-
N. K. Agius,
A. E. Sansom,
C. C. Popescu,
E. Andrae,
M. Baes,
I. Baldry,
N. Bourne,
S. Brough,
C. J. R. Clark,
C. Conselice, [......],
S. Maddox,
B. Madore,
S. Phillipps,
A. Robotham,
K. Rowlands,
M. Seibert,
M. W. L. Smith, P. Temi,
R. Tuffs,
E. Valiante
[show abstract]
[hide abstract]
ABSTRACT: We present two large, nearby (0.013$\le$z$\le$0.06) samples of Early-Type
Galaxies (ETGs): a visually classified sample of 220 ETGs, created using
source-matched data from the Galaxy and Mass Assembly (GAMA) database with
FIR/sub-mm detections from $Herschel$-ATLAS; and a visually classified sample
of 551 ETGs which are undetected with $Herschel$-ATLAS. Active galactic nuclei
(AGN) are removed from our samples using optical emission line diagnostics.
These samples are scrutinised to determine characteristics of sub-mm detected
versus undetected ETGs. We find similarities in the stellar mass distributions
of the two ETG samples but testing other properties uncovers significant
differences. The sub-mm detected sample is shown to have lower concentration
and S\'ersic indices than those in the undetected sample - a result which may
be linked to the presence of dust in the former. Optical and UV-optical colours
are also shown to be much bluer, indicating that the dust is linked with recent
star formation. The intrinsic effective radii are on average 1.5 times larger
for the sub-mm detected ETGs. Surface densities and groups data from the GAMA
database are examined for the two samples, leading to the conclusion that dusty
ETGs inhabit sparser environments than non-dusty ETGs in the nearby universe,
although environments of the brightest ETGs are shown to differ the least.
Modified Planck functions are fit to the H-ATLAS detected PACS and SPIRE fluxes
for ETGs with sub-mm flux densities of at least 3$\sigma$ in the 350$\mu$m
SPIRE band, giving a resultant mean cold dust temperature of T$_{d}$=22.1K,
with a range of 9-30K. The corresponding mean dust mass is
1.8$\times10^{7}$M$_{\odot}$, with a range of
(0.08-35.0)$\times10^{7}$M$_{\odot}$. The dust masses calculated from these
fits, normalised by stellar mass, are shown to increase with decreasing stellar
mass and bluer colours.
02/2013;
-
A. Omont,
Chentao Yang,
P. Cox,
R. Neri,
A. Beelen,
S. Bussmann,
R. Gavazzi,
P. van der Werf,
D. Riechers,
D. Downes, [......],
R. Hopwood,
C. Hoyos,
E. Ibar,
S. Maddox,
M. W. L. Smith,
E. Valiante,
J. Bock,
C. M. Bradford,
J. Glenn,
K. S. Scott
[show abstract]
[hide abstract]
ABSTRACT: Using IRAM PdBI we report the detection of H2O in six new lensed
ultra-luminous starburst galaxies at high redshift, discovered in the Herschel
H-ATLAS survey. The sources are detected either in the 2_{02}-1_{11} or
2_{11}-2_{02} H_2O emission lines with integrated line fluxes ranging from 1.8
to 14 Jy.km/s. The corresponding apparent luminosities are mu x L_H2O ~ 3-12 x
10^8 Lo, where mu is the lensing magnification factor (3 < mu < 12). These
results confirm that H2O lines are among the strongest molecular lines in such
galaxies, with intensities almost comparable to those of the high-J CO lines,
and same profiles and line widths (200-900 km/s) as the latter. With the
current sensitivity of PdBI, H2O can therefore easily be detected in high-z
lensed galaxies (with F(500um) > 100 mJy) discovered in the Herschel surveys.
Correcting the luminosities for lensing amplification, L_H2O is found to have a
strong dependence on the IR luminosity, varying as ~L_IR^{1.2}. This relation
which needs to be confirmed with better statistics, may indicate a role of
radiative (IR) excitation of the H2O lines, and implies that high-z galaxies
with L_IR >~ 10^13 Lo tend to be very strong emitters in H2O, that have no
equivalent in the local universe.
01/2013;
-
E. van Kampen,
D. J. B. Smith,
S. Maddox,
A. M. Hopkins,
I. Valtchanov,
J. A. Peacock,
M. J. Michalowski,
P. Norberg,
S. Eales,
L. Dunne, [......],
D. Hill,
D. H. Jones,
L. Kelvin,
H. Parkinson,
M. Prescott,
R. Sharp,
G. de Zotti,
S. Serjeant,
C. C. Popescu,
R. J. Tuffs
[show abstract]
[hide abstract]
ABSTRACT: We have measured the clustering properties of low-redshift (z < 0.3) sub-mm
galaxies detected at 250 micron in the Herschel-ATLAS Science Demonstration
Phase (SDP) field. We selected a sample for which we have high-quality
spectroscopic redshifts, obtained from reliably matching the 250-micron sources
to a complete (for r < 19.4) sample of galaxies from the GAMA database. Both
the angular and spatial clustering strength are measured for all z < 0.3
sources as well as for five redshift slices with thickness delta z=0.05 in the
range 0.05 < z < 0.3. Our measured spatial clustering length r_0 is comparable
to that of optically-selected, moderately star-forming (blue) galaxies: we find
values around 5 Mpc. One of the redshift bins contains an interesting
structure, at z = 0.164.
