Browsing by Author "Infante, L"

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    A catalog of faint interacting galaxies in pairs and groups .2.
    (1997) deMello, DF; Infante, L; Menanteau, F; Vieira, G
    We have completed the second part of an extensive survey of faint pairs and groups of galaxies in order to study galaxy evolution at intermediate redshifts. In this paper we present the second catalog of faint interacting galaxies of 49 equatorial fields taken with the Cerro Tololo Inter-American Observatory 4 m prime focus camera. The data set contains 11,297 galaxies within 19 < m(R) < 22, covering a total area of 2.63 deg(2). We have found 1461 isolated pairs and 30 groups with separations 2 '' < theta < 6 ''. Our results confirm the excess of galaxies in pairs and groups found in the first catalog (Infante, de Mello, & Menanteau 1996; de Mello, Infante, & Menanteau 1997). The two catalogs together cover an area of 4.86 deg(2) in the sky.
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    A large population of 'Lyman-break' galaxies in a protocluster at redshift z ≈ 4.1
    (2004) Miley, GK; Overzier, RA; Tsvetanov, ZI; Bouwens, RJ; Benítez, N; Blakeslee, JP; Ford, HC; Illingworth, GD; Postman, M; Rosati, P; Clampin, M; Hartig, GF; Zirm, AW; Röttgering, HJA; Venemans, BP; Ardila, DR; Bartko, F; Broadhurst, TJ; Brown, RA; Burrows, CJ; Cheng, ES; Cross, NJG; De Breuck, C; Feldman, PD; Franx, M; Golimowski, DA; Gronwall, C; Infante, L; Martel, AR; Menanteau, F; Meurer, GR; Sirianni, M; Kimble, RA; Krist, JE; Sparks, WB; Tran, HD; White, RL; Zheng, W
    The most massive galaxies and the richest clusters are believed to have emerged from regions with the largest enhancements of mass density(1-4) relative to the surrounding space. Distant radio galaxies may pinpoint the locations of the ancestors of rich clusters, because they are massive systems associated with 'over-densities' of galaxies that are bright in the Lyman-alpha line of hydrogen(5-7). A powerful technique for detecting high-redshift galaxies is to search for the characteristic 'Lyman break' feature in the galaxy colour, at wavelengths just shortwards of Lyalpha, which is due to absorption of radiation from the galaxy by the intervening intergalactic medium. Here we report multicolour imaging of the most distant candidate(7-9) protocluster, TNJ1338-1942 at a redshift zapproximate to4.1. We find a large number of objects with the characteristic colours of galaxies at that redshift, and we show that this excess is concentrated around the targeted dominant radio galaxy. Our data therefore indicate that TNJ1338-1942 is indeed the most distant cluster progenitor of a rich local cluster, and that galaxy clusters began forming when the Universe was only ten per cent of its present age.
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    Advanced camera for surveys observations of a strongly lensed arc in a field elliptical galaxy
    (2004) Blakeslee, JP; Zekser, KC; Benítez, N; Franx, M; White, RL; Ford, HC; Bouwens, RJ; Infante, L; Cross, NJ; Hertling, G; Holden, BP; Illingworth, GD; Motta, V; Menanteau, F; Meurer, GR; Postman, M; Rosati, P; Zheng, W
    We report the discovery of a strongly lensed arc system around a field elliptical galaxy in Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) images of a parallel field observed during NICMOS observations of the HST Ultra Deep Field. The ACS parallel data comprise deep imaging in the F435W, F606W, F775W, and F850LP bandpasses. The main arc is at a radius of 1."6 from the galaxy center and subtends about 120degrees. Spectroscopic follow-up at Magellan Observatory yields a redshift z = 0.6174 for the lensing galaxy, and we photometrically estimate z(phot) = 2.4 +/- 0.3 for the arc. We also identify a likely counterarc at a radius of 0."6 that shows structure similar to that seen in the main arc. We model this system and find a good fit to an elliptical isothermal potential of velocity dispersion a sigma approximate to 300 km s(-1), the value expected from the fundamental plane, and some external shear. Several other galaxies in the field have colors similar to the lensing galaxy and likely make up a small group.
