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[show abstract]
[hide abstract]
ABSTRACT: We use recently published measurements of the kinematics, surface brightness
and stellar mass-to-light ratio of the globular cluster NGC 2419 to examine the
possibility that this Galactic halo satellite is embedded in a low-mass dark
matter halo. NGC 2419 is a promising target for such a study, since its extreme
Galactocentric distance and large mass would have greatly facilitated the
retention of dark matter. A Markov-Chain Monte Carlo approach is used to
investigate composite dynamical models containing a stellar and a dark matter
component. We find that it is unlikely that a significant amount of dark matter
(less than approx. 6% of the luminous mass inside the tidal limit of the
cluster) can be present if the stars follow an anisotropic Michie model and the
dark matter a double power law model. However, we find that more general
models, derived using a new technique we have developed to compute
non-parametric solutions to the spherical Jeans equation, suggest the presence
of a significant dark matter fraction (approximately twice the stellar mass).
Thus the presence of a dark matter halo around NGC 2419 cannot be fully ruled
out at present, yet any dark matter within the 10 arcmin visible extent of the
cluster must be highly concentrated and cannot exceed 1.1x10^6 Solar masses
(99% confidence), in stark contrast to expectations for a plausible progenitor
halo of this structure.
10/2012;
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Alexander Karim,
Mark Swinbank,
Jackie Hodge,
Ian Smail,
Fabian Walter,
Andy Biggs,
James Simpson,
Alice Danielson,
David Alexander,
Frank Bertoldi, [......],
Helmut Dannerbauer,
Alastair Edge,
Thomas Greve,
Rob Ivison,
Kirsten Knudsen,
Karl Menten,
Eva Schinnerer,
Julie Wardlow,
Axel Weiß,
Paul van der Werf
[show abstract]
[hide abstract]
ABSTRACT: We report the first counts of faint submillimetre galaxies (SMG) in the
870-um band derived from arcsecond resolution observations with the Atacama
Large Millimeter Array (ALMA). We have used ALMA to map a sample of 122
870-um-selected submillimetre sources drawn from the (0.5x0.5)deg^2 LABOCA
Extended Chandra Deep Field South Submillimetre Survey (LESS). These ALMA maps
have an average depth of sigma(870um)~0.4mJy, some ~3x deeper than the original
LABOCA survey and critically the angular resolution is more than an order of
magnitude higher, FWHM of ~1.5" compared to ~19" for the LABOCA discovery map.
This combination of sensitivity and resolution allows us to precisely pin-point
the SMGs contributing to the submillimetre sources from the LABOCA map, free
from the effects of confusion. We show that our ALMA-derived SMG counts broadly
agree with the submillimetre source counts from previous, lower-resolution
single-dish surveys, demonstrating that the bulk of the submillimetre sources
are not caused by blending of unresolved SMGs. The difficulty which
well-constrained theoretical models have in reproducing the high-surface
densities of SMGs, thus remains. However, our observations do show that all of
the very brightest sources in the LESS sample, S(870um)>12mJy, comprise
emission from multiple, fainter SMGs, each with 870-um fluxes of <9mJy. This
implies a natural limit to the star-formation rate in SMGs of <10^3 M_Sun/yr,
which in turn suggests that the space densities of z>1 galaxies with gas masses
in excess of ~5x10^10 M_Sun is <10^-5 Mpc^-3. We also discuss the influence of
this blending on the identification and characterisation of the SMG
counterparts to these bright submillimetre sources and suggest that it may be
responsible for previous claims that they lie at higher redshifts than fainter
SMGs.
09/2012;
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Mark Swinbank,
Alexander Karim,
Ian Smail,
Jackie Hodge,
Fabian Walter,
Frank Bertoldi,
Andy Biggs,
Carlos De Breuck, Scott Chapman,
Kristen Coppin, [......],
Helmut Dannerbauer,
Rob Ivison,
Thomas Greve,
Kirsten Knudsen,
Karl Menten,
James Simpson,
Eva Schinnerer,
Julie Wardlow,
Axel Weiss,
Paul van der Werf
[show abstract]
[hide abstract]
ABSTRACT: We present ALMA 870-um (345GHz) observations of two sub-millimetre galaxies
(SMGs) drawn from an ALMA study of the 126 sub-millimeter sources from the
LABOCA Extended Chandra Deep Field South Survey (LESS). The ALMA data identify
the counterparts to these previously unidentified sub-millimeter sources and
serendipitously detect bright emission lines in their spectra which we show are
most likely to be [C II]157.74um emission yielding redshifts of z=4.42 and
z=4.44. This blind detection rate within the 7.5-GHz bandpass of ALMA is
consistent with the previously derived photometric redshift distribution of
SMGs and suggests a modest, but not dominant (<25%), tail of 870-um selected
SMGs at z>4. We find that the ratio of L_CII/L_FIR in these SMGs is much higher
than seen for similarly far-infrared-luminous galaxies at z~0, which is
attributed to the more extended gas reservoirs in these high-redshift ULIRGs.
