We describe the application of a statistical method to estimate submillimeter galaxy number counts from confusion-limited observations by the Balloon-borne Large Aperture Submillimeter Telescope ...(BLAST). Our method is based on a maximum likelihood fit to the pixel histogram, sometimes called 'P(D),' an approach which has been used before to probe faint counts, the difference being that here we advocate its use even for sources with relatively high signal-to-noise ratios. This method has an advantage over standard techniques of source extraction in providing an unbiased estimate of the counts from the bright end down to flux densities well below the confusion limit. We specifically analyze BLAST observations of a roughly 10 deg2 map centered on the Great Observatories Origins Deep Survey South field. We provide estimates of number counts at the three BLAST wavelengths 250, 350, and 500 Delta *mm; instead of counting sources in flux bins we estimate the counts at several flux density nodes connected with power laws. We observe a generally very steep slope for the counts of about -3.7 at 250 Delta *mm, and -4.5 at 350 and 500 Delta *mm, over the range ~0.02-0.5 Jy, breaking to a shallower slope below about 0.015 Jy at all three wavelengths. We also describe how to estimate the uncertainties and correlations in this method so that the results can be used for model-fitting. This method should be well suited for analysis of data from the Herschel satellite.
We directly measure redshift evolution in the mean physical properties (far-infrared luminosity, temperature, and mass) of the galaxies that produce the cosmic infrared background (CIB), using ...measurements from the Balloon-borne Large Aperture Submillimeter Telescope (BLAST), and Spitzer which constrain the CIB emission peak. This sample is known to produce a surface brightness in the BLAST bands consistent with the full CIB, and photometric redshifts are identified for all of the objects. We find that most of the 70 Delta *mm background is generated at z 1 and the 500 Delta *mm background generated at z 1. A significant growth is observed in the mean luminosity from ~109-1012 L, and in the mean temperature by 10 K, from redshifts 0 < z < 3. However, there is only weak positive evolution in the comoving dust mass in these galaxies across the same redshift range. We also measure the evolution of the far-infrared luminosity density, and the star formation rate history for these objects, finding good agreement with other infrared studies up to z ~ 1, exceeding the contribution attributed to optically selected galaxies.
BLAST: The Redshift Survey Eales, Stephen; Chapin, Edward L; Devlin, Mark J ...
The Astrophysical journal,
12/2009, Volume:
707, Issue:
2
Journal Article
Peer reviewed
Open access
The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) has recently surveyed 8.7 deg2 centered on Great Observatories Origins Deep Survey-South at 250, 350, and 500 Delta *mm. In Dye et ...al., we presented the catalog of sources detected at 5 Delta *s in at least one band in this field and the probable counterparts to these sources in other wavebands. In this paper, we present the results of a redshift survey in which we succeeded in measuring redshifts for 82 of these counterparts. The spectra show that the BLAST counterparts are mostly star-forming galaxies but not extreme ones when compared to those found in the Sloan Digital Sky Survey. Roughly one quarter of the BLAST counterparts contain an active nucleus. We have used the spectroscopic redshifts to carry out a test of the ability of photometric redshift methods to estimate the redshifts of dusty galaxies, showing that the standard methods work well even when a galaxy contains a large amount of dust. We have also investigated the cases where there are two possible counterparts to the BLAST source, finding that in at least half of these there is evidence that the two galaxies are physically associated, either because they are interacting or because they are in the same large-scale structure. Finally, we have made the first direct measurements of the luminosity function in the three BLAST bands. We find strong evolution out to z = 1, in the sense that there is a large increase in the space density of the most luminous galaxies. We have also investigated the evolution of the dust-mass function, finding similar strong evolution in the space density of the galaxies with the largest dust masses, showing that the luminosity evolution seen in many wavebands is associated with an increase in the reservoir of interstellar matter in galaxies.
We perform a combined fit to angular power spectra of unresolved infrared (IR) point sources from the Planck satellite (at 217, 353, 545, and 857 GHz, over angular scales 100 lapllap 2200), the ...Balloon-borne Large-Aperture Submillimeter Telescope (BLAST; 250, 350, and 500 mu m; 1000 lapllap 9000), and from correlating BLAST and Atacama Cosmology Telescope (ACT; 148 and 218 GHz) maps. We find that the clustered power over the range of angular scales and frequencies considered is well fitted by a simple power law of the form C super(clust) super(l) alpha l super(-n) with n = 1.25 + or - 0.06. While the IR sources are understood to lie at a range of redshifts, with a variety of dust properties, we find that the frequency dependence of the clustering power can be described by the square of a modified blackbody, v super( beta )B(v, T sub(eff)), with a single emissivity index beta = 2.20 + or - 0.07 and effective temperature T sub(eff) = 9.7 K. Our predictions for the clustering amplitude are consistent with existing ACT and South Pole Telescope results at around 150 and 220 GHz, as is our prediction for the effective dust spectral index, which we find to be alpha sub(150-220) = 3.68 + or - 0.07 between 150 and 220 GHz. Our constraints on the clustering shape and frequency dependence can be used to model the IR clustering as a contaminant in cosmic microwave background anisotropy measurements. The combined Planck and BLAST data also rule out a linear bias clustering model.
