Browsing by Author "Franx, M"

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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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    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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    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 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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    Star formation at z ∼ 6
    (2003) Bouwens, RJ; Illingworth, GD; Rosati, P; Lidman, C; Broadhurst, T; Franx, M; Ford, HC; Magee, D; Benítez, N; Blakeslee, JP; Meurer, GR; Clampin, M; Hartig, GF; Ardila, DR; Bartko, F; Brown, RA; Burrows, CJ; Cheng, ES; Cross, NJG; Feldman, PD; Golimowski, DA; Gronwall, C; Infante, L; Kimble, RA; Krist, JE; Lesser, MP; Martel, AR; Menanteau, F; Miley, GK; Postman, M; Sirianni, M; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    Using an i - z dropout criterion, we determine the space density of z similar to 6 galaxies from two deep ACS GTO fields with deep optical-IR imaging. A total of 23 objects are found over 46 arcmin(2), or similar to0.5 +/- 0.1 objects arcmin(-2) down to z(AB) similar to 27.3 (6 sigma), or a completeness-corrected similar to0.5 +/- 0.2 objects arcmin(-2) down to z(AB) similar to 26.5 (including one probable z similar to 6 active galactic nucleus). Combining deep ISAAC data for our RDCS 1252-2927 field (J(AB) similar to 25.7 and K-s;AB similar to 25.0; 5 sigma) and NICMOS data for the Hubble Deep Field North (J(110;AB) and H-160; AB similar to 27.3, 5 sigma), we verify that these dropouts have relatively. at spectral slopes, as one would expect for star-forming objects at z similar to 6. Compared with the average-color (beta = -1.3) U-dropout in the Steidel et al. z similar to 3 sample, i-dropouts in our sample range in luminosity from similar to1.5L(*) (z(AB) similar to 25.6) to similar to0.3L(*) (z(AB) similar to 27.3) with the exception of one very bright candidate at z(850; AB) similar to 24.2. The half-light radii vary from 0."09 to 0."21, or 0.5 kpc to 1.3 kpc. We derive the z similar to 6 rest-frame UV luminosity density (or star formation rate density) by using three different procedures. All three procedures use simulations based on a slightly lower redshift (z similar to 5) V-606-dropout sample from Chandra Deep Field-South ACS images. First, we make a direct comparison of our findings with a no-evolution projection of this V-dropout sample, allowing us to automatically correct for the light lost at faint magnitudes or lower surface brightnesses. We find 23% +/- 25% more i-dropouts than we predict, consistent with no strong evolution over this redshift range. Adopting previous results to z similar to 5, this works out to a mere 20% +/- 29% drop in the luminosity density from z similar to 3 to z similar to 6. Second, we use the same V-dropout simulations to derive a detailed selection function for our i-dropout sample and compute the UV-luminosity density [7.2 +/- 2.5) _x 10(25) ergs s(-1) Hz(-1) Mpc(-3) down to z(AB) similar to 27]. We find a 39% +/- 21% drop over the same redshift range (z similar to 3-6), consistent with the first estimate. This is our preferred value and suggests a star formation rate of 0.0090 +/- 0.0031 M-. yr(-1) Mpc(-3) to z(AB) similar to 27, or similar to 0.036 +/- 0.012 M-. yr(-1) Mpc(-3) by extrapolating the luminosity function to the faint limit, assuming alpha = - 1.6. Third, we follow a very similar procedure, except that we assume no incompleteness, and find a rest-frame continuum luminosity that is similar to2-3 times lower than our other two determinations. This final estimate is to be taken as a lower limit and is important if there are modest changes in the colors or surface brightnesses from z similar to 5 to z similar to 6 (the other estimates assume no large changes in the intrinsic selectability of objects). We note that all three estimates are well within the canonical range of luminosity densities necessary for reionization of the universe at this epoch by star-forming galaxies.
