30 results on '"Nicole Homeier"'
Search Results
2. Mass Selection and the Evolution of the Morphology‐Density Relation fromz= 0.8 to 0
- Author
-
K.-V. Tran, A. van der Wel, Andrew Zirm, Marc Postman, D. D. Kelson, G. D. Illingworth, Piero Rosati, Dan Magee, Holland C. Ford, R. Demarco, B. Holden, John P. Blakeslee, Nicole Homeier, and M. Franx more...
- Subjects
Morphology (linguistics) ,clusters : general [galaxies] ,COMA CLUSTER ,X-RAY DATA ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,STAR-FORMATION ,cD ,Luminosity ,CLUSTER CL 1358+62 ,Hubble space telescope ,COLOR-MAGNITUDE RELATION ,Cluster (physics) ,EARLY-TYPE GALAXIES ,Astrophysics::Galaxy Astrophysics ,Physics ,CCD SURFACE PHOTOMETRY ,Astrophysics (astro-ph) ,Sigma ,Astronomy and Astrophysics ,HUBBLE-SPACE-TELESCOPE ,Galaxy ,Redshift ,Physics and Astronomy ,evolution galaxies : fundamental parameters [galaxies] ,Space and Planetary Science ,Magnitude (astronomy) ,MEDIUM-SENSITIVITY SURVEY ,photometry [galaxies] ,DIGITAL SKY SURVEY ,elliptical and lenticular [galaxies] - Abstract
We examined the morphology-density relations for galaxy samples selected by luminosity and by mass in each of five massive X-ray clusters from z=0.023 to 0.83 for 674 spectroscopically-confirmed members. Rest-frame optical colors and visual morphologies were obtained primarily from Hubble Space Telescope images. Morphology-density relations (MDR) are derived in each cluster from a complete, luminosity-selected sample of 452 galaxies with a magnitude limit M_V < M^{*}_{V} + 1. The change in the early-type fraction with redshift matches previous work for massive clusters of galaxies. We performed a similar analysis, deriving MDRs for complete, mass-selected samples of 441 galaxies with a mass-limit of 10^{10.6} M_{\sun}. Our mass limit includes faint objects, the equivalent of =~1 mag below L^{*} for the red cluster galaxies, and encompasses =~70% of the stellar mass in cluster galaxies. The MDRs in the mass-selected sample at densities of Sigma > 50 galaxies Mpc^{-2} are similar to those in the luminosity-selected sample but show larger early-type fractions. However, the trend with redshift in the fraction of elliptical and S0 galaxies with masses > 10^{10.6} M_{\sun} differs significantly between the mass- and luminosity-selected samples. The clear trend seen in the early-type fraction from z=0 to z=~ 0.8 is not found in mass-selected samples. The early-type galaxy fraction changes much less, and is consistent with being constant at 92% +/- 4% at ��> 500 galaxies Mpc^{-2} and 83 +/- 3% at 50 < ��< 500 galaxies Mpc^{-2}. This suggests that galaxies of mass lower than > 10^{10.6} M_{\sun} play a significant role in the evolution of the early-type fraction in luminosity-selected samples. (Abstract abridged), 18 pages in emulate ApJ format, with 10 color figures, Accepted to ApJ. Version updated to reflect published version, includes new references and a correction to table 3 more...
- Published
- 2007
- Full Text
- View/download PDF
Catalog
3. Clusters at Half Hubble Time: Galaxy Structure and Colors in RX J0152.7−1357 and MS 1054−03
- Author
-
K.-V. Tran, Gerhardt R. Meurer, Holland C. Ford, Myungkook J. Jee, B. Holden, R. J. Bouwens, Marc Postman, M. Franx, Felipe Menanteau, Piero Rosati, Nicole Homeier, G. D. Illingworth, Simona Mei, John P. Blakeslee, and R. Demarco more...
- Subjects
Physics ,Star formation ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Sigma ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Advanced Camera for Surveys ,Redshift ,Galaxy ,Space and Planetary Science ,Cluster (physics) ,Astrophysics::Galaxy Astrophysics ,Galaxy cluster ,Weak gravitational lensing - Abstract
We study the photometric and structural properties of spectroscopically confirmed members in the two massive X-ray--selected z=0.83 galaxy clusters MS1054-03 and RXJ0152-1357 using three-band mosaic imaging with the Hubble Space Telescope Advanced Camera for Surveys. The samples include 105 and 140 members of MS1054-03 and RXJ0152-1357, respectively, with ACS F775W magnitude < 24.0. We develop a promising new structural classification method, based on a combination of the best-fit Sersic indices and the normalized root-mean-square residuals from the fits; the resulting classes agree well with the visual ones, but are less affected by galaxy orientation. We examine the color--magnitude relations in detail and find that the color residuals correlate with the local mass density measured from our weak lensing maps; we identify a threshold density of $\Sigma \approx 0.1$, in units of the critical density, above which the star formation appears to cease. For RXJ0152-1357, we also find a trend in the color residuals with velocity, resulting from an offset of about 980 km/s in the mean redshifts of the early- and late-type galaxies. Analysis of the color--color diagrams indicates that a range of star formation time-scales are needed to reproduce the loci of the galaxy colors. We also identify some cluster galaxies whose colors can only be explained by large amounts, $A_V \approx 1$ mag, of internal dust extinction. [Abstract shortened], Comment: 30 pages, emulateapj format; 23 figures, many in color. Accepted by ApJ; scheduled for the 10 June 2006 issue. Some figures degraded; for a higher resolution version, see: http://astro.wsu.edu/blakeslee/z1clusters/ more...
- Published
- 2006
- Full Text
- View/download PDF
4. The star cluster population in the tidal tails of NGC 6872
- Author
-
Markus Kissler-Patig, Nicole Homeier, Nate Bastian, M. Hempel, and G. Trancho
- Subjects
Physics ,education.field_of_study ,Star formation ,Astrophysics (astro-ph) ,Population ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Galaxy ,Stars ,Star cluster ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Disc ,education ,Astrophysics::Galaxy Astrophysics ,Galaxy cluster ,Dwarf galaxy - Abstract
We present a photometric analysis of the rich star cluster population in the tidal tails of NGC 6872. We find star clusters with ages between 1 - 100 Myr distributed in the tidal tails, while the tails themselves have an age of less than 150 Myr. Most of the young massive ($10^{4} \le M/M_{\odot} \le 10^{7}$) clusters are found in the outer regions of the galactic disk or the tidal tails. The mass distribution of the cluster population can be well described by power-law of the form $N(m) \propto m^{-\alpha}$, where $\alpha = 1.85 \pm 0.11$, in very good agreement with other young cluster populations found in a variety of different environments. We estimate the star formation rate for three separate regions of the galaxy, and find that the eastern tail is forming stars at $\sim 2$ times the rate of the western tail and $\sim 5$ times the rate of the main body of the galaxy. By comparing our observations with published N-body models of the fate of material in tidal tails in a galaxy cluster potential, we see that many of these young clusters will be lost into the intergalactic medium. We speculate that this mechanism may also be at work in larger galaxy clusters such as Fornax, and suggest that the so-called ultra-compact dwarf galaxies could be the most massive star clusters that have formed in the tidal tails of an ancient galactic merger., Comment: 12 pages, 10 figures, accepted A&A more...
