2,242 research outputs found
An Intensive, Large-Scale Batch Culture System to Produce the Calanoid Copepod, \u3ci\u3eAcartia tonsa\u3c/i\u3e: Appendix A
Spitzer Observations of Low Luminosity Isolated and Low Surface Brightness Galaxies
We examine the infrared properties of five low surface brightness galaxies
(LSBGs) and compare them with related but higher surface brightness galaxies,
using Spitzer Space Telescope images and spectra. All the LSBGs are detected in
the 3.6 and 4.5um bands, representing the stellar population. All but one are
detected at 5.8 and 8.0um, revealing emission from hot dust and aromatic
molecules, though many are faint or point-like at these wavelengths. Detections
of LSBGs at the far-infrared wavelengths, 24, 70, and 160um, are varied in
morphology and brightness, with only two detections at 160um, resulting in
highly varied spectral energy distributions. Consistent with previous
expectations for these galaxies, we find that detectable dust components exist
for only some LSBGs, with the strength of dust emission dependent on the
existence of bright star forming regions. However, the far-infrared emission
may be relatively weak compared with normal star-forming galaxies.Comment: 20 pages, 8 figures, accepted to Ap
IR observations of MS 1054-03: Star Formation and its Evolution in Rich Galaxy Clusters
We study the infrared (IR) properties of galaxies in the cluster MS 1054-03
at z=0.83 by combining MIPS 24 micron data with spectra of more than 400
galaxies and a very deep K-band selected catalog. 19 IR cluster members are
selected spectroscopically, and an additional 15 are selected by their
photometric redshifts. We derive the IR luminosity function of the cluster and
find strong evolution compared to the similar-mass Coma cluster. The best
fitting Schechter function gives L*_{IR}=11.49 +0.30/-0.29 L_sun with a fixed
faint end slope, about one order of magnitude larger than that in Coma. The
rate of evolution of the IR luminosity from Coma to MS 1054-03 is consistent
with that found in field galaxies, and it suggests that some internal
mechanism, e.g., the consumption of the gas fuel, is responsible for the
general decline of the cosmic star formation rate (SFR) in different
environments. The mass-normalized integrated SFR within 0.5R_200 in MS 1054-03
also shows evolution compared with other rich clusters at lower redshifts, but
the trend is less conclusive if the mass selection effect is considered. A
nonnegligible fraction (13%) of cluster members, are forming stars actively and
the overdensity of IR galaxies is about 20 compared to the field. It is
unlikely that clusters only passively accrete star forming galaxies from the
surrounding fields and have their star formation quenched quickly afterward;
instead, many cluster galaxies still have large amounts of gas, and their star
formation may be enhanced by the interaction with the cluster.Comment: 49 pages, 9 figures, accepted by Ap
Detecting new physics contributions to the D0-D0bar mixing through their effects on B decays
New physics effects may yield a detectable mass difference in the D0-D0bar
system, Delta m_D. Here we show that this has an important impact on some B -->
D decays. The effect involves a new source of CP violation, which arises from
the interference between the phases in the B --> D decays and those in the
D0-D0bar system. This interference is naturally large. New physics may well
manifest itself through Delta m_D contributions to these B decays.Comment: 10 pages, Revtex, no figures. To appear in PR
Impact of D0-D0bar mixing on the experimental determination of gamma
Several methods have been devised to measure the weak phase gamma using
decays of the type B+- --> D K+-, where it is assumed that there is no mixing
in the D0-D0bar system. However, when using these methods to uncover new
physics, one must entertain the real possibility that the measurements are
affected by new physics effects in the D0-D0bar system. We show that even
values of x_D and/or y_D around 10^{-2} can have a significant impact in the
measurement of sin^2{gamma}. We discuss the errors incurred in neglecting this
effect, how the effect can be checked, and how to include it in the analysis.Comment: 18 pages, Latex with epsfig, 8 figure
