RVSAO is a set of programs to obtain redshifts and radial velocities from digital spectra. RVSAO operates in the IRAF(Tody 1986, 1993) environment. The heart of the system is xcsao, which implements the cross-correlation method, and is a direct descendant of the system built by Tonry and Davis (1979). emsao uses intelligent heuristics to search for emission lines in spectra, then fits them to obtain a redshift. sumspec shifts and sums spectra to build templates for cross-correlation. linespec builds synthetic spectra given a list of spectral lines. bcvcorr corrects velocities for the motion of the earth. We discuss in detail the parameters necessary to run xcsao and emsao properly. We discuss the reliability and error associated with xcsao derived redshifts. We develop an internal error estimator, and we show how large, stable surveys can be used to develop more accurate error estimators. We develop a new methodology for building spectral templates for galaxy redshifts. We show how to obtain correlation velocities using emission line templates. Emission line correlations are substantially more efficient than the previous standard technique, automated emission line fitting. We compare the use of RVSAO with new methods, which use Singular Value Decomposition and $\chi^2$ fitting techniques.Comment: 42 pages, 74 figures, aastex, submitted to PASP, 13. March 1998 More info at http://tdc-www.harvard.edu/, second version with revised figure

We have discovered a star, SDSS J090745.0+024507, leaving the Galaxy with a heliocentric radial velocity of +853 ± 12 km s −1 , the largest velocity ever observed in the Milky Way halo. The star is either a hot blue horizontal branch star or a B9 main sequence star with a heliocentric distance ∼55 kpc. Corrected for the solar reflex motion and to the local standard of rest, the Galactic rest-frame velocity is +709 km s −1 . Because its radial velocity vector points 173.8 • from the Galactic center, we suggest that this star is the first example of a hyper-velocity star ejected from the Galactic center as predicted by Hills and later discussed by Yu & Tremaine. The star has [Fe/H]∼0, consistent with a Galactic center origin, and a travel time of 80 Myr from the Galactic center, consistent with its stellar lifetime. If the star is indeed traveling from the Galactic center, it should have a proper motion of 0.3 mas yr −1 observable with GAIA. Identifying additional hyper-velocity stars throughout the halo will constrain the production rate history of hyper-velocity stars at the Galactic center.

The CAIRNS (Cluster And Infall Region Nearby Survey) project is a spectroscopic survey of the infall regions surrounding eight nearby, rich, X-ray luminous clusters of galaxies. We collect 15665 redshifts (3471 new or remeasured) within ∼ 5 − 10h −1 Mpc of the centers of the clusters, making it the largest study of the infall regions of clusters. We determine cluster membership and the mass profiles of the clusters based on the phase space distribution of the galaxies. All of the clusters display decreasing velocity dispersion profiles. The mass profiles are fit well by functional forms based on numerical simulations but exclude an isothermal sphere. Specifically, NFW and Hernquist models provide good descriptions of cluster mass profiles to their turnaround radii. Our sample shows that the predicted infall pattern is ubiquitous in rich, X-ray luminous clusters over a large mass range. The caustic mass estimates are in excellent agreement with independent X-ray estimates at small radii and with virial estimates at intermediate radii. The mean ratio of the caustic mass to the X-ray mass is 1.03 ± 0.11 and the mean ratio of the caustic mass to the virial mass (when corrected for the surface pressure term) is 0.93 ± 0.07. We further demonstrate that the caustic technique provides reasonable mass estimates even in merging clusters. the infall regions of six of the eight clusters in this survey.The CAIRNS project tests whether the caustic pattern described in DG and D99 is common in nearby rich clusters and thus evaluates the feasibility of measuring cluster mass profiles at large radii from redshift surveys using the caustic technique. Other goals of CAIRNS include (1) measuring the mass-to-light ratio as a function of scale (Rines et al. 2000(Rines et al. , 2001a, (2) detecting substructures in infall regions as a probe of structure formation (Rines et al. 2001b(Rines et al. , 2002, and (3) studying the dependence of the spectroscopic properties of galaxies on environment over a large range of densities.CAIRNS also provides an important zero-redshift benchmark for comparison with more distant systems (e.g., Ellingson et al. 2001). The CNOC1 project assembled an ensemble cluster from X-ray selected clusters at moderate redshifts. The CNOC1 ensemble cluster samples galaxies up to ∼2 virial radii (see Carlberg et al. 1997a; Ellingson et al. 2001, and references therein). The caustic pattern is easily visible in the ensemble cluster, but Carlberg et al. (1997a) apply only Jeans analysis to the cluster to determine an average mass profile. Recently, Biviano & Girardi (2003) analyzed cluster redshifts from the 2dF 100,000 redshift data release. They stacked 43 poor clusters to produce an ensemble cluster containing 1345 galaxies within 2 virial radii and analyzed the properties of the ensemble cluster with both Jeans analysis and the caustic technique. Biviano & Girardi (2003) find good agreement between the two techniques; the caustic mass profile beyond the virial radius agrees well with an extrapolation of the Jeans ...