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    The luminosity function of early-type field galaxies at z≈0.75
    (2004) Cross, NJG; Bouwens, RJ; Benítez, N; Blakeslee, JP; Menanteau, F; Ford, HC; Goto, T; Holden, B; Martel, AR; Zirm, A; Overzier, R; Gronwall, C; Homeier, N; Clampin, M; Hartig, GF; Illingworth, GD; Ardila, DR; Bartko, F; Broadhurst, TJ; Brown, RA; Burrows, CJ; Cheng, ES; Feldman, PD; Franx, M; Golimowski, DA; Infante, L; Kimble, RA; Krist, JE; Lesser, MP; Meurer, GR; Miley, GK; Postman, M; Rosati, P; Sirianni, M; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    We measure the luminosity function of morphologically selected E/S0 galaxies from z = 0.5 to 1.0 using deep high-resolution Advanced Camera for Surveys (ACS) imaging data. Our analysis covers an area of 48 arcmin(2) ( 8 times the area of the Hubble Deep Field North) and extends 2 mag deeper (I similar to 24 mag) than was possible in the Deep Groth Strip Survey (DGSS). Our fields were observed as part of the ACS Guaranteed Time Observations. At 0.5 < z < 0.75, we find M-B* - 5 log h(0.7) = - 21.1 +/- 0.3 and alpha = - 0.53 +/- 0.2, and at 0.75 < z < 1.0, we find M-B*-5 log h(0.7) = - 21.4 +/- 0.2, consistent with 0.3 mag of luminosity evolution ( across our two redshift intervals). These luminosity functions are similar in both shape and number density to the luminosity function using morphological selection ( e. g., DGSS), but are much steeper than the luminosity functions of samples selected using morphological proxies such as the color or spectral energy distribution (e.g., CFRS, CADIS, or COMBO-17). The difference is due to the "blue,'' (U - V)(0) < 1.7, E/S0 galaxies, which make up to ∼ 30% of the sample at all magnitudes and an increasing proportion of faint galaxies. We thereby demonstrate the need for both morphological and structural information to constrain the evolution of galaxies. We find that the blue E/S0 galaxies have the same average sizes and Sersic parameters as the "red,'' (U - V)(0) > 1.7, E/S0 galaxies at brighter luminosities (M-B < -20.1), but are increasingly different at fainter magnitudes, where blue galaxies are both smaller and have lower Sersic parameters. We find differences in both the size-magnitude relation and the photometric plane offset for red and blue E/S0s, although neither red nor blue galaxies give a good fit to the size-magnitude relation. Fits of the colors to stellar population models suggest that most E/S0 galaxies have short star formation timescales (τ < 1 Gyr), and that galaxies have formed at an increasing rate from z similar to 8 until z similar to 2, after which there has been a gradual decline.
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    The morphology-density relation in z∼1 clusters
    (2005) Postman, M; Franx, M; Cross, NJG; Holden, B; Ford, HC; Illingworth, GD; Goto, T; Demarco, R; Rosati, P; Blakeslee, JP; Tran, KV; Benítez, N; Clampin, M; Hartig, GF; Homeier, N; Ardila, DR; Bartko, F; Bouwens, RJ; Bradley, LD; Broadhurst, TJ; Brown, RA; Burrows, CJ; Cheng, ES; Feldman, PD; Golimowski, DA; Gronwall, C; Infante, L; Kimble, RA; Krist, JE; Lesser, MP; Martel, AR; Mei, S; Menanteau, F; Meurer, GR; Miley, GK; Motta, V; Sirianni, M; Sparks, WB; Tran, HD; Tsvetanov, ZI; White, RL; Zheng, W
