269 research outputs found
AzTEC/ASTE 1.1-mm Survey of the AKARI Deep Field South: source catalogue and number counts
We present results of a 1.1 mm deep survey of the AKARI Deep Field South
(ADF-S) with AzTEC mounted on the Atacama Submillimetre Telescope Experiment
(ASTE). We obtained a map of 0.25 sq. deg area with an rms noise level of
0.32-0.71 mJy. This is one of the deepest and widest maps thus far at
millimetre and submillimetre wavelengths. We uncovered 198 sources with a
significance of 3.5-15.6 sigma, providing the largest catalog of 1.1 mm sources
in a contiguous region. Most of the sources are not detected in the
far-infrared bands of the AKARI satellite, suggesting that they are mostly at z
~ 1.5 given the detection limits. We constructed differential and cumulative
number counts in the ADF-S, the Subaru/XMM Newton Deep Field (SXDF), and the
SSA 22 field surveyed by AzTEC/ASTE, which provide currently the tightest
constraints on the faint end. The integration of the best-fit number counts in
the ADF-S find that the contribution of 1.1 mm sources with fluxes >=1 mJy to
the cosmic infrared background (CIB) at 1.1 mm is 12-16%, suggesting that the
large fraction of the CIB originates from faint sources of which the number
counts are not yet constrained. We estimate the cosmic star-formation rate
density contributed by 1.1 mm sources with >=1 mJy using the best-fit number
counts in the ADF-S and find that it is lower by about a factor of 5-10
compared to those derived from UV/optically-selected galaxies at z ~ 2-3. The
fraction of stellar mass of the present-day universe produced by 1.1 mm sources
with >=1 mJy at z >= 1 is ~20%, calculated by the time integration of the
star-formation rate density. If we consider the recycled fraction of >0.4,
which is the fraction of materials forming stars returned to the interstellar
medium, the fraction of stellar mass produced by 1.1 mm sources decrease to
<~10%.Comment: 15 pages, 12 figure, accepted for publication in MNRA
Initial Results from the Nobeyama Molecular Gas Observations of Distant Bright Galaxies
We present initial results from the CO survey toward high redshift galaxies
using the Nobeyama 45m telescope. Using the new wide bandwidth spectrometer
equipped with a two-beam SIS receiver, we have robust new detections of three
high redshift (z=1.6-3.4) submillimeter galaxies (SXDF 1100.001, SDP9, and
SDP17), one tentative detection (SDSS J160705+533558), and one non-detection
(COSMOS-AzTEC1). The galaxies observed during the commissioning phase are
sources with known spectroscopic redshifts from previous optical or from
wide-band submm spectroscopy. The derived molecular gas mass and line widths
from Gaussian fits are ~10^11 Msun and 430-530 km/s, which are consistent with
previous CO observations of distant submm galaxies and quasars. The
spectrometer that allows a maximum of 32 GHz instantaneous bandwidth will
provide new science capabilities at the Nobeyama 45m telescope, allowing us to
determine redshifts of bright submm selected galaxies without any prior
redshift information.Comment: 4 pages, 1 figure, PASJ Letter Accepte
Detection of an ultra-bright submillimeter galaxy in the Subaru/XMM-Newton Deep Field using AzTEC/ASTE
We report the detection of an extremely bright (37 mJy at 1100 m
and 91 mJy at 880 m) submillimeter galaxy (SMG),
AzTEC-ASTE-SXDF1100.001 (hereafter referred to as SXDF1100.001 or Orochi),
discovered in 1100 m observations of the Subaru/XMM-Newton Deep Field
using AzTEC on ASTE. Subsequent CARMA 1300 m and SMA 880 m
observations successfully pinpoint the location of Orochi and suggest that it
has two components, one extended (FWHM of 4) and one
compact (unresolved). Z-Spec on CSO has also been used to obtain a wide band
spectrum from 190 to 308 GHz, although no significant emission/absorption lines
are found. The derived upper limit to the line-to-continuum flux ratio is
0.1--0.3 (2 ) across the Z-Spec band.