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    Advanced camera for surveys photometry of the cluster RDCS 1252.9-2927
    (2003) Blakeslee, JP; Franx, M; Postman, M; Rosati, P; Holden, BP; Illingworth, GD; Ford, HC; Cross, NJG; Gronwall, C; Benítez, N; Bouwens, RJ; Broadhurst, TJ; Clampin, M; Demarco, R; Golimowski, DA; Hartig, GF; Infante, L; Martel, AR; Miley, GK; Menanteau, F; Meurer, GR; Sirianni, M; White, RL
    We investigate the color-magnitude (CM) relation of galaxies in the distant X-ray-selected cluster RDCS 1252.9 - 2927 z = 1.24 at using images obtained with the Advanced Camera for Surveys on the Hubble Space Telescope in the F775W and F850LP bandpasses. We select galaxies based on morphological classifications extending about 3.5 mag down the galaxy luminosity function, augmented by spectroscopic membership information. At the core of the cluster is an extensive early-type galaxy population surrounding a central pair of galaxies that show signs of dynamical interaction. The early-type population defines a tight sequence in the CM diagram, with an intrinsic scatter in observed (i(775)-z(850)) of 0.029 +/- 0.007 mag based on 52 galaxies or 0.024 +/- 0.008 mag for similar to30 elliptical galaxies. Simulations using the latest stellar population models indicate an age scatter for the elliptical galaxies of about 34%, with a mean age tau(L) greater than or similar to 2.6 Gyr (corresponding to z(L) greater than or similar to 2.7), and the last star formation occurring at z(end) greater than or similar to 1.5 Transforming to rest-frame (U-B), we conclude that the slope end and scatter in the CM relation for morphologically selected early-type galaxies show little or no evidence of evolution out to z approximate to 1.2. Thus, elliptical galaxies were already well established in X-ray - luminous clusters when the universe was a third of its present age.
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    CCD sequences in the Shapley supercluster of galaxies .1. The LCO-Toronto telescope data
    (1996) Infante, L; Slezak, E; Quintana, H
    We present R CCD photometric sequences of stars for calibrating ESO/SERC (R) survey plates in the region of the Shapley supercluster of galaxies.
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    CCD sequences in the shapley supercluster of galaxies .2. The ESO data
    (1996) Slezak, E; Infante, L; Quintana, H
    We present V and R CCD photometric sequences of stars and galaxies for calibrating ESO/SERC (R) survey plates in the region of the Shapley supercluster of galaxies.
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    Cepheid variables in the Large Magellanic Cloud cluster NGC 1866.: I.: New BVRI CCD photometry
    (2000) Gieren, WP; Gómez, M; Storm, J; Moffett, TJ; Infante, L; Barnes, TG; Geisler, D; Fouqué, P
    We report BV(RI)(C) CCD photometric data for a group of seven Cepheid variables in the young, rich cluster NGC 1866 in the Large Magellanic Cloud. The photometry was obtained as part of a program to determine accurate distances to these Cepheids by means of the infrared surface brightness technique and to improve the LMC Cepheid database for constructing Cepheid P-L and P-L-C relations. Using the new data together with data from the literature, we have determined improved periods for all variables. For five fundamental mode pulsators, the light curves are now of excellent quality and will lead to accurate distance and radius determinations once complete infrared light curves and radial velocity curves for these variables become available.
