The local space density of dwarf galaxies

We estimate the luminosity function of field galaxies over a range of ten magnitudes (-22 < M_{B_J} < -12 for H_0 = 100 km/s/Mpc) by counting the number of faint APM galaxies around Stromlo-APM redshift survey galaxies at known distance. The faint end of the luminosity function rises steeply at M_{B_J} \approx -15, implying that the space density of dwarf galaxies is at least two times larger than predicted by a Schechter function with flat faint-end slope. Such a high abundance of dwarf galaxies at low redshift can help explain the observed number counts and redshift distributions of faint galaxies without invoking exotic models for galaxy evolution.Comment: 20 pages, 5 included postscript figures, uses AAS LaTex macros. Accepted for publication in the Astrophysical Journal. Two figures and associated discussion added; results and conclusions unchange

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Sex-specific ultrasonic vocalization patterns and alcohol consumption in high alcohol-drinking (HAD-1) rats

Ultrasonic vocalizations (USVs) have been established as an animal model of emotional status and are often utilized in drug abuse studies as motivational and emotional indices. Further USV functionality has been demonstrated in our recent work showing accurate identification of selectively-bred high versus low alcohol-consuming male rats ascertained exclusively from 22 to 28 kHz and 50–55 kHz FM USV acoustic parameters. With the hypothesis that alcohol-sensitive sex differences could be revealed through USV acoustic parameters, the present study examined USVs and alcohol consumption in male and female selectively bred high-alcohol drinking (HAD-1) rats. For the current study, we examined USV data collected during a 12-week experiment in male and female HAD-1 rats. Experimental phases included Baseline (2 weeks), 4-h EtOH Access (4 weeks), 24-h EtOH Access (4 weeks) and Abstinence (2 weeks). Findings showed that both male and female HAD-1 rats spontaneously emitted a large number of 22–28 kHz and 50–55 kHz FM USVs and that females drank significantly more alcohol compared to males over the entire course of the experiment. Analyses of USV acoustic characteristics (i.e. mean frequency, duration, bandwidth and power) revealed distinct sex-specific phenotypes in both 50–55 kHz FM and 22–28 kHz USV transmission that were modulated by ethanol exposure. Moreover, by using a linear combination of these acoustic characteristics, we were able to develop binomial logistic regression models able to discriminate between male and female HAD-1 rats with high accuracy. Together these results highlight unique emotional phenotypes in male and female HAD-1 rats that are differentially modulated by alcohol experience

Occurrence statistics of cold, streaming ions in the near‐Earth magnetotail: Survey of Polar‐TIDE observations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95347/1/jgra17705.pd

Detection of Gravitational Lensing in the Cosmic Microwave Background

Gravitational lensing of the cosmic microwave background (CMB), a long-standing prediction of the standard cosmolgical model, is ultimately expected to be an important source of cosmological information, but first detection has not been achieved to date. We report a 3.4 sigma detection, by applying quadratic estimator techniques to all sky maps from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, and correlating the result with radio galaxy counts from the NRAO VLA Sky Survey (NVSS). We present our methodology including a detailed discussion of potential contaminants. Our error estimates include systematic uncertainties from density gradients in NVSS, beam effects in WMAP, Galactic microwave foregrounds, resolved and unresolved CMB point sources, and the thermal Sunyaev-Zeldovich effect.Comment: 27 pages, 20 figure

Endothelium-Dependent GenderDifferences inthe Response of the Rat Pulmonary Arteryto theThromboxane Mimic(U46619)1

ABSTRACT The pulmonaryarteriesof ratswere studiedinorderto determine the existence of sexual dimorphism. Gender differences, in the sensitivity (EC@)and maximum contractility (T,,,@) of ring prepa rations of the main pulmonary arteries of adult male and female rats, were evaluated with the syntheticendoperoxideanalog [(15S)-hydroxy-11a,9a-(epoxymethano)-prosta-5Z, I 3E-dienoic acid,] (U46619) and norepinephrine. There were no significant gender differences in the T@ values obtained with either U46619 or norepinephnne. However, when the intimal surface of vessel segments from female rats was rubbed, U46619 but not norep inephnne elicited a significantly lower T@. In contrast, no change inT@ was observedwithdenudedvesselsegmentsfrommales. Removal of the endothelium did not significantly affect the ECse of U46619 or norepinephnne in segmentsfrom either sex. The inhibitory effect of verapamil on the U46619-induced contractile responsewas studiedon both intactand denudedvesselsfrom rats of both gender. The T@ of intact vesselsfrom males but not femaleswas significantly attenuatedby verapamil(P &lt; .05). The ECrevalues with verapamil were not significantly different in any of the vessel preparations. We suggest that the endothelium of the pulmonaryartery of female rats significantly potentiates the contractile response to U46619 and attenuates the inhibitory effectof verapamil. Sexual dimorphism in the vascular reactivity of isolated pulmonary blood vessels is of considerable interest owing to the reported gender differences in the incidence of primary pulmonary hypertension. After sexual maturation, women pres ent with this disease three times more frequently than men (Wagenvoort and Wagenvoort, 1970). Recent studies demonstrate that the endothelium mediates the response of the underlying smooth muscle to several ago nists (DeMey and Vanhoutte, 1982; Singer and Peach, 1983) and may be involved in the development of pulmonary hyper tension (Molteni et at., 1984). An EDRF was reported by Furchgott and Zawadski (1980) and has subsequently been verified in various vascular preparations including the human pulmonary artery In addition to EDRF, the pulmonary endothelium may also release a contractile substance. Exuded lung surface fluid and lymph fluid collected during vasoconstriction, caused by bilat eral and unilateral hypoxia, elicited contractile responses of isolated helical strip preparations of the canine pulmonary artery (Benumofet at., 1978). In addition, hypoxic vasoconstric tion of porcine pulmonary artery rings requires the presence of the endothelium and may involve the release of an endothe lium-dependent contractile factor The purpose of this study was to investigate in pulmonary this drug is currently used in the clinic for treating primary pulmonary hypertension Methods Animals. A total of 51 mature(12 weeksof age)Sprague-Dawley rats from the Charles River Breeding Laboratories (Wilmington, MA) were housed in a controlled environment with food and water ad libitum. The females and males weighed 234.2 ±6.42 and 260.83 Â