Indeed, in one system we show that the [C II] emission shows hints of extended
emission on >3kpc scales. Finally, we use the volume probed by our ALMA survey
to show that the bright end of the [C II] luminosity function evolves strongly
between z=0 and z~4.4, reflecting the increased ISM cooling in galaxies as a
result of their higher star-formation rates. These observations demonstrate
that even with short integrations, ALMA is able to detect the dominant fine
structure cooling lines from high-redshift ULIRGs, measure their energetics and
trace their evolution with redshift.
09/2012;
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Kristen Coppin,
Alice Danielson,
James E. Geach,
Jacqueline Hodge,
Mark Swinbank,
Julie Wardlow,
Frank Bertoldi,
Andy Biggs,
Niel Brandt,
Paola Caselli, [......],
Rob Ivison,
Alex Karim,
Kirsten Knudsen,
Karl Menten,
Eva Schinnerer,
Ian Smail,
Marco Spaans,
Fabian Walter,
Tracy Webb,
Paul van der Werf
[show abstract]
[hide abstract]
ABSTRACT: We present Herschel-PACS spectroscopy of the [OI]63um far-infrared cooling
line from a sample of six unlensed and spectroscopically-confirmed
870um-selected submillimetre (submm) galaxies (SMGs) at 1.1<z<1.6 from the
LABOCA Extended Chandra Deep Field South (ECDFS) Submm Survey (LESS). This is
the first survey of [OI]63um, one of the main photodissociation region (PDR)
cooling lines, in SMGs. New high-resolution ALMA interferometric 870um
continuum imaging confirms that these six Herschel-targeted SMG counterparts
are bona fide sources of submm emission. We detect [OI]63um in two SMGs with a
SNR >3, tentatively detect [OI]63um in one SMG, and constrain the line flux for
the non-detections. We also exploit the combination of submm continuum
photometry from 250-870um and our new PACS continuum measurements to constrain
the far-infrared (FIR) luminosity, L_FIR, in these SMGs to < 30%. We find that
SMGs do not show a deficit in their [OI]63um-to-far-infrared continuum
luminosity ratios (with ratios ranging from ~0.5-1.5%), similar to what was
seen previously for the [CII]158um-to-FIR ratios in SMGs. These observed ratios
are about an order of magnitude higher than what is seen typically for local
ultra luminous infrared galaxies (ULIRGs), which adds to the growing body of
evidence that SMGs are not simply `scaled up' versions of local ULIRGs. Rather,
the PDR line-to-L_FIR ratios suggest that the star formation modes of SMGs are
likely more akin to that of local normal (lower-luminosity) star-forming
galaxies, with the bulk of the star formation occurring in extended regions,
galaxy-scale (~kpc) in size. These observations represent the first step
towards a census of the major PDR cooling lines in typical SMGs that will be
attainable with ALMA, enabling detailed modelling to probe the global
properties of the star formation and the evolutionary status of SMGs.
08/2012;
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Chris Simpson,
Steve Rawlings,
Rob Ivision,
Masayuki Akiyama,
Omar Almaini,
Emma Bradshaw, Scott Chapman,
Rob Chuter,
Scott Croom,
Jim Dunlop,
Sebastien Foucaud,
Will Hartley
[show abstract]
[hide abstract]
ABSTRACT: We present spectroscopic and eleven-band photometric redshifts for galaxies
in the 100-uJy Subaru/XMM-Newton Deep Field radio source sample. We find good
agreement between our redshift distribution and that predicted by the SKA
Simulated Skies project. We find no correlation between K-band magnitude and
radio flux, but show that sources with 1.4-GHz flux densities below ~1mJy are
fainter in the near-infrared than brighter radio sources at the same redshift,
and we discuss the implications of this result for spectroscopically-incomplete
samples where the K-z relation has been used to estimate redshifts. We use the
infrared--radio correlation to separate our sample into radio-loud and
radio-quiet objects and show that only radio-loud hosts have spectral energy
distributions consistent with predominantly old stellar populations, although
the fraction of objects displaying such properties is a decreasing function of
radio luminosity. We calculate the 1.4-GHz radio luminosity function (RLF) in
redshift bins to z=4 and find that the space density of radio sources increases
with lookback time to z~2, with a more rapid increase for more powerful
sources. We demonstrate that radio-loud and radio-quiet sources of the same
radio luminosity evolve very differently. Radio-quiet sources display strong
evolution to z~2 while radio-loud AGNs below the break in the radio luminosity
function evolve more modestly and show hints of a decline in their space
density at z>1, with this decline occurring later for lower-luminosity objects.
