4,293 research outputs found
Extending the redshift distribution of submm galaxies: Identification of a z~4 submm galaxy
We present the identification of a bright submillimeter galaxy (SMG) in the
field of Abell 2218. The galaxy has a spectroscopic redshift of ~4, and is
currently the highest redshift SMG known. It is detected at all wavelengths
from optical to submm, including the Spitzer IRAC bands. We discuss the
properties of this galaxy, which is undergoing intense star formation at a
rate~600 Msun/yr. We also compare the properties to those of radio-preselected
submm-bright galaxies. The z~4 result extends the redshift distribution of
SMGs.Comment: 4 pages, 4 figures, uses asp2004.sty. To appear in the proceedings of
the conference "Infrared Diagnostics of Galaxy Evolution", Pasadena, CA,
14-16 November 2005, ed. R. Char
Physical properties and morphology of a newly identified compact z=4.04 lensed submillimeter galaxy in Abell 2218
We present the identification of a bright submm source, SMMJ163555.5+661300,
detected in the lensing cluster Abell2218, for which we have accurately
determined the position using observations from the Submillimeter Array (SMA).
The identified optical counterpart has a spectroscopic redshift of
z=4.044+-0.001 if we attribute the single emission line detected at
lambda=6140AA to Lyman-alpha. This redshift identification is in good agreement
with the optical/near-infrared photometric redshift as well as the submm flux
ratio S_450/S_850~1.6, the radio-submm flux ratio S_1.4/S_850 < 0.004, and the
24um to 850um flux ratio S_24/S_850 < 0.005. Correcting for the gravitational
lensing amplification of ~5.5, we find that the source has a far-infrared
luminosity of 1.3x10^12 Lsun, which implies a star formation rate of 230
Msun/yr. This makes it the lowest-luminosity SMG known at z>4 to date. Previous
CO(4-3) emission line obserations yielded a non-detection, for which we derived
an upper limit of the CO line luminosity of L'_CO = 0.3x10^10 K km/s/pc^2,
which is not inconsistent with the L'_CO - L_FIR relation for starburst
galaxies. The best fit model to the optical and near-infrared photometry give a
stellar population with an age of 1.4 Gyr and a stellar mass of 1.6x10^10 Msun.
The optical morphology is compact and in the source plane the galaxy has an
extent of ~6kpc x 3kpc with individual star forming knots of <500 pc in size.
J163556 is not resolved in the SMA data and we place a strict upper limit on
the size of the starburst region of 8kpc x 3kpc, which implies a lower limit on
the star formation rate surface density of 12 Msun/yr/kpc^2. The redshift of
J163556 extends the redshift distribution of faint, lensed SMGs, and we find no
evidence that these have a different redshift distribution than bright SMGs.Comment: Accepted for publication in ApJ. 11 pages, 7 figure
Extended modular operad
This paper is a sequel to [LoMa] where moduli spaces of painted stable curves
were introduced and studied. We define the extended modular operad of genus
zero, algebras over this operad, and study the formal differential geometric
structures related to these algebras: pencils of flat connections and Frobenius
manifolds without metric. We focus here on the combinatorial aspects of the
picture. Algebraic geometric aspects are treated in [Ma2].Comment: 38 pp., amstex file, no figures. This version contains additional
references and minor change
A direct D-bar reconstruction algorithm for recovering a complex conductivity in 2-D
A direct reconstruction algorithm for complex conductivities in
, where is a bounded, simply connected Lipschitz
domain in , is presented. The framework is based on the
uniqueness proof by Francini [Inverse Problems 20 2000], but equations relating
the Dirichlet-to-Neumann to the scattering transform and the exponentially
growing solutions are not present in that work, and are derived here. The
algorithm constitutes the first D-bar method for the reconstruction of
conductivities and permittivities in two dimensions. Reconstructions of
numerically simulated chest phantoms with discontinuities at the organ
boundaries are included.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in [insert name of journal]. IOP Publishing Ltd is
not responsible for any errors or omissions in this version of the manuscript
or any version derived from it. The Version of Record is available online at
10.1088/0266-5611/28/9/09500
- …