Genetic linkage map of a wild genome: genomic structure, recombination and sexual dimorphism in bighorn sheep

<p>Abstract</p> <p>Background</p> <p>The construction of genetic linkage maps in free-living populations is a promising tool for the study of evolution. However, such maps are rare because it is difficult to develop both wild pedigrees and corresponding sets of molecular markers that are sufficiently large. We took advantage of two long-term field studies of pedigreed individuals and genomic resources originally developed for domestic sheep (<it>Ovis aries</it>) to construct a linkage map for bighorn sheep, <it>Ovis canadensis</it>. We then assessed variability in genomic structure and recombination rates between bighorn sheep populations and sheep species.</p> <p>Results</p> <p>Bighorn sheep population-specific maps differed slightly in contiguity but were otherwise very similar in terms of genomic structure and recombination rates. The joint analysis of the two pedigrees resulted in a highly contiguous map composed of 247 microsatellite markers distributed along all 26 autosomes and the X chromosome. The map is estimated to cover about 84% of the bighorn sheep genome and contains 240 unique positions spanning a sex-averaged distance of 3051 cM with an average inter-marker distance of 14.3 cM. Marker synteny, order, sex-averaged interval lengths and sex-averaged total map lengths were all very similar between sheep species. However, in contrast to domestic sheep, but consistent with the usual pattern for a placental mammal, recombination rates in bighorn sheep were significantly greater in females than in males (~12% difference), resulting in an autosomal female map of 3166 cM and an autosomal male map of 2831 cM. Despite differing genome-wide patterns of heterochiasmy between the sheep species, sexual dimorphism in recombination rates was correlated between orthologous intervals.</p> <p>Conclusions</p> <p>We have developed a first-generation bighorn sheep linkage map that will facilitate future studies of the genetic architecture of trait variation in this species. While domestication has been hypothesized to be responsible for the elevated mean recombination rate observed in domestic sheep, our results suggest that it is a characteristic of <it>Ovis </it>species. However, domestication may have played a role in altering patterns of heterochiasmy. Finally, we found that interval-specific patterns of sexual dimorphism were preserved among closely related <it>Ovis </it>species, possibly due to the conserved position of these intervals relative to the centromeres and telomeres. This study exemplifies how transferring genomic resources from domesticated species to close wild relative can benefit evolutionary ecologists while providing insights into the evolution of genomic structure and recombination rates of domesticated species.</p

Extragalactic Foregrounds of the Cosmic Microwave Background: Prospects for the MAP Mission

(Abridged) While the major contribution to the Cosmic Microwave Background (CMB) anisotropies are the sought-after primordial fluctuations produced at the surface of last scattering, other effects produce secondary fluctuations at lower redshifts. Here, we study the extragalactic foregrounds of the CMB in the context of the upcoming MAP mission. We first survey the major extragalactic foregrounds and show that discrete sources, the Sunyaev-Zel'dovich (SZ) effect, and gravitational lensing are the most dominant ones for MAP. We then show that MAP will detect (>5 sigma) about 46 discrete sources and 10 SZ clusters directly with 94 GHz fluxes above 2 Jy. The mean SZ fluxes of fainter clusters can be probed by cross-correlating MAP with cluster positions extracted from existing catalogs. For instance, a MAP-XBACs cross-correlation will be sensitive to clusters with S(94GHz)>200mJy, and will thus provide a test of their virialization state and a measurement of their gas fraction. Finally, we consider probing the hot gas on supercluster scales by cross-correlating the CMB with galaxy catalogs. Assuming that galaxies trace the gas, we show that a cross-correlation between MAP and the APM catalog should yield a marginal detection, or at least a four-fold improvement on the COBE upper limits for the rms Compton y-parameter.Comment: 27 LaTeX pages, including 5 ps figures and 2 tables. To appear in ApJ. Minor revisions to match accepted version. Color figures and further links available at http://www.astro.princeton.edu/~refreg

The Seyfert Population in the Local Universe

The magnitude-limited catalog of the Southern Sky Redshift Survey (SSRS2), is used to characterize the properties of galaxies hosting Active Galactic Nuclei. Using emission-line ratios, we identify a total of 162 (3%) Seyfert galaxies out of the parent sample with 5399 galaxies. The sample contains 121 Seyfert 2 galaxies and 41 Seyfert 1. The SSRS2 Seyfert galaxies are predominantly in spirals of types Sb and earlier, or in galaxies with perturbed appearance as the result of strong interactions or mergers. Seyfert galaxies in this sample are twice as common in barred hosts than the non-Seyferts. By assigning galaxies to groups using a percolation algorithm we find that the Seyfert galaxies in the SSRS2 are more likely to be found in binary systems, when compared to galaxies in the SSRS2 parent sample. However, there is no statistically significant difference between the Seyfert and SSRS2 parent sample when systems with more than 2 galaxies are considered. The analysis of the present sample suggests that there is a stronger correlation between the presence of the AGN phenomenon with internal properties of galaxies (morphology, presence of bar, luminosity) than with environmental effects (local galaxy density, group velocity dispersion, nearest neighbor distance).Comment: 35 pages, 13 figures, Accepted to be publised in Astronomical Journa