61 research outputs found
An upper limit to [C II] emission in a z ~= 5 galaxy
Low-ionization-state far-infrared (FIR) emission lines may be useful
diagnostics of star-formation activity in young galaxies, and at high redshift
may be detectable from the ground. In practice, however, very little is known
concerning how strong such line emission might be in the early Universe. We
attempted to detect the 158 micron [C II] line from a lensed galaxy at z =
4.926 using the Caltech Submillimeter Observatory. This source is an ordinary
galaxy, in the sense that it shows high but not extreme star formation, but
lensing makes it visible. Our analysis includes a careful consideration of the
calibrations and weighting of the individual scans. We find only modest
improvement over the simpler reduction methods, however, and the final spectrum
remains dominated by systematic baseline ripple effects. We obtain a 95 per
cent confidence upper limit of 33 mJy for a 200 km/s full width at half maximum
line, corresponding to an unlensed luminosity of 1x10^9 L_sun for a standard
cosmology. Combining this with a marginal detection of the continuum emission
using the James Clerk Maxwell Telescope, we derive an upper limit of 0.4 per
cent for the ratio of L_CII/L_FIR in this object.Comment: 5 pages, 2 figures, accepted for publication in MNRA
An overview of the planned CCAT software system
CCAT will be a 25m diameter sub-millimeter telescope capable of operating in
the 0.2 to 2.1mm wavelength range. It will be located at an altitude of 5600m
on Cerro Chajnantor in northern Chile near the ALMA site. The anticipated first
generation instruments include large format (60,000 pixel) kinetic inductance
detector (KID) cameras, a large format heterodyne array and a direct detection
multi-object spectrometer. The paper describes the architecture of the CCAT
software and the development strategy.Comment: 17 pages, 6 figures, to appear in Software and Cyberinfrastructure
for Astronomy III, Chiozzi & Radziwill (eds), Proc. SPIE 9152, paper ID
9152-10
Submillimetre Constraints on Hyper-Extremely Red Objects in the Subaru Deep Field
We have mapped the submillimetre wavelength continuum emission from the
Subaru Deep Field (SDF) at 450 and 850 microns with the Submillimetre
Common-User Bolometer Array (SCUBA) detector on the James Clerk Maxwell
Telescope (JCMT). The near-IR image of the SDF is one of the deepest near-IR
images available and contains four `hyper extremely red objects' (HEROs). These
data allow us to test the connection between `extremely red objects' (EROs)
found in IR surveys and the population of bright submillimetre sources found
with SCUBA. We present a weak measurement of the average flux of the four
K-band selected HEROs of 1.15 (+/-0.46) mJy, which fails to support the
hypothesis that HEROs should be bright SCUBA sources. Our data are consistent
with the HEROs being objects with SEDs like that of Arp220 out to z~1.7,
however, the extinction in the HEROs must be about 1 magnitude greater in the
J-band than is the case for Arp220 and they would need to be 1.7 times as
luminous as Arp220. On the other hand, an evolutionary model of elliptical
galaxies at z~2-3 in a dusty starburst phase is also in agreement with the
submillimetre data, as was originally proposed for the HEROs.Comment: 7 pages, 5 figures, accepted for publication in MNRAS July 5th, 200
BLAST: the Redshift Survey
The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) has recently
surveyed ~8.7 deg^2 centered on GOODS-South at 250, 350, and 500 microns. In
Dye et al. (2009) we presented the catalogue of sources detected at 5-sigma 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.Comment: Accepted for publication in the Astrophysical Journal. Maps and
associated results are available at http://blastexperiment.info
BLAST Observations of the South Ecliptic Pole field: Number Counts and Source Catalogs
We present results from a survey carried out by the Balloon-borne Large
Aperture Submillimeter Telescope (BLAST) on a 9 deg^2 field near the South
Ecliptic Pole at 250, 350 and 500 {\mu}m. The median 1{\sigma} depths of the
maps are 36.0, 26.4 and 18.4 mJy, respectively. We apply a statistical method
to estimate submillimeter galaxy number counts and find that they are in
agreement with other measurements made with the same instrument and with the
more recent results from Herschel/SPIRE. Thanks to the large field observed,
the new measurements give additional constraints on the bright end of the
counts. We identify 132, 89 and 61 sources with S/N>4 at 250, 350, 500 {\mu}m,
respectively and provide a multi-wavelength combined catalog of 232 sources
with a significance >4{\sigma} in at least one BLAST band. The new BLAST maps
and catalogs are available publicly at http://blastexperiment.info.Comment: 25 pages, 6 figures, 4 tables, Accepted by ApJS. Maps and catalogs
available at http://blastexperiment.info
Submillimeter Number Counts From Statistical Analysis of BLAST Maps
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 analyse BLAST observations of a roughly 10 sq. deg. map centered
on the Great Observatories Origins Deep Survey South (GOODS-S) field. We
provide estimates of number counts at the three BLAST wavelengths, 250, 350,
and 500 microns; 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 microns and -4.5
at 350 and 500 microns, 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.Comment: Accepted for publication in the Astrophysical Journal; see associated
data and other papers at http://blastexperiment.info
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