1,682 research outputs found

    Local u'g'r'i'z' Standard Stars in the Chandra Deep Field-South

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    Because several observing programs are underway in various spectral regimes to explore the Chandra Deep Field South (CDF-S), the value of local photometric standards is obvious. As part of an NOAO Surveys Program to establish u'g'r'i'z' standard stars in the southern hemisphere, we have observed the central region of the CDF-S to create local standards for use by other investigators using these filters. As a courtesy, we present the CDF-S standards to the public now, although the main program will not finish until mid-2005.Comment: Accepted by AJ (scheduled for October 2003 issue). 26 pages, 5 tables, 5 figures. High resolution version of Figure 7 available at http://home.fnal.gov/~dtucker/Southern_ugriz/index.htm

    The Luminosity Function of Galaxies in the Las Campanas Redshift Survey

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    We present the RR-band luminosity function for a sample of 18678 galaxies, with average redshift z=0.1z = 0.1, from the Las Campanas Redshift Survey. The luminosity function may be fit by a Schechter function with M∗=−20.29±0.02+5log⁥hM^* = -20.29 \pm 0.02 + 5 \log h, α=−0.70±0.05\alpha = -0.70 \pm 0.05, and $\phi^* = 0.019 \pm 0.001 \ h^3 Mpc~Mpc^{-3},forabsolutemagnitudes, for absolute magnitudes -23.0 \leq M - 5 \log h \leq -17.5.Wecompareourluminosityfunctiontothatfromotherredshiftsurveys;inparticularournormalizationisconsistentwiththatoftheStromlo−APMsurvey,andisthereforeafactoroftwobelowthatimpliedbythe. We compare our luminosity function to that from other redshift surveys; in particular our normalization is consistent with that of the Stromlo-APM survey, and is therefore a factor of two below that implied by the b_J \approx 20brightgalaxycounts.Ournormalizationthusindicatesthatmuchmoreevolutionisneededtomatchthefaintgalaxycountdata,comparedtominimalevolutionmodelswhichnormalizeat bright galaxy counts. Our normalization thus indicates that much more evolution is needed to match the faint galaxy count data, compared to minimal evolution models which normalize at b_J \approx 20.Also,weshowthatourfaint−endslope. Also, we show that our faint-end slope \alpha = -0.7,though‘‘shallowerâ€Čâ€Čthantypicalpreviousvalues, though ``shallower'' than typical previous values \alpha = -1,resultsprimarilyfromfittingthedetailedshapeoftheLCRSluminosityfunction,ratherthanfromanyabsenceofintrinsicallyfaintgalaxiesfromoursurvey.Finally,using[OII]3727equivalentwidth, results primarily from fitting the detailed shape of the LCRS luminosity function, rather than from any absence of intrinsically faint galaxies from our survey. Finally, using [OII] 3727 equivalent width W_{\lambda} = 5 A˚ asthedividingline,wefindsignificantdifferencesintheluminosityfunctionsofemissionandnon−emissiongalaxies,particularlyintheir~\AA \ as the dividing line, we find significant differences in the luminosity functions of emission and non-emission galaxies, particularly in their \alphavalues.EmissiongalaxieshaveSchechterparameters values. Emission galaxies have Schechter parameters M^* = -20.03 \pm 0.03 + 5 \log hand and \alpha = -0.9 \pm 0.1,whilenon−emissiongalaxiesaredescribedby, while non-emission galaxies are described by M^* = -20.22 \pm 0.02 + 5 \log hand and \alpha = -0.3 \pm 0.1$. (abridged abstract)Comment: 41 pages, including 13 postscript figures, uses AASTEX v4.0 style files. Important clarification of R-band definition, plus correction of luminosity densities and updated references. Main conclusions unchanged. Final version to appear in Ap

    The 8 o'clock Arc: A Serendipitous Discovery of a Strongly Lensed Lyman Break Galaxy in the SDSS DR4 Imaging Data

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    We report on the serendipitous discovery of the brightest Lyman Break Galaxy (LBG) currently known, a galaxy at z=2.73 that is being strongly lensed by the z=0.38 Luminous Red Galaxy (LRG) SDSS J002240.91+143110.4. The arc of this gravitational lens system, which we have dubbed the "8 o'clock arc" due to its time of discovery, was initially identified in the imaging data of the Sloan Digital Sky Survey Data Release 4 (SDSS DR4); followup observations on the Astrophysical Research Consortium (ARC) 3.5m telescope at Apache Point Observatory confirmed the lensing nature of this system and led to the identification of the arc's spectrum as that of an LBG. The arc has a spectrum and a redshift remarkably similar to those of the previous record-holder for brightest LBG (MS 1512-cB58, a.k.a "cB58"), but, with an estimated total magnitude of (g,r,i) = (20.0,19.2,19.0) and surface brightness of (mu_g,mu_r,mu_i) = (23.3, 22.5, 22.3) mag/arcsec^2, the 8 o'clock arc is thrice as bright. The 8 o'clock arc, which consists of three lensed images of the LBG, is 162deg (9.6arcsec) long and has a length-to-width ratio of 6:1. A fourth image of the LBG -- a counter-image -- can also be identified in the ARC 3.5m g-band images. A simple lens model for the system assuming a singular isothermal ellipsoid potential yields an Einstein radius of 2.91+/-0.14 arcsec, a total mass for the lensing LRG (within the (10.6+/-0.5)/h kpc enclosed by the lensed images) of 1.04x10^12/h Msun, and a magnification factor for the LBG of 12.3(+15/-3.6). The LBG itself is intrinsically quite luminous (approximately 6L*) and shows indications of massive recent star formation, perhaps as high as 160/h Msun/year.Comment: 4 pages 5 figures, submitted to ApJ Letter