Based on the analysis of the derived spectral energy distribution from
optical to radio wavelengths of possible counterparts near the SMA/CARMA peak
position, we suggest that Orochi is a lensed, optically dark SMG lying at behind a foreground, optically visible (but red) galaxy at . The deduced apparent (i.e., no correction for magnification) infrared
luminosity () and star formation rate (SFR) are
and 11000 yr, respectively, assuming that the
is dominated by star formation. These values suggest that Orochi
will consume its gas reservoir within a short time scale (
yr), which is indeed comparable to those in extreme starbursts like the centres
of local ULIRGs.Comment: 18 pages, 13 figure
SXDF-UDS-CANDELS-ALMA 1.5 arcmin deep survey
We have conducted 1.1 mm ALMA observations of a contiguous or 1.5 arcmin window in the SXDF-UDS-CANDELS. We achieved a 5
sensitivity of 0.28 mJy, providing a flat sensus of dusty star-forming galaxies
with (for =40K) up to
thanks to the negative K-correction at this wavelength. We detected 5
brightest sources (S/N6) and 18 low-significance sources (5S/N4; these
may contain spurious detections, though). One of the 5 brightest ALMA sources
( mJy) is extremely faint in the WFC3 and
VLT/HAWK-I images, demonstrating that a contiguous ALMA imaging survey is able
to uncover a faint dust-obscured population that is invisible in deep
optical/near-infrared surveys. We found a possible [CII]-line emitter at
or a low- CO emitting galaxy within the field, which may allow us
to constrain the [CII] and/or the CO luminosity functions across the history of
the universe.Comment: 4 pages, 2 figures, 1 table, to appear in the proceedings of IAU
Symposium 319 "Galaxies at High Redshift and Their Evolution over Cosmic
Time", eds. S. Kaviraj & H. Ferguso
AzTEC millimeter survey of the COSMOS field - III. Source catalog over 0.72 sq. deg. and plausible boosting by large-scale structure
We present a 0.72 sq. deg. contiguous 1.1mm survey in the central area of the
COSMOS field carried out to a 1sigma ~ 1.26 mJy/beam depth with the AzTEC
camera mounted on the 10m Atacama Submillimeter Telescope Experiment (ASTE). We
have uncovered 189 candidate sources at a signal-to-noise ratio S/N >= 3.5, out
of which 129, with S/N >= 4, can be considered to have little chance of being
spurious (< 2 per cent). We present the number counts derived with this survey,
which show a significant excess of sources when compared to the number counts
derived from the ~0.5 sq. deg. area sampled at similar depths in the Scuba HAlf
Degree Extragalactic Survey (SHADES, Austermann et al. 2010). They are,
however, consistent with those derived from fields that were considered too
small to characterize the overall blank-field population. We identify
differences to be more significant in the S > 5 mJy regime, and demonstrate
that these excesses in number counts are related to the areas where galaxies at
redshifts z < 1.1 are more densely clustered. The positions of optical-IR
galaxies in the redshift interval 0.6 < z < 0.75 are the ones that show the
strongest correlation with the positions of the 1.1mm bright population (S > 5
mJy), a result which does not depend exclusively on the presence of rich
clusters within the survey sampled area. The most likely explanation for the
observed excess in number counts at 1.1mm is galaxy-galaxy and galaxy-group
lensing at moderate amplification levels, that increases in amplitude as one
samples larger and larger flux densities. This effect should also be detectable
in other high redshift populations.Comment: 21 pages, 17 figures, accepted for publication in MNRA
Obscured star formation in Lyα blobs at z = 3.1
We present results from the AzTEC/ASTE 1.1-mm imaging survey of 35 Lyα blobs (LABs) found in the SSA22 protocluster at z = 3.1. These 1.1-mm data reach an rms noise level of 0.7–1 mJy beam^(−1), making this the largest millimetre-wave survey of LABs to date. While one (or possibly two) out of 35 LABs might be detected at 3σ level, no significant (≥3.5σ) emission is found in any of individual 35 LABs. From this, we estimate 3σ upper limits on the far-infrared luminosity of L_FIR < 2 × 10^(12) L_⊙ (the dust temperature of 35 K and the emissivity index of 1.5 are assumed). Stacking analysis reveals that the 1.1-mm flux density averaged over the LABs is S_(1.1 mm) < 0.40 mJy (3σ), which places a constraint of LFIR < 4.5 × 10^(11) L_⊙. These data constrain the dust spectral energy distributions of the LABs more tightly than ever if their spectral indices at rest-frame wavelength of ≈ 240 μm are similar to those found in (ultra-)luminous infrared galaxies at 0.2 < z < 0.3. Our results suggest that LABs on average have little ultraluminous obscured star formation, in contrast to a long-believed picture that LABs undergo an intense episode of dusty star formation activities with star formation rates of ∼10^3  M_⊙ yr^(−1). Observations with the Atacama Large Millimeter/submillimeter Array are needed to directly study the obscured part of star formation activity in the LABs