- Published
- 2005
- Full Text
- View/download PDF
5. The Effect of Type Ibc Contamination in Cosmological Supernova Samples
- Author
-
Nicole Homeier
- Subjects
Physics ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Type (model theory) ,Contamination ,Lambda ,Omega ,Redshift ,Distance modulus ,Supernova ,Space and Planetary Science - Abstract
We explore the effect of contamination of intermediate redshift Type Ia supernova samples by Type Ibc supernovae. Simulating observed samples of Ia and mixed Ibc/Ia populations at a range of redshifts for an underlying cosmological concordance model (\Omega_{m}=0.27, \Omega_{\Lambda}=0.73), we find that even small contamination levels, 2-5% may bias the derived \Omega_{\Lambda} and \Omega_{m} towards larger values. We thus emphasize the need for clean samples of Type Ia SNe for accurate measurements of the cosmological parameters. We also simulate a SN sample similar to the fiducial SNAP detected distribution (Kim et al. 2004), but include Ibc contamination. For this distribution we illustrate the effect of Ibc contamination on the distance modulus vs. redshift diagram for low and high precision measurements., Comment: ApJ accepted more...
- Published
- 2005
- Full Text
- View/download PDF
6. Massive star formation in the W49 giant molecular cloud: Implications for the formation of massive star clusters
- Author
-
Nicole Homeier and João Alves
- Subjects
Physics ,education.field_of_study ,Stellar mass ,Star formation ,Molecular cloud ,Astrophysics (astro-ph) ,Population ,Extinction (astronomy) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Stars ,Star cluster ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,education ,Astrophysics::Galaxy Astrophysics ,Luminosity function (astronomy) - Abstract
We present results from JHKs imaging of the densest region of the W49 molecular cloud. In a recent paper (Alves & Homeier 2003), we reported the detection of (previously unknown) massive stellar clusters in the well-known giant radio HII region W49A, and here we continue our analysis. We use the extensive line-of-sight extinction to isolate a population of objects associated with W49A. We constrain the slope of the stellar luminosity function by constructing an extinction-limited luminosity function, and use this to obtain a mass function. We find no evidence for a top-heavy MF, and the slope of the derived mass function is -1.6 \pm 0.3. We identify candidate massive stars from our color-magnitude diagram, and we use these to estimate the current total stellar mass of 5-7x10^4 M_sun in the region of the W49 molecular cloud covered by our survey. Candidate ionizing stars for several ultra-compact HII regions are detected, with many having multipe candidate sources. On the global molecular cloud scale in W49, massive star formation apparently did not proceed in a single concentrated burst, but in small groups, or subclusters. This may be an essential physical description for star formation in what will later be termed a 'massive star cluster'., Accepted for publication in Astronomy & Astrophysics more...
- Published
- 2005
- Full Text
- View/download PDF
7. Panchromatic Study of Nearby Ultraviolet-bright Starburst Galaxies: Implications for Massive Star Formation and High-Redshift Galaxies
- Author
-
Anne L. Kinney, C. J. Conselice, STScI, U. Wisconsin-Madison, Daniela Calzetti, Nicole Homeier, and J. S. Gallagher
- Subjects
Physics ,Brightness ,Star formation ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,medicine.disease_cause ,Redshift ,Galaxy ,Panchromatic film ,Space and Planetary Science ,medicine ,Ejecta ,Ultraviolet ,Visible spectrum - Abstract
We present a panchromatic study of nearby starburst galaxies from the ultraviolet to the visible, including narrow band H(alpha) using WIYN and HST data, to determine how star formation processes affect the morphology and integrated fluxes of nearby starbursts. We find the UV/H(alpha) morphology of starbursts tend to differ, although not in a standard or predictable manner. From our sample of six nearby starbursts, three systems show a good correlation between UV and H(alpha) fluxes, but we find differences in UV and H(alpha) morphology between the other three. Occasionally we find systems with well defined H II regions without the corresponding brightness in the UV, and vice-versa. We discuss the likely mechanisms behind these differences which include: starburst ages, dust absorption, stellar energy ejecta through SNe and winds, as well as leakage of UV photons from stellar clusters. We conclude that the large scale morphological features in starbursts are primarily due to both age and absorption from a `picket fence' dust distribution. We further demonstrate the similarity and differences between these nearby starbursts and high redshift star forming galaxies. The overall morphology of our sample of starbursts changes little between UV and visible wavelengths. If high redshift galaxies are similar to these starbursts, their morphologies should change little between rest-frame UV and optical. We also show that FIR and UV spectral energy distributions and slopes can be used to determine large scale morphological features for extreme starbursts, with the steepest FIR slopes correlating with the most disturbed galaxies., Comment: 34 Pages with figures; Appearing in January 2000 Astronomical Journal more...
- Published
- 2000
- Full Text
- View/download PDF
8. Evolution of the color-magnitude relation in galaxy clusters at z ∼ 1 from the ACS intermediate redshift cluster survey
- Author
-
Arjen van der Wel, Simona Mei, Brad Holden, Holland C. Ford, Marijn Franx, Garth D. Illingworth, John P. Blakeslee, Nicole Homeier, James G. Bartlett, Myungkook J. Jee, Piero Rosati, Roderik Overzier, Marc Postman, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), APC - Cosmologie, AstroParticule et Cosmologie (APC (UMR_7164)), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Physique Corpusculaire et Cosmologie - Collège de France (PCC), Collège de France (CdF)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-AstroParticule et Cosmologie (APC (UMR_7164)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris more...
- Subjects
RAY-SELECTED ,[SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO] ,Population ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,CAMERA ,01 natural sciences ,cD ,[PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO] ,CHANDRA X-RAY ,ELLIPTIC GALAXIES ,ADVANCED ,0103 physical sciences ,Galaxy formation and evolution ,clusters: general [galaxies] ,10. No inequality ,education ,010303 astronomy & astrophysics ,Lenticular galaxy ,RED SEQUENCE ,Galaxy cluster ,Astrophysics::Galaxy Astrophysics ,evolution [galaxies] ,Physics ,education.field_of_study ,010308 nuclear & particles physics ,Astrophysics (astro-ph) ,Velocity dispersion ,Astronomy and Astrophysics ,HUBBLE-SPACE-TELESCOPE ,VLT DEEP SURVEY ,DISTANT CLUSTERS ,Galaxy ,Redshift ,Physics and Astronomy ,Space and Planetary Science ,galaxies: clusters: general ,galaxies: elliptical and lenticular, cD ,Elliptical galaxy ,DIGITAL SKY SURVEY ,galaxies: evolution ,CLUSTERS ,MORPHOLOGY-DENSITY RELATION ,elliptical and lenticular [galaxies] - Abstract
We apply detailed observations of the Color-Magnitude Relation (CMR) with the ACS/HST to study galaxy evolution in eight clusters at z~1. The early-type red sequence is well defined and elliptical and lenticular galaxies lie on similar CMRs. We analyze CMR parameters as a function of redshift, galaxy properties and cluster mass. For bright galaxies (M_B < -21mag), the CMR scatter of the elliptical population in cluster cores is smaller than that of the S0 population, although the two become similar at faint magnitudes. While the bright S0 population consistently shows larger scatter than the ellipticals, the scatter of the latter increases in the peripheral cluster regions. If we interpret these results as due to age differences, bright elliptical galaxies in cluster cores are on average older than S0 galaxies and peripheral elliptical galaxies (by about 0.5Gyr). CMR zero point, slope, and scatter in the (U-B)_z=0 rest-frame show no significant evolution out to redshift z~1.3 nor significant dependence on cluster mass. Two of our clusters display CMR zero points that are redder (by ~2sigma) than the average (U-B)_z=0 of our sample. We also analyze the fraction of morphological early-type and late-type galaxies on the red sequence. We find that, while in the majority of the clusters most (80% to 90%) of the CMR population is composed of early-type galaxies, in the highest redshift, low mass cluster of our sample, the CMR late-type/early-type fractions are similar (~50%), with most of the late-type population composed of galaxies classified as S0/a. This trend is not correlated with the cluster's X-ray luminosity, nor with its velocity dispersion, and could be a real evolution with redshift., ApJ, in press, 27 pages, 22 figures more...