09/2012;
-
D. J. B. Smith,
L. Dunne,
E. da Cunha,
K. Rowlands,
S. J. Maddox,
H. L. Gomez,
D. G. Bonfield,
S. Charlot,
S. P. Driver,
C. C. Popescu, [......],
R. Hopwood,
E. Ibar,
R. J. Ivison,
L. Kelvin,
B. F. Madore,
M. Pohlen,
E. E. Rigby,
A. Robotham,
M. Seibert, P. Temi
[show abstract]
[hide abstract]
ABSTRACT: We present a pan-chromatic analysis of an unprecedented sample of 1402 250
micron-selected galaxies at z < 0.5 (mean z = 0.24) from the Herschel-ATLAS
survey. We complement our Herschel 100-500 micron data with UV-K-band
photometry from the Galaxy And Mass Assembly (GAMA) survey and apply the
MAGPHYS energy-balance technique to produce pan-chromatic SEDs for a
representative sample of 250 micron selected galaxies spanning the most recent
5 Gyr of cosmic history. We derive estimates of physical parameters, including
star formation rates, stellar masses, dust masses and infrared luminosities.
The typical H-ATLAS galaxy at z < 0.5 has a far-infrared luminosity in the
range 10^10 - 10^12 Lsolar (SFR: 1-50 Msolar/yr) thus is broadly representative
of normal star forming galaxies over this redshift range. We show that 250
micron-selected galaxies contain a larger mass of dust at a given infra-red
luminosity or star formation rate than previous samples selected at 60 micron
from IRAS. We derive typical SEDs for H-ATLAS galaxies, and show that the
emergent SED shape is most sensitive to specific star formation rate. The
optical-UV SEDs also become more reddened due to dust at higher redshifts. Our
template SEDs are significantly cooler than existing infra-red templates. They
may therefore be most appropriate for inferring total IR luminosities from
moderate redshift submillimetre selected samples and for inclusion in models of
the lower redshift submillimetre galaxy populations.
08/2012;
-
R. S. Bussmann,
M. A. Gurwell,
Hai Fu,
D. J. B. Smith,
S. Dye,
R. Auld,
M. Baes,
A. J. Baker,
D. Bonfield,
A. Cava, [......],
E. Pascale,
M. Pohlen,
D. A. Riechers,
E. Rigby,
Douglas Scott, P. Temi,
P. P. Van der Werf,
A. Verma,
J. Wardlow,
D. Wilner
[show abstract]
[hide abstract]
ABSTRACT: We present high-spatial resolution imaging obtained with the Submillimeter
Array (SMA) at 880um and the Keck Adaptive Optics (AO) system at Ks-band of a
gravitationally lensed sub-millimeter galaxy (SMG) at z=4.243 discovered in the
Herschel-Astrophysical Terahertz Large Area Survey. The SMA data (angular
resolution ~0.6") resolve the dust emission into multiple lensed images, while
the Keck AO Ks-band data (angular resolution ~0.1") resolve the lens into a
pair of galaxies separated by 0.3". We present an optical spectrum of the
foreground lens obtained with the Gemini-South telescope that provides a lens
redshift of z_lens = 0.595 +/- 0.005. We develop and apply a new lens modeling
technique in the visibility plane that shows that the SMG is magnified by a
factor of mu = 4.1 +/- 0.2 and has an intrinsic infrared (IR) luminosity of
L_IR = (2.1 +/- 0.2) x 10^13 Lsun. We measure a half-light radius of the
background source of r_s = 4.4 +/- 0.5 kpc which implies an IR luminosity
surface density of Sigma_IR = (3.4 +/- 0.9) x 10^11 Lsun kpc^-2, a value that
is typical of z > 2 SMGs but significantly lower than IR luminous galaxies at
z~0. The two lens galaxies are compact (r_lens ~ 0.9 kpc) early-types with
Einstein radii of theta_E1 = 0.57 +/- 0.01 and theta_E2 = 0.40 +/- 0.01 that
imply masses of M_lens1 = (7.4 +/- 0.5) x 10^10 Msun and M_lens2 = (3.7 +/-
0.3) x 10^10 Msun. The two lensing galaxies are likely about to undergo a
dissipationless merger, and the mass and size of the resultant system should be
similar to other early-type galaxies at z~0.6. This work highlights the
importance of high spatial resolution imaging in developing models of strongly
lensed galaxies discovered by Herschel.