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    Clustering of star-forming galaxies near a radio galaxy at z=5.2
    (2006) Overzier, RA; Miley, GK; Bouwens, RJ; Cross, NJG; Zirm, AW; Benítez, N; Blakeslee, JP; Clampin, M; Demarco, R; Ford, HC; Hartig, GF; Illingworth, GD; Martel, AR; Röttgering, HJA; Venemans, B; Ardila, DR; Bartko, F; Bradley, LD; Broadhurst, TJ; Coe, D; Feldman, PD; Franx, M; Golimowski, DA; Goto, T; Gronwall, C; Holden, B; Homeier, N; Infante, L; Kimble, RA; Krist, JE; Mei, S; Menanteau, F; Meurer, GR; Motta, V; Postman, M; Rosati, P; Sirianni, M; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    We present HSTACS observations of the most distant radio galaxy known, TNJ0924-2201 at z = 5.2. This radio galaxy has six spectroscopically confirmed Ly alpha-emitting companion galaxies and appears to lie within an overdense region. The radio galaxy is marginally resolved in i(775) and z(850), showing continuum emission aligned with the radio axis, similar to what is observed for lower redshift radio galaxies. Both the half-light radius and the UV star formation rate are comparable to the typical values found for Lyman break galaxies at z similar to 4-5. The Ly alpha emitters are sub-L-* galaxies, with deduced star formation rates of 1-10 M-circle dot yr(-1). One of the Ly alpha emitters is only detected in Ly alpha. Based on the star formation rate of similar to 3 M-circle dot yr(-1) calculated from Ly alpha, the lack of continuum emission could be explained if the galaxy is younger than similar to 2 Myr and is producing its first stars. Observations in V(606)i(775)z(850) were used to identify additional Lyman break galaxies associated with this structure. In addition to the radio galaxy, there are 22 V-606 break (z similar to 5) galaxies with z(850) < 26.5 (5 sigma), two of which are also in the spectroscopic sample. We compare the surface density of similar to 2 arcmin(-2) to that of similarly selected V-606 dropouts extracted from GOODS and the UDF parallel fields. We find evidence for an overdensity to very high confidence (> 99%), based on a counts-in-cells analysis applied to the control field. The excess suggests that the V-606 break objects are associated with a forming cluster around the radio galaxy.
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    Discovery of A z=4.93, X-ray-selected quasar by the Chandra multiwavelength project (chaMP)
    (2002) Silverman, JD; Green, PJ; Kim, DW; Wilkes, BJ; Cameron, RA; Morris, D; Dosaj, A; Smith, C; Infante, L; Smith, PS; Jannuzi, BT; Mathur, S
    We present X-ray and optical observations of CXOMP J213945.0-234655, a high-redshift (z = 4.93) quasar discovered through the Chandra Multiwavelength Project (ChaMP). This object is the most distant X-ray-selected quasar published, with a rest-frame X-ray luminosity of L-x = 5.9 x 10(44) ergs s(-1) (measured in the 0.3-2.5 keV band and corrected for Galactic absorption). CXOMP J213945.0-234655 is a g' dropout object (>26.2), with r' = 22.87 and i' = 21.36. The rest- frame X-ray-to-optical flux ratio is similar to quasars at lower redshifts and slightly X-ray bright relative to z > 4 optically selected quasars observed with Chandra. The ChaMP is beginning to acquire significant numbers of high-redshift quasars to investigate the X-ray luminosity function out to. z similar to 5.
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    Evolution in the cluster early-type galaxy size-surface brightness relation at z ≃ 1
    (2005) Holden, BP; Blakeslee, JP; Postman, M; Illingworth, GD; Demarco, R; Franx, M; Rosati, P; Bouwens, RJ; Martel, AR; Ford, H; Clampin, M; Hartig, GF; Benítez, N; Cross, NJG; Homeier, N; Lidman, C; Menanteau, F; Zirm, A; Ardila, DR; Bartko, F; Bradley, LD; Broadhurst, TJ; Brown, RA; Burrows, CJ; Cheng, ES; Feldman, PD; Golimowski, DA; Goto, T; Gronwall, C; Infante, L; Kimble, RA; Krist, JE; Lesser, MP; Magee, D; Mei, S; Meurer, GR; Miley, GK; Motta, V; Sirianni, M; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    We investigate the evolution in the distribution of surface brightness, as a function of size, for elliptical and S0 galaxies in the two clusters RDCS J1252.9 - 2927 ( z = 1: 237) and RX J0152.7 - 