If the radio luminosities of these sources are a function of their black hole
spins then slowly-rotating black holes must have a plentiful fuel supply for
longer, perhaps because they have yet to encounter the major merger that will
spin them up and use the remaining gas in a major burst of star formation.
01/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We present an analysis of the globular cluster NGC 2419, using a polytropic
model in Modified Newtonian Dynamics (MOND) to reproduce recently published
high quality data of the structure and kinematics of the system. We show that a
specific MOND polytropic model of NGC 2419 suggested by a previous study can be
completely ruled out by the data. Furthermore, the highest likelihood fit
polytrope in MOND is a substantially worse model (by a factor of approximately
5000) than a Newtonian Michie model studied in an earlier contribution by Ibata
et al. (2011). We conclude that the structure and dynamics of NGC 2419 favor
Newtonian dynamics and do indeed challenge the MOND theory.
10/2011;
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R. G. Carlberg,
Harvey B. Richer,
Alan W. McConnachie,
Mike Irwin,
Rodrigo A. Ibata,
Aaron L. Dotter, Scott Chapman,
Mark Fardal,
A. M. N. Ferguson,
G. F. Lewis,
Julio F. Navarro,
Thomas H. Puzia,
and David Valls-Gabaud
[show abstract]
[hide abstract]
ABSTRACT: The Pan Andromeda Archeological Survey (PAndAS) CFHT Megaprime survey of the M31-M33 system has found a star stream which extends about 120 kpc NW from the center of M31. The great length of the stream, and the likelihood that it does not significantly intersect the disk of M31, means that it is unusually well suited for a measurement of stream gaps and clumps along its length as a test for the predicted thousands of dark matter sub-halos. The main result of this paper is that the density of the stream varies between zero and about three times the mean along its length on scales of 2-20 kpc. The probability that the variations are random fluctuations in the star density is less than 10–5. As a control sample, we search for density variations at precisely the same location in stars with metallicity higher than the stream [Fe/H] = [0, –0.5] and find no variations above the expected shot noise. The lumpiness of the stream is not compatible with a low mass star stream in a smooth galactic potential, nor is it readily compatible with the disturbance caused by the visible M31 satellite galaxies. The stream's density variations appear to be consistent with the effects of a large population of steep mass function dark matter sub-halos, such as found in LCDM simulations, acting on an approximately 10 Gyr old star stream. The effects of a single set of halo substructure realizations are shown for illustration, reserving a statistical comparison for another study.
The Astrophysical Journal 03/2011; 731(2):124. · 6.02 Impact Factor
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Jenny C. Richardson,
Mike Irwin,
Alan W. McConnachie,
Nicolas F. Martin,
Aaron Dotter,
Annette M. N. Ferguson,
Rodrigo A. Ibata, Scott Chapman,
Geraint F. Lewis,
Nial R. Tanvir,
R. Michael Rich
[show abstract]
[hide abstract]
ABSTRACT: We present the discovery of five new dwarf galaxies, Andromeda XXIII-XXVII,
located in the outer halo of M31. These galaxies were found in the second year
of data from the Pan-Andromeda Archaeological Survey (PAndAS) of the M31/M33
subgroup. This survey now provides an almost complete panoramic view of the M31
halo out to an average projected radius of ~150 kpc. The metal-poor stellar
density map for this whole region serves, not only as an illustration of the
discovery space for satellite galaxies, but also gives a birds-eye view of the
ongoing assembly process of an L* disk galaxy. Four of the new dwarfs appear as
well-defined spatial over-densities of stars lying on the expected locus of
metal-poor red giant branch stars at the distance of M31. The fifth
over-density, And XXVII, is embedded in an extensive stream of such stars and
is possibly the remnant of a strong tidal disruption event. All five satellites
have metallicities and luminosities typical of dwarf spheroidal galaxies and
continue the trend whereby the brighter dwarf spheroidal satellites of M31
generally have much larger half-light radii than their Milky Way counterparts.