07/2012;
-
A. I. Harris,
A. J. Baker,
D. T. Frayer,
Ian Smail,
A. M. Swinbank,
D. A. Riechers,
P. P. van der Werf,
R. Auld,
M. Baes,
R. S. Bussmann, [......],
R. Hopwood,
E. Ibar,
R. J. Ivison,
M. J. Jarvis,
S. Maddox,
M. Negrello,
E. Rigby,
D. J. B. Smith, P. Temi,
J. Wardlow
[show abstract]
[hide abstract]
ABSTRACT: We report measurements of the carbon monoxide ground state rotational
transition (12C16O J = 1--0) with the Zpectrometer ultra-wideband spectrometer
on the 100-m diameter Green Bank Telescope. The sample comprises 11 galaxies
with redshifts between z = 2.1 and 3.5 from a total sample of 24 targets
identified by Herschel-ATLAS photometric colors from the SPIRE instrument. Nine
of the CO measurements are new redshift determinations, substantially adding to
the number of detections of galaxies with rest-frame peak submillimeter
emission near 100um. The CO detections confirm the existence of massive gas
reservoirs within these luminous dusty star-forming galaxies (DSFGs). The CO
redshift distribution of the 350um-selected galaxies is strikingly similar to
the optical redshifts of 850um-selected submillimeter galaxies (SMGs) in 2.1 <
z < 3.5. Spectroscopic redshifts break a temperature-redshift degeneracy;
optically thin dust models fit to the far-infrared photometry indicate
characteristic dust temperatures near 34 K for most of the galaxies we detect
in CO. Detections of two warmer galaxies and statistically significant
nondetections hint at warmer or molecule-poor DSFGs with redshifts difficult
determine from from Herschel-SPIRE photometric colors alone. Many of the
galaxies identified by H-ATLAS photometry are expected to be amplified by
foreground gravitational lenses. Analysis of CO linewidths and luminosities
provides a method for finding approximate gravitational lens magnifications mu
from spectroscopic data alone, yielding mu ~ 3--20. Corrected for
magnification, most galaxy luminosities are consistent with an ultra-luminous
infrared galaxy (ULIRG) classification, but three are candidate hyper-LIRGs
with luminosities greater than 10^13 L_sun.
04/2012;
-
J González-Nuevo,
A Lapi,
S Fleuren,
S Bressan,
L Danese,
G De Zotti,
M Negrello,
Z -Y Cai,
L Fan,
W Sutherland, [......],
A Dariush,
J Fritz,
R Hopwood,
E Ibar,
S Maddox,
E Pascale,
M Pohlen,
E Rigby,
D Smith, P Temi
apj. 04/2012; 749:65.
-
S. Fleuren,
W. Sutherland,
L. Dunne,
D. J. B. Smith,
S. J. Maddox,
J. González-Nuevo,
J. Findlay,
R. Auld,
M. Baes,
N. A. Bond, [......],
E. Pascale,
M. Pohlen,
M. Prescott,
E. E. Rigby,
A. Robotham,
D. Scott, P. Temi,
M. A. Thompson,
E. Valiante,
P. van der Werf
[show abstract]
[hide abstract]
ABSTRACT: We identify near-infrared Ks band counterparts to Herschel-ATLAS sub-mm
sources, using a preliminary object catalogue from the VISTA VIKING survey. The
sub-mm sources are selected from the H-ATLAS Phase 1 catalogue of the GAMA 9h
field, which includes all objects detected at 250, 350 or 500 um with the SPIRE
instrument. We apply and discuss a likelihood ratio (LR) method for VIKING
candidates within a search radius of 10" of the 22,000 SPIRE sources with a 5
sigma detection at 250 um. We find that 11,294(51%) of the SPIRE sources have a
best VIKING counterpart with a reliability $R\ge 0.8$, and the false
identification rate of these is estimated to be 4.2%. We expect to miss ~5% of
true VIKING counterparts. There is evidence from Z-J and J-Ks colours that the
reliable counterparts to SPIRE galaxies are marginally redder than the field
population. We obtain photometric redshifts for ~68% of all (non-stellar)
VIKING candidates with a median redshift of 0.405. Comparing to the results of
the optical identifications supplied with the Phase I catalogue, we find that
the use of medium-deep near-infrared data improves the identification rate of
reliable counterparts from 36% to 51%.
