26 research outputs found
Gravitational Lensing at Millimeter Wavelengths
With today's millimeter and submillimeter instruments observers use
gravitational lensing mostly as a tool to boost the sensitivity when observing
distant objects. This is evident through the dominance of gravitationally
lensed objects among those detected in CO rotational lines at z>1. It is also
evident in the use of lensing magnification by galaxy clusters in order to
reach faint submm/mm continuum sources. There are, however, a few cases where
millimeter lines have been directly involved in understanding lensing
configurations. Future mm/submm instruments, such as the ALMA interferometer,
will have both the sensitivity and the angular resolution to allow detailed
observations of gravitational lenses. The almost constant sensitivity to dust
emission over the redshift range z=1-10 means that the likelihood for strong
lensing of dust continuum sources is much higher than for optically selected
sources. A large number of new strong lenses are therefore likely to be
discovered with ALMA, allowing a direct assessment of cosmological parameters
through lens statistics. Combined with an angular resolution <0.1", ALMA will
also be efficient for probing the gravitational potential of galaxy clusters,
where we will be able to study both the sources and the lenses themselves, free
of obscuration and extinction corrections, derive rotation curves for the
lenses, their orientation and, thus, greatly constrain lens models.Comment: 69 pages, Review on quasar lensing. Part of a LNP Topical Volume on
"Dark matter and gravitational lensing", eds. F. Courbin, D. Minniti. To be
published by Springer-Verlag 2002. Paper with full resolution figures can be
found at ftp://oden.oso.chalmers.se/pub/tommy/mmviews.ps.g
The Great Observatories All-Sky LIRG survey: herschel image atlas and aperture photometry
Far-infrared images and photometry are presented for 201 Luminous and Ultraluminous Infrared Galaxies [LIRGs: log ({L}_{\mathrm{IR}}/{L}_{\odot })=11.00\mbox{--}11.99, ULIRGs: log ({L}_{\mathrm{IR}}/{L}_{\odot })=12.00\mbox{--}12.99], in the Great Observatories All-Sky LIRG Survey (GOALS), based on observations with the Herschel Space Observatory Photodetector Array Camera and Spectrometer (PACS) and the Spectral and Photometric Imaging Receiver (SPIRE) instruments. The image atlas displays each GOALS target in the three PACS bands (70, 100, and 160 μm) and the three SPIRE bands (250, 350, and 500 μm), optimized to reveal structures at both high and low surface brightness levels, with images scaled to simplify comparison of structures in the same physical areas of ~100 × 100 kpc2. Flux densities of companion galaxies in merging systems are provided where possible, depending on their angular separation and the spatial resolution in each passband, along with integrated system fluxes (sum of components). This data set constitutes the imaging and photometric component of the GOALS Herschel OT1 observing program, and is complementary to atlases presented for the Hubble Space Telescope, Spitzer Space Telescope, and Chandra X-ray Observatory. Collectively, these data will enable a wide range of detailed studies of active galactic nucleus and starburst activity within the most luminous infrared galaxies in the local universe
Resolving molecular gas in the central galaxies of cooling flow clusters
We present aperture synthesis images of the CO (1-0) line emission in five central galaxies in cooling flow clusters using the Owens Valley Millimeter Array. Three of the five sources are significantly resolved, but the majority of the emission is from a compact (1022 cm-2) column density. We review the implications of these results and the prospects for observations in the near future
Gigamasers: the key to the dust-obscured star formation history of the Universe?
We discuss the possibility of using OH and H2O gigamasers to trace the
redshift distribution of luminous, dust-obscured, star-forming galaxies. It has
long been thought that ultraluminous, interacting galaxies should host
gigamasers due to their vast pumping IR luminosity, the large column density of
molecules available to populate the maser states and the turbulent motion of
the gas in these dynamically complex systems which allows unsaturated maser
emission. OH masers may thus be well-suited to the redshift-blind detection of
ultraluminous and hyperluminous infrared galaxies (L_FIR >= 10^12 L_sun) such
as those uncovered by the SCUBA submillimetre camera. The bandwidth requirement
is low, <1 GHz for z=1-10 (lower still if additional redshift constraints are
available) and the dual-line 1665-/1667-MHz OH spectral signature can act as a
check on the reality of detections.Comment: 4 pages, 1 figure, MNRAS Lette
Submillimeter Imaging of the Luminous Infrared Galaxy Pair VV 114
We report on 450- and 850-micron observations of the interacting galaxy pair,
VV114E+W (IC1623), taken with the SCUBA camera on the James Clerk Maxwell
Telescope, and near-infrared observations taken with UFTI on the UK Infrared
Telescope. The system VV114 is in an early stage of a gas-rich merger. We
detect submillimeter (sub-mm) emission extended over 30 arcsec (12 kpc) and
find a good correlation between the spatial distribution of the sub-mm and CO
emission. Both the CO and sub-mm emission peak near the reddest region of
VV114E and extend toward VV114W. The bulk of the sub-mm emission resides in the
central region showing the largest CO velocity gradients, which is thought to
mark the kinematic centroid of the merger remnant. We derived a total dust mass
of 1.2x10^{8} M_sun, assuming a power-law distribution of dust temperatures.
The sub-mm observations suggest that the majority of the dust is relatively
cool (T_d ~20--25 K), and the total dust mass is about 4 times higher than that
inferred from the IRAS data alone. The system will likely evolve into a compact
starburst similar to Arp220.Comment: Accepted to AJ 22Mar99, 8 pages including 2 figures, fig1_color.ps is
a color version of Fig. 1 which will be published electronically by A
Near-Infrared Colors of Submillimeter-selected Galaxies
We report on deep near-infrared (NIR) observations of submillimeter-selected
galaxies (SMGs) with the Near Infrared Camera (NIRC) on the Keck I telescope.