- Published
- 2009
- Full Text
- View/download PDF
9. VLT and ACS observations of RDCS J1252.9-2927: dynamical structure and galaxy populations in a massive cluster at z=1.237
- Author
-
Paolo Tozzi, Nicole Homeier, G. Hartig, Garth D. Illingworth, Brad Holden, Leopoldo Infante, R. Gobat, Ricardo Demarco, Marc Postman, V. Mainieri, Roderik Overzier, Veronica Motta, Alessandro Rettura, Mario Nonino, Narciso Benítez, V. Strazzullo, Piero Rosati, A. van der Wel, Myungkook J. Jee, W. Zheng, Christopher Lidman, Andrew Zirm, Holland C. Ford, John P. Blakeslee, Marisa Girardi, Simona Mei, Mark Clampin, Felipe Menanteau, Spencer A. Stanford, Demarco, R., Rosati, P., Lidman, C., Girardi, Marisa, Nonino, M., Rettura, A., Strazzullo, Veronica, van der Wel, A., Ford, H. C., Mainieri, V., Holden, B. P., Stanford, S. A., Blakeslee, J. P., Gobat, R., Postman, M., Tozzi, P., Overzier, R. A., Zirm, A. W., Benítez, N., Homeier, N. L., Illingworth, G. D., Infante, L., Jee, M. J., Mei, S., Menanteau, F., Motta, V., Zheng, W., Clampin, M., and Hartig, G. more...
- Subjects
J1252.9-2927) ,Structure formation ,clusters : general [galaxies] ,H-ALPHA ,Dark matter ,FOS: Physical sciences ,DEEP-FIELD-NORTH ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Advanced Camera for Surveys ,0103 physical sciences ,Cluster (physics) ,COLOR-MAGNITUDE RELATION ,STAR-FORMING GALAXIES ,TO-LIGHT RATIOS ,galaxy clusters ,Astrophysics::Solar and Stellar Astrophysics ,010306 general physics ,010303 astronomy & astrophysics ,Galaxy cluster ,Astrophysics::Galaxy Astrophysics ,Physics ,clusters : individual (ClG [galaxies] ,SCALE-INDEPENDENT METHOD ,Astrophysics (astro-ph) ,Astronomy and Astrophysics ,HUBBLE-SPACE-TELESCOPE ,HIGH-REDSHIFT CLUSTERS ,Redshift ,Galaxy ,Stars ,COMPACT BLUE GALAXIES ,Physics and Astronomy ,Space and Planetary Science ,MORPHOLOGY-DENSITY RELATION - Abstract
We present results from an extensive spectroscopic survey, carried out with VLT FORS, and from an extensive multiwavelength imaging data set from the HST Advanced Camera for Surveys and ground based facilities, of the cluster of galaxies RDCS J1252.9-2927. We have spectroscopically confirmed 38 cluster members in the redshift range 1.22 < z < 1.25. A cluster median redshift of z=1.237 and a rest-frame velocity dispersion of 747^{+74}_{-84} km/s are obtained. Using the 38 confirmed redshifts, we were able to resolve, for the first time at z > 1, kinematic structure. The velocity distribution, which is not Gaussian at the 95% confidence level, is consistent with two groups that are also responsible for the projected east-west elongation of the cluster. The groups are composed of 26 and 12 galaxies with velocity dispersions of 486^{+47}_{-85} km/s and 426^{+57}_{-105} km/s, respectively. The elongation is also seen in the intracluster gas and the dark matter distribution. This leads us to conclude that RDCS J1252.9-2927 has not yet reached a final virial state. We extend the analysis of the color-magnitude diagram of spectroscopic members to more than 1 Mpc from the cluster center. The scatter and slope of non-[OII]-emitting cluster members in the near-IR red sequence is similar to that seen in clusters at lower redshift. Furthermore, most of the galaxies with luminosities greater than ~ K_s*+1.5 do not show any [OII], indicating that these more luminous, redder galaxies have stopped forming stars earlier than the fainter, bluer galaxies. Our observations provide detailed dynamical and spectrophotometric information on galaxies in this exceptional high-redshift cluster, delivering an in-depth view of structure formation at this epoch only 5 Gyr after the Big Bang., 29 pages. 16 figures. ApJ accepted. Tables 2,3 and 5, figure 1 and the full figure 5 will be available in the paper and electronic editions from ApJ. v2: minor corrections to the abstract and text to match the Journal's version more...
- Published
- 2007
10. Hubble Space Telescope ACS multiband coronagraphic imaging of the debris disk around β pictoris
- Author
-
T. J. Broadhurst, Andrew Zirm, George F. Hartig, G. K. Miley, Myungkook J. Jee, Tomotsugu Goto, William B. Sparks, R. Demarco, R. A. Kimble, M. Franx, Hien D. Tran, Nicole Homeier, Nicholas Cross, C. Gronwall, E. S. Cheng, Felipe Menanteau, R. L. White, Andre Martel, Bradford P. Holden, David R. Ardila, Zlatan Tsvetanov, Marc Postman, M. Clampin, Simona Mei, Narciso Benítez, L. Infante, D. A. Golimowski, Holland C. Ford, Marco Sirianni, P. D. Feldman, John Krist, Piero Rosati, John P. Blakeslee, Larry Bradley, WeiKang Zheng, R. J. Bouwens, C. J. Burrows, Michael Lesser, Robert A. Brown, F. Bartko, Gerhardt R. Meurer, V. Motta, and G. D. Illingworth more...
- Subjects
Physics ,Debris disk ,Number density ,Flux ,Astronomy and Astrophysics ,Astrophysics ,Advanced Camera for Surveys ,Power law ,Silicate ,chemistry.chemical_compound ,Amplitude ,chemistry ,Space and Planetary Science ,Beta Pictoris - Abstract
著者人数:43名, Accepted: 2006-02-13, 資料番号: SA1000396000
- Published
- 2006
11. Evolution of the Color-Magnitude relation in High-Redshift Clusters: Early-type Galaxies in the Lynx Supercluster at z~1.26
- Author
-
Garth D. Illingworth, Myungkook J. Jee, Alessandro Rettura, Nicole Homeier, Holland C. Ford, John P. Blakeslee, Brad Holden, Simona Mei, Marijn Franx, Marco Sirianni, Ricardo Demarco, Marc Postman, and Piero Rosati more...