Measurements of Lifetimes and a Limit on the Lifetime Difference in the Neutral D-Meson System
Using the large hadroproduced charm sample collected in experiment E791 at
Fermilab, we report the first directly measured constraint on the decay-width
difference Delta Gamma for the mass eigenstates of the D0-D0bar system. We
obtain our result from lifetime measurements of the decays D0 --> K-pi+ and D0
--> K-K+, under the assumption of CP invariance, which implies that the CP
eigenstates and the mass eigenstates are the same. The lifetime of D0 --> K-K+
(the CP-even final state is \tau_KK = 0.410 +/- 0.011 +/- 0.006 ps, and the
lifetime of D0 --> K-pi+ (an equal mixture of CP-odd and CP-even final states
is tau_Kpi = 0.413 +/- 0.003 +/- 0.004 ps. The decay-width difference is Delta
Gamma = 2(Gamma_KK - Gamma_Kpi) = 0.04 +/- 0.14 +/- 0.05 ps^-1. We relate these
measurements to measurements of mixing in the neutral D-meson system.Comment: 8 pages + 3 figures + 2 table
Spitzer view on the evolution of star-forming galaxies from z=0 to z~3
We use a 24 micron selected sample containing more than 8,000 sources to
study the evolution of star-forming galaxies in the redshift range from z=0 to
z~3. We obtain photometric redshifts for most of the sources in our survey
using a method based on empirically-built templates spanning from ultraviolet
to mid-infrared wavelengths. The accuracy of these redshifts is better than 10%
for 80% of the sample. The derived redshift distribution of the sources
detected by our survey peaks at around z=0.6-1.0 (the location of the peak
being affected by cosmic variance), and decays monotonically from z~1 to z~3.
We have fitted infrared luminosity functions in several redshift bins in the
range 0<z<~3. Our results constrain the density and/or luminosity evolution of
infrared-bright star-forming galaxies. The typical infrared luminosity (L*)
decreases by an order of magnitude from z~2 to the present. The cosmic star
formation rate (SFR) density goes as (1+z)^{4.0\pm0.2} from z=0 to z=0.8. From
z=0.8 to z~1.2, the SFR density continues rising with a smaller slope. At
1.2<z<3, the cosmic SFR density remains roughly constant. The SFR density is
dominated at low redshift (z<0.5) by galaxies which are not very luminous in
the infrared (L_TIR<1.e11 L_sun, where L_TIR is the total infrared luminosity,
integrated from 8 to 1000 micron). The contribution from luminous and
ultraluminous infrared galaxies (L_TIR>1.e11 L_sun) to the total SFR density
increases steadily from z~0 up to z~2.5, forming at least half of the
newly-born stars by z~1.5. Ultraluminous infrared galaxies (L_TIR>1.e12 L_sun)
play a rapidly increasing role for z>~1.3.Comment: 28 pages, 17 figures, accepted for publication in Ap
A Search for Dark Matter Annihilation with the Whipple 10m Telescope
We present observations of the dwarf galaxies Draco and Ursa Minor, the local
group galaxies M32 and M33, and the globular cluster M15 conducted with the
Whipple 10m gamma-ray telescope to search for the gamma-ray signature of
self-annihilating weakly interacting massive particles (WIMPs) which may
constitute astrophysical dark matter (DM). We review the motivations for
selecting these sources based on their unique astrophysical environments and
report the results of the data analysis which produced upper limits on excess
rate of gamma rays for each source. We consider models for the DM distribution
in each source based on the available observational constraints and discuss
possible scenarios for the enhancement of the gamma-ray luminosity. Limits on
the thermally averaged product of the total self-annihilation cross section and
velocity of the WIMP, , are derived using conservative estimates for
the magnitude of the astrophysical contribution to the gamma-ray flux. Although
these limits do not constrain predictions from the currently favored
theoretical models of supersymmetry (SUSY), future observations with VERITAS
will probe a larger region of the WIMP parameter phase space, and
WIMP particle mass (m_\chi).Comment: 33 pages, 12 figures, accepted for publication in the Astrophysical
Journa
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