-
R. J. Ivison,
A. M. Swinbank,
Ian Smail,
A. I. Harris,
R. S. Bussmann,
A. Cooray,
P. Cox,
Hai Fu,
A. Kovacs,
M. Krips, [......],
S. Maddox,
A. Omont,
D. Scott,
S. Serjeant,
M. W. L. Smith,
M. A. Thompson,
E. Valiante,
I. Valtchanov,
J. Vieira,
P. van der Werf
[show abstract]
[hide abstract]
ABSTRACT: Exploiting the relationship between CO luminosity and line width determined
for fainter starbursts, we identify and remove lensed sources from the widest
Herschel extragalactic imaging survey to yield a sample of intrinsically
luminous galaxies. Panchromatic observations of the best candidate HyLIRG then
led to the discovery of at least four luminous galaxies across a ~100-kpc
region at z=2.41. Our technique separates HyLIRGs from the more numerous,
strongly lensed population, and can also pinpoint clusters of starbursting
proto-ellipticals. Via sub-arcsecond interferometric imaging we have measured
accurate gas and star-formation surface densities. The two brightest galaxies
span ~3 kpc FWHM in submm/radio continuum and CO J=4-3, and double that in CO
J=1-0. The broad CO line is due partly to the multitude of constituent galaxies
and partly to large rotational velocities in two counter-rotating gas disks --
a scenario predicted to lead to the most intense starbursts, which will
therefore come in pairs. The disks have M(dyn) of several x 10^11 Msun, and gas
fractions of ~40%. Velocity dispersions are modest so the disks are unstable,
potentially on scales commensurate with their radii: these galaxies are
undergoing extreme bursts of star formation, not confined to their nuclei, at
close to the Eddington limit. Their specific star-formation rates place them
~>5x above the main sequence, which supposedly comprises large gas disks like
these. Their high star-formation efficiencies are difficult to reconcile with a
simple volumetric star-formation law. N-body and dark matter simulations
suggest this system is the progenitor of a B(inary)-type ~10^14.6-Msun cluster.
02/2013;
-
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;
-
M. W. L. Smith, S. A. Eales,
H. L. Gomez,
J. Roman Duval,
J. Fritz,
R. Braun,
M. Baes,
G. J. Bendo,
J. A. D. L Blommaert,
M. Boquien, [......],
J. Kirk,
V. Lebouteiller,
S. Madden,
E. Mentuch,
B. O'Halloran,
M. J. Page,
B. Schulz,
L. Spinoglio,
J. Verstappen,
C. D. Wilson
[show abstract]
[hide abstract]
ABSTRACT: We present an analysis of the dust and gas in Andromeda, using Herschel
images sampling the entire far-infrared peak. We fit a modified-blackbody model
to ~4000 quasi-independent pixels with spatial resolution of ~140pc and find
that a variable dust-emissivity index (beta) is required to fit the data. We
find no significant long-wavelength excess above this model suggesting there is
no cold dust component. We show that the gas-to-dust ratio varies radially,
increasing from ~20 in the center to ~70 in the star-forming ring at 10kpc,
consistent with the metallicity gradient. In the 10kpc ring the average beta is
~1.9, in good agreement with values determined for the Milky Way (MW). However,
in contrast to the MW, we find significant radial variations in beta, which
increases from 1.9 at 10kpc to ~2.5 at a radius of 3.1kpc and then decreases to
1.7 in the center. The dust temperature is fairly constant in the 10kpc ring
(ranging from 17-20K), but increases strongly in the bulge to ~30K. Within
3.1kpc we find the dust temperature is highly correlated with the 3.6 micron
flux, suggesting the general stellar population in the bulge is the dominant
source of dust heating there. At larger radii, there is a weak correlation
between the star formation rate and dust temperature. We find no evidence for
'dark gas' in M31 in contrast to recent results for the MW. Finally, we
obtained an estimate of the CO X-factor by minimising the dispersion in the
gas-to-dust ratio, obtaining a value of (1.9+/-0.4)x10^20 cm^-2 [K kms^-1]^-1.