    We measure the morphology-density relation (MDR) and morphology-radius relation (MRR) for galaxies in seven z similar to 1 clusters that have been observed with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope. Simulations and independent comparisons of our visually derived morphologies indicate that ACS allows one to distinguish between E, S0, and spiral morphologies down to z(850) = 24, corresponding to L/L* 0.21 and 0.30 at z = 0.83 and 1.24, respectively. We adopt density and radius estimation methods that match those used at lower redshift in order to study the evolution of the MDR and MRR. We detect a change in the MDR between 0: 8 < z < 1.2 and that observed at z similar to 0, consistent with recent work; specifically, the growth in the bulge-dominated galaxy fraction, f(E+S0), with increasing density proceeds less rapidly at z similar to 1 than it does at z similar to 0. At z similar to 1 and Sigma >= 500 galaxies Mpc(-2), we find < f(E+S0)> = 0.72 +/- 0.10. At z similar to 0, an E + S0 population fraction of this magnitude occurs at densities about 5 times smaller. The evolution in the MDR is confined to densities Sigma greater than or similar to 40 galaxies Mpc(-2) and appears to be primarily due to a deficit of S0 galaxies and an excess of Sp+Irr galaxies relative to the local galaxy population. The f(E)-density relation exhibits no significant evolution between z = 1 and 0. We find mild evidence to suggest that the MDR is dependent on the bolometric X-ray luminosity of the intracluster medium. Implications for the evolution of the disk galaxy population in dense regions are discussed in the context of these observations.
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    The multiwavelength survey by Yale-Chile (MUSYC)
    (2006) Gawiser, E; van Dokkum, PG; Herrera, D; Maza, J; Castander, FJ; Infante, L; Lira, P; Quadri, R; Toner, R; Treister, E; Urry, CM; Altmann, M; Assef, R; Christlein, D; Coppi, PS; Durán, MF; Franx, M; Galaz, G; Huerta, L; Liu, C; López, S; Méndez, R; Moore, DC; Rubio, M; Ruiz, MT; Toft, S; Yi, SK
    We present UBVRIz' optical images taken with MOSAIC on the CTIO 4 m telescope of the 0.32 deg(2) Extended Hubble Deep Field-South. This is one of four fields comprising the MUSYC survey, which is optimized for the study of galaxies at z=3, active galactic nucleus (AGN) demographics, and Galactic structure. Our methods used for astrometric calibration, weighted image combination, and photometric calibration in AB magnitudes are described. We calculate corrected aperture photometry and its uncertainties and find through tests that these provide a significant improvement upon standard techniques. Our photometric catalog of 62,968 objects is complete to a total magnitude of R-AB=25, with R-band counts consistent with results from the literature. We select z similar or equal to 3 Lyman break galaxy (LBG) candidates from their UVR colors and find a sky surface density of 1.4 arcmin(-2) and an angular correlation function w(theta) (2.3 +/- 1.0)theta(-0.8), consistent with previous findings that high-redshift Lyman break galaxies reside in massive dark matter halos. Our images and catalogs are available online.
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    The physical nature of Lyα-emitting galaxies at z=3.1
    (2006) Gawiser, E; van Dokkum, PG; Gronwall, C; Ciardullo, R; Blanc, GA; Castander, FJ; Feldmeier, J; Francke, H; Franx, M; Haberzettl, L; Herrera, D; Hickey, T; Infante, L; Lira, P; Maza, J; Quadri, R; Richardson, A; Schawinski, K; Schirmer, M; Taylor, EN; Treister, E; Urry, CM; Virani, SN
    We selected 40 candidate Ly alpha-emitting galaxies ( LAEs) at z similar or equal to 3.1 with observed-frame equivalent widths greater than 150 and inferred emission-line fluxes above 2.5 x 10(-17) ergs cm(-2) s(-1) from deep narrowband and broadband MUSYC images of the Extended Chandra Deep Field South. Covering 992 arcmin(2), this is the largest "blank field" surveyed for LAEs at z similar to 3, allowing an improved estimate of the space density of this population of ( 3 +/- 1) x 10(-4) h(70)(3) Mpc(-3). Spectroscopic follow-up of 23 candidates yielded 18 redshifts, all at z similar or equal to 3.1. Over 80% of the LAEs are dimmer in continuum magnitude than the typical Lyman break galaxy ( LBG) spectroscopic limit of R = 25.5 ( AB), with a median continuum magnitude R similar or equal to 27 and very blue continuum colors, V-z similar or equal to 0. Over 80% of the LAEs have the right UVR colors to be selected as LBGs, but only 10% also have R <= 25.5. Stacking the UBVRIzJK fluxes reveals that LAEs have stellar masses similar or equal to 5 x 10(8) h(70)(-2) M-circle dot and minimal dust extinction, A(V) less than or similar to 0.1. Inferred star formation rates are similar or equal to 6 h(70)(-2) M-circle dot yr(-1), yielding a cosmic star formation rate density of 2 x 10(-3) h(70) M-circle dot yr(-1) Mpc(-3). None of our LAE candidates show evidence for rest-frame emission-line equivalent widths EWrest > 240 (A) over circle that might imply a nonstandard initial mass function. One candidate is detected by Chandra, implying an AGN fraction of 2% +/- 2% for LAE candidate samples. In summary, LAEs at z similar to 3 have rapid star formation, low stellar mass, little dust obscuration, and no evidence for a substantial AGN component.
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    Ultracompact dwarf galaxies in Abell 1689
    (2004) Mieske, S; Infante, L; Benítez, N; Coe, D; Blakeslee, JP; Zekser, K; Ford, HC; Broadhurst, TJ; Illingworth, GD; Hartig, GF; Clampin, M; Ardila, DR; Bartko, F; Bouwens, RJ; Brown, RA; Burrows, CJ; Cheng, ES; Cross, NJG; Feldman, PD; Franx, M; Golimowski, DA; Goto, T; Gronwall, C; Holden, B; Homeier, N; Kimble, RA; Krist, JE; 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
    The properties of ultracompact dwarf (UCD) galaxy candidates in Abell 1689 (z = 0.183) are investigated, based on deep high-resolution images from the Hubble Space Telescope Advanced Camera for Surveys. A UCD candidate has to be unresolved, have i < 28 mag (M-V < -11.5 mag), and satisfy color limits derived from Bayesian photometric redshifts. We find 160 UCD candidates with 22 mag < i < 28 mag. We estimate that about 100 of these are cluster members, based on their spatial distribution and photometric redshifts. For i greater than or similar to 26.8 mag, the radial and luminosity distribution of the UCD candidates can be explained well by Abell 1689's globular cluster ( GC) system. For i less than or similar to 26.8 mag, there is an overpopulation of 15 +/- 5 UCD candidates with respect to the GC luminosity function. For i less than or similar to 26 mag, the radial distribution of UCD candidates is more consistent with the dwarf galaxy population than with the GC system of Abell 1689. The UCD candidates follow a color-magnitude trend with a slope similar to that of Abell 1689's genuine dwarf galaxy population, but shifted fainter by about 2-3 mag. Two of the three brightest UCD candidates (M-V similar or equal to -17 mag) are slightly resolved. At the distance of Abell 1689, these two objects would have King profile core radii of similar or equal to35 pc and r(eff) similar or equal to 300 pc, implying luminosities and sizes 2-3 times those of M32's bulge. Additional photometric redshifts obtained with late-type stellar and elliptical galaxy templates support the assignment of these two resolved sources to Abell 1689 but also allow for up to four foreground stars among the six brightest UCD candidates. Our findings imply that in Abell 1689 there are greater than or equal to10 UCDs with M-V < -12.7 mag, probably created by stripping "normal" dwarf or spiral galaxies. Compared with the UCDs in the Fornax Cluster - the location of their original discovery - they are brighter, larger, and have colors closer to normal dwarf galaxies. This suggests that they may be in an intermediate stage of the stripping process. Checking the photometric redshifts of the brightest UCD candidates with spectroscopy would be the next step to definitely confirm the existence of UCDs in Abell 1689.