We constrain the evolution of the rest-frame far-infrared (FIR) luminosity function out to high redshift, by combining several pieces of complementary information provided by the deep Balloon-borne ...Large-Aperture Submillimeter Telescope surveys at 250, 350 and 500 μm, as well as other FIR and millimetre data. Unlike most other phenomenological models, we characterize the uncertainties in our fitted parameters using Monte Carlo Markov Chains. We use a bivariate local luminosity function that depends only on FIR luminosity and 60-to-100 μm colour, along with a single library of galaxy spectral energy distributions indexed by colour, and apply simple luminosity and density evolution. We use the surface density of sources, Cosmic Infrared Background (CIB) measurements and redshift distributions of bright sources, for which identifications have been made, to constrain this model. The precise evolution of the FIR luminosity function across this crucial range has eluded studies at longer wavelengths (e.g. using SCUBA and MAMBO) and at shorter wavelengths (e.g. with Spitzer), and should provide a key piece of information required for the study of galaxy evolution. Our adoption of Monte Carlo methods enables us not only to find the best-fitting evolution model, but also to explore correlations between the fitted parameters. Our model-fitting approach allows us to focus on sources of tension coming from the combination of data sets. We specifically find that our choice of parametrization has difficulty fitting the combination of CIB measurements and redshift distribution of sources near 1 mm. Existing and future data sets will be able to dramatically improve the fits, as well as break strong degeneracies among the models. Two particular examples that we find to be crucial are: obtaining robust information on redshift distributions and placing tighter constraints on the range of spectral shapes for low-luminosity (L
FIR < 1010 L⊙) sources.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
We have identified radio and/or mid-infrared counterparts to 198 out of 350 sources detected at >=5 Delta *s over ~9 deg2 centered on the Chandra Deep Field South by the Balloon-borne Large Aperture ...Submillimeter Telescope (BLAST) at 250, 350, and 500 Delta *mm. We have matched 114 of these counterparts to optical sources with previously derived photometric redshifts and fitted spectral energy distributions to the BLAST fluxes and fluxes at 70 and 160 Delta *mm acquired with the Spitzer Space Telescope. In this way, we have constrained dust temperatures, total far-infrared/millimeter luminosities, and star formation rates for each source. Our findings show that, on average, the BLAST sources lie at significantly lower redshifts and have significantly lower rest-frame dust temperatures compared to submillimeter sources detected in surveys conducted at 850 Delta *mm. We demonstrate that an apparent increase in dust temperature with redshift in our sample arises as a result of selection effects. Finally, we provide the full multiwavelength catalog of >=5 Delta *s BLAST sources contained within the complete ~9 deg2 survey area.
Over the course of two flights, the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) made resolved maps of seven nearby (<25 Mpc) galaxies at 250, 350, and 500 Delta *mm. During its 2005 ...June flight from Sweden, BLAST observed a single nearby galaxy, NGC 4565. During the 2006 December flight from Antarctica, BLAST observed the nearby galaxies NGC 1097, NGC 1291, NGC 1365, NGC 1512, NGC 1566, and NGC 1808. We fit physical dust models to a combination of BLAST observations and other available data for the galaxies observed by Spitzer. We fit a modified blackbody to the remaining galaxies to obtain total dust mass and mean dust temperature. For the four galaxies with Spitzer data, we also produce maps and radial profiles of dust column density and temperature. We measure the fraction of BLAST detected flux originating from the central cores of these galaxies and use this to calculate a 'core fraction,' an upper limit on the 'active galactic nucleus fraction' of these galaxies. We also find our resolved observations of these galaxies give a dust mass estimate 5-19 times larger than an unresolved observation would predict. Finally, we are able to use these data to derive a value for the dust mass absorption coefficient of Delta *k = 0.29 +/- 0.03 m2 kg-1 at 250 Delta *mm. This study is an introduction to future higher-resolution and higher-sensitivity studies to be conducted by Herschel and SCUBA-2.
We carry out a multi-wavelength study of individual galaxies detected by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) and identified at other wavelengths, using data spanning the ...radio to the ultraviolet (UV). We develop a Monte Carlo method to account for flux boosting, source blending, and correlations among bands, which we use to derive deboosted far-infrared (FIR) luminosities for our sample. We estimate total star-formation rates (SFRs) for BLAST counterparts with z <= 0.9 by combining their FIR and UV luminosities. Star formation is heavily obscured at L FIR 1011 L , z 0.5, but the contribution from unobscured starlight cannot be neglected at L FIR 1011 L , z 0.25. We assess that about 20% of the galaxies in our sample show indication of a type 1 active galactic nucleus, but their submillimeter emission is mainly due to star formation in the host galaxy. We compute stellar masses for a subset of 92 BLAST counterparts; these are relatively massive objects, with a median mass of ~1011 M , which seem to link the 24 Delta *mm and Submillimetre Common-User Bolometer Array (SCUBA) populations, in terms of both stellar mass and star formation activity. The bulk of the BLAST counterparts at z 1 appears to be run-of-the-mill star-forming galaxies, typically spiral in shape, with intermediate stellar masses and practically constant specific SFRs. On the other hand, the high-z tail of the BLAST counterparts significantly overlaps with the SCUBA population, in terms of both SFRs and stellar masses, with observed trends of specific SFR that support strong evolution and downsizing.
The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) operated successfully during a 250 hr flight over Antarctica in 2006 December (BLAST06). As part of the calibration and pointing ...procedures, the red hypergiant star VY CMa was observed and used as the primary calibrator. Details of the overall BLAST06 calibration procedure are discussed. The 1 Delta *s uncertainty on the absolute calibration is accurate to 9.5%, 8.7%, and 9.2% at the 250, 350, and 500 Delta *mm bands, respectively. The errors are highly correlated between bands resulting in much lower errors for the derived shape of the 250-500 Delta *mm continuum. The overall pointing error is < 5'' rms for the 36'', 42'', and 60'' beams. The performance of optics and pointing systems is discussed.
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