04/2012;
-
T. J. Parkin,
C. D. Wilson,
K. Foyle,
M. Baes,
G. J. Bendo,
A. Boselli,
M. Boquien,
A. Cooray,
D. Cormier,
J. I. Davies, [......],
V. Lebouteiller,
S. Madden,
E. Mentuch,
M. J. Page,
M. Pohlen,
A. Remy,
H. Roussel,
M. Sauvage,
M. W. L. Smith,
L. Spinoglio
[show abstract]
[hide abstract]
ABSTRACT: We present photometry of the nearby galaxy NGC 5128 (Centaurus A) observed
with the PACS and SPIRE instruments on board the Herschel Space Observatory, at
70, 160, 250, 350 and 500 {\mu}m, as well as new CO J = 3-2 observations taken
with the HARP-B instrument on the JCMT. Using a single component modified
blackbody, we model the dust spectral energy distribution within the disk of
the galaxy using all five Herschel wavebands, and find dust temperatures of ~30
K towards the centre of the disk and a smoothly decreasing trend to ~20 K with
increasing radius. We find a total dust mass of (1.59 \pm 0.05) \times 10^7
M\odot, and a total gas mass of (2.7 \pm 0.2) \times 10^9 M\odot. The average
gas-to-dust mass ratio is 103 \pm 8 but we find an interesting increase in this
ratio to approximately 275 toward the centre of Cen A. We discuss several
possible physical processes that may be causing this effect, including dust
sputtering, jet entrainment and systematic variables such as the XCO factor.
Dust sputtering by X-rays originating in the AGN or the removal of dust by the
jets are our most favoured explanations.
02/2012;
-
K. Foyle,
C. D. Wilson,
E. Mentuch,
G. Bendo,
A. Dariush,
T. Parkin,
M. Pohlen,
M. Sauvage,
M. W. L. Smith,
H. Roussel,
M. Baes,
M. Boquien,
A. Boselli,
D. L. Clements,
A. Cooray,
J. I. Davies, S. A. Eales,
S. Madden,
M. J. Page,
Spinoglio
[show abstract]
[hide abstract]
ABSTRACT: We examine the dust and gas properties of the nearby, barred galaxy M83,
which is part of the Very Nearby Galaxy Survey. Using images from the PACS and
SPIRE instruments of Herschel, we examine the dust temperature and dust mass
surface density distribution. We find that the nuclear, bar and spiral arm
regions exhibit higher dust temperatures and masses compared to interarm
regions. However, the distribution of dust temperature and mass are not
spatially coincident. Assuming a trailing spiral structure, the dust
temperature peaks in the spiral arms lie ahead of the dust surface density
peaks. The dust mass surface density correlates well with the distribution of
molecular gas as traced by CO (J=3-2) images (JCMT) and the star formation rate
as traced by H?2 with a correction for obscured star formation using 24 micron
emission. Using HI images from THINGS to trace the atomic gas component, we
make total gas mass surface density maps and calculate the gas-to-dust ratio.
We find a mean gas-to-dust ratio of 84 \pm 4 with higher values in the inner
region assuming a constant CO-to-H2 conversion factor. We also examine the
gas-to-dust ratio using CO-to-H2 conversion factor that varies with
metallicity.
01/2012;
-
J. Fritz,
G. Gentile,
M. W. L. Smith,
W. K. Gear,
R. Braun,
J. Roman Duval,
G. J. Bendo,
M. Baes, S. A. Eales,
J. Verstappen, [......],
J. Kirk,
S. C. Madden,
M. J. Page,
A. Remy,
H. Roussel,
L. Spinoglio,
D. Thilker,
M. Vaccari,
C. D. Wilson,
C. Waelkens
[show abstract]
[hide abstract]
ABSTRACT: We have obtained Herschel images at five wavelengths from 100 to 500 micron
of a ~5.5x2.5 degree area centred on the local galaxy M31 (Andromeda), our
nearest neighbour spiral galaxy, as part of the Herschel guaranteed time
project "HELGA". The main goals of HELGA are to study the characteristics of
the extended dust emission, focusing on larger scales than studied in previous
observations of Andromeda at an increased spatial resolution, and the obscured
star formation. In this paper we present data reduction and Herschel maps, and
provide a description of the far-infrared morphology, comparing it with
features seen at other wavelengths. We use high--resolution maps of the atomic
hydrogen, fully covering our fields, to identify dust emission features that
can be associated to M31 with confidence, distinguishing them from emission
coming from the foreground Galactic cirrus. Thanks to the very large extension
of our maps we detect, for the first time at far-infrared wavelengths, three
arc-like structures extending out to ~21, ~26 and ~31 kpc respectively, in the
south-western part of M31. The presence of these features, hosting ~2.2e6 Msol
of dust, is safely confirmed by their detection in HI maps. Overall, we
estimate a total dust mass of ~5.8e7 Msol, about 78% of which is contained in
the two main ring-like structures at 10 and 15 kpc, at an average temperature
of 16.5 K. We find that the gas-to-dust ratio declines exponentially as a
function of the galacto-centric distance, in agreement with the known
metallicity gradient, with values ranging from 66 in the nucleus to ~275 in the
outermost region. [Abridged]
12/2011;
-
M. W. L. Smith,
H. L. Gomez, S. A. Eales,
L. Ciesla,
A. Boselli,
L. Cortese,
G. J. Bendo,
M. Baes,
S. Bianchi,
M. Clemens, [......],
W. K. Gear,
S. Madden,
E. Mentuch,
P. Panuzzo,
M. Pohlen,
L. Spinoglio,
J. Verstappen,
C. Vlahakis,
C. D. Wilson,
E. M. Xilouris
[show abstract]
[hide abstract]
ABSTRACT: We present Herschel observations of 62 Early-Type Galaxies (ETGs), including
39 galaxies morphologically classified as S0+S0a and 23 galaxies classified as
ellipticals using SPIRE at 250, 350 and 500 microns (and PACS 100 and 160
microns for 19 sources) as part of the volume-limited Herschel Reference
Survey. We detect dust emission in 24% of the ellipticals and 62% of the S0s.
