1,721,080 research outputs found
Spatially Resolving the 350-\u3bcm Continuum, Cold-Dust Emission in Nearby Elliptical Galaxies: Recent Results
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Galaxy Clustering in Far-Infrared SWIRE Fields
Full text linkWe present measurements of galaxy clustering detected in the six
SWIRE fields in all MIPS channels at 24, 70, and 160 microns. The measurements
include the low-order 2-point angular correlation functions, and high-order
probes including probability distribution functions and Rényi information
NGC 1377: an extragalactic proto-starburst
Full text linkNGC 1377 is the archetype of a class of galaxies called nascent starbursts, selected by their very high infrared to radio continuum flux ratios and their high dust temperatures. This nearby galaxy is an ideal test case to refine the understanding of the mechanisms of the infrared-radio correlation of star-forming galaxies; to characterize the physical conditions of an embedded starburst at its very onset; and to gain a better knowledge of the activity of a class of ultraluminous galaxies sharing the main infrared-radio properties of NGC 1377. We present new data on NGC 1377 obtained as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS) Legacy program and discuss briefly our interpretation of the combined optical, infrared and radio properties
Infrared Sources in the Small Magellanic Cloud: First Results
Full text linkWe have imaged the entire Small Magellanic Cloud (SMC), one of the two nearest star-forming dwarf galaxies, in all seven IRAC and MIPS bands. The low mass and low metallicity (1/6 solar) of the SMC make it the best local analog for primitive galaxies at high redshift. By studying the properties of dust and star formation in the SMC at high resolution, we can gain understanding of similar distant galaxies that can only be observed in much less detail.
In this contribution, we present a preliminary analysis of the properties of point sources detected in the Spitzer Survey of the Small Magellanic Cloud (S^(3)MC). We find ∼400,000 unresolved or marginally resolved sources in our IRAC images, and our MIPS 24 μm mosaic contains ~17,000 point sources. Source counts decline rapidly at the longer MIPS wavelengths. We use colorcolor and color-magnitude diagrams to investigate the nature of these objects, cross-correlate their positions with those of known sources at other wavelengths, and show examples of how these data can be used to identify interesting classes of objects such as carbon stars and young stellar objects. For additional examples of some of the questions that can be studied with these data, please see the accompanying contributions by Alberto Bolatto (survey information and images), Adam Leroy (dust and gas in a low-metallicity environment), Karin Sandstrom (far infrared-radio continuum correlation), and Snezana Stanimirovic (on a young supernova remnant in the The SMC) mosaic images and point source catalogs we have made have been released to the public on our website (http://celestial.berkeley.edu/spitzer)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A Spatially Resolved Study of the Cold Dust in NGC 205
Full text linkWe present IRAC and MIPS observations of NGC 205, the dwarf
elliptical companion of M31, obtained with the Spitzer Space Telescope. The
extended dust emission is spatially concentrated in three main emission regions.
Based on our mid-to-far infrared flux density measurements alone, we derive a
total dust mass estimate of the order of 3.2 × 10^4 M_⊙, at a temperature of ~20K.
The gas mass associated with this component matches the predicted mass returned
by the dying stars from the last burst of star formation in NGC 205
(~0.5 Gyr ago). Analysis of the Spitzer data combined with previous 1.1mm
observations over a small central region or “Core” (18" diameter), suggest the
presence of very cold (T ~ 12K) dust and a dust mass 16 times higher than is estimated
from the Spitzer measurements alone. Assuming a gas to dust mass ratio
of 100, these two datasets, i.e. with and without the millimeter observations,
suggest a total gas mass range of 3.2 × 10^6 to 5 × 10^7 M_⊙
The z ~ 3 QSO Luminosity Function with SWIRE
Full text linkWe use a simple optical/infrared photometric selection of high redshift QSOs which identifies a Lyman Break in the optical and requires a red IRAC color to distinguish QSOs from common interlopers. We find 100 U-dropout (z ~ 3) QSO candidates with r′ < 22 within 11.2 deg^2 in the ELAIS-N1 & ELAIS-N2 fields in the Spitzer Wide-area Infrared Extragalactic (SWIRE) Legacy Survey. Spectroscopy of 10 candidates shows that they are all QSOs with 2.83 < z < 3.44. We use detailed simulations which incorporate variations in QSO SEDs, IGM transmission and imaging depth to derive a completeness of 85- 90% between 3.0 < z < 3.4. The resulting luminosity function is two magnitudes fainter than SDSS and, when combined with those data, gives a faint end slope β = 1.62±0.18, consistent with measurements at z < 2 and steeper than initial measurements at the same redshift
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