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Search Results: 1 - 10 of 5298 matches for " Mauro Giavalisco "
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The Clustering Properties of Lyman-Break Galaxies at Redshift z~3
Cristiano Porciani,Mauro Giavalisco
Physics , 2001, DOI: 10.1086/324198
Abstract: We present a new measure of the angular two-point correlation function of Lyman-break galaxies (LBGs) at z~3, obtained from the variance of galaxy counts in 2-dimensional cells. By avoiding binning of the angular separations, this method is significantly less affected by shot noise than traditional measures, and allows for a more accurate determination of the correlation function. We used a sample of about 1,000 galaxies with R<=25.5 extracted from the survey by Steidel and collaborators, and found the following results. At scales in the range 30<~theta<~100 arcsec, the angular correlation function w(theta) can be accurately described as a power law with slope beta=0.50 +0.25-0.50(1 sigma random)-0.10(systematic), shallower than the measure presented by Giavalisco et al. However, the spatial correlation length, derived by Limber deprojection, is in very good agreement with the previous measures, confirming the strong spatial clustering of these sources. We discuss in detail the effects of both random and systematic errors, in particular of the so called ``integral constraint'' bias, to which we set a lower limit using numerical simulations. This suggests that the current samples do not yet provide a ``fair representation'' of the large-scale distribution of LBGs at z~3. An intriguing result of our analysis is that at angular separations smaller than theta<~30 arcsec the correlation function seems to depart from the power-law fitted at larger scales and become smaller. This feature is detected at the ~90 per cent confidence level and, if real, it can provide information on the number density and spatial distribution of LBGs within their host halos as well as the size and the mass of the halos.
Clustering Segregation With UV Luminosity in Lyman-Break Galaxies at z~3 and Its Implications
Mauro Giavalisco,Mark Dickinson
Physics , 2000, DOI: 10.1086/319715
Abstract: We report on the clustering properties of Lyman-break galaxies (LBGs) at z~3. The correlation length of flux-limited samples of LBGs depends on their rest-frame ultraviolet (UV) luminosity at lambda ~1700 Angstrom, with fainter galaxies being less strongly clustered in space. It decreases by a factor ~3 over the range of limiting magnitudes that we have probed, namely 25
The Great Observatories Origins Deep Survey
Mark Dickinson,Mauro Giavalisco,for the GOODS team
Physics , 2002, DOI: 10.1007/10899892_78
Abstract: The Great Observatories Origins Deep Survey (GOODS) is designed to gather the best and deepest multiwavelength data for studying the formation and evolution of galaxies and active galactic nuclei, the distribution of dark and luminous matter at high redshift, the cosmological parameters from distant supernovae, and the extragalactic background light. The program uses the most powerful space- and ground-based telescopes to cover two fields, each 10'x16', centered on the Hubble Deep Field North and the Chandra Deep Field South, already the sites of extensive observations from X-ray through radio wavelengths. GOODS incorporates 3.6-24 micron observations from a SIRTF Legacy Program, four-band ACS imaging from an HST Treasury Program, and extensive new ground-based imaging and spectroscopy. GOODS data products will be made available on a rapid time-scale, enabling community research on a wide variety of topics. Here we describe the project, emphasizing its application for studying the mass assembly history of galaxies.
Hubble Space Telescope Imaging of Star-Forming Galaxies at Redshifts z>3
Mauro Giavalisco,Charles C. Steidel,F. Duccio Macchetto
Physics , 1996, DOI: 10.1086/177859
Abstract: We present HST images of star-forming galaxies at redshifts z>3. These galaxies have been color selected for having a Lyman discontinuity in the otherwise flat (in f_\nu units) UV spectra of unreddened star formation. The spectroscopic confirmation of these z>3 galaxies is reported in a companion paper (Steidel et al. 1996). The HST images probe the rest-frame UV at 1400--1900 Ang and show that the morphologies of the z>3 galaxies are generally compact, although we find a few cases of more diffuse light profiles and objects comprised of multiple compact structures. Overall, the dispersion of morphologies is relatively narrow, in contrast to the variety found in star-forming galaxies at intermediate redshifts (z~1). The galaxies with compact morphology are typically characterized by a small but resolved ``core'', approximately <0.7 arcsec in radius, or about 5 h_50 (8.5 h_50) kpc with q_0=0.5 (0.05), and half-light radii of 0.2--0.3 arcsec, or 1.4--2.1 h_50 (2.4--3.6 h_50) kpc. These sizes and scale lengths are similar to those of present-day bulges or intermediate-luminosity spheroids. The ``cores'' are often surrounded by lower surface-brightness nebulosities, generally asymmetrically distributed. The minority of more diffuse galaxies do not possess this core, and an exponential function provides a very good fit to their light profiles. In contrast to highly elongated or irregular structures, such as ``chain galaxies'', that are found at $z \sim 1$, the z>3 galaxies are characterized by a relatively high degree of spherical symmetry. Morphology, space density, star-formation rates, masses, and epoch of the star-formation phase all support the hypothesis that we have identified the progenitors of present-day luminous galaxies at the epoch when they were forming the stars of