- Subjects
Physics ,education.field_of_study ,Stellar population ,Population ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Advanced Camera for Surveys ,Galaxy ,Redshift ,Space and Planetary Science ,Supercluster ,Cluster (physics) ,Elliptical galaxy ,education - Abstract
Color-magnitude relations have been derived in the clusters RX J0849+4452 and RX J0848+4453 at z~1.26. The color-magnitude relation was determined from Advanced Camera for Surveys imaging in the WFC F775W (i_775) and F850LP (z_850) filters combined with ground-based spectroscopy. Early-type cluster candidates have been identified according to the Postman et al. morphological classification. In both clusters the bright red early-type population defines a tight color-magnitude relation very similar in color, although the two clusters present different X-ray luminosities and shapes, with RX J0849+4452 being three times more X-ray luminous and more compact, and having a temperature two times higher. The elliptical galaxy color-magnitude relations (CMR) in RX J0849+4452 and RX J0848+4453 show an intrinsic (i_775-z_850) color scatter of 0.026 +/- 0.012 mag and 0.024 +/- 0.015 mag, respectively, within 2 arcminutes (~1Mpc at z=1.26) from the cluster X-ray emission centers. Simple modeling of the scatters using stellar population models from Bruzual and Charlot, gives a mean luminosity-weighted age t > 2.5 Gyr (z_f > 2.75). S0 galaxies follow the elliptical CMR; they show larger scatters about the CMR. The intrinsic scatter decreases and the CMR slopes are steeper at smaller radii, within both clusters. We conclude that old stellar populations in cluster elliptical galaxies are already in place at z=1.26, both in the more evolved cluster RX J0849+4452, and in its less evolved companion RX J0848+4453. Even at a lookback time of 9 Gyr, in the early merging and buildup of massive clusters, the bulk of the stellar content of the bright elliptical galaxy population was in place - apparently formed some 2.5~Gyr earlier at z~3, 22 pages, 8 figures; ApJ, in press more...
- Published
- 2006
12. The Possible z=0.83 Precursors of z=0 M* Early-type Cluster Galaxies
- Author
-
Daniel D. Kelson, Marc Postman, Garth D. Illingworth, Piero Rosati, Nicole Homeier, Marijn Franx, Kim-Vy Tran, Ricardo Demarco, Brad Holden, Holland C. Ford, and John P. Blakeslee
- Subjects
Physics ,Field (physics) ,Stellar mass ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Galaxy ,Early type ,Space and Planetary Science ,Coma Cluster ,Cluster (physics) ,Spectral energy distribution ,Astrophysics::Galaxy Astrophysics - Abstract
We examine the distribution of stellar masses of galaxies in MS 1054-03 and RX J0152.7-1357, two X-ray selected clusters of galaxies at z=0.83. Our stellar mass estimates, from spectral energy distribution fitting, reproduce the dynamical masses as measured from velocity dispersions and half-light radii with a scatter of 0.2 dex in the mass for early-type galaxies. When we restrict our sample of members to high stellar masses, > 1e11.1 Msun (M* in the Schechter mass function for cluster galaxies), we find that the fraction of early-type galaxies is 79 +/- 6% at z=0.83 and 87 +/- 6% at z=0.023 for the Coma cluster, consistent with no evolution. Previous work with luminosity-selected samples finds that the early-type fraction in rich clusters declines from =~80% at z=0 to =~60% at z=0.8. The observed evolution in the early-type fraction from luminosity-selected samples must predominately occur among sub-M* galaxies. As M* for field and group galaxies, especially late-types, is below M* for clusters galaxies, infall could explain most of the recent early-type fraction growth. Future surveys could determine the morphological distributions of lower mass systems which will confirm or refute this explanation., 5 pages in emulate ApJ format with three color figures. Accepted for publication in ApJ Letters, v642n2. Updated to correct grammatical and typographic errors found by the journal more...
- Published
- 2006
13. Lyman break galaxies, Lya emitters and a radio galaxy in a protocluster at z=4.1
- Author
-
Nicholas Cross, Holland C. Ford, Narciso Benítez, G. K. Miley, Bram Venemans, R. J. Bouwens, Simona Mei, G. D. Illingworth, Zlatan Tsvetanov, Dan Coe, H. J. A. Röttgering, J. D. Kurk, Roderik Overzier, Isa Oliveira, John P. Blakeslee, WeiKang Zheng, Nicole Homeier, Andre Martel, R. Demarco, and Andrew Zirm more...
- Subjects
Physics ,Field (physics) ,Stellar mass ,Star formation ,Radio galaxy ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Sigma ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Galaxy ,Redshift ,Space and Planetary Science ,Cluster (physics) ,Astrophysics::Galaxy Astrophysics - Abstract
We present deep HST/ACS observations in g,r,i,z towards the z=4.1 radio galaxy TN J1338-1942 and its overdensity of >30 spectroscopically confirmed Lya emitters (LAEs). We select 66 g-band dropouts to z=27, 6 of which are also a LAE. Although our color-color selection results in a relatively broad redshift range centered on z=4.1, the field of TN J1338-1942 is richer than the average field at the >5 sigma significance, based on a comparison with GOODS. The angular distribution is filamentary with about half of the objects clustered near the radio galaxy, and a small, excess signal (2 sigma) in the projected pair counts at separations of 10^14 Msun structure, confirming that it is possible to find and study cluster progenitors in the linear regime at z>4., Accepted for publication in ApJ (33 pages, 19 figures, emulateapj). v3 includes updated methods, discussion and referencing more...
- Published
- 2006
14. The Formation Epoch of Early-Type Galaxies in the z ~ 0.9 CL1604 Supercluster
- Author
-
Garth D. Illingworth, Simona Mei, Nicole Homeier, Felipe Menanteau, Bradford P. Holden, Piero Rosati, Holland C. Ford, Andrew Zirm, Larry Bradley, Myungkook J. Jee, M. Franx, John P. Blakeslee, Ricardo Demarco, Marc Postman, and A. van der Wel more...