With an extended sample of M31 satellite galaxies we also revisit the spatial
distribution of this population and find that, within the current limits of the
PAndAS survey, the surface density of satellites is essentially constant out to
150 kpc. This corresponds to a radial density distribution of satellites
varying as 1/r, a result seemingly in conflict with the predictions of
cosmological simulations. (Abridged)
02/2011;
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Asantha Cooray,
Steve Eales, Scott Chapman,
David L. Clements,
Olivier Dore,
Duncan Farrah,
Matt J. Jarvis,
Manoj Kaplinghat,
Mattia Negrello,
Alessandro Melchiorri, [......],
Licia Verde,
Aprajita Verma,
Patricio Vielva,
Marco P. Viero,
Baltasar Vila Vilaro,
Julie Wardlow,
Grant Wilson,
Edward L. Wright,
C. Kevin Xu,
Min S. Yun
[show abstract]
[hide abstract]
ABSTRACT: A large sub-mm survey with Herschel will enable many exciting science opportunities, especially in an era of wide-field optical and radio surveys and high resolution cosmic microwave background experiments. The Herschel-SPIRE Legacy Survey (HSLS), will lead to imaging data over 4000 sq. degrees at 250, 350, and 500 micron. Major Goals of HSLS are: (a) produce a catalog of 2.5 to 3 million galaxies down to 26, 27 and 33 mJy (50% completeness; 5 sigma confusion noise) at 250, 350 and 500 micron, respectively, in the southern hemisphere (3000 sq. degrees) and in an equatorial strip (1000 sq. degrees), areas which have extensive multi-wavelength coverage and are easily accessible from ALMA. Two thirds of the of the sources are expected to be at z > 1, one third at z > 2 and about a 1000 at z > 5. (b) Remove point source confusion in secondary anisotropy studies with Planck and ground-based CMB data. (c) Find at least 1200 strongly lensed bright sub-mm sources leading to a 2% test of general relativity. (d) Identify 200 proto-cluster regions at z of 2 and perform an unbiased study of the environmental dependence of star formation. (e) Perform an unbiased survey for star formation and dust at high Galactic latitude and make a census of debris disks and dust around AGB stars and white dwarfs. Comment: White paper supplement to the proposal submitted by the HSLS science team to ESA for Herschel open-time programs
07/2010;
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Asantha Cooray,
Steve Eales, Scott Chapman,
David L. Clements,
Olivier Dore,
Duncan Farrah,
Matt J. Jarvis,
Manoj Kaplinghat,
Mattia Negrello,
Alessandro Melchiorri, [......],
Licia Verde,
Aprajita Verma,
Patricio Vielva,
Marco P. Viero,
Baltasar Vila Vilaro,
Julie Wardlow,
Grant Wilson,
Edward L. Wright,
C. Kevin Xu,
Min S. Yun
[show abstract]
[hide abstract]
ABSTRACT: A large sub-mm survey with Herschel will enable many exciting science
opportunities, especially in an era of wide-field optical and radio
surveys and high resolution cosmic microwave background experiments. The
Herschel-SPIRE Legacy Survey (HSLS), will lead to imaging data over 4000
sq. degrees at 250, 350, and 500 micron. Major Goals of HSLS are: (a)
produce a catalog of 2.5 to 3 million galaxies down to 26, 27 and 33 mJy
(50% completeness; 5 sigma confusion noise) at 250, 350 and 500 micron,
respectively, in the southern hemisphere (3000 sq. degrees) and in an
equatorial strip (1000 sq. degrees), areas which have extensive
multi-wavelength coverage and are easily accessible from ALMA. Two
thirds of the of the sources are expected to be at z > 1, one third
at z > 2 and about a 1000 at z > 5. (b) Remove point source
confusion in secondary anisotropy studies with Planck and ground-based
CMB data. (c) Find at least 1200 strongly lensed bright sub-mm sources
leading to a 2% test of general relativity. (d) Identify 200
proto-cluster regions at z of 2 and perform an unbiased study of the
environmental dependence of star formation. (e) Perform an unbiased
survey for star formation and dust at high Galactic latitude and make a
census of debris disks and dust around AGB stars and white dwarfs.
