We present axisymmetric maximum disk mass models for a sample of 74 spiral galaxies taken from the southern sky Fabry-Perot Tully-Fisher survey (Schommer et al. 1993). The sample contains galaxies spanning a large range of morphologies and having rotation widths from 180 km/sec to 680 km/secs. For each galaxy we have an I-band image and a 2-d H_alpha velocity field. The distribution of mass is modeled as a sum of disk and bulge components with distinct, constant mass-to-light ratios. No dark matter halo is included in the fits. The models reproduce the overall structure of the rotation curves in the majority of galaxies, providing good fits to galaxies which exhibit pronounced structural differences in their surface brightness profiles. 75% of galaxies for which the rotation curve is measured to R_23.5 or beyond are well fit by a mass-traces-light model for the entire region within R_23.5. The models for about 20% of the galaxies do not fit well; the failure of most of these models is traced directly to non-axisymmetric structures, primarily bars but also strong spiral arms. The median I-band M/L of the disk plus bulge is 2.4+/-0.9 h_75 in solar units, consistent with normal stellar populations. These results require either that the mass of dark matter within the optical disk of spiral galaxies is small, or that its distribution is very precisely coupled to the distribution of luminous matter.Comment: accepted by AJ, 29 pages, 8 figures, uses emulateapj.st

We present the detection of 34 Lyα emission-line galaxy candidates in a 80× 80 × 60 co-moving Mpc region surrounding the known z = 2.38 galaxy cluster J2143-4423. The space density of Lyα emitters is comparable to that found by Steidel et al. when targeting a cluster at redshift 3.09, but is a factor of 5.8 ± 2.5 greater than that found by field samples at similar redshifts. The distribution of these galaxy candidates contains several 5-10 Mpc scale voids. We compare our observations with mock catalogs derived from the VIRGO consortium λCDM n-body simulations. Fewer than 1% of the mock catalogues contain voids as large as we observe. Our observations thus tentatively suggest that the galaxy distribution at redshift 2.38 contains larger voids than predicted by current models. Three of the candidate galaxies and one previously discovered galaxy have the large luminosities and extended morphologies of "Lyα blobs".

International audienceWe trace the disk of HD 169142 (A8 Ve) from 0.57" to 1.4" (~80-200 AU projected distance) in 1.1 μm scattered light with HST NICMOS coronagraphy. The azimuthally symmetric disk has a peak azimuthally medianed surface brightness (SB) of ~5 mJy arcsec-2 at 0.57" from the star, and drops ~r-3. This radial SB profile is consistent with the presence of spatially resolved PAH emission and a Meeus group I IR SED only if the inner disk is either substantially flatter than the outer disk or partially devoid of material. Analysis of new HST ACS FUV imagery in tandem with archival IUE data indicates M˙acc<=10-9 Msolar yr-1. We estimate the age of HD 169142 to be 6+6-3 Myr by identifying 2MASS 18242929-2946559, located 9.3" to the southwest, as a 130 mas separation weak-line T Tauri binary that is comoving with HD 169142 at the 4 σ confidence level. We find no evidence for any additional stellar companion in either the ACS or Chandra ACIS-S data at r<=1''. HD 169142 has previously been interpreted as a slowly rotating, chemically peculiar star. However, by combining the disk inclination and vsini from the literature, we find that the star has vequatorial~240 km s-1, making it a rapid rotator, similar to Altair or Vega. The UV data for HD 169142 are consistent with gravity darkening, while the X-ray luminosity and spectrum resembles early F stars at the age of the β Pictoris moving group, rather than mid-A stars. In this context, spectral features previously interpreted as evidence for chemical peculiarity are more likely to reflect the presence of a strong photospheric latitudinal temperature gradient. With such a gradient, HD 169142 should closely resemble Vega at the epoch of central disk clearing

We present Hubble Space T elescope and ground-based observations of a pair of galaxies at a redshift of 2.38, which are collectively known as 2142[4420 B1. Both galaxies are luminous extremely red objects (EROs) and are separated by They are embedded within a 100 kpc scale di †use Lya nebula 0A .8. (or blob) of luminosity D1044 ergs s~1. The radial proÐles and colors of both red objects are most naturally explained if they are young elliptical galaxies, the most distant galaxies of this type found to date. It is not possible, however, to rule out a model in which they are abnormally compact, extremely dusty starbursting disk galaxies. If they are elliptical galaxies, their stellar populations have inferred masses of D1011 and ages of D7 ] 108 yr. Both galaxies have color gradients : their centers are signiÐcantly M _ bluer than their outer regions. The surface brightness of both galaxies is roughly 1 order of magnitude greater than would be predicted by the Kormendy relation. A chain of di †use star formation extending 1A from the galaxies may be evidence that they are interacting or merging. The Lya nebula surrounding the galaxies shows apparent velocity substructure of amplitude D700 km s~1. We propose that the Lya emission from this nebula may be produced by fast shocks that are powered either by a galactic superwind or by the release of gravitational potential energy.