- Subjects
Epoch (astronomy) ,Population ,NEARBY CLUSTERS ,evolution [cD galaxies] ,FOS: Physical sciences ,Astrophysics ,lenticular ,Advanced Camera for Surveys ,ADVANCED CAMERA ,DEPENDENCE ,Supercluster ,COLOR-MAGNITUDE RELATION ,Cluster (physics) ,RED-SEQUENCE ,education ,elliptical and [galaxies] ,Physics ,education.field_of_study ,Astrophysics (astro-ph) ,Astronomy and Astrophysics ,HIGH-REDSHIFT CLUSTERS ,HUBBLE-SPACE-TELESCOPE ,ENVIRONMENTAL ,EVOLUTION ,Redshift ,Galaxy ,clusters : individual (Cl 1604) [galaxies] ,Physics and Astronomy ,Space and Planetary Science ,KECK SPECTROSCOPY ,Magnitude (astronomy) ,FUNDAMENTAL-PLANE - Abstract
We analyse the cluster color-magnitude relation (CMR) for early-type galaxies in two of the richer clusters in the z ~ 0.9 supercluster system to derive average ages and formation redshifts for the early-type galaxy population. Both clusters were observed with the Advanced Camera for Surveys aboard the {\it Hubble Space Telescope} through the F606W and F814W filters, which brackets the rest-frame 4000 ��break at the cluster redshifts of z\sim 0.9. We fit the zeropoint and slope of the red cluster sequence, and model the scatter about this relation to estimate average galaxy ages and formation redshifts. We find intrinsic scatters of 0.038-0.053 mag in ($V_{606}-I_{814}$) for the E and E+S0 populations, corresponding to average ages of 3.5-3.7 Gyr and formation redshifts z_{f}=2.4-2.6. We find at least one significant difference between the Cl1604+4304 and Cl1604+4321 early-type CMRs. Cl1604+4321, the less X-ray luminous and massive of the two, lacks bright L^* ellipticals. We combine the galaxy samples to fit a composite CMR down to 0.15L^*, and find that the slope of the combined cluster CMR is significantly steeper than for RX J0152.7-1357 but consistent with MS 1054-03, both at similar redshift. The slope of the Cl1604 CMR at the bright end (L > 0.5L^*) is flatter and consistent with the CMR slopes found for other high redshift clusters. We find evidence for increasing scatter with increasing magnitude along the early-type CMR, consistent with a 'downsizing' scenario, indicating younger mean ages with decreasing galaxy mass., replaced to fix bizarre shift in vertical centering, ApJ accepted more...
- Published
- 2006
- Full Text
- View/download PDF
15. An overdensity of galaxies near the most distant radio-loud quasar
- Author
-
G. D. Illingworth, R. L. White, T. J. Broadhurst, Marc Postman, M. Franx, Larry Bradley, Felipe Menanteau, Gerhardt R. Meurer, Bradford P. Holden, Nicole Homeier, George F. Hartig, V. Motta, G. K. Miley, Narciso Benítez, M. Clampin, Simona Mei, WeiKang Zheng, Andre Martel, C. Gronwall, E. S. Cheng, Hien D. Tran, Rychard Bouwens, Marco Sirianni, Holland C. Ford, Michael Lesser, Robert A. Brown, Zlatan Tsvetanov, P. D. Feldman, Nicholas Cross, William B. Sparks, F. Bartko, D. A. Golimowski, John Krist, P. Rosati, M. K. Jee, L. Infante, C. J. Burrows, Tomotsugu Goto, John P. Blakeslee, R. A. Kimble, Roderik Overzier, David R. Ardila, R. Demarco, and Andrew Zirm more...
- Subjects
Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Redshift ,Galaxy ,Space and Planetary Science ,Substructure ,Astrophysics::Solar and Stellar Astrophysics ,Merge (version control) ,Astrophysics::Galaxy Astrophysics - Abstract
著者人数:44名, Accepted: 2005-11-22, 資料番号: SA1000634000
- Published
- 2006
16. Imprints of Environment on Cluster and Field Late-type Galaxies at z~1
- Author
-
Andrew Zirm, Ricardo Demarco, Marc Postman, Holland C. Ford, Felipe Menanteau, John P. Blakeslee, Simona Mei, Garth D. Illingworth, and Nicole Homeier
- Subjects
Physics ,Field (physics) ,Color difference ,Star formation ,media_common.quotation_subject ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Asymmetry ,Redshift ,Galaxy ,Space and Planetary Science ,Cluster (physics) ,Irregular galaxy ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We present a comparison of late-type galaxies (Sa and later) in intermediate redshift clusters and the field using ACS imaging of four cluster fields: CL0152-1357, CL1056-0337 (MS1054), CL1604+4304, and CL1604+4321. Concentration, asymmetry, and clumpiness parameters are calculated for each galaxy in blue (F606W or F625W) and red (F775W or F814W) filters. Galaxy half-light radii, disk scale lengths, color gradients, and overall color are compared. We find marginally significant differences in the asymmetry distributions of spiral and irregular galaxies in the X-ray luminous and X-ray faint clusters. The massive clusters contain fewer galaxies with large asymmetries. The physical sizes of the cluster and field populations are similar; no significant differences are found in half-light radii or disk scale lengths. The most significant difference is in rest-frame $U-B$ color. Late-type cluster galaxies are significantly redder, $\sim 0.3$ magnitudes at rest-frame $U-B$, than their field counterparts. Moreover, the intermediate-redshift cluster galaxies tend to have blue inward color gradients, in contrast to the field galaxies, but similar to late-type galaxies in low redshift clusters. These blue inward color gradients are likely to be the result of enhanced nuclear star formation rates relative to the outer disk. Based on the significant rest-frame color difference, we conclude that late-type cluster members at $z\sim0.9$ are not a pristine infalling field population; some difference in past and/or current star formation history is already present. This points to high redshift ``groups'', or filaments with densities similar to present-day groups, as the sites where the first major effects of environment are imprinted., updated title more...
- Published
- 2005
17. A Dynamical Simulation of the Debris Disk Around HD 141569A
- Author
-
John Krist, Hien D. Tran, Chris Burrows, Nicholas Cross, Zlatan Tsvetanov, Randy A. Kimble, Marijn Franx, André R. Martel, David R. Ardila, Mark Clampin, Larry Bradley, Gerhardt R. Meurer, Michael Lesser, John P. Blakeslee, Felipe Menanteau, Caryl Gronwall, W. Zheng, Andrew Zirm, William B. Sparks, Richard L. White, Garth D. Illingworth, Rachel A. Brown, Paul D. Feldman, Edward Cheng, Brad Holden, Narciso Benítez, George K. Miley, Rychard Bouwens, Holland C. Ford, Nicole Homeier, Tom Broadhurst, F. Bartko, David A. Golimowski, Marc Postman, Tomotsugu Goto, Marco Sirianni, G. Hartig, Leopoldo Infante, and S. H. Lubow more...
- Subjects
Physics ,Debris disk ,Planetesimal ,Spiral galaxy ,Track (disk drive) ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Orbital eccentricity ,Astrophysics ,Radiation pressure ,Space and Planetary Science ,Planet ,Binary star ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
We study the dynamical origin of the structures observed in the scattered-light images of the resolved debris disk around HD 141569A. We explore the roles of radiation pressure from the central star, gas drag from the gas disk, and the tidal forces from two nearby stars in creating and maintaining these structures. We use a simple one-dimensional axisymmetric model to show that the presence of the gas helps confine the dust and that a broad ring of dust is produced if a central hole exists in the disk. This model also suggests that the disk is in a transient, excited dynamical state, as the observed dust creation rate applied over the age of the star is inconsistent with submillimeter mass measurements. We model in two dimensions the effects of a fly-by encounter between the disk and a binary star in a prograde, parabolic, coplanar orbit. We track the spatial distribution of the disk's gas, planetesimals, and dust. We conclude that the surface density distribution reflects the planetesimal distribution for a wide range of parameters. Our most viable model features a disk of initial radius 400 AU, a gas mass of 50 M_earth, and beta = 4 and suggests that the system is being observed within 4000 yr of the fly-by periastron. The model reproduces some features of HD 141569A's disk, such as a broad single ring and large spiral arms, but it does not reproduce the observed multiple spiral rings or disk asymmetries nor the observed clearing in the inner disk. For the latter, we consider the effect of a 5 M_Jup planet in an eccentric orbit on the planetesimal distribution of HD 141569A., Comment: Accepted to ApJ more...