06/2010;
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[show abstract]
[hide abstract]
ABSTRACT: We use a sample of newly-discovered globular clusters from the Pan-Andromeda Archaeological Survey (PAndAS) in combination with previously-catalogued objects to map the spatial distribution of globular clusters in the M31 halo. At projected radii beyond ~30 kpc, where large coherent stellar streams are readily distinguished in the field, there is a striking correlation between these features and the positions of the globular clusters. Adopting a simple Monte Carlo approach, we test the significance of this association by computing the probability that it could be due to the chance alignment of globular clusters smoothly distributed in the M31 halo. We find the likelihood of this possibility is low, below 1%, and conclude that the observed spatial coincidence between globular clusters and multiple tidal debris streams in the outer halo of M31 reflects a genuine physical association. Our results imply that the majority of the remote globular cluster system of M31 has been assembled as a consequence of the accretion of cluster-bearing satellite galaxies. This constitutes the most direct evidence to date that the outer halo globular cluster populations in some galaxies are largely accreted. Comment: Accepted for publication in ApJ Letters
05/2010;
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Kristen Coppin, Scott Chapman,
Ian Smail,
Mark Swinbank,
Fabian Walter,
Julie Wardlow,
Axel Weiss,
David M. Alexander,
Niel Brandt,
Helmut Dannerbauer, [......],
James Dunlop,
Alastair Edge,
Bjorn Emonts,
Thomas Greve,
Minh Huynh,
Rob Ivison,
Kirsten Knudsen,
Karl Menten,
Eva Schinnerer,
Paul van der Werf
[show abstract]
[hide abstract]
ABSTRACT: We have detected the CO(2-1) transition from the submillimetre galaxy (SMG) LESSJ033229.4-275619 at z=4.755 using the new Compact Array Broadband Backend system on the Australian Telescope Compact Array. These data have identified a massive gas reservoir available for star formation for the first time in an SMG at z~5. We use the luminosity and velocity width (FWHM of 160 km/s) of the CO(2--1) line emission to constrain the gas and dynamical mass of Mgas~1.6x10^10 Msun and Mdyn(<2kpc)~5x10^10 (0.25/sin^2(i)) Msun, respectively, similar to that observed for SMGs at lower redshifts of z~2-4, although we note that our observed CO FWHM is a factor of ~3 narrower than typically seen in SMGs. Together with the stellar mass we estimate a total baryonic mass of Mbary~1x10^11 Msun, consistent with the dynamical mass for this young galaxy within the uncertainties. Dynamical and baryonic mass limits of high-redshift galaxies are useful tests of galaxy formation models: using the known z~4-5 SMGs as examples of massive baryonic systems, we find that their space density is consistent with that predicted by current galaxy formation models. In addition, these observations have helped to confirm that z~4-5 SMGs possess the baryonic masses and gas consumption timescales necessary to be the progenitors of the luminous old red galaxies seen at z~3. Our results provide a preview of the science that ALMA will enable on the formation and evolution of the earliest massive galaxies in the Universe. Comment: Accepted for publication in MNRAS Letters July 5, 2010: 5 pages, 3 figures
04/2010;
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[show abstract]
[hide abstract]
ABSTRACT: We present a quantitative morphological analysis using HST NICMOS H160- and ACS I775- band imaging of 25 spectroscopically confirmed submillimetre galaxies (SMGs) which have redshifts between z=0.7-3.4. Our analysis also employs a comparison sample of more typical star-forming galaxies at similar redshifts (such as LBGs) which have lower far-infrared luminosities. This is the first large-scale study of the morphologies of SMGs in the near-infrared at ~0.1" resolution (<1kpc). We find that the half light radii of the SMGs (r_h=2.3+/-0.3 and 2.8+/-0.4kpc in the observed I- and H-bands respectively) and asymmetries are not statistically distinct from the comparison sample of star-forming galaxies. However, we demonstrate that the SMG morphologies differ more between the rest-frame UV and optical-bands than typical star-forming galaxies and interpret this as evidence for structured dust obscuration. We show that the composite observed H-band light profile of SMGs is better fit with a Sersic index with n~2, suggesting the stellar