43 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
Witnessing the Birth of the Red Sequence: ALMA High-resolution Imaging of [C II] and Dust in Two Interacting Ultra-red Starbursts at z = 4.425
Exploiting the sensitivity and spatial resolution of the Atacama Large Millimeter/submillimeter Array, we have studied the morphology and the physical scale of the interstellar medium—both gas and dust—in SGP 38326, an unlensed pair of interacting starbursts at z = 4.425. SGP 38326 is the most luminous star bursting system known at z > 4, with a total IR luminosity of L IR ~ 2.5 × 1013 L ⊙ and a star formation rate of ~ 4500 M ⊙ yr−1. SGP 38326 also contains a molecular gas reservoir among the most massive yet found in the early universe, and it is the likely progenitor of a massive, red-and-dead elliptical galaxy at z ~ 3. Probing scales of ~0farcs1 or ~800 pc we find that the smooth distribution of the continuum emission from cool dust grains contrasts with the more irregular morphology of the gas, as traced by the [C ii] fine structure emission. The gas is also extended over larger physical scales than the dust. The velocity information provided by the resolved [C ii] emission reveals that the dynamics of the two interacting components of SGP 38326 are each compatible with disk-like, ordered rotation, but also reveals an ISM which is turbulent and unstable. Our observations support a scenario where at least a subset of the most distant extreme starbursts are highly dissipative mergers of gas-rich galaxies
Observations of the High Redshift Universe
(Abridged) In these lectures aimed for non-specialists, I review progress in
understanding how galaxies form and evolve. Both the star formation history and
assembly of stellar mass can be empirically traced from redshifts z~6 to the
present, but how the various distant populations inter-relate and how stellar
assembly is regulated by feedback and environmental processes remains unclear.
I also discuss how these studies are being extended to locate and characterize
the earlier sources beyond z~6. Did early star-forming galaxies contribute
significantly to the reionization process and over what period did this occur?
Neither theory nor observations are well-developed in this frontier topic but
the first results presented here provide important guidance on how we will use
more powerful future facilities.Comment: To appear in `First Light in Universe', Saas-Fee Advanced Course 36,
Swiss Soc. Astrophys. Astron. in press. 115 pages, 64 figures (see
http://www.astro.caltech.edu/~rse/saas-fee.pdf for hi-res figs.) For lecture
ppt files see
http://obswww.unige.ch/saas-fee/preannouncement/course_pres/overview_f.htm
Clarifying the nature of the brightest submillimetre sources: interferometric imaging of LH850.02
We present high-resolution interferometric imaging of LH850.02, the brightest
850- and 1200-micron submillimetre (submm) galaxy in the Lockman Hole. Our
observations were made at 890 micron with the Submillimetre Array (SMA). Our
high-resolution submm imaging detects LH850.02 at >6-sigma as a single compact
(size < 1 arcsec or < 8 kpc) point source and yields its absolute position to
~0.2-arcsec accuracy. LH850.02 has two alternative radio counterparts within
the SCUBA beam (LH850.02N & S), both of which are statistically very unlikely
to be so close to the SCUBA source position by chance. However, the precise
astrometry from the SMA shows that the submm emission arises entirely from
LH850.02N, and is not associated with LH850.02S (by far the brighter of the two
alternative identifications at 24-micron). Fits to the optical-infrared
multi-colour photometry of LH850.02N & S indicate that both lie at z~3.3, and
are therefore likely to be physically associated. At these redshifts, the 24
micron--to--submm flux density ratios suggest that LH850.02N has an Arp220-type
starburst-dominated far-IR SED, while LH850.02S is more similar to Mrk231, with
less dust-enshrouded star-formation activity, but a significant contribution at
24-micron (rest-frame ~5-6 micron) from an active nucleus. This complex mix of
star-formation and AGN activity in multi-component sources may be common in the
high redshift ultraluminous galaxy population, and highlights the need for
precise astrometry from high resolution interferometric imaging for a more
complete understanding.Comment: MNRAS, in pres
The SCUBA HAlf Degree Extragalactic Survey (SHADES) - V. Submillimetre properties of near-infrared-selected galaxies in the Subaru/XMM -Newton deep field
We have studied the submillimetre ( submm) properties of the following classes of near- infraredselected ( NIR- selected) massive galaxies at high redshifts: BzK- selected star- forming galaxies ( BzKs); distant red galaxies ( DRGs); and extremely red objects ( EROs). We used the SCUBA HAlf Degree Extragalactic Survey ( SHADES), the largest uniform submm survey to date. Partial overlap of SIRIUS/ NIR images and SHADES in Subaru/ XMM - Newton deep field has allowed us to identify four submm- bright NIR- selected galaxies, which are detected in the mid- IR, 24 m, and the radio, 1.4 GHz. We find that all of our submm- bright NIR- selected galaxies satisfy the BzK selection criteria, i. e. BzK = ( z - K) AB - ( B - z) AB >= - 0.2, except for one galaxy whose B - z and z - K colours are however close to the BzK colour boundary. Two of the submm- bright NIR- selected galaxies satisfy all of the selection criteria we considered, i. e. they belong to the BzK - DRG - ERO overlapping population, or ` extremely red' BzKs. Although these extremely red BzKs are rare ( 0.25 arcmin(-2)), up to 20 per cent of this population could be submm galaxies. This fraction is significantly higher than that found for other galaxy populations studied here. Via a stacking analysis, we have detected the 850- mu m flux of submm- faint BzKs and EROs in our SCUBAmaps. While the contribution of z similar to 2 BzKs to the submm background is about 10 - 15 per cent and similar to that from EROs typically at z similar to 1, BzKs have a higher fraction (similar to 30 per cent) of submm flux in resolved sources compared with EROs and submm sources as a whole. From the spectral energy distribution ( SED) fitting analysis for both submm- bright and submm- faint BzKs, we found no clear signature that submm- bright BzKs are experiencing a specifically luminous evolutionary phase, compared with submm- faint BzKs. An alternative explanation might be that submm- bright BzKs are more massive than submm- faint ones
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Reflections on designing a Biology/Humanities interdisciplinary module
This paper uses the reflections of a recent workshop on biology and the humanities subject
areas to consider the potential for designing a first year interdisciplinary module that brings
together teachers and learners in the Biosciences with their counterparts in English and
History. It considers three building blocks of module design: aims and objectives; teaching
and learning strategies; and assessment; and provides a commentary on the discussion of
interdisciplinarity in the broader literature. The authors argue that interdisciplinary teaching
and learning must be transformative, but not in the way many previous advocates of
interdisciplinarity have assumed. Rather than transcending disciplines, the authors contend
that the aim should be to enhance disciplinary understanding. Learners should emerge
from the interdisciplinary module not having lost their identity as biologists, but having
enhanced it. They should have become ‘better’ biologists in the sense of having developed
a broader, critical understanding of the precepts of their discipline, as a first step to an
understanding of biology inflected with a literary and historical awareness