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We present the properties of Ly Alpha emitters (LAEs) at z = 5.7 in the Subaru Deep Field. A photometric sample of 89 LAE candidates is constructed from narrow-band (NB816) data down to NB816 = 26.0 (AB) in a continuous 725 arcmin^2 area. Spectra of 39 objects satisfying the photometric selection criteria for LAEs were obtained with Subaru and Keck II Telescopes, among which 28 were confirmed LAEs, one was a nearby galaxy, and eight were unclassified. We also obtained spectra of another 24 NB816-excess objects in the field, identifying six additional LAEs. We find that the Ly Alpha luminosity function derived from the photometric sample is reproduced well by a Schechter function with L* = (7.9+3.0-2.2) x 10^42 erg/s and phi* = (6.3+3.0-2.0) x 10^-4 Mpc^-3 for alpha = -1.5 (fixed) over the whole luminosity range of L ~= 3x10^42 - 3x10^43 erg/s. We then measure rest-frame Ly Alpha equivalent widths (EWs) for the confirmed LAEs, to find that the median among the 28 objects satisfying the photometric selection criteria is W_0^i = 233 A. We infer that 30% - 40% of LAEs at z=5.7 exceed W_0^i = 240 A. These large-EW objects probably cannot be accounted for by ordinary star-forming populations with a Salpeter IMF. We also find that LAEs with fainter far-UV luminosities have larger EWs. Finally, we derive the far-UV luminosity function of LAEs down to M_UV ~= -19.6 using the photometric sample, and compare it with that of Lyman-break galaxies (LBGs). We find that as high as about 80% of LBGs at z ~ 6 have W_0^i >= 100 A, in sharp contrast to lower-z counterparts.

We present the properties of Ly Alpha emitters (LAEs) at z = 5.7 in the Subaru Deep Field. A photometric sample of 89 LAE candidates is constructed from narrow-band (NB816) data down to NB816 = 26.0 (AB) in a continuous 725 arcmin^2 area. Spectra of 39 objects satisfying the photometric selection criteria for LAEs were obtained with Subaru and Keck II Telescopes, among which 28 were confirmed LAEs, one was a nearby galaxy, and eight were unclassified. We also obtained spectra of another 24 NB816-excess objects in the field, identifying six additional LAEs. We find that the Ly Alpha luminosity function derived from the photometric sample is reproduced well by a Schechter function with L* = (7.9+3.0-2.2) x 10^42 erg/s and phi* = (6.3+3.0-2.0) x 10^-4 Mpc^-3 for alpha = -1.5 (fixed) over the whole luminosity range of L ~= 3x10^42 - 3x10^43 erg/s. We then measure rest-frame Ly Alpha equivalent widths (EWs) for the confirmed LAEs, to find that the median among the 28 objects satisfying the photometric selection criteria is W_0^i = 233 A. We infer that 30% - 40% of LAEs at z=5.7 exceed W_0^i = 240 A. These large-EW objects probably cannot be accounted for by ordinary star-forming populations with a Salpeter IMF. We also find that LAEs with fainter far-UV luminosities have larger EWs. Finally, we derive the far-UV luminosity function of LAEs down to M_UV ~= -19.6 using the photometric sample, and compare it with that of Lyman-break galaxies (LBGs). We find that as high as about 80% of LBGs at z ~ 6 have W_0^i >= 100 A, in sharp contrast to lower-z counterparts.

The recently initiated Arecibo Legacy Fast ALFA ( ALFALFA) survey aims to map similar to 7000 deg(2) of the high Galactic latitude sky visible from Arecibo, providing a H I line spectral database covering the redshift range between -1600 and 18,000 km s(-1) with similar to 5 km s(-1) resolution. Exploiting Arecibo's large collecting area and small beam size, ALFALFA is specifically designed to probe the faint end of the H I mass function in the local universe and will provide a census of H I in the surveyed sky area to faint flux limits, making it especially useful in synergy with wide-area surveys conducted at other wavelengths. ALFALFA will also provide the basis for studies of the dynamics of galaxies within the Local Supercluster and nearby superclusters, allow measurement of the H I diameter function, and enable a first wide-area blind search for local H I tidal features, H I absorbers at z < 0.06, and OH megamasers in the redshift range 0.16 < z < 0.25. Although completion of the survey will require some 5 years, public access to the ALFALFA data and data products will be provided in a timely manner, thus allowing its application for studies beyond those targeted by the ALFALFA collaboration. ALFALFA adopts a two-pass, minimum intrusion, drift scan observing technique that samples the same region of sky at two separate epochs to aid in the discrimination of cosmic signals from noise and terrestrial interference. Survey simulations, which take into account large-scale structure in the mass distribution and incorporate experience with the ALFA system gained from tests conducted during its commissioning phase, suggest that ALFALFA will detect on the order of 20,000 extragalactic H I line sources out to z similar to 0.06, including several hundred with H I masses M-HI < 10(7.5) M-circle dot.