structure of SMGs is best described by a spheroid/elliptical galaxy light distribution. We also compare the sizes and stellar masses of SMGs to local and high-redshift populations, and find that the SMGs have stellar densities which are comparable to local early-type galaxies, as well as luminous, red and dense galaxies at z~1.5 which have been proposed as direct SMG descendants, although the SMG stellar masses and sizes are systematically larger. Overall, our results suggest that the physical processes occuring within the galaxies are too complex to be simply characterised by the rest-frame UV/optical morphologies which appear to be essentially decoupled from all other observables, such as bolometric luminosity, stellar or dynamical mass. Comment: Accepted for publication in MNRAS. 12 pages, 8 figs. High resolution version available at: http://astro.dur.ac.uk/~ams/papers/smg_morph.pdf
02/2010;
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Nicolas F. Martin,
Alan W. McConnachie,
Mike Irwin,
Lawrence M. Widrow,
Annette M. N. Ferguson,
Rodrigo A. Ibata,
John Dubinski,
Arif Babul, Scott Chapman,
Mark Fardal,
Geraint F. Lewis,
Julio Navarro,
and R. Michael Rich
[show abstract]
[hide abstract]
ABSTRACT: We present the discovery of two new dwarf galaxies, Andromeda XXI and Andromeda XXII, located in the surroundings of the Andromeda and Triangulum galaxies (M31 and M33). These discoveries stem from the first year data of the Pan-Andromeda Archaeological Survey, a photometric survey of the M31/M33 group conducted with the Megaprime/MegaCam Wide-Field Camera mounted on the Canada-France-Hawaii Telescope. Both satellites appear as spatial overdensities of stars which, when plotted in a color-magnitude diagram, follow metal-poor, [Fe/H] = –1.8, red giant branches at the distance of M31/M33. Andromeda XXI is a moderately bright dwarf galaxy (MV = –9.9 ± 0.6), albeit with low surface brightness, emphasizing again that many relatively luminous M31 satellites still remain to be discovered. It is also a large satellite, with a half-light radius close to 1 kpc, making it the fourth largest Local Group dwarf spheroidal galaxy after the recently discovered Andromeda XIX, Andromeda II, and Sagittarius around the Milky Way, and supports the trend that M31 satellites are larger than their Milky Way counterparts. Andromeda XXII is much fainter (MV = –6.5 ± 0.8) and lies a lot closer in projection to M33 than it does to M31 (42 versus 224 kpc), suggesting that it could be the first Triangulum satellite to be discovered. Although this is a very exciting possibility in the context of a past interaction of M33 with M31 and the fate of its satellite system, a confirmation will have to await a good distance estimate to confirm its physical proximity to M33. Along with the dwarf galaxies found in previous surveys of the M31 surroundings, these two new satellites bring the number of dwarf spheroidal galaxies in this region to 20.
The Astrophysical Journal 10/2009; 705(1):758. · 6.02 Impact Factor
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Kristen Coppin,
Ian Smail,
David M. Alexander,
Axel Weiss,
Fabian Walter,
Mark Swinbank,
Thomas Greve,
Attila Kovacs,
Carlos De Breuck,
Mark Dickinson, [......],
Minh Huynh,
Kirsten Knudsen,
Anton Koekemoer,
Bret Lehmer,
Karl Menten,
Casey Papovich,
Hans-Walter Rix,
Eva Schinnerer,
Julie Wardlow,
Paul van der Werf
[show abstract]
[hide abstract]
ABSTRACT: We report on the identification of the highest redshift submm-selected source currently known: LESSJ033229.4-275619. This source was detected in the Large Apex BOlometer CAmera (LABOCA) Extended Chandra Deep Field South (ECDFS) Submillimetre Survey (LESS), a sensitive 870-um survey (~1.2-mJy rms) of the full 30'x30' ECDFS with the LABOCA camera on the Atacama Pathfinder EXperiment (APEX) telescope. The submm emission is identified with a radio counterpart for which optical spectroscopy provides a redshift of z=4.76. We show that the bolometric emission is dominated by a starburst with a star formation rate of ~1000 Msun/yr, although we also identify a moderate luminosity Active Galactic Nucleus (AGN) in this galaxy. Thus it has characteristics similar to those of z~2 submm galaxies (SMGs), with a mix of starburst and obscured AGN signatures. This demonstrates that ultraluminous starburst activity is not just restricted to the hosts of the most luminous (and hence rare) QSOs at z~5, but was also occurring in less extreme galaxies at a time when