Near-Infrared Observations of BL Lacertae Host Galaxies
C. C. Cheung,C. Megan Urry,Riccardo Scarpa,Mauro Giavalisco
Physics , 2003, DOI: 10.1086/379227
Abstract: Multi-band near-infrared images of twelve BL Lacertae objects were obtained with the 2.5m telescope at the Las Campanas Observatory in order to determine the properties of their underlying host galaxies. Resolved emission was clearly detected in eight of the lowest redshift targets (up to z~0.3), and was modeled with a de Vaucouleurs r^{1/4} surface brightness law. We find that the morphologies match the elliptical galaxy profiles well, and that the BL Lac objects reside in large and luminous, but otherwise normal hosts -- consistent with previous studies done predominantly at optical wavelengths. The median absolute K-band magnitude of the galaxies in this study is -26.2, the average half-light radius is 4.2 +/- 2.3 kpc, and their average integrated R-K color is 2.7 +/- 0.3 mag. These are well within the range of values measured previously in the H-band by Kotilainen et al. and Scarpa et al. in a comparable number of targets. Taking their data together with our results, we find a best-fit K-band Kormendy relation of \mu_{e} = 4.3 log_{10} (r_{e}/kpc) + 14.2 mag arcsec^{-2}, virtually identical to that obtained for normal ellipticals. Finally, the near-infrared colors determined for five galaxies (average J-K = 0.8 +/- 0.3 mag) are the first such measurements for BL Lac hosts, and match those expected from old stellar populations at the BL Lac redshifts.
Spectroscopy of Lyman Break Galaxies in the Hubble Deep Field
Charles C. Steidel,Mauro Giavalisco,Mark Dickinson,Kurt L. Adelberger
Physics , 1996, DOI: 10.1086/118019
Abstract: We report on the initial results of a spectroscopic investigation of galaxies in the Hubble Deep Field which exhibit spectral discontinuities between the F450W and F300W passbands, indicative of the presence of the Lyman continuum break in the redshift range 2.4 < z < 3.4. We have employed color selection criteria similar to those we have used for selecting high redshift galaxy candidates from ground--based images. We find that, as for the ground--based color selection, the criteria are very successful in selecting high redshift objects. Of the 8 galaxies observed (selected from a list of 23 candidates with magnitudes equivalent to R <= 25.3, five have confirmed redshifts in the range 2.59 <= z <= 3.22, with the remaining 3 being indeterminate because of contamination from nearby brighter objects. As expected, the HST filter system is sensitive to a somewhat broader range of redshifts than our ground--based U_nGR filter system, and therefore the surveyed volume per unit area on the sky is correspondingly larger. The distribution of candidates on the plane of the sky is clearly non--uniform, consistent with the available ground--based data on the high redshift galaxies. Most Lyman break objects in the Hubble Deep Field exhibit a similar range of morphological properties to the z > 3 galaxies we have previously identified in other fields, characterized by very compact cores (some with multiple components) with half--light radii of 0.2-0.3 arcseconds, often surrounded by more diffuse and asymmetric ``halos''. A few of the brighter HDF Lyman break galaxies, however, have particularly unusual morphologies.
Probing Outflows in z= 1~2 Galaxies through FeII/FeII* Multiplets
Yuping Tang,Mauro Giavalisco,Yicheng Guo,Jaron Kurk
Physics , 2014, DOI: 10.1088/0004-637X/793/2/92
Abstract: We report on a study of the 2300-2600\AA FeII/FeII* multiplets in the rest-UV spectra of star-forming galaxies at 1.01.5 \AA and of the FeII* emission lines to W_r>0.5 \AA. Whenever we can measure the systemic redshift of the galaxies from the [OII] emission line, we find that both the FeII and MgII absorption lines are blueshifted, indicative that both species trace gaseous outflows. We also find, however, that the FeII gas has generally lower outflow velocity relative to that of MgII. We investigate the variation of FeII line profiles as a function of the radiative transfer properties of the lines, and find that transitions with higher oscillator strengths are more blueshifted in terms of both line centroids and line wings. We discuss the possibility that FeII lines are suppressed by stellar absorptions. The lower velocities of the FeII lines relative to the MgII doublet, as well as the absence of spatially extended FeII* emission in 2D stacked spectra, suggest that most clouds responsible for the FeII absorption lie close (3~4 kpc) to the disks of galaxies. We show that the FeII/FeII* multiplets offer unique probes of the kinematic structure of galactic outflows.