ABSTRACT. The Hectospec is a 300 optical fiber fed spectrograph commissioned at the MMT in the spring of 2004. In the configuration pioneered by the Autofib instrument at the Anglo-Australian Telescope, Hectospec's fiber probes are arranged in a radial "fisherman on the pond" geometry and held in position with small magnets. A pair of high-speed, six-axis robots move the 300 fiber buttons between observing configurations within ∼300 s, and to an accuracy of ∼25 mm. The optical fibers run for 26 m between the MMT's focal surface and the bench spectrograph, operating at . Hectochelle, another high-dispersion bench spectrograph R ∼ 1000-2000 offering , is also available. The system throughput, including all losses in the telescope optics, fibers, R ∼ 35,000 and spectrograph, peaks at ∼10% at the grating blaze in 1Љ FWHM seeing. Correcting for aperture losses at the 1Љ .5 diameter fiber entrance aperture, the system throughput peaks at ∼17%, close to our prediction of 20%. Hectospec has proven to be a workhorse instrument at the MMT. Together, Hectospec and Hectochelle have been scheduled for of the available nights since its commissioning. Hectospec has returned approximately 60,000 1 3 reduced spectra for 16 scientific programs during its first year of operation.

The infall regions of galaxy clusters represent the largest gravitationally bound structures in a ΛCDM universe. Measuring cluster mass profiles into the infall regions provides an estimate of the ultimate mass of these haloes. We use the caustic technique to measure cluster mass profiles from galaxy redshifts obtained with the Hectospec Cluster Survey (HeCS), an extensive spectroscopic survey of galaxy clusters with MMT/Hectospec. We survey 58 clusters selected by X-ray flux at 0.1

We calculate the stellar mass-metallicity relation at five epochs ranging to z ∼ 2.3. We quantify evolution in the shape of the mass-metallicity relation as a function of redshift; the mass-metallicity relation flattens at late times. There is an empirical upper limit to the gas-phase oxygen abundance in star-forming galaxies that is independent of redshift. From examination of the mass-metallicity relation and its observed scatter we show that the flattening at late times is a consequence of evolution in the stellar mass where galaxies enrich to this empirical upper metallicity limit; there is also evolution in the fraction of galaxies at a fixed stellar mass that enrich to this limit. The stellar mass where metallicities begin to saturate is ∼ 0.7 dex smaller in the local universe than it is at z ∼ 0.8.

The Zwicky Catalog of galaxies (ZC), with m_Zw<=15.5mag, has been the basis for the Center for Astrophysics (CfA) redshift surveys. To date, analyses of the ZC and redshift surveys based on it have relied on heterogeneous sets of galaxy coordinates and redshifts. Here we correct some of the inadequacies of previous catalogs by providing: (1) coordinates with <~2 arcsec errors for all of the Nuzc catalog galaxies, (2) homogeneously estimated redshifts for the majority (98%) of the data taken at the CfA (14,632 spectra), and (3) an estimate of the remaining "blunder" rate for both the CfA redshifts and for those compiled from the literature. For the reanalyzed CfA data we include a calibrated, uniformly determined error and an indication of the presence of emission lines in each spectrum. We provide redshifts for 7,257 galaxies in the CfA2 redshift survey not previously published; for another 5,625 CfA redshifts we list the remeasured or uniformly re-reduced value. Among our new measurements, Nmul are members of UZC "multiplets" associated with the original Zwicky catalog position in the coordinate range where the catalog is 98% complete. These multiplets provide new candidates for examination of tidal interactions among galaxies. All of the new redshifts correspond to UZC galaxies with properties recorded in the CfA redshift compilation known as ZCAT. About 1,000 of our new measurements were motivated either by inadequate signal-to-noise in the original spectrum or by an ambiguous identification of the galaxy associated with a ZCAT redshift. The redshift catalog we include here is ~96% complete to m_Zw<=15.5, and ~98% complete (12,925 galaxies out of a total of 13,150) for the RA(1950) ranges [20h--4h] and [8h--17h] and DEC(1950) range [-2.5d--50d]. (abridged)Comment: 34 pp, 7 figs, PASP 1999, 111, 43

It has been shown (S. Lawrence, 2001, Nature, 411, 521) that journal articles which have been posted without charge on the internet are more heavily cited than those which have not been. Using data from the NASA Astrophysics Data System (ads.harvard.edu) and from the ArXiv e-print archive at Cornell University (arXiv.org) we examine the causes of this effect.Recently Lawrence (2001) and Brody, et al. (2004) have demonstrated that articles which are available on-line at no charge are cited at substantially higher rates than those which are not. Kurtz (2004) has shown that restrictive access policies can cut article downloads to half the free access rate.There are (at least) three possible, and non-exclusive, explanations for the effect noted by Lawrence (2001) and Brody, et al. (2004).