02/2012;
-
J. González-Nuevo,
A. Lapi,
S. Fleuren,
S. Bressan,
L. Danese,
G. De Zotti,
M. Negrello,
Z. -Y. Cai,
L. Fan,
W. Sutherland, [......],
A. Dariush,
J. Fritz,
R. Hopwood,
E. Ibar,
S. Maddox,
E. Pascale,
M. Pohlen,
E. Rigby,
D. Smith, P. Temi
[show abstract]
[hide abstract]
ABSTRACT: While the selection of strongly lensed galaxies with 500{\mu}m flux density
S_500>100 mJy has proven to be rather straightforward (Negrello et al. 2010),
for many applications it is important to analyze samples larger than the ones
obtained when confining ourselves to such a bright limit. Moreover, only by
probing to fainter flux densities is possible to exploit strong lensing to
investigate the bulk of the high-z star-forming galaxy population. We describe
HALOS (the Herschel-ATLAS Lensed Objects Selection), a method for efficiently
selecting fainter candidate strongly lensed galaxies, reaching a surface
density of ~1.5-2 deg^-2, i.e. a factor of about 4 to 6 higher than that at the
100 mJy flux limit. HALOS will allow the selection of up to ~1000 candidate
strongly lensed galaxies (with amplifications \mu>2) over the full H-ATLAS
survey area. Applying HALOS to the H-ATLAS Science Demonstration Phase field
(~14.4 deg^2) we find 31 candidate strongly lensed galaxies, whose candidate
lenses are identified in the VIKING near-infrared catalog. Using the available
information on candidate sources and candidate lenses we tentatively estimate a
~72% purity of the sample. The redshift distribution of the candidate lensed
sources is close to that reported for most previous surveys for lensed
galaxies, while that of candidate lenses extends to substantially higher
redshifts than found in the other surveys. The counts of candidate strongly
lensed galaxies are also in good agreement with model predictions (Lapi et al.
2011). Even though a key ingredient of the method is the deep near-infrared
VIKING photometry, we show that H-ATLAS data alone allow the selection of a
similarly deep sample of candidate strongly lensed galaxies with an efficiency
close to 50%; a slightly lower surface density (~1.45 deg^-2) can be reached
with a ~70% efficiency.
02/2012;
-
N. Bourne,
S. J. Maddox,
L. Dunne,
R. Auld,
M. Baes,
I. K. Baldry,
D. G. Bonfield,
A. Cooray,
S. M. Croom,
A. Dariush, [......],
R. Hopwood,
R. J. Ivison,
D. H. Jones,
L. S. Kelvin,
J. Liske,
J. Loveday,
P. Norberg,
A. S. G. Robotham,
G. Rodighiero, P. Temi
[show abstract]
[hide abstract]
ABSTRACT: We use the Herschel-ATLAS survey to conduct the first large-scale statistical
study of the submm properties of optically selected galaxies. Using ~80,000
r-band selected galaxies from 126 deg^2 of the GAMA survey, we stack into submm
imaging at 250, 350 and 500{\mu}m to gain unprecedented statistics on the dust
emission from galaxies at z < 0.35. We find that low redshift galaxies account
for 5% of the cosmic 250{\mu}m background (4% at 350{\mu}m; 3% at 500{\mu}m),
of which approximately 60% comes from 'blue' and 20% from 'red' galaxies
(rest-frame g - r). We compare the dust properties of different galaxy
populations by dividing the sample into bins of optical luminosity, stellar
mass, colour and redshift. In blue galaxies we find that dust temperature and
luminosity correlate strongly with stellar mass at a fixed redshift, but red
galaxies do not follow these correlations and overall have lower luminosities
and temperatures. We make reasonable assumptions to account for the
contaminating flux from lensing by red sequence galaxies and conclude that
galaxies with different optical colours have fundamentally different dust
emission properties. Results indicate that while blue galaxies are more
luminous than red galaxies due to higher temperatures, the dust masses of the
two samples are relatively similar. Dust mass is shown to correlate with
stellar mass, although the dust/stellar mass ratio is much higher for low
stellar mass galaxies, consistent with the lowest mass galaxies having the
highest specific star formation rates. We stack the 250{\mu}m/NUV luminosity
ratio, finding results consistent with greater obscuration of star formation at
lower stellar mass and higher redshift. Submm luminosities and dust masses of
all galaxies are shown to evolve strongly with redshift, indicating a fall in
the amount of obscured star formation in ordinary galaxies over the last four
billion years.
