1,058 research outputs found
A New Detection of Extragalactic Anomalous Microwave Emission in a Compact, Optically-Faint Region of NGC\,4725
We discuss the nature of a discrete, compact radio source (NGC 4725 B)
located 1.9 kpc from the nucleus in the nearby star-forming galaxy NGC
4725, which we believe to be a new detection of extragalactic Anomalous
Microwave Emission (AME). Based on detections at 3, 15, 22, 33, and 44 GHz, NGC
4725 B is a Jy radio source peaking at 33 GHz. While the source
is not identified in photometry, we detect counterparts in the
mid-infrared /IRAC bands (3.6, 4.5, 5.8, 8.0 m) that appear to be
associated with dust emission in the central region of NGC 4725. Consequently,
we conclude that NGC 4725 B is a new detection of AME, and very similar to a
recent detection of AME in an outer-disk star-forming region in NGC 6946. We
find that models of electric dipole emission from rapidly rotating ultra-small
grains are able to reproduce the radio spectrum for reasonable interstellar
medium conditions. Given the lack of an optical counterpart and the shape of
the radio spectrum, NGC 4725 B appears consistent with a nascent star-forming
region in which young ( Myr) massive stars are still highly
enshrouded by their natal cocoons of gas and dust with insufficient supernovae
occurring to produce a measurable amount of synchrotron emission.Comment: 10 pages, 4 figures, accepted for publication in Ap
Where's the Dust?: The Deepening Anomaly of Microwave Emission in NGC 4725 B
We present new Atacama Large Millimeter Array (ALMA) observations toward NGC 4725 B, a discrete, compact, optically faint region within the star-forming disk of the nearby galaxy NGC 4725 that exhibits strong anomalous microwave emission (AME). These new ALMA data include continuum observations centered at 92, 133, 203, and 221 GHz accompanied by spectral observations of the ¹²CO ( J = 2 → 1) line. NGC 4725 B is detected in the continuum at all frequencies, although the detection at 203 GHz is marginal. While molecular gas is not detected at the exact location of NGC 4725 B, there is molecular gas in the immediate vicinity (i.e., ≾100 pc) along with associated diffuse 8 μm emission. When combined with existing Very Large Array continuum data at 1.5, 3, 5.5, 9, 14, 22, 33, and 44 GHz, the spectrum is best fit by a combination of AME, synchrotron, and free–free emission that is free–free absorbed below ~6 GHz. Given the strength of the AME, there is surprisingly no indication of millimeter dust emission associated with NGC 4725 B on ≾6" spatial scales at the sensitivity of the ALMA interferometric data. Based on the properties of the nearest molecular gas complex and the inferred star formation rate, NGC 4725 B is consistent with being an extremely young (~3–5 Myr) massive (≾10⁵ M_⊙) cluster that is undergoing active cluster feedback. However, the lack of millimeter thermal dust emission is difficult to reconcile with a spinning dust origin of the 30 GHz emission. On the other hand, modeling NGC 4725 B as a new class of background radio galaxy is also unsatisfactory
Recent results from the canfranc dark matter search with germanium detectors
Two germanium detectors are currently operating in the Canfranc Underground
Laboratory at 2450 m.w.e looking for WIMP dark matter. One is a 2 kg 76Ge IGEX
detector (RG-2) which has an energy threshold of 4 keV and a low-energy
background rate of about 0.3 c/keV/kg/day. The other is a small (234 g) natural
abundance Ge detector (COSME), of low energy threshold (2.5 keV) and an energy
resolution of 0.4 keV at 10 keV which is looking for WIMPs and for solar
axions. The analysis of 73 kg-days of data taken by COSME in a search for solar
axions via their photon Primakoff conversion and Bragg scattering in the Ge
crystal yields a 95% C.L. limit for the axion-photon coupling g < 2.8 10^-9
GeV^-1. These data, analyzed for WIMP searches provide an exclusion plot for
WIMP-nucleon spin-independent interaction which improves previous plots in the
low mass region. On the other hand, the exclusion plot derived from the 60
kg-days of data from the RG-2 IGEX detector improves the exclusion limits
derived from other ionization (non thermal) germanium detector experiments in
the region of WIMP masses from 30 to 100 GeV recently singled out by the
reported DAMA annual modulation effect.Comment: 6 pages, talk given at IDM2000, York, September 200
Recommended from our members
Reaching Part Per Trillion Clean-Up Criteria for Mercury in Water
In the last couple of years, emphasis on environmental mercury contamination and elimination of mercury use has increased. The U.S. Department of Energy has for many decades maintained a stockpile of elemental mercury for operations and, as a consequence of its routine use, spills have occurred. These historical spills have resulted in some contamination of water streams and soils. In this work we examine a newly developed technique for removal of mercury from contaminated groundwater. In this application the mercury concentration was approximately 2.3 parts per billion and the treatment criterion was 200 parts per trillion. Several forms of mercury species contributed to the contamination. The treatment technique developed for this water was to convert all forms of mercury, through a series of fast chemical reactions, to elemental mercury, which was air-stripped from the water. This paper presents preliminary laboratory work on the method
Few smooth d-polytopes with n lattice points
We prove that, for fixed n there exist only finitely many embeddings of
Q-factorial toric varieties X into P^n that are induced by a complete linear
system. The proof is based on a combinatorial result that for fixed nonnegative
integers d and n, there are only finitely many smooth d-polytopes with n
lattice points. We also enumerate all smooth 3-polytopes with at most 12
lattice points. In fact, it is sufficient to bound the singularities and the
number of lattice points on edges to prove finiteness.Comment: 20+2 pages; major revision: new author, new structure, new result
The IGEX experiment revisited: a response to the critique of Klapdor-Kleingrothaus,Dietz, and Krivosheina
This paper is a response to the article "Critical View to" the IGEX
neutrinoless double-beta decay experiment..."published in Phys. Rev.D, Volume
65 (2002) 092007," by H.V.Klapdor-Kleingrothaus, A. Dietz, and I.V.Krivosheina,
published as preprint hep-ph/0403056. The criticisms are confronted, and the
questions raised are answered. We demonstrate that the lower limit quoted by
IGEX, for the half life of Ge-76 neutrinoless double beta decay, 1.57x10**25 y,
is correct and that there was no "arithmetical error"-as claimed in the "
Critical Review" article
Revealing the molecular signatures of host-pathogen interactions.
Advances in sequencing technology and genome-wide association studies are now revealing the complex interactions between hosts and pathogen through genomic variation signatures, which arise from evolutionary co-existence
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