Halpha imaging observations of 125 galaxies obtained with the 2.1 m telescope of the San Pedro Martir Observatory (SPM) (Baja California, Mexico) are presented. The observed galaxies are mostly Virgo cluster members (77), with 36 objects in the Coma/A1367 supercluster and 12 in the clusters A2197 and A2199 taken as fillers. Halpha+[NII] fluxes and equivalent widths, as well as images of the detected targets are presented

We analyze the structural and dynamical properties of a sample of 324 nearby elliptical and dwarf elliptical galaxies observed during an extensive near-IR survey in the H band (1.65 mum). The fundamental plane is determined and a significant tilt is assessed. The origins of such a tilt are investigated by means of a spherically symmetric, isotropic, pressure-supported dynamical model relying on the observed surface brightness profiles. The systematic variation of the shape coefficient converting the measured central velocity dispersion sigma(0) into the virial rms velocity sigma(rms) is found to be the main cause of the tilt, due to aperture effects. Moreover, the ratio between the dynamical mass M-dyn and the total H-band luminosity L-H turns out to be roughly constant along the luminosity sequence of ellipticals: H-band luminosity is therefore a reliable and cheap estimator of the dynamical mass of the E galaxies

Halpha [NII] imaging observations of 369 late-type (spiral) galaxies in the Virgo cluster and in the Coma/A1367 supercluster are analyzed, covering 3 rich nearby clusters (A1367, Coma and Virgo) and nearly isolated galaxies in the Great-Wall. They constitute an optically selected sample (m(p) < 16.0) observed with &SIM;60% completeness. These observations provide us with the current (T < 10(7) yrs) star formation properties of galaxies that we study as a function of the clustercentric projected distances (Theta). The expected decrease of the star formation rate (SFR), as traced by the Halpha EW, with decreasing Theta is found only when galaxies brighter than M-p similar to -19.5 are considered. Fainter objects show no or reverse trends. We also include in our analysis Near Infrared data, providing information on the old (T > 109 yrs) stars. Put together, the young and the old stellar indicators give the ratio of currently formed stars over the stars formed in the past, or "birthrate" parameter b. For the considered galaxies we also determine the "global gas content" combining HI with CO observations. We define the "gas deficiency" parameter as the logarithmic difference between the gas content of isolated galaxies of a given Hubble type and the measured gas content. For the isolated objects we find that b decreases with increasing NIR luminosity. In other words less massive galaxies are currently forming stars at a higher rate than their giant counterparts which experienced most of their star formation activity at earlier cosmological epochs. The gas-deficient objects, primarily members of the Virgo cluster, have a birthrate significantly lower than the isolated objects with normal gas content and of similar NIR luminosity. This indicates that the current star formation is regulated by the gaseous content of spirals. Whatever mechanism (most plausibly ram-pressure stripping) is responsible for the pattern of gas deficiency observed in spiral galaxies members of rich

There is significant evidence suggesting that mergers of galaxies produce elliptical galaxies. To determine whether the known kinematic properties of elliptical galaxies are consistent with those of their suggested progenitors, we have examined the stellar velocity dispersion in 11 nuclear regions within starbursting infrared-luminous galaxies. All of these galaxies are in some stage of merging. The new data are presented and statistically analyzed in combination with data from the literature. We find that the kinematic and photometric properties of these galaxies suggest that they are the progenitors of low- luminosity (L < L*) elliptical galaxies. Dissipative collapse of gas followed by star formation is apparently not producing a core of high-density high-velocity dispersion stars like those found in very bright elliptical galaxies. We suggest that only the ultraluminous infrared galaxies can possibly produce L* ellipticals. We further present the results of population synthesis models that show that intermediate-age stellar populations should contribute significantly to the light of merger remnants even after the morphological signs of merging have vanished., Pub. in the Astrophysical Journal, v497, p163-167, 10 Apr 1998.