01/2012;
-
Sam Kim,
Julie L. Wardlow,
Asantha Cooray,
S. Fleuren,
W. Sutherland,
A. A. Khostovan,
R. Auld,
M. Baes,
R. S. Bussmann,
S. Buttiglione, [......],
M. Jarvis,
S. Maddox,
M. J. Michałowski,
E. Pascale,
M. Pohlen,
E. Rigby,
D. Scott,
D. J. B. Smith, P. Temi,
P. van der Werf
[show abstract]
[hide abstract]
ABSTRACT: We use spitzer-IRAC data to identify near-infrared counterparts to
submillimeter galaxies detected with Herschel-SPIRE at 250um in the Herschel
Astrophysical Terahertz Large Area Survey (H-ATLAS). Using a likelihood ratio
analysis we identify 146 reliable IRAC counterparts to 123 SPIRE sources out of
the 159. We find that, compared to the field population, the SPIRE counterparts
occupy a distinct region of 3.6 and 4.5um color-magnitude space, and we use
this property to identify a further 23 counterparts to 13 SPIRE sources. The
IRAC identification rate of 86% is significantly higher than those that have
been demonstrated with wide-field ground-based optical and near-IR imaging of
Herschel fields. We estimate a false identification rate of 3.6%, corresponding
to 4 to 5 sources. Among the 73 counterparts that are undetected in SDSS, 57
have both 3.6 and 4.5um coverage. Of these 43 have [3.6] - [4.5]> 0 indicating
that they are likely to be at z > 1.4. Thus, ~ 40% of identified SPIRE galaxies
are likely to be high redshift (z > 1.4) sources. We discuss the statistical
properties of the IRAC-identified SPIRE galaxy sample including far-IR
luminosities, dust temperatures, star-formation rates, and stellar masses. The
majority of our detected galaxies have 10^10 to 10^11 L_sun total IR
luminosities and are not intense starbursting galaxies as those found at z ~ 2,
but they have a factor of 2 to 3 above average specific star-formation rates
compared to near-IR selected galaxy samples.
12/2011;
-
K. Rowlands,
L. Dunne,
S. Maddox,
N. Bourne,
H. L. Gomez,
S. Kaviraj,
S. P. Bamford,
S. Brough,
S. Charlot,
E. da Cunha, [......],
J. Liske,
J. Loveday,
B. Madore,
P. Norberg,
C. C. Popescu,
E. E. Rigby,
A. Robotham,
G. Rodighiero,
M. Seibert,
R. J. Tuffs
[show abstract]
[hide abstract]
ABSTRACT: We present the dust properties and star formation histories of local submillimetre-selected galaxies, classified by optical morphology. Most of the galaxies are late types and very few are early types. The early-type galaxies (ETGs) that are detected contain as much dust as typical spirals, and form a unique sample that has been blindly selected at submillimetre wavelengths. Additionally, we investigate the properties of the most passive, dusty spirals.We morphologically classify 1087 galaxies detected in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) Science Demonstration Phase data. Comparing to a control sample of optically selected galaxies, we find 5.5 per cent of luminous ETGs are detected in H-ATLAS. The H-ATLAS ETGs contain a significant mass of cold dust: the mean dust mass is 5.5 × 107 M⊙, with individual galaxies ranging from 9 × 105 to 4 × 108 M⊙. This is comparable to that of spiral galaxies in our sample, and is an order of magnitude more dust than that found for the control early-types, which have a median dust mass inferred from stacking of (0.8–4.0) × 106 M⊙ for a cold dust temperature of 25–15 K. The early-types detected in H-ATLAS tend to have bluer NUV − r colours, higher specific star formation rates and younger stellar populations than early-types which are optically selected, and may be transitioning from the blue cloud to the red sequence.We also find that H-ATLAS and control early-types inhabit similar low-density environments. We investigate whether the observed dust in H-ATLAS early-types is from evolved stars, or has been acquired from external sources through interactions and mergers. We conclude that the dust in H-ATLAS and control ETGs cannot be solely from stellar sources, and a large contribution from dust formed in the interstellar medium or external sources is required. Alternatively, dust destruction may not be as efficient as predicted. We also explore the properties of the most passive spiral galaxies in our sample with specific star formation rate (SSFR) < 10−11 yr−1. We find these passive spirals have lower dust-to-stellar mass ratios, higher stellar masses and older stellar population ages than normal spirals. The passive spirals inhabit low-density environments similar to those of the normal spiral galaxies in our sample. This shows that the processes which turn spirals passive do not occur solely in the intermediate-density environments of group and cluster outskirts.
Monthly Notices of the Royal Astronomical Society 11/2011; 419(3):2545 - 2578. · 4.90 Impact Factor
-
A. Lapi,
J. González-Nuevo,
L. Fan,
A. Bressan,
G. De Zotti,
L. Danese,
M. Negrello,
L. Dunne,
S. Eales,
S. Maddox, [......],
M. J. Michałowski,
E. Pascale,
M. Pohlen,
E. Rigby,
G. Rodighiero,
S. Serjeant,
D. J. B. Smith, P. Temi,
J. Wardlow,
and P. van der Werf
[show abstract]
[hide abstract]
ABSTRACT: Exploiting the Herschel Astrophysical Terahertz Large Area Survey Science Demonstration Phase survey data, we have determined the luminosity functions (LFs) at rest-frame wavelengths of 100 and 250 μm and at several redshifts z 1, for bright submillimeter galaxies with star formation rates (SFRs) 100 M ☉ yr–1. We find that the evolution of the comoving LF is strong up to z 2.5, and slows down at higher redshifts. From the LFs and the information on halo masses inferred from clustering analysis, we derived an average relation between SFR and halo mass (and its scatter). We also infer that the timescale of the main episode of dust-enshrouded star formation in massive halos (M H 3 × 1012 M ☉) amounts to ~7 × 108 yr. Given the SFRs, which are in the range of 102-103 M ☉ yr–1, this timescale implies final stellar masses of the order of 1011-1012 M ☉. The corresponding stellar mass function matches the observed mass function of passively evolving galaxies at z 1. The comparison of the statistics for submillimeter and UV-selected galaxies suggests that the dust-free, UV bright phase is 102 times shorter than the submillimeter bright phase, implying that the dust must form soon after the onset of star formation. Using a single reference spectral energy distribution (SED; the one of the z 2.3 galaxy SMM J2135-0102), our simple physical model is able to reproduce not only the LFs at different redshifts >1 but also the counts at wavelengths ranging from 250 μm to 1 mm. Owing to the steepness of the counts and their relatively broad frequency range, this result suggests that the dispersion of submillimeter SEDs of z > 1 galaxies around the reference one is rather small.
