Browsing by Author "Mei, Simona"

Now showing 1 - 9 of 9
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    A GEMINI/GMOS STUDY OF INTERMEDIATE LUMINOSITY EARLY-TYPE VIRGO CLUSTER GALAXIES. I. GLOBULAR CLUSTER AND STELLAR KINEMATICS
    (2015) Li, Biao; Peng, Eric W.; Zhang, Hong-xin; Blakeslee, John P.; Côté, Patrick; Ferrarese, Laura; Jordán Colzani, Andrés Cristóbal; Liu, Chengze; Mei, Simona; Puzia, Thomas H.
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    SURFACE BRIGHTNESS FLUCTUATIONS IN THE HUBBLE SPACE TELESCOPE ACS/WFC F814W BANDPASS AND AN UPDATE ON GALAXY DISTANCES
    (2010) Blakeslee, John P.; Cantiello, Michele; Mei, Simona; Cote, Patrick; DeGraaff, Regina Barber; Ferrarese, Laura; Jordan, Andres; Peng, Eric W.; Tonry, John L.; Worthey, Guy
    We measure surface brightness fluctuation (SBF) magnitudes in the F814W filter and (g(475)-I-814) colors for nine bright early-type Fornax cluster galaxies imaged with the Hubble Space Telescope Advanced Camera for Surveys (ACS). The goal is to achieve the first systematic SBF calibration for the ACS/F814W bandpass. Because of its much higher throughput, F814W is more efficient for SBF studies of distant galaxies than the ACS/F850LP bandpass that has been used to study nearby systems. Over the color range spanned by the sample galaxies, 1.06 < (g(475)-I-814) < 1.32 (AB mag), the dependence of SBF magnitude (m) over bar (814) on (g(475)-I-814) is linear to a good approximation, with slope similar to 2. When the F850LP SBF distance measurements from the ACS Fornax Cluster Survey are used to derive absolute (M) over bar (814) magnitudes, the dependence on (g(475)-I-814) becomes extremely tight, with a slope of 1.8 +/- 0.2 and a scatter of 0.03 mag. The small observed scatter indicates both that the estimated random errors are correct and that the intrinsic deviations from the SBF-color relation are strongly correlated between the F814W and F850LP bandpasses, as expected. The agreement with predictions from stellar population models is good, both in slope and zero point, indicating that our mean Fornax distance of 20 Mpc is accurate. The models predict curvature in the relation beyond the color limits of our sample; thus, the linear calibration should not be extrapolated naively. In the appendices, we reconsider the Tonry ground-based and Jensen NICMOS SBF distance catalogs; we provide a correction formula to ameliorate the small apparent bias in the former and the offset needed to make the latter consistent with other SBF studies. We also tabulate two new SBF distances to galaxies observed in the ACS Virgo Cluster Survey.
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    THE ACS FORNAX CLUSTER SURVEY. IV. DEPROJECTION OF THE SURFACE BRIGHTNESS PROFILES OF EARLY-TYPE GALAXIES IN THE VIRGO AND FORNAX CLUSTERS: INVESTIGATING THE "CORE/POWER-LAW DICHOTOMY"
    (2011) Glass, Lisa; Ferrarese, Laura; Cote, Patrick; Jordan, Andres; Peng, Eric; Blakeslee, John P.; Chen, Chin-Wei; Infante, Leopoldo; Mei, Simona; Tonry, John L.; West, Michael J.
    Although early observations with the Hubble Space Telescope (HST) pointed to a sharp dichotomy among early-type galaxies in terms of the logarithmic slope gamma' of their central surface brightness profiles, several studies in the past few years have called this finding into question. In particular, recent imaging surveys of 143 early-type galaxies belonging to the Virgo and Fornax Clusters using the Advanced Camera for Surveys (ACS) on board HST have not found a dichotomy in gamma', but instead a systematic progression from central luminosity deficit to excess relative to the inward extrapolation of the best-fitting global Sersic model. Given that earlier studies also found that the dichotomy persisted when analyzing the deprojected density profile slopes, we investigate the distribution of the three-dimensional luminosity density profiles of the ACS Virgo and Fornax Cluster Survey galaxies. Having fitted the surface brightness profiles with modified Sersic models, we then deproject the galaxies using an Abel integral and measure the inner slopes gamma(3D) of the resulting luminosity density profiles at various fractions of the effective radius R-e. We find no evidence of a dichotomy, but rather, a continuous variation in the central luminosity profiles as a function of galaxy magnitude. We introduce a parameter, Delta(3D), that measures the central deviation of the deprojected luminosity profiles from the global Sersic fit, showing that this parameter varies smoothly and systematically along the luminosity function.