- Published
- 2005
- Full Text
- View/download PDF
18. High-Resolution Imaging of the SSCs in NGC 1569 and NGC 1705
- Author
-
Marco Sirianni, Gerhardt R. Meurer, Randy A. Kimble, Nicole Homeier, and M. Clampin
- Subjects
Physics ,Initial mass function ,Resolution (electron density) ,Astronomy ,Virial mass ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Galaxy ,Hubble sequence ,Luminosity ,symbols.namesake ,Star cluster ,symbols ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,High resolution imaging ,Astrophysics::Galaxy Astrophysics - Abstract
We observed the local starburst galaxies, NGC 1569 and NGC 1705 with the HST/ACS High Resolution Channel in the U, V, and I filters. The superb resolution of the images (0.018 arcsec pix−1) shows, for the first time, the real morphology of the Super Star Clusters. We derive the structural parameters and total luminosity and recalculate, with the new parameters, the virial mass of the clusters. more...
- Published
- 2005
- Full Text
- View/download PDF
19. Hubble Space Telescope Advanced Camera for Surveys coronagraphic imaging of the AU microscopii debris disk
- Author
-
Gerhardt R. Meurer, Narciso Benítez, Bradford P. Holden, Felipe Menanteau, George F. Hartig, David A. Golimowski, Piero Rosati, Nicole Homeier, M. Clampin, Simona Mei, Rychard Bouwens, Hien D. Tran, C. J. Burrows, Paul D. Feldman, Michael Lesser, André R. Martel, Zlatan Tsvetanov, Marc Postman, William B. Sparks, John Krist, Leopoldo Infante, Robert A. Brown, Nicholas Cross, Holland C. Ford, George K. Miley, Randy A. Kimble, Tom Broadhurst, M. Franx, David R. Ardila, Ricardo Demarco, Larry Bradley, Tomotsugu Goto, F. Bartko, Marco Sirianni, John P. Blakeslee, Caryl Gronwall, R. L. White, W. Zheng, V. Motta, Garth D. Illingworth, and E. S. Cheng more...
- Subjects
Physics ,Brightness ,Debris disk ,Line-of-sight ,Radiation pressure ,Space and Planetary Science ,Spectral energy distribution ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Radius ,Advanced Camera for Surveys ,Galaxy - Abstract
We present Hubble Space Telescope Advanced Camera for Surveys multicolor coronagraphic images of the recently discovered edge-on debris disk around the nearby (� 10 pc) M dwarf AU Microscopii. The disk is seen between r ¼ 0B75 and 15 00 (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 � 75 AU. The disk’s radial brightness profile is generally flat forr < 15 AU, then decreases gradually (I / r � 1:8 )o ut tor � 43 AU, beyond which it falls rapidly (I / r � 4:7 ). Within 50 AU the midplane is straight and aligned with the star, and beyond that it deviates by � 3 � , 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 1 � and the outer disk by � 3 � . The inclination of the outer disk and moderate forward scattering (g � 0:4) can explain the apparentbow. The intrinsic, deprojected FWHM thickness is 1.5–10 AU, increasing with radius. The models indicate that the disk is clear of dust within � 12 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. more...
- Published
- 2005
20. The Luminosity Functions of the Galaxy Cluster MS1054-0321 at z=0.83 based on ACS Photometry
- Author
-
P. D. Feldman, Nicholas Cross, Michael Lesser, Marc Postman, Andrew Zirm, John Krist, Robert A. Brown, Zlatan Tsvetanov, D. A. Golimowski, R. Demarco, Larry Bradley, Andre Martel, Myungkook J. Jee, Felipe Menanteau, K.-V. Tran, Nicole Homeier, Narciso Benítez, George F. Hartig, T. J. Broadhurst, G. K. Miley, WeiKang Zheng, C. J. Burrows, Dan Magee, V. Motta, R. J. Bouwens, R. L. White, F. Bartko, Tomotsugu Goto, Hien D. Tran, G. D. Illingworth, Bradford P. Holden, Roderik Overzier, M. Franx, Gerhardt R. Meurer, David R. Ardila, L. Infante, John P. Blakeslee, Holland C. Ford, C. Gronwall, E. S. Cheng, William B. Sparks, M. Clampin, Simona Mei, and Marco Sirianni more...
- Subjects
Physics ,Star formation ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Galaxy ,Photometry (optics) ,Space and Planetary Science ,Cluster (physics) ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Galaxy cluster ,Astrophysics::Galaxy Astrophysics - Abstract
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 MS1054-0321. Our analyses are based on imaging performed with the ACS onboard the HST in the F606W, F775W and F850LP passbands and extensive spectroscopic data obtained with the Keck LRIS. 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. We also find a 2sigma deficit of intrinsically faint, red galaxies (i-z>0.5, Mi>-19) in this cluster. This trend may suggest that faint, red galaxies (which are common in z30 Mpc^-2, coinciding with the environment where the galaxy star formation rate and the morphology-density relation start to appear. (abridged), ApJ in press, references updated more...
- Published
- 2004
21. A VLT spectroscopic survey of RX J0152.7-1357, a forming cluster of galaxies at z=0.837
- Author
-
Marisa Girardi, Ricardo Demarco, Evan Scannapieco, Stefano Borgani, Piero Rosati, Spencer A. Stanford, Narciso Benítez, Joseph Silk, Paolo Tozzi, Nicole Homeier, Mario Nonino, Gordon K. Squires, V. Mainieri, Tom Broadhurst, Christopher Lidman, Demarco, R., Rosati, P., Lidman, C., Homeier, N. L., Scannapieco, E., Benitez, N., Mainieri, V., Nonino, M., Girardi, Marisa, Stanford, S. A., Tozzi, P., Borgani, Stefano, Silk, J., Squires, G., and Broadhurst, T. J. more...