The Internal Ultraviolet-to-Optical Color Dispersion: Quantifying the Morphological K-Correction
Casey Papovich,Mauro Giavalisco,Mark Dickinson,Christopher J. Conselice,Henry C. Ferguson
Physics , 2003, DOI: 10.1086/378976
Abstract: We present a quantitative measure of the internal color dispersion within galaxies, which quantifies differences in morphology as a function of wavelength. We apply this statistic to a local galaxy sample with archival images at 1500 and 2500 Angstroms from the Ultraviolet Imaging Telescope, and ground-based B-band observations to investigate how the color dispersion relates to global galaxy properties. The intenal color dispersion generally correlates with transformations in galaxy morphology as a function of wavelength, i.e., it quantifies the morphological K-correction. Mid-type spiral galaxies exhibit the highest dispersion in their internal colors, which stems from differences in the bulge, disk, and spiral-arm components. Irregulars and late-type spirals show moderate internal color dispersion, which implies that young stars generally dominate the colors. Ellipticals, lenticulars, and early-type spirals generally have low or negligible internal color dispersion, which indicates that the stars contributing to the UV-to-optical emission have a very homogeneous distribution. We discuss the application of the internal color dispersion to high-redshift galaxies in deep, Hubble Space Telescope images. By simulating local galaxies at cosmological distances, many of the galaxies have luminosities that are sufficiently bright at rest--frame optical wavelengths to be detected within the limits of the currently deepest near-infrared surveys even with no evolution. Under assumptions that the luminosity and color evolution of the local galaxies conform with the measured values of high-redshift objects, we show that galaxies' intrinsic internal color dispersion remains measurable out to z ~ 3.
The z ~ 4 Lyman Break Galaxies: Colors and Theoretical Predictions
Rafal Idzi,Rachel Somerville,Casey Papovich,Henry C. Ferguson,Mauro Giavalisco,Claudia Kretchmer,Jennifer Lotz
Physics , 2003, DOI: 10.1086/378579
Abstract: We investigate several fundamental properties of z ~ 4 Lyman-break galaxies by comparing observations with the predictions of a semi-analytic model based on the Cold Dark Matter theory of hierarchical structure formation. We use a sample of B_{435}-dropouts from the Great Observatories Origins Deep Survey, and complement the ACS optical B_{435}, V_{606}, i_{775}, and z_{850} data with the VLT ISAAC J, H, and K_{s} observations. We extract B_{435}-dropouts from our semi-analytic mock catalog using the same color criteria and magnitude limits that were applied to the observed sample. We find that the i_{775} - K_{s} colors of the model-derived and observed B_{435}-dropouts are in good agreement. However, we find that the i_{775}-z_{850} colors differ significantly, indicating perhaps that either too little dust or an incorrect extinction curve have been used. Motivated by the reasonably good agreement between the model and observed data we present predictions for the stellar masses, star formation rates, and ages for the z ~ 4 Lyman-break sample. We find that according to our model the color selection criteria used to select our z ~ 4 sample surveys 67% of all galaxies at this epoch down to z_{850} < 26.5. We find that our model predicts a roughly 40% mass build-up between the z \~ 4 and z ~ 3 epochs for the UV rest-frame L* galaxies. Furthermore, according to our model, at least 50% of the total stellar mass resides in relatively massive UV-faint objects that fall below our observational detection limit.
High Redshift Galaxies in the Hubble Deep Field. Color Selection and Star Formation History to z=4
Piero Madau,Henry C. Ferguson,Mark E. Dickinson,Mauro Giavalisco,Charles C. Steidel,Andrew Fruchter
Physics , 1996, DOI: 10.1093/mnras/283.4.1388
Abstract: The Lyman decrement associated with the cumulative effect of HI in QSO absorption systems along the line of sight provides a distinctive feature for identifying galaxies at z>2.5. The Hubble Deep Field (HDF) observations offer the opportunity to exploit the ubiquitous effect of intergalactic absorption and obtain useful statistical constraints on the redshift distribution of galaxies considerably fainter than current spectroscopic limits. We model the HI cosmic opacity as a function of redshift, including scattering in resonant lines of the Lyman series and Lyman-continuum absorption, and use stellar population synthesis models with a wide variety of ages, metallicities, dust contents, and redshifts, to derive color selection criteria that provide a robust separation between high redshift and low redshift galaxies. From the HDF images we construct a sample of star-forming galaxies at 2
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