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    The ACS Fornax Cluster survey.: I.: Introduction to the survey and data reduction procedures
    (2007) Jordan, Andres; Blakeslee, John P.; Cote, Patrick; Ferrarese, Laura; Infante, Leopoldo; Mei, Simona; Merritt, David; Peng, Eric W.; Tonry, John L.; West, Michael J.
    The Fornax Cluster is a conspicuous cluster of galaxies in the southern hemisphere and the second largest collection of early-type galaxies within less than or similar to 20 Mpc after the Virgo Cluster. In this paper, we present a brief introduction to the ACS Fornax Cluster Survey - a program to image, in the F475W (g(475)) and F850LP (z(850)) bandpasses, 43 early-type galaxies in Fornax using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. Combined with a companion survey of Virgo, the ACS Virgo Cluster Survey, this represents the most comprehensive imaging survey to date of early-type galaxies in cluster environments in terms of depth, spatial resolution, sample size, and homogeneity. We describe the selection of the program galaxies, their basic properties, and the main science objectives of the survey, which include the measurement of luminosities, colors, and structural parameters for globular clusters associated with these galaxies, an analysis of their isophotal properties and surface brightness profiles, and an accurate calibration of the surface brightness fluctuation distance indicator. Finally, we discuss the data reduction procedures adopted for the survey.
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    The Next Generation Virgo Cluster Survey (NGVS). XXXII. A Search for Globular Cluster Substructures in the Virgo Galaxy Cluster Core
    (2018) Powalka, Mathieu; Puzia, Thomas H.; Lancon, Ariane; Longobardi, Alessia; Peng, Eric W.; Duc, Pierre-Alain; Alamo-Martinez, Karla; Blakeslee, John P.; Cote, Patrick; Cuillandre, Jean-Charles; Durrell, Patrick; Eigenthaler, Paul; Ferrarese, Laura; Guhathakurta, Puragra; Gwyn, S. D. J.; Hudelot, Patrick; Liu, Chengze; Mei, Simona; Munoz, Roberto P.; Roediger, Joel; Sanchez-Janssen, Ruben; Toloba, Elisa; Zhang, Hongxin
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    THE NEXT GENERATION VIRGO CLUSTER SURVEY. XXII. SHELL FEATURE EARLY-TYPE DWARF GALAXIES IN THE VIRGO CLUSTER
    (IOP PUBLISHING LTD, 2017) Paudel, Sanjaya; Smith, Rory; Duc, Pierre Alain; Cote, Patrick; Cuillandre, Jean Charles; Ferrarese, Laura; Blakeslee, John P.; Boselli, Alessandro; Cantiello, Michele; Gwyn, S. D. J.; Guhathakurta, Puragra; Mei, Simona; Mihos, J. Christopher; Peng, Eric W.; Powalka, Mathieu; Sanchez Janssen, Ruben; Toloba, Elisa; Zhang, Hongxin
    The Next Generation Virgo Cluster Survey is a deep (with a 2 sigma detection limit mu g = 29 mag arcsec(-2) in the g-band) optical panchromatic survey targeting the Virgo cluster from its core to virial radius, for a total areal coverage of 104 square degrees. As such, the survey is well suited for the study of galaxies' outskirts, haloes, and low surface brightness features that arise from dynamical interactions within the cluster environment. We report the discovery of extremely faint (mu g > 25 mag arcsec(-2)) shells in three Virgo cluster early-type dwarf galaxies: VCC. 1361, VCC. 1447, and VCC. 1668. Among them, VCC. 1447 has an absolute magnitude Mg = -11.71 mag and is the least massive galaxy with a shell system discovered to date. We present a detailed study of these low surface brightness features. We detect between three and four shells in each of our galaxies. Within the uncertainties, we find no evidence of a color difference between the galaxy main body and shell features. The observed arcs of the shells are located up to several effective radii of the galaxies. We further explore the origin of these low surface brightness features with the help of idealized numerical simulations. We find that a near equal mass merger is best able to reproduce the main properties of the shells, including their quite symmetric appearance and their alignment along the major axis of the galaxy. The simulations provide support for a formation scenario in which a recent merger, between two near-equal mass, gas-free dwarf galaxies, forms the observed shell systems.