- Subjects
Physics ,galaxy cluster ,galaxy spectroscopy ,education.field_of_study ,Star formation ,galaxy clusters ,Astrophysics (astro-ph) ,Population ,FOS: Physical sciences ,Velocity dispersion ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Redshift ,Galaxy ,Space and Planetary Science ,Intracluster medium ,Peculiar velocity ,Astrophysics::Solar and Stellar Astrophysics ,education ,Galaxy cluster ,Astrophysics::Galaxy Astrophysics - Abstract
We present the results of an extensive spectroscopic survey of RX J0152.7-1357, one of the most massive distant clusters of galaxies known. Multi-object spectroscopy, carried out with FORS1 and FORS2 on the ESO Very Large Telescope (VLT), has allowed us to measure more than 200 redshifts in the cluster field and to confirm 102 galaxies as cluster members. The mean redshift of the cluster is $z=0.837 \pm 0.001$ and we estimate the velocity dispersion of the overall cluster galaxy distribution to be $\sim 1600 \mathrm{km \ s^{-1}}$. The distribution of cluster members is clearly irregular, with two main clumps that follow the X-ray cluster emission mapped by Chandra. A third clump of galaxies to the east of the central structure and at the cluster redshift has also been identified. The two main clumps have velocity dispersions of $\sim919$ and $\sim737 \mathrm{km s^{-1}}$ respectively, and the peculiar velocity of the two clumps suggests that they will merge into a single more massive cluster. A segregation in the star formation activity of the member galaxies is observed. All star forming galaxies are located outside the high-density peaks, which are populated only by passive galaxies. A population of red galaxies (belonging to the cluster red sequence) with clear post-starburst spectral features and [OII] ($\lambda$3727) emission lines is observed in the outskirts of the cluster. Two AGNs, which were previously confused with the diffuse X-ray emission from the intracluster medium in ROSAT and BeppoSAX observations, are found to be cluster members., Comment: 16 pages. 13 figures. Accepted for publication in Astronomy & Astrophysics. Tables 4 and 5 available in printed version. Corrected typos and missing references more...
- Published
- 2004
22. The Evolutionary Status of Clusters of Galaxies at Z ∼ 1
- Author
-
Nicole Homeier, Marc Postman, Myungkook J. Jee, Richard L. White, Piero Rosati, Brad Holden, John P. Blakeslee, G. D. Illingworth, Ricardo Demarco, and Holland C. Ford
- Subjects
Physics ,Spiral galaxy ,Astrophysics::High Energy Astrophysical Phenomena ,Intracluster medium ,Metallicity ,Cluster (physics) ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Astrophysics::Galaxy Astrophysics ,Redshift ,Galaxy ,Luminosity function (astronomy) ,Luminosity - Abstract
Combined HST, X-ray, and ground-based optical studies show that clusters of galaxies are largely "in place" by $z \sim 1$, an epoch when the Universe was less than half its present age. High resolution images show that elliptical, S0, and spiral galaxies are present in clusters at redshifts up to $z \sim 1.3$. Analysis of the CMDs suggest that the cluster ellipticals formed their stars several Gyr earlier, near redshift 3. The morphology--density relation is well established at $z\sim1$, with star-forming spirals and irregulars residing mostly in the outer parts of the clusters and E/S0s concentrated in dense clumps. The intracluster medium has already reached the metallicity of present-day clusters. The distributions of the hot gas and early-type galaxies are similar in $z\sim1$ clusters, indicating both have largely virialized in the deepest potentials wells. In spite of the many similarities between $z\sim1$ and present-day clusters, there are significant differences. The morphologies revealed by the hot gas, and particularly the early-type galaxies, are elongated rather than spherical. We appear to be observing the clusters at an epoch when the sub-clusters and groups are still assembling into a single regular cluster. Support for this picture comes from CL0152 where the gas appears to be lagging behind the luminous and dark mass in two merging sub-components. Moreover, the luminosity difference between the first and second brightest cluster galaxies at $z\sim1$ is smaller than in 93% of present-day Abell clusters, which suggests that considerable luminosity evolution through merging has occurred since that epoch. Evolution is also seen in the bolometric X-ray luminosity function. more...
- Published
- 2004
- Full Text
- View/download PDF
23. Ultracompact dwarf galaxies in Abell 1689: A photometric study with the advanced camera for surveys
- Author
-
Piero Rosati, D. A. Golimowski, C. J. Burrows, Hien D. Tran, P. D. Feldman, Bradford P. Holden, Nicholas Cross, Andre Martel, George F. Hartig, G. K. Miley, R. J. Bouwens, Zlatan Tsvetanov, WeiKang Zheng, R. A. Kimble, Tomotsugu Goto, John Krist, R. L. White, Michael Lesser, William B. Sparks, David R. Ardila, Robert A. Brown, L. Infante, K. Zekser, Holland C. Ford, Gerhardt R. Meurer, John P. Blakeslee, M. Clampin, G. D. Illingworth, M. Franx, Marco Sirianni, Dan Coe, Felipe Menanteau, Nicole Homeier, F. Bartko, C. Gronwall, E. S. Cheng, T. J. Broadhurst, Marc Postman, S. Mieske, and Narciso Benítez more...
- Subjects
Physics ,education.field_of_study ,Population ,Astronomy and Astrophysics ,Astrophysics ,Galaxy ,Space and Planetary Science ,Bulge ,Globular cluster ,Elliptical galaxy ,Fornax Cluster ,education ,Dwarf galaxy ,Luminosity function (astronomy) - Abstract
The properties of Ultra Compact Dwarf (UCD) galaxy candidates in Abell 1689 (z=0.183) are investigated, based on deep high resolution ACS images. A UCD candidate has to be unresolved, have i 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 more...
- Published
- 2004
24. Results from a Near Infrared Search for Emission-line Stars in the Inner Galaxy: Spectra of New Wolf-Rayet Stars
- Author
-
Anna Pasquali, Nicole Homeier, Robert Blum, Peter S. Conti, and Augusto Damineli
- Subjects
Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Continuum (design consultancy) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Galactic plane ,Galaxy ,Spectral line ,Stars ,Wolf–Rayet star ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Emission spectrum ,Spectroscopy ,Astrophysics::Galaxy Astrophysics - Abstract
We present follow-up spectroscopy of emission line candidates detected on near-infrared narrow band images in the inner Galaxy (Homeier et al. 2003). The filters are optimized for the detection of Wolf-Rayet stars and other objects which exhibit emission--lines in the 2 $\mu$m region. Approximately three square degrees along the Galactic plane have been analyzed in seven narrow--filters (four emission--lines and three continuum). We have discovered 4 new Wolf-Rayet stars and present coordinates, finding charts, and K-band spectra., Comment: To appear in Astronomy & Astrophysics more...
- Published
- 2003
25. Uncovering the Beast: Discovery of Embedded Massive Stellar Clusters in W49A
- Author
-
Nicole Homeier and João Alves
- Subjects
Physics ,Stars ,Space and Planetary Science ,Molecular cloud ,Astrophysics (astro-ph) ,Lyman continuum photons ,Cluster (physics) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Starburst region ,Astrophysics - Abstract
We present subarcsecond J, H, and Ks images (FWHM ~ 0.5") of an unbiased 5'x 5' (16pc x 16pc) survey of the densest region of the W49 giant molecular cloud. The observations reveal 4 massive stellar clusters (with stars as massive as \~120 Msun), the larger (Cluster 1) about 3 pc East of the well known Welch ring of ultra-compact Hii regions. Cluster 1 is a) extincted by at least Av > 20 mag of foreground (unrelated and local) extinction, b) has more than 30 mag of internal inhomogeneous visual extinction implying that it is still deeply buried in its parental molecular cloud, and c) is powering a 6 pc diameter giant Hii region seen both at the NIR and radio continuum. We also identify the exciting sources of several UCHii regions. The census of massive stars in W49A agrees or is slightly overabundant when compared with the number of Lyman continuum photons derived from radio observations. We argue that although the formation of the Welch ring could have been triggered by Cluster 1, the entire W49A starburst region seems to have been multi-seeded instead of resulting from a coherent trigger., ApJ Letters accepted. All figures provided as nice resolution jpeg/gif files. Get full-res version at http://www.eso.org/~jalves/W49A.pdf more...