The Astrophysical Journal 11/2011; 742(1):24. · 6.02 Impact Factor
-
K. Rowlands,
L. Dunne,
S. Maddox,
N. Bourne,
H. L. Gomez,
S. Kaviraj,
S. P. Bamford,
S. Brough,
S. Charlot,
E. da Cunha, [......],
J. Liske,
J. Loveday,
B. Madore,
P. Norberg,
C. C. Popescu,
E. E. Rigby,
A. Robotham,
G. Rodighiero,
M. Seibert,
R. J. Tuffs
[show abstract]
[hide abstract]
ABSTRACT: We present the dust properties and star-formation histories of local
submillimetre-selected galaxies in Herschel-ATLAS, classified by optical
morphology. The early-type galaxies (ETGs) that are detected contain as much
dust as typical spirals, and form a unique sample that has been blindly
selected at submillimetre wavelengths.
Comparing H-ATLAS galaxies to a control sample of optically selected
galaxies, we find 5.5% of luminous ETGs are detected in H-ATLAS. The H-ATLAS
ETGs contain a significant mass of cold dust: the mean dust mass is 5.5x10^7
Msun, with individual galaxies ranging from 9x10^5-4x10^8 Msun. This is
comparable to that of spirals in our sample, and is an order of magnitude more
dust than that found for the control ETGs, which have a median dust mass
inferred from stacking of (0.8-4.0)x10^6 Msun. The ETGs detected in H-ATLAS
have bluer NUV-r colours, higher specific star-formation rates and younger
stellar populations than ETGs which are optically selected, and may be
transitioning from the blue cloud to the red sequence. We also find that
H-ATLAS and control ETGs inhabit similar low-density environments. We conclude
that the dust in H-ATLAS and control ETGs cannot be solely from stellar
sources, and a large contribution from dust formed in the ISM or external
sources is required. Alternatively, dust destruction may not be as efficient as
predicted.
We also explore the properties of the most passive spiral galaxies in our
sample with SSFR<10^-11/yr. We find these passive spirals have lower
dust-to-stellar mass ratios, higher stellar masses and older stellar population
ages than normal spirals. The passive spirals inhabit low density environments
similar to those of the normal spiral galaxies in our sample. This shows that
the processes which turn spirals passive do not occur solely in the
intermediate density environments of group and cluster outskirts. (Abridged)
09/2011;
-
K. E. K. Coppin,
J. E. Geach,
Ian Smail,
L. Dunne,
A. C. Edge,
R. J. Ivison,
S. Maddox,
R. Auld,
M. Baes,
S. Buttiglione, [......],
M. Negrello,
E. Pascale,
M. Pohlen,
E. Rigby,
G. Rodighiero,
D. Scott,
S. Serjeant,
D. J. B. Smith, P. Temi,
P. van der Werf
[show abstract]
[hide abstract]
ABSTRACT: We report the detection of a significant excess in the surface density of far-infrared sources from the Herschel-Astrophysical Terahertz Large Area Survey within ∼1 Mpc of the centres of 66 optically selected clusters of galaxies in the Sloan Digital Sky Survey with 〈z〉∼ 0.25. From the analysis of the multiwavelength properties of their counterparts we conclude that the far-infrared emission is associated with dust-obscured star formation and/or active galactic nuclei (AGN) within galaxies in the clusters themselves. The excess reaches a maximum at a radius of ∼0.8 Mpc, where we find 1.0 ± 0.3 S250 > 34 mJy sources on average per cluster above what would be expected for random field locations. If the far-infrared emission is dominated by star formation (as opposed to AGN) then this corresponds to an average star formation rate of ∼7 M⊙ yr−1 per cluster in sources with LIR > 5 × 1010 L⊙. Although lensed sources make a negligible contribution to the excess signal, a fraction of the sources around the clusters could be gravitationally lensed, and we have identified a sample of potential cases of cluster-lensed Herschel sources that could be targeted in follow-up studies.