    Improved uâ€Čgâ€Črâ€Čiâ€Čzâ€Ču'g'r'i'z' to UBVRCICUBVR_CI_C Transformation Equations for Main Sequence Stars

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    We report improved transformation equations between the uâ€Čgâ€Črâ€Čiâ€Čzâ€Ču'g'r'i'z' and UBVRCICUBVR_CI_C photometric systems. Although the details of the transformations depend on luminosity class, we find a typical rms scatter on the order of 0.001 magnitude if the sample is limited to main sequence stars. Furthermore, we find an accurate transformation requires complex, multi-color dependencies for the bluer bandpasses. Results for giant stars will be reported in a subsequent paper.Comment: 7 pages, 8 figure

    Heat transfer between fluids in two phase flow

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    Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1961.MIT Institute Archives copy bound with: Rheology of blood plasma / Paul M. Cox, Jr., Henry L. Gabelnick. 1961.Includes bibliographical references (leaves 38-39).by Allan S. Douglas, Edward L. Tucker.B.S

    Loose Groups of Galaxies in the Las Campanas Redshift Survey

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    A ``friends-of-friends'' percolation algorithm has been used to extract a catalogue of dn/n = 80 density enhancements (groups) from the six slices of the Las Campanas Redshift Survey (LCRS). The full catalogue contains 1495 groups and includes 35% of the LCRS galaxy sample. A clean sample of 394 groups has been derived by culling groups from the full sample which either are too close to a slice edge, have a crossing time greater than a Hubble time, have a corrected velocity dispersion of zero, or contain a 55-arcsec ``orphan'' (a galaxy with a mock redshift which was excluded from the original LCRS redshift catalogue due to its proximity to another galaxy -- i.e., within 55 arcsec). Median properties derived from the clean sample include: line-of-sight velocity dispersion sigma_los = 164km/s, crossing time t_cr = 0.10/H_0, harmonic radius R_h = 0.58/h Mpc, pairwise separation R_p = 0.64/h Mpc, virial mass M_vir = (1.90x10^13)/h M_sun, total group R-band luminosity L_tot = (1.30x10^11)/h^2 L_sun, and R-band mass-to-light ratio M/L = 171h M_sun/L_sun; the median number of observed members in a group is 3.Comment: 32 pages of text, 27 figures, 7 tables. Figures 1, 4, 6, 7, and 8 are in gif format. Tables 1 and 3 are in plain ASCII format (in paper source) and are also available at http://www-sdss.fnal.gov:8000/~dtucker/LCLG . Accepted for publication in the September 2000 issue of ApJ

    The Cut & Enhance method : selecting clusters of galaxies from the SDSS commissioning data

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    We describe an automated method, the Cut & Enhance method (CE) for detecting clusters of galaxies in multi-color optical imaging surveys. This method uses simple color cuts, combined with a density enhancement algorithm, to up-weight pairs of galaxies that are close in both angular separation and color. The method is semi-parametric since it uses minimal assumptions about cluster properties in order to minimize possible biases. No assumptions are made about the shape of clusters, their radial profile or their luminosity function. The method is successful in finding systems ranging from poor to rich clusters of galaxies, of both regular and irregular shape. We determine the selection function of the CE method via extensive Monte Carlo simulations which use both the real, observed background of galaxies and a randomized background of galaxies. We use position shuffled and color shuffled data to perform the false positive test. We have also visually checked all the clusters detected by the CE method. We apply the CE method to the 350 deg^2 of the SDSS (Sloan Digital Sky Survey) commissioning data and construct a SDSS CE galaxy cluster catalog with an estimated redshift and richness for each cluster. The CE method is compared with other cluster selection methods used on SDSS data such as the Matched Filter (Postman et al. 1996, Kim et al. 2001), maxBCG technique (Annis et al. 2001) and Voronoi Tessellation (Kim et al. 2001). The CE method can be adopted for cluster selection in any multi-color imaging surveys.Comment: 62 pages, 32 figures, Accepted for publication in the Astronomical Journal, "the CE galaxy cluster catalog can be downloaded from, http://astrophysics.phys.cmu.edu/~tomo/ce/

    Optical Identification of Cepheids in 19 Host Galaxies of Type Ia Supernovae and NGC 4258 with the Hubble Space Telescope

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    We present results of an optical search for Cepheid variable stars using the Hubble Space Telescope (HST) in 19 hosts of Type Ia supernovae (SNe Ia) and the maser-host galaxy NGC 4258, conducted as part of the SH0ES project (Supernovae and H0 for the Equation of State of dark energy). The targets include 9 newly imaged SN Ia hosts using a novel strategy based on a long-pass filter that minimizes the number of HST orbits required to detect and accurately determine Cepheid properties. We carried out a homogeneous reduction and analysis of all observations, including new universal variability searches in all SN Ia hosts, that yielded a total of 2200 variables with well-defined selection criteria -- the largest such sample identified outside the Local Group. These objects are used in a companion paper to determine the local value of H0 with a total uncertainty of 2.4%.Comment: ApJ, in press. v2 adds missing co-author to arXiv metadata and text in acknowledgment
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