1357 ( z = 0: 837). We use multicolor imaging with the Advanced Camera for Surveys on the Hubble Space Telescope to determine these sizes and surface brightnesses. Using three different estimates of the surface brightnesses, we find that we reliably estimate the surface brightness for the galaxies in our sample with a scatter of < 0.2 mag and with systematic shifts of <= 0.05 mag. We construct samples of galaxies with early- type morphologies in both clusters. For each cluster, we use a magnitude limit in a band that closely corresponds to the rest- frame B, to magnitude limit of M-B = - 18: 8 at z = 0, and select only those galaxies within the color- magnitude sequence of the cluster or by using our spectroscopic redshifts. We measure evolution in the rest- frame B surface brightness and find - 1: 41 +/- 0: 14 mag from the Coma Cluster of galaxies for RDCS J1252.9 - 2927 and - 0: 90 +/- 0: 12 mag of evolution for RX J0152.7 - 1357, or an average evolution of ( - 1: 13 +/- 0: 15) z mag. Our statistical errors are dominated by the observed scatter in the size - surface brightness relation, sigma = 0: 42 +/- 0: 05 mag for RX J0152.7 - 1357 and sigma = 0: 76 +/- 0: 10 mag for RDCS J1252.9 - 2927. We find no statistically significant evolution in this scatter, although an increase in the scatter could be expected. Overall, the pace of luminosity evolution we measure agrees with that of the fundamental plane of early- type galaxies, implying that the majority of massive early- type galaxies observed at z similar or equal to 1 formed at high redshifts.
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    Evolution of the color-magnitude relation in high-redshift clusters
    (2006) Mei, S; Blakeslee, JP; Stanford, SA; Holden, BP; Rosati, P; Strazzullo, V; Homeier, N; Postman, M; Franx, M; Rettura, A; Ford, H; Illingworth, GD; Ettori, S; Bouwens, RJ; Demarco, R; Martel, AR; Clampin, M; Hartig, GF; Eisenhardt, P; Ardila, DR; Bartko, F; Benítez, N; Bradley, LD; Broadhurst, TJ; Brown, RA; Burrows, CJ; Cheng, ES; Cross, NJG; Feldman, PD; Golimowski, DA; Goto, T; Gronwall, C; Infante, L; Kimble, RA; Krist, JE; Lesser, MP; Menanteau, F; Meurer, GR; Miley, GK; Motta, V; Sirianni, M; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    The color-magnitude relation has been determined for the RDCS J0910+5422 cluster of galaxies at redshift z = 1.106. Cluster members were selected from the Hubble Space Telescope Advanced Camera for Surveys (HST ACS) images, combined with ground-based near-IR imaging and optical spectroscopy. The observed early-type color-magnitude relation (CMR) in i(775) - z(850) versus z(850) shows an intrinsic scatter in color of 0.060 +/- 0.009 mag, within 10 from the cluster X-ray emission center. Both the elliptical and the S0 galaxies show small scatter about the CMR of 0.042 +/- 0.010 and 0.044 +/- 0.020 mag, respectively. From the scatter about the CMR, a mean luminosity weighted age t > 3: 3 Gyr (z(f) approximate to 3) is derived for the elliptical galaxies, assuming a simple stellar population modeling (single-burst solar metallicity). Strikingly, the S0 galaxies in RDCS J0910+5422 are systematically bluer in i(775) - z(850), by 0.07 +/- 0.02 mag, than the ellipticals. The ellipticity distribution as a function of color indicates that the face-on S0s in this particular cluster have likely been classified as elliptical. Thus, if anything, the offset in color between the elliptical and S0 populations may be even more significant. The color offset between S0 and E galaxies corresponds to an age difference of approximate to 1 Gyr for a single-burst solar-metallicity model. A solar-metallicity model with an exponential decay in star formation will reproduce the offset for an age of 3.5 Gyr; i.e., the S0s have evolved gradually from star-forming progenitors. The early-type population in this cluster appears to be still forming. The blue early-type disk galaxies in RDCS J0910+5422 likely represent the direct progenitors of the more evolved S0s that follow the same red sequence as elliptical galaxies in other clusters. Thirteen red galaxy pairs are observed, and the galaxies associated in pairs constitute similar to 40% of the CMR galaxies in this cluster.