Monthly Notices of the Royal Astronomical Society 08/2011; 416(1):680 - 688. · 4.90 Impact Factor
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I. Valtchanov,
J. Virdee,
R. J. Ivison,
B. Swinyard,
P. van der Werf,
D. Rigopoulou,
E. da Cunha,
R. Lupu,
D. J. Benford,
D. Riechers, [......],
E. Pascale,
M. Pohlen,
E. Rigby,
G. Rodighiero,
D. J. B. Smith, P. Temi,
J. Carpenter,
A. Bolatto,
M. Gurwell,
J. D. Vieira
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ABSTRACT: We present Herschel-Spectral and Photometric Imaging Receiver (SPIRE) Fourier transform spectrometer (FTS) and radio follow-up observations of two Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS)-detected strongly lensed distant galaxies. In one of the targeted galaxies H-ATLAS J090311.6+003906 (SDP.81), we detect [O iii] 88 μm and [C ii] 158 μm lines at a signal-to-noise ratio of ∼5. We do not have any positive line identification in the other fainter target H-ATLAS J091305.0−005343 (SDP.130). Currently, SDP.81 is the faintest submillimetre galaxy with positive line detections with the FTS, with continuum flux just below 200 mJy in the 200–600 μm wavelength range. The derived redshift of SDP.81 from the two detections is z = 3.043 ± 0.012, in agreement with ground-based CO measurements. This is the first detection by Herschel of the [O iii] 88 μm line in a galaxy at redshift higher than 0.05. Comparing the observed lines and line ratios with a grid of photodissociation region (PDR) models with different physical conditions, we derive the PDR cloud density n ≈ 2000 cm−3 and the far-ultraviolet ionizing radiation field G0≈ 200 (in units of the Habing field – the local Galactic interstellar radiation field of 1.6 × 10−6 W m−2). Using the CO-derived molecular mass and the PDR properties, we estimate the effective radius of the emitting region to be 500–700 pc. These characteristics are typical for star-forming, high-redshift galaxies. The radio observations indicate that SDP.81 deviates significantly from the local far-infrared/radio (FIR/radio) correlation, which hints that some fraction of the radio emission is coming from an active galactic nucleus (AGN). The constraints on the source size from millimetre-wave observations put a very conservative upper limit of the possible AGN contribution to less than 33 per cent. These indications, together with the high [O iii]/FIR ratio and the upper limit of [O i] 63 μm/[C ii] 158 μm, suggest that some fraction of the ionizing radiation is likely to originate from the AGN.
Monthly Notices of the Royal Astronomical Society 08/2011; 415(4):3473 - 3484. · 4.90 Impact Factor
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D. J. B. Smith,
L. Dunne,
S. J. Maddox,
S. Eales,
D. G. Bonfield,
M. J. Jarvis,
W. Sutherland,
S. Fleuren,
E. E. Rigby,
M. A. Thompson, [......],
M. Prescott,
A. Robotham,
G. Rodighiero,
D. Scott,
M. Seibert,
R. Sharp, P. Temi,
R. J. Tuffs,
P. van der Werf,
E. van Kampen
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ABSTRACT: We present a technique to identify optical counterparts of 250-μm-selected sources from the Herschel–ATLAS survey. Of the 6621 250 μm > 32-mJy sources in our science demonstration catalogue we find that ∼60 per cent have counterparts brighter than r = 22.4 mag in the Sloan Digital Sky Survey. Applying a likelihood ratio technique we are able to identify 2423 of the counterparts with a reliability R > 0.8. This is approximately 37 per cent of the full 250-μm catalogue. We have estimated photometric redshifts for each of these 2423 reliable counterparts, while 1099 also have spectroscopic redshifts collated from several different sources, including the GAMA survey. We estimate the completeness of identifying counterparts as a function of redshift, and present evidence that 250-μm-selected Herschel–ATLAS galaxies have a bimodal redshift distribution. Those with reliable optical identifications have a redshift distribution peaking at z ≈ 0.25 ± 0.05, while submillimetre colours suggest that a significant fraction with no counterpart above the r-band limit have z > 1. We also suggest a method for selecting populations of strongly lensed high-redshift galaxies. Our identifications are matched to UV–NIR photometry from the GAMA survey, and these data are available as part of the Herschel–ATLAS public data release.
Monthly Notices of the Royal Astronomical Society 08/2011; 416(2):857 - 872. · 4.90 Impact Factor
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A. Omont,
R. Neri,
P. Cox,
R. Lupu,
M. Guélin,
P. van der Werf,
A. Weiß,
R. Ivison,
M. Negrello,
L. Leeuw, [......],
M. Pohlen,
E. Rigby,
D Smith,
A J Baker,
J. Bock,
C. M. Bradford,
J. Glenn,
A. I. Harris,
K. S. Scott,
J. Zmuidzinas
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ABSTRACT: The Herschel survey, H-ATLAS, with its large areal coverage, has recently
discovered a number of bright, strongly lensed high-z submillimeter galaxies.