The mean temperature of the dust is 23.9+/-0.8 K, warmer than that found for
late-type galaxies in the Virgo Cluster. Including the non-detections, the mean
dust mass is log(Mdust) = 5.9+/-0.1 and 5.2+/-0.1 Msun for the S0s and
elliptical galaxies respectively. The mean dust-to-stellar mass is
log(Mdust/Mstar) = -4.4+/-0.1 (S0s) and -5.8+/-0.1 (ellipticals). Virtually all
the galaxies lie close to the red sequence yet the large number of detections
of cool dust, the gas-to-dust ratios and the ratios of far-infrared to radio
emission all suggest that many ETGs contain a cool interstellar medium similar
to that in late-type galaxies. The mean dust-to-stellar mass ratio for S0s is
approximatly a factor of ten less than for early-type spirals and the sizes of
the dust sources in the S0s are also much smaller. We show that the difference
cannot be explained by either the different bulge-to-disk ratios or
environmental effects such as ram-pressure stripping. The wide range in the
dust-to-stellar mass ratio for ETGs and the lack of a correlation between dust
mass and optical luminosity suggest that much of the dust in the ETGs detected
by Herschel has been acquired as the result of gravitational interactions;
these interactions are unlikely to have had a major effect on the stellar
masses of the ETGs. The Herschel observations tentatively suggest that in the
most massive ETGs, the mass of the interstellar medium is unconnected to the
evolution of the stellar populations.
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
-
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;
-
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
[show abstract]
[hide abstract]
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;
-
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]
[hide abstract]
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;
-
N. Sacchi,
L. Spinoglio,
C. D. Wilson,
J. Kamenetzky,
N. Rangwala,
A. Rykala,
K. G. Isaak,
G. J. Bendo,
M. Bradford,
J. Glenn, [......],
M. W. L. Smith,
J. A. Stevens,
S. Sundar,
M. Symeonidis,
M. Trichas,
M. Vaccari,
L. Vigroux,
H. Wozniak,
G. S. Wright,
W. W. Zeilinger
[show abstract]
[hide abstract]
ABSTRACT: We present the 450-1550 GHz spectra of three nearby Seyfert galaxies (NGC1068, NGC7130 and NGC7582) taken with the Herschel SPIRE FTS. For the case of NGC1068 we reconstruct the nuclear spectral line energy distribution (SLED) of the CO lines, applying nonLTE radiative transfer and a Bayesian likelihood analysis to estimate the physical properties of the molecular gas in the circumnuclear region. Groundbased observations of the low-J transitions with high (few arcsec) angular resolution are required to reconstruct the nuclear SLED avoiding contamination from colder molecular gas on larger galactic scales. We find evidence for a very warm molecular gas component with a density ~10^3.9 cm-3, similar to that found in previous works (Papadopoulos & Seaquist 1999, Usero et al. 2004, Kamenetzky et al. 2011), but with a much higher temperature (~ 550 K instead of 20-160 K). The higher-J transitions of CO are compatible with being excited in X-ray dissociation regions (XDR). However, in order to explain the entire CO SLED a comparable contribution from photodissociation regions (PDR) is required.