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    Faint dwarf spheroidals in the Fornax Cluster - A flat luminosity function
    (2003) Hilker, M; Mieske, S; Infante, L
    We have discovered similar or equal to70 very faint dwarf galaxies in the Fornax Cluster. These dSphs candidates follow the same magnitude-surface brightness relation as their counterparts in the Local Group, and even extend it to fainter limits. The faintest dSph candidate in our sample has an absolute magnitude of M-V similar or equal to -8.8 mag and a central surface brightness of mu(V) similar or equal to 27 mag/arcsec(2). There exists a tight color-magnitude relation for the early-type galaxies in Fornax that extends from the giant to the dwarf regime. The faint-end slope of the luminosity function of the early-type dwarfs is flat (alpha similar or equal to -1.1 +/- 0.1), contrary to the results obtained by Kambas et al. (2000).
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    Faint galaxies in deep advanced camera for surveys observations
    (2004) Benítez, N; Ford, H; Bouwens, R; Menanteau, F; Blakeslee, J; Gronwall, C; Illingworth, G; Meurer, G; Broadhurst, TJ; Clampin, M; Franx, M; Hartig, GF; Magee, D; Sirianni, M; Ardila, DR; Bartko, F; Brown, RA; Burrows, CJ; Cheng, ES; Cross, NJG; Feldman, PD; Golimowski, DA; Infante, L; Kimble, RA; Krist, JE; Lesser, MP; Levay, Z; Martel, AR; Miley, GK; Postman, M; Rosati, P; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    We present the analysis of the faint galaxy population in the Advanced Camera for Surveys (ACS) Early Release Observation fields VV 29 ( UGC 10214) and NGC 4676. These observations cover a total area of 26.3 arcmin(2) and have depths close to that of the Hubble Deep Fields in the deepest part of the VV 29 image, with 10 sigma detection limits for point sources of 27.8, 27.6, and 27.2 AB magnitudes in the g(F475W), V-F606W, and I-F814W bands, respectively.
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    Feedback and brightest cluster galaxy formation
    (2005) Zirm, AW; Overzier, RA; Miley, GK; Blakeslee, JP; Clampin, M; De Breuck, C; Demarco, R; Ford, HC; Hartig, GF; Homeier, N; Illingworth, GD; Martel, AR; Röttgering, HJA; Venemans, B; Ardila, DR; Bartko, F; Benítez, NB; Bouwens, RJ; Bradley, LD; Broadhurst, TJ; Brown, RA; Burrows, CJ; Cheng, ES; Cross, NJG; Feldman, PD; Franx, M; Golimowski, DA; Goto, T; Gronwall, C; Holden, B; Infante, L; Kimble, RA; Krist, JE; Lesser, MP; Mei, S; Menanteau, F; Meurer, GR; Motta, V; Postman, M; Rosati, P; Sirianni, M; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    We present deep optical imaging of the z 4: 1 radio galaxy TN J1338 - 1942, obtained using the Advanced Camera for Surveys ( ACS) on board the Hubble Space Telescope, as well as ground- based near- infrared imaging data from the European Southern Observatory ( ESO) Very Large Telescope ( VLT). The radio galaxy is known to reside within a large galaxy overdensity ( both in physical extent and density contrast). There is good evidence that this `` protocluster'' region is the progenitor of a present- day rich galaxy cluster. TN J1338 is the dominant galaxy in the protocluster in terms of size and luminosity ( in both the optical and near- infrared) and therefore seems destined to evolve into the brightest cluster galaxy. The high spatial resolution ACS images reveal several kiloparsec- scale features within and around the radio galaxy. The continuum light is aligned with the radio axis and is resolved into two clumps in the i(775) and z(850) bands. These components have luminosities similar to 10(9) L-circle dot and sizes of a few kpc. The estimated nebular continuum, scattered light, synchrotron- and inverse Compton - scattering contributions to the aligned continuum light are only a few percent of the observed total, indicating that the observed flux is likely dominated by forming stars. The estimated star formation rate for the whole radio galaxy is similar to 200M(circle dot) yr(-1). A simple model in which the jet has triggered star formation in these continuum knots is consistent with the available data. A striking, but small, linear feature is evident in the z850 aligned light and may be indicative of a large- scale shock associated with the advance of the radio jet. The rest of the aligned light also seems morphologically consistent with star formation induced by shocks associated with the radio source, as seen in other high- z radio galaxies ( e. g., 4C 41.17). An unusual feature is seen in Ly alpha emission. A wedge- shaped extension emanates from the radio galaxy perpendicularly to the radio axis. This `` wedge'' naturally connects to the surrounding asymmetric, large- scale (similar to 100 kpc) Ly alpha halo. We posit that the wedge is a starburst- driven superwind associated with the first major epoch of formation of the brightest cluster galaxy. The shock and wedge are examples of feedback processes due to both active galactic nucleus and star formation in the earliest stages of massive galaxy formation.