the Universe was less than 10% of its current age. Assuming that we are seeing the major phase of star formation in this galaxy, then we demonstrate that it would be identified as a luminous distant red galaxy at z~3 and that the current estimate of the space density of z>4 SMGs is only sufficient to produce ~10% of the luminous red galaxy population at these early times. However, this leaves open the possibility that some of these galaxies formed through less intense, but more extended star formation events. If the progenitors of all of the luminous red galaxies at z~3 go through an ultraluminous starburst at z>4 then the required volume density of z>4 SMGs will exceed that predicted by current galaxy formation models by more than an order of magnitude. Comment: 10 pages, 4 figures, 1 table, Accepted for publication in MNRAS Feb 23
02/2009;
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Mark Swinbank,
Cedric Lacey,
Ian Smail,
Carlton Baugh,
Carlos Frenk,
Andrew Blain, Scott Chapman,
Kristen Coppin,
Rob Ivison,
Laura Hainline,
Juan Gonzalez
[show abstract]
[hide abstract]
ABSTRACT: We use the combined GALFORM semi-analytical model of galaxy formation and GRASIL spectrophotometric code to investigate the properties of galaxies selected via their sub-mm emission. Our fiducial model has previously been shown to fit the properties of local ULIRGs, as well as the number counts of faint sub-mm galaxies. Here, we test the model in detail by comparing the SEDs and stellar, dynamical, gas and halo masses of sub-mm galaxies against observational data. We precisely mimic the sub-mm and radio selection function of the observations and show that the predicted far-infrared properties of model galaxies with S_850>5mJy and S_1.4>30uJy are in good agreement with observations. Although the dust emission model does not assume a single dust temperature, the far-infrared SEDs are well described by single component modified black-body spectrum with characteristic temperature 32+/-5K. We also find evidence that the observations may have uncovered evolution in the far-infrared--radio relation in ULIRGs out to z~2. We show that the predicted redshift distribution of sub-mm galaxies provides a reasonable fit to the observational data with a median redshift z=2.0, with the radio-selected subset predicted to make up approximately 75% of the population. However, the predicted K-band and mid-infrared (3--8um) flux densities of the sub-mm galaxies (and LBGs) are up to a factor 10x fainter than observed. This discrepancy may indicate that the stellar masses of the sub-mm galaxies in the model are too low: M~10^10Mo, while observations suggest more massive systems, M~10^11Mo. Finally, we discuss the potential modifications to the models which may improve the fit to the observational data. [Abridged]
10/2008;
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Kristen Coppin,
Mark Halpern,
Douglas Scott,
Colin Borys,
James Dunlop,
Loretta Dunne,
Rob Ivison,
Jeff Wagg,
Itziar Aretxaga,
Elia Battistelli, [......],
Tim Jenness,
Eelco Van Kampen,
Cedric Lacey,
Angela Mortier,
Alexandra Pope,
Robert Priddey,
Stephen Serjeant,
Ian Smail,
Jason Stevens,
Mattia Vaccari
[show abstract]
[hide abstract]
ABSTRACT: ABSTRACTA follow-up survey using the Submillimetre High-Angular Resolution Camera (SHARC-II) at 350 μm has been carried out to map the regions around several 850-μm-selected sources from the Submillimetre HAlf Degree Extragalactic Survey (SHADES). These observations probe the infrared (IR) luminosities and hence star formation rates in the largest existing, most robust sample of submillimetre galaxies (SMGs). We measure 350-μm flux densities for 24 850-μm sources, seven of which are detected at ≥2.5σ within a 10 arcsec search radius of the 850-μm positions. When results from the literature are included the total number of 350-μm flux density constraints of SHADES SMGs is 31, with 15 detections. We fit a modified blackbody to the far-IR (FIR) photometry of each SMG, and confirm that typical SMGs are dust-rich (Mdust≃ 9 × 108 M⊙), luminous (LFIR≃ 2 × 1012 L⊙) star-forming galaxies with intrinsic dust temperatures of ≃35 K and star formation rates of ≃400 M⊙ yr−1. We have measured the temperature distribution of SMGs and find that the underlying distribution is slightly broader than implied by the error bars, and that most SMGs are at 28 K with a few hotter. We also place new constraints on the 350-μm source counts, N350(>25 mJy) ∼ 200–500 deg−2.
