.arcsec. pixels of the IRAS All Sky Survey. We describe the main
instrumental effects encountered in our data, outline our data reduction and
analysis scheme and present astrometry and photometry of the detected point
sources. With a formal signal to noise ratio of 6.75 we have source detection
limits of 90 mJy at 60 um and 50 mJy at 90 um. To these limits we find
cumulated number densities of 5+-3.5 per sq.deg. at 60 um and 14.8+-5.0 per
sq.deg.at 90 um. These number densities of sources are found to be lower than
previously reported results from ISO but the data do not allow us to
discriminate between no-evolution scenarios and various evolutionary models.Comment: 15 pages, 11 figures, accepted by Astronomy & Astrophysic
Determination of confusion noise for far-infrared measurements
We present a detailed assessment of the far-infrared confusion noise imposed
on measurements with the ISOPHOT far-infrared detectors and cameras aboard the
ISO satellite. We provide confusion noise values for all measurement
configurations and observing modes of ISOPHOT in the 90<=lambda<=200um
wavelength range. Based on these results we also give estimates for cirrus
confusion noise levels at the resolution limits of current and future
instruments of infrared space telescopes: Spitzer/MIPS, ASTRO-F/FIS and
Herschel/PACS.Comment: A&A accepted; FITS files and appendices are available at:
http://www.konkoly.hu/staff/pkisscs/confnoise
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