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    Hubble Space Telescope ACS coronagraphic imaging of the circumstellar disk around HD 141569A
    (2003) Clampin, M; Krist, JE; Ardila, DR; Golimowski, DA; Hartig, GF; Ford, HC; Illingworth, GD; Bartko, F; Benítez, N; Blakeslee, JP; Bouwens, RJ; Broadhurst, TJ; Brown, RA; Burrows, CJ; Cheng, ES; Cross, NJG; Feldman, PD; Franx, M; Gronwall, C; Infante, L; Kimble, RA; Lesser, MP; Martel, AR; Menanteau, F; Meurer, GR; Miley, GK; Postman, M; Rosati, P; Sirianni, M; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    Multicolor coronagraphic images of the circumstellar disk around HD 141569A have been obtained with the Hubble Space Telescope Advanced Camera for Surveys. The B, V, and I images show that the disk's previously described multiple-ring structure is actually a continuous distribution of dust with a tightly wound spiral structure. Extending from the disk are two, more open spiral arms, one of which appears to reach the nearby binary star HD 141569BC. Diffuse dust is seen up to 1200 AU from HD 141569A. Although planets may exist in the inner region of the disk, tidal interaction with HD 141569BC seems more likely to be the cause of these phenomena. The disk appears redder than the star ( B - V = 0.21 and V - I = 0.25), and its color is spatially uniform. A scattering asymmetry factor of g = 0.25 - 0.35 is derived. The azimuthal density distribution is asymmetric, varying by a factor of similar to3 at some radii.
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    Hubble Space Telescope Advanced Camera for Surveys coronagraphic imaging of the AU microscopii debris disk
    (2005) Krist, JE; Ardila, DR; Golimowski, DA; Clampin, M; Ford, HC; Illingworth, GD; Hartig, GF; Bartko, F; Benítez, N; Blakeslee, JP; Bouwens, RJ; Bradley, LD; Broadhurst, TJ; Brown, RA; Burrows, CJ; Cheng, ES; Cross, NJG; Demarco, R; Feldman, PD; Franx, M; Goto, T; Gronwall, C; Holden, B; Homeier, N; Infante, L; Kimble, RA; Lesser, MP; Martel, AR; Mei, S; Menanteau, F; Meurer, GR; Miley, GK; Motta, V; Postman, M; Rosati, P; Sirianni, M; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    We present Hubble Space Telescope Advanced Camera for Surveys multicolor coronagraphic images of the recently discovered edge-on debris disk around the nearby (similar to10 pc) M dwarf AU Microscopii. The disk is seen between r = 0".75 and 15" (7.5-150 AU) from the star. It has a thin midplane with a projected FWHM thickness of 2.5-3.5 AU within r < 50 AU of the star that increases to 6.5-9 AU at r similar to 75 AU. The disk's radial brightness profile is generally flat for r < 15 AU, then decreases gradually (I proportional to r(1.8)) out to r approximate to 43 AU, beyond which it falls rapidly (I proportional to r(-4.7)). Within 50 AU the midplane is straight and aligned with the star, and beyond that it deviates by similar to3degrees, resulting in a bowed appearance that was also seen in ground-based images. Three-dimensional modeling of the disk shows that the inner region (r < 50 AU) is inclined to the line of sight by less than 1degrees and the outer disk by similar to3degrees. The inclination of the outer disk and moderate forward scattering (g approximate to 0.4) can explain the apparent bow. The intrinsic, deprojected FWHM thickness is 1.5-10 AU, increasing with radius. The models indicate that the disk is clear of dust within similar to12 AU of the star, in general agreement with the previous prediction of 17 AU based on the infrared spectral energy distribution. The disk is blue, being 60% brighter at B than I relative to the star. One possible explanation for this is that there is a surplus of very small grains compared with other imaged debris disks that have more neutral or red colors. This may be due to the low radiation pressure exerted by the late-type star. Observations at two epochs show that an extended source seen along the midplane is a background galaxy.