Monthly Notices of the Royal Astronomical Society 03/2008; 384(4):1597 - 1610. · 4.90 Impact Factor
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Kristen Coppin,
Mark Halpern,
Douglas Scott,
Colin Borys,
James Dunlop,
Loretta Dunne,
Rob Ivison,
Jeff Wagg,
Itziar Aretxaga,
Elia Battistelli, [......],
Tim Jenness,
Eelco van Kampen,
Cedric Lacey,
Angela Mortier,
Alexandra Pope,
Robert Priddey,
Stephen Serjeant,
Ian Smail,
Jason Stevens,
Mattia Vaccari
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ABSTRACT: A follow-up survey using the Submillimetre High-Angular Resolution Camera (SHARC-II) at 350 microns has been carried out to map the regions around several 850 micron-selected sources from the Submillimetre HAlf Degree Extragalactic Survey (SHADES). These observations probe the infrared luminosities and hence star-formation rates in the largest existing, most robust sample of submillimetre galaxies (SMGs). We measure 350 micron flux densities for 24 850 micron sources, seven of which are detected at >2.5-sigma within a 10 arcsec search radius of the 850 micron positions. When results from the literature are included the total number of 350 micron flux density constraints of SHADES SMGs is 31, with 15 detections. We fit a modified blackbody to the far-infrared (FIR) photometry of each SMG, and confirm that typical SMGs are dust-rich (Mdust~9x10^8 Msun), luminous (Lfir~2x10^12 Lsun), star-forming galaxies with intrinsic dust temperatures of ~35 K and star-formation rates of ~400 Msun/yr. We have measured the temperature distribution of SMGs and find that the underlying distribution is slightly broader than implied by the error bars, and that most SMGs are at 28 K with a few hotter. We also place new constraints on the 350 micron source counts, N350(>25mJy)~200-500 deg^-2. Comment: Accepted for publication in MNRAS Dec 04 2007: 15 pages; 8 figures. Details: correction of typo in 2 source coordinates in Table 2, minor wording changes, added reference, minor change to Fig. 6
11/2007;
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Itziar Aretxaga,
David H. Hughes,
Kristen Coppin,
Angela M. J. Mortier,
Jeff Wagg,
James S. Dunlop,
Edward L. Chapin,
Stephen A. Eales,
Enrique Gaztañaga,
Mark Halpern, [......],
Duncan Farrah,
Matt J. Jarvis,
Robert G. Mann,
Alexandra Pope,
Robert Priddey,
Steve Rawlings,
Marc Seigar,
Laura Silva,
Chris Simpson,
Mattia Vaccari
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ABSTRACT: We present the redshift distribution of the Submillimetre Common-User Bolometer Array (SCUBA) Half Degree Survey (SHADES) galaxy population based on the rest-frame radio–mm–far-infrared (FIR) colours of 120 robustly detected 850 μm sources in the Lockman Hole East (LH) and Subaru XMM–Newton Deep Field (SXDF). The redshift distribution derived from the full spectral energy distribution (SED) information is shown to be narrower than that determined from the radio–sub-mm spectral index, as more photometric bands contribute to a higher redshift accuracy. The redshift distribution of sources derived from at least two photometric bands peaks at z≈ 2.4 and has a near-Gaussian distribution, with 50 per cent (interquartile range) of sources at z= 1.8–3.1. We find a statistically significant difference between the measured redshift distributions in the two fields; the SXDF peaking at a slightly lower redshift (median z≈ 2.2) than the LH (median z≈ 2.7), which we attribute to the noise properties of the radio observations. We demonstrate, however, that there could also be field-to-field variations that are consistent with the measured differences in the redshift distributions and, hence, that the incomplete area observed by SHADES with SCUBA, despite being the largest sub-mm survey to date, may still be too small to fully characterize the bright sub-mm galaxy population. Finally, we present a brief comparison with the predicted, or assumed, redshift distributions of sub-mm galaxy formation and evolution models, and we derive the contribution of these SHADES sources and the general sub-mm galaxy population to the star formation rate density at different epochs.
Monthly Notices of the Royal Astronomical Society 08/2007; 379(4):1571 - 1588. · 4.90 Impact Factor
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ABSTRACT: We present two-dimensional spectroscopy covering the rest-frame wavelengths of strong optical emission lines in six luminous submillimetre galaxies at z=1.3--2.5. Together with HST ACS and NICMOS imaging we map the dynamics and morphologies of these systems on scales from 4--11kpc. Four of the systems show multiple components in their spatially-resolved spectra with average velocity offsets of ~180km/s across 8kpc in projection. From the ensemble properties from our survey and the literature, we estimate the typical dynamical masses of bright sub-mm galaxies as (5+/-3) x10^{11}Mo. This is similar to recent estimates of their stellar masses -- suggesting that the dynamics of the central regions of these galaxies are baryon dominated, with a substantial fraction of those baryons in stars by the epoch of observation. Combining our dynamical mass estimates with stellar luminosities for this population we investigate whether submillimetre galaxies can evolve onto the Faber-Jackson relation for local ellipticals. Adopting a typical lifetime of tau_{burst}~300Myr for the submillimetre-luminous phase we find that the stellar populations of sub-mm galaxies should fade to place them on the Faber-Jackson relation, at M_K ~ -25.1. Furthermore, using the same starburst lifetime we correct the observed space density of submillimetre galaxies for the duty cycle to derive a volume density of the progenitors of ~1x10^{-4} Mpc^{-3}. This is consistent with the space density of local luminous early-type galaxies with M_K ~ -25.1, indicating that submillimetre galaxies can evolve onto the scaling relations observed for local early-type galaxies, and the observed population at z~2 is then sufficient to account for the formation of the whole population of >~3 L^{*} ellipticals seen at z~0.
07/2006;
