We investigate the correlation between far-infrared (FIR) and radio luminosities in distant galaxies, a lynchpin of modern astronomy. We use data from the Balloon-borne Large Aperture Submillimetre ...Telescope (BLAST), Spitzer, the Large Apex BOlometer CamerA (LABOCA), the Very Large Array and the Giant Metre-wave Radio Telescope (GMRT) in the Extended Chandra Deep Field South (ECDFS). For a catalogue of BLAST 250-μm-selected galaxies, we remeasure the 70–870-μm flux densities at the positions of their most likely 24-μm counterparts, which have a median interquartile redshift of 0.74 0.25, 1.57. From these, we determine the monochromatic flux density ratio, q250(= log10S250 μm/S1400 MHz), and the bolometric equivalent, qIR. At z≈ 0.6, where our 250-μm filter probes rest-frame 160-μm emission, we find no evolution relative to q160 for local galaxies. We also stack the FIR and submm images at the positions of 24-μm- and radio-selected galaxies. The difference between qIR seen for 250-μm- and radio-selected galaxies suggests that star formation provides most of the IR luminosity in ≲100-μJy radio galaxies, but rather less for those in the mJy regime. For the 24-μm sample, the radio spectral index is constant across 0 < z < 3, but qIR exhibits tentative evidence of a steady decline such that qIR∝ (1 +z)−0.15±0.03– significant evolution, spanning the epoch of galaxy formation, with major implications for techniques that rely on the FIR/radio correlation. We compare with model predictions and speculate that we may be seeing the increase in radio activity that gives rise to the radio background.
We present Cygnus X in a new multi-wavelength perspective based on an unbiased BLAST survey at 250, 350, and 500 Delta *mm, combined with rich data sets for this well-studied region. Our primary goal ...is to investigate the early stages of high-mass star formation. We have detected 184 compact sources in various stages of evolution across all three BLAST bands. From their well-constrained spectral energy distributions, we obtain the physical properties mass, surface density, bolometric luminosity, and dust temperature. Some of the bright sources reaching 40 K contain well-known compact H II regions. We relate these to other sources at earlier stages of evolution via the energetics as deduced from their position in the luminosity-mass (L-M) diagram. The BLAST spectral coverage, near the peak of the spectral energy distribution of the dust, reveals fainter sources too cool (~10 K) to be seen by earlier shorter-wavelength surveys like IRAS. We detect thermal emission from infrared dark clouds and investigate the phenomenon of cold 'starless cores' more generally. Spitzer images of these cold sources often show stellar nurseries, but these potential sites for massive star formation are 'starless' in the sense that to date there is no massive protostar in a vigorous accretion phase. We discuss evolution in the context of the L-M diagram. Theory raises some interesting possibilities: some cold massive compact sources might never form a cluster containing massive stars, and clusters with massive stars might not have an identifiable compact cold massive precursor.
We present the 250, 350, and 500 Delta *mm detection of bright submillimeter emission in the direction of the Bullet Cluster measured by the Balloon-borne Large-Aperture Submillimeter Telescope ...(BLAST). The 500 Delta *mm centroid is coincident with an AzTEC 1.1 mm point-source detection at a position close to the peak lensing magnification produced by the cluster. However, the 250 Delta *mm and 350 Delta *mm centroids are elongated and shifted toward the south with a differential shift between bands that cannot be explained by pointing uncertainties. We therefore conclude that the BLAST detection is likely contaminated by emission from foreground galaxies associated with the Bullet Cluster. The submillimeter redshift estimate based on 250-1100 Delta *mm photometry at the position of the AzTEC source is z phot = 2.9+0.6 -0.3, consistent with the infrared color redshift estimation of the most likely Infrared Array Camera counterpart. These flux densities indicate an apparent far-infrared (FIR) luminosity of L FIR = 2 X 1013 L. When the amplification due to the gravitational lensing of the cluster is removed, the intrinsic FIR luminosity of the source is found to be L FIR <= 1012 L, consistent with typical luminous infrared galaxies.