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    Internal color properties of resolved spheroids in the deep Hubble Space Telescope advanced camera for surveys field of UGC 10214
    (2004) Menanteau, F; Ford, HC; Illingworth, GD; Sirianni, M; Blakeslee, JP; Meurer, GR; Martel, AR; Benítez, N; Postman, M; Franx, M; Ardila, DR; Bartko, F; Bouwens, RJ; Broadhurst, TJ; Brown, RA; Burrows, CJ; Cheng, ES; Clampin, M; Cross, NJG; Feldman, PD; Golimowski, DA; Gronwall, C; Hartig, GF; Infante, L; Kimble, RA; Krist, JE; Lesser, MP; Miley, GK; Rosati, P; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    We study the internal color properties of a morphologically selected sample of spheroidal galaxies taken from the Hubble Space Telescope (HST) Advanced Camera for Surveys ( ACS) Early Release Observation program of UGC 10214 ("the Tadpole''). By taking advantage of the unprecedented high resolution of the ACS in this very deep data set, we are able to characterize spheroids at subarcsecond scales. Using the V-606 and I-814 bands, we construct V - I color maps and extract color gradients for a sample of spheroids at I-814 < 24 mag. We assess the ability of the ACS to make resolved color studies of galaxies by comparing its results with the multicolor data from the Hubble Deep Fields (HDFs). Here we report that with ACS WFC data using less than ∼ 1/10 the exposure of the WFPC2 HDFs, it is possible to confidently carry out resolved studies of faint galaxies at similar magnitude limits. We also investigate the existence of a population of morphologically classified spheroids that show extreme variation in their internal color properties, similar to the ones reported in the HDFs. These are displayed as blue cores and inverse color gradients with respect to those accounted for from metallicity variations. Following the same analysis, we find a similar fraction of early-type systems ( ∼ 30% - 40%) that show nonhomologous internal colors, suggestive of recent star formation activity. We present two statistics for quantifying the internal color variation in galaxies and tracing blue cores, from which we estimate the ratio of nonhomogeneous to homogeneous internal colors as a function of redshift up to z≲1.2. We find that it can be described as about constant as a function of redshift, with a small increase with redshift for the fraction of spheroids that present strong color dispersions. The implications of a constant fraction at all redshifts suggests the existence of a relatively permanent population of evolving spheroids up to z≲1. We discuss the implications of this in the context of spheroidal formation.