The strong magnification makes it possible to study molecular species other
than CO, which are otherwise difficult to observe in high-z galaxies. Among the
lensed galaxies already identified by H-ATLAS, the source J090302.9-014127B
(SDP.17b) at z = 2.305 is remarkable due to its excitation conditions and a
tentative detection of the H2O 202-111 emission line (Lupu et al. 2010). We
report observations of this line in SDP.17b using the IRAM interferometer
equipped with its new 277- 371GHz receivers. The H2O line is detected at a
redshift of z = 2.3049+/-0.0006, with a flux of 7.8+/-0.5 Jy km s-1 and a FWHM
of 250+/-60 km s-1. The new flux is 2.4 times weaker than the previous
tentative detection, although both remain marginally consistent within
1.6-sigma. The intrinsic line luminosity and ratio of H2O(202-111)/CO8-7 seem
comparable with those of the nearby starburst/enshrouded-AGN Mrk 231,
suggesting that SDP.17b could also host a luminous AGN. The detection of a
strong H2O 202-111 line in SDP.17b implies an efficient excitation mechanism of
the water levels that must occur in very dense and warm interstellar gas.
07/2011;
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Pierre Cox,
M. Krips,
R. Neri,
A. Omont,
R. Gusten,
K. M. Menten,
F. Wyrowski,
A Weiss,
A. Beelen,
M. A. Gurwell, [......],
M. Michalowski,
E. Pascale,
M. Pohlen,
E. Rigby,
D. J. B. Smith,
A. M. Swinbank, P. Temi,
I. Valtchanov,
P. van der Werf,
G. De Zotti
[show abstract]
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ABSTRACT: We report ground-based follow-up observations of the exceptional source,
ID141, one the brightest sources detected so far in the H-ATLAS cosmological
survey. ID141 was observed using the IRAM 30-meter telescope and Plateau de
Bure interferometer (PdBI), the Submillimeter Array (SMA) and the Atacama
Pathfinder Experiment (APEX) submillimeter telescope to measure the dust
continuum and emission lines of the main isotope of carbon monoxide and carbon
([C I] and [C II]). The detection of strong CO emission lines with the PdBI
confirms that ID141 is at high redshift (z=4.243 +/- 0.001). The strength of
the continuum and emission lines suggests that ID141 is gravitationally lensed.
The width (Delta V (FWHM) ~ 800 km/s}) and asymmetric profiles of the CO and
carbon lines indicate orbital motion in a disc or a merger. The properties
derived for ID141 are compatible with a ultraluminous (L_FIR ~ 8.5 +/- 0.3 x
10^13/mu_L Lsun, where mu_L is the amplification factor, dense (n ~ 10^4 cm^-3)
and warm (T_kin ~ 40K) starburst galaxy, with an estimated star-formation rate
of (0.7 to 1.7) x 10^4/mu_L Msun/yr. The carbon emission lines indicate a dense
(n ~ 10^4 cm^-3) Photo-Dominated Region, illuminated by a far-UV radiation
field a few thousand times more intense than that in our Galaxy. In conclusion,
the physical properties of the high-z galaxy, ID141, are remarkably similar to
those of local ultraluminous infrared galaxies.
07/2011;
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A. Dariush,
L. Cortese,
S. Eales,
E. Pascale,
M. W. L. Smith,
L. Dunne,
S. Dye,
D Scott,
R. Auld,
M. Baes, [......],
C. C. Popescu,
A. S. G. Robotham,
G. Rodighiero,
M. Prescott,
E. Rigby,
M. Seibert,
D. J. B. Smith, P. Temi,
R. J. Tuffs,
P. van der Werf
[show abstract]
[hide abstract]
ABSTRACT: We investigate the ultraviolet and optical properties and environment of low
redshift galaxies detected in the Herschel Astrophysical Terahertz Large Area
Survey (H-ATLAS) science demonstration data. We use the Sloan Digital Sky
Survey seventh release and the Galaxy And Mass Assembly database to select
galaxies with r_Petro < 19.0 mag in the redshift range 0.02 < z < 0.2 and look
for their submillimeter counterparts in H-ATLAS. Our results show that at low
redshift, H-ATLAS detects mainly blue/star-forming galaxies with a minor
contribution from red systems which are highly obscured by dust. In addition we
find that the colour of a galaxy rather than the local density of its
environment determines whether it is detectable by H-ATLAS. The average dust
temperature of galaxies that are simultaneously detected by both PACS and SPIRE
is 25K \pm 4K, independent of environment. This analysis provides a glimpse of
the potential of the H-ATLAS data to investigate the submillimeter properties
of galaxies in the local universe.
06/2011;