IAU SymposiumIAU Symposium; 01/2011
-
J. I. Davies,
C. D. Wilson,
R. Auld,
M. Baes,
M. J. Barlow,
G. J. Bendo,
J. J. Bock,
A. Boselli,
M. Bradford,
V. Buat, [......],
L. Spinoglio,
J. A. Stevens,
S. Srinivasan,
M. Symeonidis,
M. Trichas,
M. Vaccari,
L. Vigroux,
H. Wozniak,
G. S. Wright,
W. W. Zeilinger
[show abstract]
[hide abstract]
ABSTRACT: Galactic cirrus emission at far-infrared wavelengths affects many extragalactic observations. Separating this emission from that associated with extragalactic objects is both important and difficult. In this paper we discuss a particular case, the M81 group, and the identification of diffuse structures prominent in the infrared, but also detected at optical wavelengths. The origin of these structures has previously been controversial, ranging from them being the result of a past interaction between M81 and M82 or due to more local Galactic emission. We show that over of order a few arcminute scales the far-infrared (Herschel 250 &\mu&m) emission correlates spatially very well with a particular narrow velocity (2-3 km/s) component of the Galactic HI. We find no evidence that any of the far-infrared emission associated with these features actually originates in the M81 group. Thus we infer that the associated diffuse optical emission must be due to galactic light back scattered off dust in our galaxy. Ultra-violet observations pick out young stellar associations around M81, but no detectable far-infrared emission. We consider in detail one of the Galactic cirrus features, finding that the far-infrared HI relation breaks down below arc minute scales and that at smaller scales there can be quite large dust temperature variations. Comment: 6 pages, 4 figures, accepted for publication in MNRAS
10/2010;
-
[show abstract]
[hide abstract]
ABSTRACT: We present a new efficient technique for measuring evolution of the galaxy luminosity function. The method reconstructs the evolution over the luminosity-redshift plane using any combination of three input data set types: (i) number counts, (ii) galaxy redshifts and (iii) integrated background flux measurements. The evolution is reconstructed in adaptively sized regions of the plane according to the input data as determined by a Bayesian formalism. We demonstrate the performance of the method using a range of different synthetic input data sets. We also make predictions of the accuracy with which forthcoming surveys conducted with Submillimetre Common-User Bolometer Array 2 and the Herschel Space Satellite will be able to measure evolution of the submillimetre luminosity function using the method.
Monthly Notices of the Royal Astronomical Society 07/2010; 405(4):2406 - 2418. · 4.90 Impact Factor
-
M. Pohlen,
L. Cortese,
M. W. L. Smith, S. A. Eales,
A. Boselli,
G. J. Bendo,
H. L. Gomez,
A. Papageorgiou,
R. Auld,
M. Baes, [......],
J. A. Stevens,
S. Srinivasan,
M. Symeonidis,
M. Trichas,
M. Vaccari,
L. Vigroux,
C. D. Wilson,
H. Wozniak,
G. S. Wright,
W. W. Zeiliner
[show abstract]
[hide abstract]
ABSTRACT: By combining Herschel-SPIRE data with archival Spitzer, HI, and CO maps, we investigate the spatial distribution of gas and dust in the two famous grand-design spirals M99 and M100 in the Virgo cluster. Thanks to the unique resolution and sensitivity of the Herschel-SPIRE photometer, we are for the first time able to measure the distribution and extent of cool, submillimetre (submm)-emitting dust inside and beyond the optical radius. We compare this with the radial variation in both the gas mass and the metallicity. Although we adopt a model-independent, phenomenological approach, our analysis provides important insights. We find the dust extending to at least the optical radius of the galaxy and showing breaks in its radial profiles at similar positions as the stellar distribution. The colour indices f350/f500 and f250/f350 decrease radially consistent with the temperature decreasing with radius. We also find evidence of an increasing gas to dust ratio with radius in the outer regions of both galaxies. Comment: LaTeX, 5 pages, 5 figures, Astronomy and Astrophysics, Herschel Special Issue, in press as a Letter
05/2010;
-
L. Cortese,
G. J. Bendo,
A. Boselli,
J. I. Davies,
H. L. Gomez,
M. Pohlen,
R. Auld,
M. Baes,
J. J. Bock,
M. Bradford, [......],
J. A. Stevens,
S. Srinivasan,
M. Symeonidis,
M. Trichas,
M. Vaccari,
L. Vigroux,
C. D. Wilson,
H. Wozniak,
G. S. Wright,