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    Luminosity functions of the galaxy cluster MS 1054-0321 at z=0.83 based on ACS photometry
    (2005) Goto, T; Postman, M; Cross, NJG; Illingworth, GD; Tran, K; Magee, D; Franx, M; Benítez, N; Bouwens, RJ; Demarco, R; Ford, HC; Homeier, NL; Martel, AR; Menanteau, F; Clampin, M; Hartig, GF; Ardila, DR; Bartko, F; Blakeslee, JP; Bradley, LD; Broadhurst, TJ; Brown, RA; Burrows, CJ; Cheng, ES; Feldman, PD; Golimowski, DA; Gronwall, C; Holden, B; Infante, L; Jee, MJ; Krist, JE; Lesser, MP; Mei, S; Meurer, GR; Miley, GK; Motta, V; Overzier, R; Sirianni, M; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W; Zirm, A
    We present new measurements of the galaxy luminosity function (LF) and its dependence on local galaxy density, color, morphology, and clustocentric radius for the massive z = 0.83 cluster MS 1054-0321. Our analyses are based on imaging performed with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST) in the F606W, F775W, and F850LP passbands and extensive spectroscopic data obtained with the Keck Low-Resolution Imaging Spectrograph. Our main results are based on a spectroscopically selected sample of 143 cluster members with morphological classifications derived from the ACS observations. Our three primary findings are (1) the faint-end slope of the LF is steepest in the bluest filter, (2) the LF in the inner part of the cluster (or highest density regions) has a flatter faint-end slope, and (3) the fraction of early-type galaxies is higher at the bright end of the LF, and gradually decreases toward fainter magnitudes. These characteristics are consistent with those in local galaxy clusters, indicating that, at least in massive clusters, the common characteristics of cluster LFs are established at z = 0.83. These results provide additional support for the hypothesis that the formation of galaxies in MS 1054-0321 began at redshifts considerably greater than unity. We also find a 2 sigma deficit of intrinsically faint, red galaxies (i(775)-z(850) greater than or equal to 0.5, M-i > -19) in this cluster. Although the significance is marginal, this trend may suggest that faint, red galaxies (which are common in z < 0.1 rich clusters) have not yet been created in this cluster at z = 0.83. The giant-to-dwarf ratio in MS 1054-0321 starts to increase inwards of the virial radius or when Sigma > 30 Mpc(-2), coinciding with the environment where the galaxy star formation rate and the morphology-density relation start to appear. A physical process that begins to become effective at around the virial radius or Sigma similar to 30 Mpc(-2) may thus be responsible for the evolution of color and luminosity of cluster galaxies.
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    Photometry of the central regions in a complete sample of high Bautz-Morgan-type Abell clusters.: I.: Observations and data calibration
    (2000) Quintana, H; Infante, L; Fouque, P; Carrasco, ER; Cuevas, H; Hertling, G; Nuñez, I
    We present CCD photometry of 209 southern Abell clusters selected according to Bautz-Morgan type I, I-II, and II. We have performed total photometry in the GUM r bandpass, classified stars and galaxies, and obtained structural parameters for the images. To estimate the photometric and structural errors on the CCD images and the completeness limits of our photometry, we performed realistic simulations of stars and galaxies and ran our classification algorithms. Here, we present central galaxy counts and metric photometry of the brightest cluster,:members, for which we give accurate positions, and compare this photometry with values in the literature. A linear magnitude-redshift relation has been derived from the tenth-ranked galaxy in each cluster. Photometric redshifts have been estimated for 57 clusters. We provide either spectroscopic or photometric redshifts for all the clusters in our sample. Further analysis of these data will be presented in further publications.
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    Quasars clustering at z ∼ 3 on scales ≲ 10 h-1 Mpc
    (2003) Infante, L; Varela, J; Moles, M; Hertling, G; García, A; Menanteau, F
    We test the hypothesis of whether high-redshift quasi-stellar objects (QSOs) would preferentially appear in small groups or pairs and whether they are associated with massive young clusters. We carried out a photometric search for Lyalpha emitters on scales less than or similar to 10 h(-1) Mpc in the fields of a sample of 47 z approximate to 3 known QSOs. Wide and narrowband filter color-magnitude diagrams were generated for each of the 6'.6 x 6'.6 fields. A total of 13 nonresolved objects with a significant color excess were detected as QSO candidates at a redshift similar to that of the target. All the candidates are significantly fainter than the reference QSOs, with only two of them within 2 mag of the central object. Follow-up spectroscopic observations have shown that five, i.e., about 40% of the candidates, are QSOs at the same redshift of the target; four are QSOs at different z ( two of them probably being a lensed pair at z = 1.47); two candidates are unresolved H II galaxies at z similar to 0.3; and one unclassified and one candidate turned out to be a CCD flaw. These data indicate that at least 10% of the QSOs at z similar to 3 do have companions. We have also detected a number of resolved, rather bright Lyalpha emitter candidates. Most likely, a large fraction of them might be bright galaxies with [O II] emission, at z approximate to 0.3. The fainter population of our candidates corresponds to the current expectations. Thus, there are no strong indications for the existence of an overdensity of Lyalpha galaxies brighter than m approximate to 25 around QSOs at z approximate to 3.