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    The Next Generation Virgo Cluster Survey. XXIII. Fundamentals of Nuclear Star Clusters over Seven Decades in Galaxy Mass
    (2019) Sanchez-Janssen, Ruben; Cote, Patrick; Ferrarese, Laura; Peng, Eric W.; Roediger, Joel; Blakeslee, John P.; Emsellem, Eric; Puzia, Thomas H.; Spengler, Chelsea; Taylor, James; Alamo-Martinez, Karla A.; Boselli, Alessandro; Cantiello, Michele; Cuillandre, Jean-Charles; Duc, Pierre-Alain; Durrell, Patrick; Gwyn, Stephen; MacArthur, Lauren A.; Lancon, Ariane; Lim, Sungsoon; Liu, Chengze; Mei, Simona; Miller, Bryan; Munoz, Roberto; Mihos, J. Christopher; Paudel, Sanjaya; Powalka, Mathieu; Toloba, Elisa
    Using deep, high-resolution optical imaging from the Next Generation Virgo Cluster Survey, we study the properties of nuclear star clusters (NSCs) in a sample of nearly 400 quiescent galaxies in the core of Virgo with stellar masses 10(5) less than or similar to M-*/M-circle dot less than or similar to 10(12). The nucleation fraction reaches a peak value f(n) approximate to 90% for M-* approximate to 10(9) M-circle dot galaxies and declines for both higher and lower masses, but nuclei populate galaxies as small as M-* approximate to 5 x 10(5) M-circle dot. Comparison with literature data for nearby groups and clusters shows that at the low-mass end nucleation is more frequent in denser environments. The NSC mass function peaks at M-NSC approximate to 7 x 10(5) M-circle dot, a factor 3-4 times larger than the turnover mass for globular clusters (GCs). We find a nonlinear relation between the stellar masses of NSCs and those of their host galaxies, with a mean nucleus-to-galaxy mass ratio that drops to M-NSC/M-* approximate to 3.6 x 10(-3) for M-* approximate to 5 x 10(9) M-circle dot galaxies. Nuclei in both more and less massive galaxies are much more prominent: M-NSC proportional to M-*(0.46) at the low-mass end, where nuclei are nearly 50% as massive as their hosts. We measure an intrinsic scatter in NSC masses at a fixed galaxy stellar mass of 0.4 dex, which we interpret as evidence that the process of NSC growth is significantly stochastic. At low galaxy masses we find a close connection between NSCs and GC systems, including very similar occupation distributions and comparable total masses. We discuss these results in the context of current dissipative and dissipationless models of NSC formation.
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    THE. NEXT. GENERATION. VIRGO. CLUSTER. SURVEY. XX. RedGOLD. BACKGROUND. GALAXY. CLUSTER. DETECTIONS
    (2016) Licitra, Rossella; Mei, Simona; Raichoor, Anand; Erben, Thomas; Hildebrandt, Hendrik; Muñoz, Roberto P.; Van Waerbeke, Ludovic; Côté, Patrick; Cuillandre, Jean-Charles; Puzia, Thomas H.
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    Trends in the globular cluster luminosity function of early-type galaxies
    (2006) Jordan, Andres; McLaughlin, Dean E.; Cote, Patrick; Ferrarese, Laura; Peng, Eric W.; Blakeslee, John P.; Mei, Simona; Villegas, Daniela; Merritt, David; Tonry, John L.; West, Michael J.
    We present results from a study of the globular cluster luminosity function (GCLF) in a sample of 89 early-type galaxies observed as part of the ACS Virgo Cluster Survey. Using a Gaussian parameterization of the GCLF, we find a highly significant correlation between the GCLF dispersion, sigma, and the galaxy luminosity, M-B,M- gal, the sense that the GC systems in fainter galaxies have narrower luminosity functions. The GCLF dispersions in the Milky Way and M31 are fully consistent with this trend, implying that the correlation between sigma and galaxy luminosity is more fundamental than older suggestions that GCLF shape is a function of galaxy Hubble type. We show that the sigma-M-B,M- gal relation results from a bona fide narrowing of the distribution of (logarithmic) cluster j- M B, gal masses in fainter galaxies. We further show that this behavior is mirrored by a steepening of the GC mass function for relatively high masses, M >= 3 x 10(5) M-circle dot, a mass regime in which the shape of the GCLF is not strongly affected by dynamical evolution over a Hubble time. We argue that this trend arises from variations in initial conditions and requires explanation by theories of cluster formation. Finally, we confirm that in bright galaxies the GCLF "turns over" at the canonical mass scale of M-TO similar or equal to 2 x 10(5) M-circle dot. However, we find that M-TO scatters to lower values [approximate to(1-2) x 10(5) M-circle dot] in galaxies fainter than M-B,M- gal greater than or similar to -18.5, an important consideration if the GCLF is to be used as a distance indicator for dwarf ellipticals.