W. W. Zeilinger
[show abstract]
[hide abstract]
ABSTRACT: We present Herschel-SPIRE observations of the perturbed galaxy NGC4438 in the Virgo cluster. These images reveal the presence of extra-planar dust up to ~4-5 kpc away from the galaxy's disk. The dust closely follows the distribution of the stripped atomic and molecular hydrogen, supporting the idea that gas and dust are perturbed in a similar fashion by the cluster environment. Interestingly, the extra-planar dust lacks a warm temperature component when compared to the material still present in the disk, explaining why it was missed by previous far-infrared investigations. Our study provides evidence for dust stripping in clusters of galaxies and illustrates the potential of Herschel data for our understanding of environmental effects on galaxy evolution. Comment: 5 pages, 2 figures. Accepted for publication on the A&A Herschel Special Issue
05/2010;
-
S. A. Eales,
M. W. L. Smith,
C. D. Wilson,
G. J. Bendo,
L. Cortese,
M. Pohlen,
A. Boselli,
H. L. Gomez,
R. Auld,
M. Baes, [......],
L. Spinoglio,
S. Srinivasan,
J. A. Stevens,
M. Symeonidis,
M. Trichas,
M. Vaccari,
L. Vigroux,
H. Wozniak,
G. S. Wright,
W. W. Zeilinger
[show abstract]
[hide abstract]
ABSTRACT: The standard method of mapping the interstellar medium in a galaxy, by observing the molecular gas in the CO 1-0 line and the atomic gas in the 21-cm line, is largely limited with current telescopes to galaxies in the nearby universe. In this letter, we use SPIRE observations of the galaxies M99 and M100 to explore the alternative approach of mapping the interstellar medium using the continuum emission from the dust. We have compared the methods by measuring the relationship between the star-formation rate and the surface density of gas in the galaxies. We find the two methods give relationships with a similar dispersion, confirming that observing the continuum emission from the dust is a promising method of mapping the interstellar medium in galaxies. Comment: Astronomy and Astrophysics in press
05/2010;
-
B. O'Halloran,
M. Galametz,
S. C. Madden,
F. Galliano,
S. Hony,
M. Sauvage,
M. Pohlen,
G. J. Bendo,
R. Auld,
M. Baes, [......],
J. A. Stevens,
S Sundar,
M. Symeonidis,
M. Trichas,
M. Vaccari,
L. Vigroux,
C. D. Wilson,
H. Wozniak,
G. S. Wright,
W. W. Zeilinger
[show abstract]
[hide abstract]
ABSTRACT: We present Herschel SPIRE and PACS photometeric observations of the low metallicity (Z ~ 0.35 solar) nearby dwarf galaxy, NGC 1705, in six wavelength bands as part of the Dwarf Galaxy Survey guaranteed time Herschel Key Program. We confirm the presence of two dominant circumnuclear IR-bright regions surrounding the central super star cluster that had been previously noted at mid-IR wavelengths and in the sub-mm by LABOCA. On constructing a global spectral energy distribution using the SPIRE and PACS photometry, in conjunction with archival IR measurements, we note the presence of an excess at sub-mm wavelengths. This excess suggests the presence of a significant cold dust component within NGC 1705 and was modeled as an additional cold component in the SED. Although alternative explanations for the sub-mm excess beyond 350 microns, such as changes to the dust emissivity cannot be ruled out, the most likely explanation for the observed submillimetre excess is that of an additional cold dust component. Comment: 5 pages, 2 figures, accepted for publication in A&A (Herschel special issue)
05/2010;
-
S. A. Eales,
G Raymond,
I. G. Roseboom,
B. Altieri,
A. Amblard,
V. Arumugam,
R. Auld,
H. Aussel,
T. Babbedge,
A. Blain, [......],
M. Trichas,
K. E. Tugwell,
M. Vaccari,
I. Valtchanov,
L. Vigroux,
L Wang,
R Ward,
G Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: We have carried out two extremely deep surveys with SPIRE, one of the two cameras on Herschel, at 250 microns, close to the peak of the far-infrared background. We have used the results to investigate the evolution of the rest-frame 250-micron luminosity function out to z=2. We find evidence for strong evolution out to a redshift of around 1 but evidence for at most weak evolution beyond this redshift. Our results suggest that a significant part of the stars and metals in the Universe today were formed at z<1.4 in spiral galaxies. Comment: Astronomy and Astrophysics, Herschel Special Issue, in press as a Letter; 5 pages
http://dx.doi.org/10.1051/0004-6361/201014675. 05/2010;