- Published
- 2003
26. The Ionized Gas in Local Starburst Galaxies: Global and Small--Scale Feedback from Star Formation
- Author
-
Christopher J. Conselice, Daniela Calzetti, John S. Gallagher, Denise A. Smith, Nicole Homeier, Jason Harris, and Lisa J. Kewley
- Subjects
Physics ,Star formation ,Metallicity ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Galaxy ,Luminosity ,Interstellar medium ,Space and Planetary Science ,Ionization ,Astrophysics::Galaxy Astrophysics ,Dwarf galaxy ,Line (formation) - Abstract
Abridged: The small-- and intermediate--scale structure and the fraction of the ISM ionized by non--radiative processes is investigated in a small sample of four local starburst galaxies, imaged with the HST WFPC2. The sample comprises three dwarf galaxies, NGC3077, NGC4214, and NGC5253, and one giant spiral, NGC5236 (M83). The galaxies span a range in metallicity, luminosity, and environment, enabling the investigation of non--radiative ionization processes in a variety of galactic conditions. For this purpose, the four galaxies were imaged in the lines of H-beta(4861 A), [OIII](5007 A), H-alpha(6563 A), and [SII](6717,6731 A). The non--photoionized gas in these galaxies has been traced on scales ranging from a few tens of pc to a few hundred pc, providing a full budget for this ionized gas component. Using the `maximum starburst line' of Kewley et al. (2001) to discriminate between photoionized and non--photoionized gas, we find that in all four galaxies non--photoionization processes are responsible for a small fraction of the total H-alpha emission, at the level of 3%--4%. The starbursts in the three dwarf galaxies deposit a significant fraction, 70%-100%, of their mechanical energy into the surrounding interstellar medium and require time--extended (a few x 10^7 yr to ~10^8 yr) star formation, in order to account for the observed luminosity of the non--photoionized gas. In the massive spiral, the non--photoionized gas is concentrated in localized areas surrounded by active star--formation, with no evidence for extended structures (as those in the dwarfs). This confirms the picture that starbursts remain confined events in massive galaxies, likely due to the deep potential well. more...
- Published
- 2003
- Full Text
- View/download PDF
27. The Star Cluster System of the NGC 7673 Starburst
- Author
-
Anna Pasquali, Nicole Homeier, and John S. Gallagher
- Subjects
Physics ,education.field_of_study ,Bright star ,Population ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Redshift ,Galaxy ,Stars ,Star cluster ,Space and Planetary Science ,Hubble space telescope ,Astrophysics::Solar and Stellar Astrophysics ,education ,Astrophysics::Galaxy Astrophysics - Abstract
We investigate the star cluster system in the starburst galaxy NGC 7673 using archival Hubble Space Telescope WFPC2 broad-band images. For the first time we are able to examine the internal structures of the prominent optical clumps in this galaxy. The clumps are composed of young stars, 16-33 % of which are in bright star clusters. We identify 268 star cluster candidates in both the F555W and F814W images, and 50 clusters with the F255W filter. These data allow us to estimate ages and masses using color-magnitude and two-color diagrams for our sample. We find a population of young, < 6 Myr clusters located throughout the galaxy with concentrations in the clumps. Star cluster mass estimates are 5-50 x 10^4 M_solar for the brightest objects. The starburst remains active in physically well-separated regions, indicating a widespread starburst trigger. We discuss clump lifetimes, their implications for the future evolution of NGC 7673, and possible relationships to high redshift starbursts., 18 pages, 15 figures. Accepted for publication in Astronomy & Astrophysics more...
- Published
- 2002
- Full Text
- View/download PDF
28. Merger-Induced Starbursts
- Author
-
Nicole Homeier and J. S. Gallagher
- Published
- 2002
- Full Text
- View/download PDF
29. A Near-Infrared Survey for Galactic Wolf-Rayet Stars
- Author
-
Anna Pasquali, Augusto Damineli, Robert Blum, Peter S. Conti, and Nicole Homeier
- Subjects
Physics ,Stellar population ,Star formation ,Milky Way ,Metallicity ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Galactic plane ,Galaxy ,Wolf–Rayet star ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Stellar evolution ,Astrophysics::Galaxy Astrophysics - Abstract
Most of the Milky Way's evolved massive stellar population is hidden from view. We can attempt to remedy this situation with near-infrared observations, and in this paper we present our method for detecting Wolf-Rayet stars in highly extincted regions and apply it to the inner Galaxy. Using narrow band filters at K-band wavelengths, we demonstrate how WR stars can be detected in regions where they are optically obscured. Candidates are selected for spectroscopic follow-up from our relative line and continuum photometry. The final results of applying this method with a NIR survey in the Galactic plane will provide a more complete knowledge of the structure of the galactic disk, the role of metallicity in massive stellar evolution, and environments of massive star formation. In this paper we briefly describe the survey set-up and report on recent progress. We have discovered four emission-line objects in the inner Galaxy: two with nebular emission lines, and two new WR stars, both of late WC subtype., Comment: 3 pages, to appear in "A Massive Star Odyssey: from Main Sequence to Supernova", ed. K. A. van der Hucht, Proc. IAU Symp. 212 (San Francisco: ASP), in prep more...
- Published
- 2002
- Full Text
- View/download PDF
30. Kinematics and Structure of the Starburst Galaxy NGC 7673
- Author
-
Nicole Homeier and John S. Gallagher
- Subjects
Physics ,Spiral galaxy ,Astrophysics (astro-ph) ,Velocity dispersion ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Dust lane ,Galaxy ,Stars ,Star cluster ,Space and Planetary Science ,Dynamical time scale ,Dispersion (optics) ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
The morphology and kinematics of the luminous blue starburst galaxy NGC 7673 are explored using the WIYN 3.5m telescope. Signs of a past kinematic disturbance are detected in the outer galaxy; the most notable feature is a luminous ripple located 1.55 arc minutes from the center of NGC 7673. Sub-arc second imaging in B and R filters also reveals red dust lanes and blue star clusters that delineate spiral arms in the bright inner disk and narrow band Halpha imaging shows that the luminous star clusters are associated with giant H II regions. The Halpha kinematics measured with echelle imaging spectroscopy using the WIYN DensePak fiber array imply that these HII regions are confined to a smoothly rotating disk. The velocity dispersion in ionized gas in the disk is approximately 24 km/s, which sets an upper bound on the dispersion of young stellar populations. Broad emission components with velocity dispersion approx. 63 km/s are found in some regions are likely produced by mechanical power supplied by massive, young stars; a violent starburst is occurring in a kinematically calm disk. Although the asymmetric outer features point to a merger or interaction as the starburst trigger, the inner disk structure constrains the strength of the event to the scale of a minor merger or weak interaction that occurred at least an outer disk dynamical time scale in the past., 16 pages, 7 figures, to appear in the September 1, 1999 issue of the Astrophysical Journal more...
- Published
- 1999
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.