We detect correlations in the cosmic far-infrared background due to the clustering of star-forming galaxies in observations made with the Balloon-borne Large Aperture Submillimeter Telescope, at 250, ...350, and 500 mum. We perform jackknife and other tests to confirm the reality of the signal. The measured correlations are well fitted by a power law over scales of 5'-25', with DeltaI/I = 15.1% +/- 1.7%. We adopt a specific model for submillimeter sources in which the contribution to clustering comes from sources in the redshift ranges 1.3 < = z < = 2.2, 1.5 < = z < = 2.7, and 1.7 < = z < = 3.2, at 250, 350, and 500 mum, respectively. With these distributions, our measurement of the power spectrum, P(k theta), corresponds to linear bias parameters, b = 3.8 +/- 0.6, 3.9 +/- 0.6, and 4.4 +/- 0.7, respectively. We further interpret the results in terms of the halo model, and find that at the smaller scales, the simplest halo model fails to fit our results. One way to improve the fit is to increase the radius at which dark matter halos are artificially truncated in the model, which is equivalent to having some star-forming galaxies at z > = 1 located in the outskirts of groups and clusters. In the context of this model, we find a minimum halo mass required to host a galaxy is log(M min/M ) = 11.5+0.4 -0.1, and we derive effective biases b eff = 2.2 +/- 0.2, 2.4 +/- 0.2, and 2.6 +/- 0.2, and effective masses, 12.8 +/- 0.2, and 12.7 +/- 0.2, at 250, 350 and 500 mum, corresponding to spatial correlation lengths of r 0 = 4.9, 5.0, and, respectively. Finally, we discuss implications for clustering measurement strategies with Herschel and Planck.
We present first results from an unbiased 50 deg{sup 2} submillimeter Galactic survey at 250, 350, and 500 mum from the 2006 flight of the Balloon-borne Large Aperture Submillimeter Telescope. The ...map has resolution ranging from 36'' to 60'' in the three submillimeter bands spanning the thermal emission peak of cold starless cores. We determine the temperature, luminosity, and mass of more than 1000 compact sources in a range of evolutionary stages and an unbiased statistical characterization of the population. From comparison with C{sup 18}O data, we find the dust opacity per gas mass, kappar= 0.16 cm{sup 2} g{sup -1} at 250 mum, for cold clumps. We find that 2% of the mass of the molecular gas over this diverse region is in cores colder than 14 K, and that the mass function for these cold cores is consistent with a power law with index alpha = -3.22 +- 0.14 over the mass range 14 M{sub sun} < M < 80 M{sub sun}. Additionally, we infer a mass-dependent cold core lifetime of t{sub c} (M) = 4 x 10{sup 6}(M/20 M{sub sun}){sup -0.9} yr-longer than what has been found in previous surveys of either low or high-mass cores, and significantly longer than free fall or likely turbulent decay times. This implies some form of non-thermal support for cold cores during this early stage of star formation.
We present Cygnus X in a new multi-wavelength perspective based on an unbiased BLAST survey at 250, 350, and 500 {mu}m, combined with rich data sets for this well-studied region. Our primary goal is ...to investigate the early stages of high-mass star formation. We have detected 184 compact sources in various stages of evolution across all three BLAST bands. From their well-constrained spectral energy distributions, we obtain the physical properties mass, surface density, bolometric luminosity, and dust temperature. Some of the bright sources reaching 40 K contain well-known compact H II regions. We relate these to other sources at earlier stages of evolution via the energetics as deduced from their position in the luminosity-mass (L-M) diagram. The BLAST spectral coverage, near the peak of the spectral energy distribution of the dust, reveals fainter sources too cool ({approx}10 K) to be seen by earlier shorter-wavelength surveys like IRAS. We detect thermal emission from infrared dark clouds and investigate the phenomenon of cold 'starless cores' more generally. Spitzer images of these cold sources often show stellar nurseries, but these potential sites for massive star formation are 'starless' in the sense that to date there is no massive protostar in a vigorous accretion phase. We discuss evolution in the context of the L-M diagram. Theory raises some interesting possibilities: some cold massive compact sources might never form a cluster containing massive stars, and clusters with massive stars might not have an identifiable compact cold massive precursor.
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