Unveiling the Nature of Submillimeter Galaxy SXDF850.6
We present an 880 micron Submillimeter Array (SMA) detection of the
submillimeter galaxy SXDF850.6. SXDF850.6 is a bright source (S(850 micron) = 8
mJy) detected in the SCUBA Half Degree Extragalactic Survey (SHADES), and has
multiple possible radio counterparts in its deep radio image obtained at the
VLA. Our new SMA detection finds that the submm emission coincides with the
brightest radio emission that is found ~8" north of the coordinates determined
from SCUBA. Despite the lack of detectable counterparts in deep UV/optical
images, we find a source at the SMA position in near-infrared and longer
wavelength images. We perform SED model fits to UV-optical-IR photometry (u, B,
V, R, i', z', J, H, K, 3.6 micron, 4.5 micron, 5.8 micron, and 8.0 micron) and
to submm-radio photometry (850 micron, 880 micron, 1100 micron, and 21 cm)
independently, and we find both are well described by starburst templates at a
redshift of z ~= 2.2 (+/- 0.3). The best-fit parameters from the UV-optical-IR
SED fit are a redshift of z = 1.87 (+0.15/-0.07), a stellar mass of M_star =
2.5 +2.2/-0.3 x 10^11 M_sun, an extinction of A_V = 3.0 (+0.3/-1.0) mag, and an
age of 720 (+1880/-210) Myr. The submm-radio SED fit provides a consistent
redshift of z ~ 1.8-2.5, an IR luminosity of L_IR = (7-26) x 10^12 L_sun, and a
star formation rate of 1300-4500 M_sun/yr. These results suggest that SXDF850.6
is a mature system already having a massive amount of old stellar population
constructed before its submm bright phase and is experiencing a dusty
starburst, possibly induced by major mergers.Comment: 7 pages, 5 figures, Accepted for publication in Astrophysical Journa
AzTEC/ASTE 1.1-mm survey of the AKARI Deep Field South: source catalogue and number counts
This article has been accepted for publication in Monthly Notices Of The Royal Astronomical Society ©: 2010 K. B. Hatsukade et al. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present results of a 1.1-mm deep survey of the AKARI Deep Field South (ADF-S) with AzTEC mounted on the Atacama Submillimetre Telescope Experiment (ASTE). We obtained a map of 0.25-deg2 area with an rms noise level of 0.32–0.71 mJy. This is one of the deepest and widest maps thus far at millimetre and submillimetre wavelengths. We uncovered 198 sources with a significance of 3.5σ–15.6σ, providing the largest catalogue of 1.1-mm sources in a contiguous region. Most of the sources are not detected in the far-infrared bands of the AKARI satellite, suggesting that they are mostly at z≥ 1.5 given the detection limits. We constructed differential and cumulative number counts in the ADF-S, the Subaru/XMM–Newton Deep Field and the SSA 22 field surveyed by AzTEC/ASTE, which provide currently the tightest constraints on the faint end. The integration of the best-fitting number counts in the ADF-S finds that the contribution of 1.1-mm sources with fluxes of ≥1 mJy to the cosmic infrared background (CIB) at 1.1 mm is 12–16 per cent, suggesting that the large fraction of the CIB originates from faint sources of which the number counts are not yet constrained. We estimate the cosmic star formation rate density contributed by 1.1-mm sources with ≥1 mJy using the best-fitting number counts in the ADF-S and find that it is lower by about a factor of 5–10 compared to those derived from UV/optically selected galaxies at z∼ 2–3. The fraction of stellar mass of the present-day universe produced by 1.1-mm sources with ≥1 mJy at z≥ 1 is ∼20 per cent, calculated by the time integration of the star formation rate density. If we consider the recycled fraction of >0.4, which is the fraction of materials forming stars returned to the interstellar medium, the fraction of stellar mass produced by 1.1-mm sources decreases to ≲10 per cent
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