We have identified K-band candidate counterparts for 12 out of 15 sources in
the SCUBA Cluster Lens Survey. Three SMGs remain non-detections with K-band
limits of K>23 mag, corrected for lensing. Compensating for lensing we find a
median magnitude of K=22+/-1 mag for the SMG population, but the range of NIR
flux densities spans more than a factor of 400. For SMGs with confirmed
counterparts based on accurate positions from radio, CO, and/or millimeter
continuum interferometric observations, the median NIR color is J-K=2.6+/-0.6
mag. The NIR-bright SMGs (K<19 mag) have colors of J-K =~ 2 mag, while the
faint SMGs tend to be extremely red in the NIR (J-K>3 mag). We argue that a
color selection criterion of J-K>~3 mag can be used to help identify
counterparts of SMGs that are undetected at optical and radio wavelengths. The
number density of sources with J-K>3 mag is 5 arcmin^{-2} at K<22.5 mag,
greater than that of SMGs with S(850um)>2 mJy. It is not clear if the excess
represents less luminous infrared-bright galaxies with S(850um)<~2 mJy, or if
the faint extremely red NIR galaxies represent a different population of
sources that could be spatially related to the SMGs.Comment: Accepted, Astronomical Journal (scheduled for Feb04), 11 pages
including 3 figures (fig1a, fig1b, fig2
Locating the Starburst in the SCUBA Galaxy SMM J14011+0252
We present new, multi-wavelength, high-resolution imaging of the luminous,
submillimeter galaxy, SMM J14011+0252, an interacting starburst at z = 2.56.
Our observations comprise optical imaging from the HST, sensitive radio mapping
from the VLA and CO observations from OVRO and BIMA. Aided by well-constrained
gravitational amplification, we use these new data to map the distribution of
gas and both obscured and unobscured starlight. The maps show that the gas and
star formation are extended on scales of >= 10 kpc, much larger than starbursts
seen in local ultraluminous galaxies, and larger than the rest-frame UV-bright
components of SMM J14011+0252, J1/J2. The most vigorous star formation is
marked by peaks in both the molecular gas and radio emission, ~1'' north of
J1/J2, in the vicinity of J1n, an apparent faint extension of J1. Using new
sub-0.5'' K-band imaging from UKIRT, we identify J1n as an extremely red object
(ERO). We suggest that while J1 and J2 are clearly associated with the submm
source, they are merely windows through the dust, or unobscured companions to a
large and otherwise opaque star-forming system. Hence, their rest-frame UV
properties are unlikely to be relevant for understanding the detailed internal
physics of the starburst.Comment: 4 pages (color and b/w figures); ApJ Letters, in pres
The Discovery of a New Massive Molecular Gas Component Associated with the Submillimeter Galaxy SMM J02399-0136
We present CO(1–0), CO(3–2), and CO(7–6) observations using the Green Bank Telescope (GBT) and the Atacama Large Millimeter Array (ALMA) of the z = 2.8 submillimeter galaxy SMM J02399−0136. This was the first submillimeter-selected galaxy discovered and remains an archetype of the class, comprising a merger of several massive and active components, including a quasar-luminosity AGN and a highly obscured, gas-rich starburst spread over a ~25 kpc extent. The GBT CO(1–0) line profile is comprised of two distinct velocity components separated by about 600 km s−1 and suggests the presence of a new component of molecular gas that had not been previously identified. The CO(3–2) observations with ALMA show that this new component, designated W1, is associated with a large extended structure stretching 13 kpc westward from the AGN. W1 is not detected in the ALMA CO(7–6) data, implying that this gas has much lower CO excitation than the central starburst regions, which are bright in CO(7–6). The molecular gas mass of W1 is about 30% of the total molecular gas mass in the system, depending on the CO-to-H2 conversion factor. W1 is arguably a merger remnant; alternatively, it could be a massive molecular outflow associated with the AGN, or perhaps inflowing metal-enriched molecular gas fueling the ongoing activity
A mid-infrared imaging survey of submillimeter-selected galaxies with the Spitzer space telescope
We present Spitzer-IRAC and MIPS mid-IR observations of a sample of 73 radio-detected submillimeter-selected galaxies (SMGs) with spectroscopic redshifts, the largest such sample published to date. From our data, we find that IRAC colors of SMGs are much more uniform as compared with rest-frame UV and optical colors, and z>1.5 SMGs tend to be redder in their mid-IR colors than both field galaxies and lower-z SMGs. However, the IRAC colors of the SMGs overlap those of field galaxies sufficiently that color-magnitude and color-color selection criteria suggested in the literature to identify SMG counterparts produce ambiguous counterparts within an 8'' radius in 20%-35% of cases. We use a rest-frame J-H versus H-K color-color diagram and a S 24/S 8.0 versus S 8.0/S 4.5 color-color diagram to determine that 13%-19% of our sample are likely to contain active galactic nuclei which dominate their mid-IR emission. We observe in the rest-frame JHK colors of our sample that the rest-frame near-IR emission of SMGs does not resemble that of the compact nuclear starburst observed in local ultraluminous IR galaxies and is consistent with more widely distributed star formation. We take advantage of the fact that many high-z galaxy populations selected at different wavelengths are detected by Spitzer to carry out a brief comparison of mid-IR properties of SMGs to UV-selected high-z galaxies, 24 μm-selected galaxies, and high-z radio galaxies, and find that SMGs have mid-IR fluxes and colors which are consistent with being more massive and more reddened than UV-selected galaxies, while the IRAC colors of SMGs are most similar to powerful high-z radio galaxies