Browsing by Author "Ferrarese, Laura"

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    An evolutionary continuum from nucleated dwarf galaxies to star clusters
    (2023) Wang, Kaixiang; Peng, Eric W.; Liu, Chengze; Mihos, J. Christopher; Cote, Patrick; Ferrarese, Laura; Taylor, Matthew A.; Blakeslee, John P.; Cuillandre, Jean-Charles; Duc, Pierre-Alain; Guhathakurta, Puragra; Gwyn, Stephen; Ko, Youkyung; Lancon, Ariane; Lim, Sungsoon; Macarthur, Lauren A.; Puzia, Thomas; Roediger, Joel; Sales, Laura V.; Sanchez-Janssen, Ruben; Spengler, Chelsea; Toloba, Elisa; Zhang, Hongxin; Zhu, Mingcheng
    Systematic studies1-4 have revealed hundreds of ultra-compact dwarf galaxies (UCDs5) in the nearby Universe. With half-light radii rh of approximately 10-100 parsecs and stellar masses M* approximate to 106-108 solar masses, UCDs are among the densest known stellar systems6. Although similar in appearance to massive globular clusters7, the detection of extended stellar envelopes4,8,9, complex star formation histories10, elevated mass-to-light ratio11,12 and supermassive black holes13-16 suggest that some UCDs are remnant nuclear star clusters17 of tidally stripped dwarf galaxies18,19, or even ancient compact galaxies20. However, only a few objects have been found in the transient stage of tidal stripping21,22, and this assumed evolutionary path19 has never been fully traced by observations. Here we show that 106 galaxies in the Virgo cluster have morphologies that are intermediate between normal, nucleated dwarf galaxies and single-component UCDs, revealing a continuum that fully maps this morphological transition and fills the 'size gap' between star clusters and galaxies. Their spatial distribution and redder colour are also consistent with stripped satellite galaxies on their first few pericentric passages around massive galaxies23. The 'ultra-diffuse' tidal features around several of these galaxies directly show how UCDs are forming through tidal stripping and that this evolutionary path can include an early phase as a nucleated ultra-diffuse galaxy24,25. These UCDs represent substantial visible fossil remnants of ancient dwarf galaxies in galaxy clusters, and more low-mass remnants probably remain to be found.
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    Dark Matter in Ultra-diffuse Galaxies in the Virgo Cluster from Their Globular Cluster Populations
    (2018) Toloba, Elisa; Lim, Sungsoon; Peng, Eric; Sales, Laura V.; Guhathakurta, Puragra; Mihos, J. Christopher; Cote, Patrick; Boselli, Alessandro; Cuillandre, Jean-Charles; Ferrarese, Laura; Gwyn, Stephen; Lancon, Ariane; Munoz, Roberto; Puzia, Thomas H.
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    The ACS Fornax Cluster Survey. III. Globular Cluster Specific Frequencies of Early-type Galaxies
    (2019) Liu, Yiqing; Peng, Eric W.; Jordan, Andres; Blakeslee, John P.; Cote, Patrick; Ferrarese, Laura; Puzia, Thomas H.
    The globular cluster (GC) specific frequency (SN), defined as the number of GCs per unit galactic luminosity, represents the efficiency of GC formation (and survival) compared to field stars. Despite the naive expectation that star cluster formation should scale directly with star formation, this efficiency varies widely across galaxies. To explore this variation, we measure the z-band GC specific frequency (S-N,S- z) for 43 early-type galaxies (ETGs) from the Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) Fornax Cluster Survey. Combined with the homogeneous measurements of S-N,S- z in 100 ETGs from the HST/ACS Virgo Cluster Survey from Peng et al., we investigate the dependence of S-N,S- z on mass and environment over a range of galaxy properties. We find that S-N,S- z behaves similarly in the two galaxy clusters, despite the clusters' order-of-magnitude difference in mass density. The S-N,S- z is low in intermediate-mass ETGs (-20 < M-z < -23) and increases with galaxy luminosity. It is elevated at low masses, on average, but with a large scatter driven by galaxies in dense environments. The densest environments with the strongest tidal forces appear to strip the GC systems of low-mass galaxies. However, in low-mass galaxies that are not in strong tidal fields, denser environments correlate with enhanced GC formation efficiencies. Normalizing by inferred halo masses, the GC mass fraction, eta = (3.36 +/- 0.2) x 10(-5), is constant for ETGs with stellar masses M-star <= 3 x 10(10) M-circle dot, in agreement with previous studies. The lack of correlation between the fraction of GCs and the nuclear light implies only a weak link between the infall of GCs and the formation of nuclei.
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    The ACS Fornax Cluster Survey. XII. Diffuse Star Clusters in Early-type Galaxies
    (2016) Liu, Yiqing; Peng, Eric W.; Lim, Sungsoon; Jordán Colzani, Andrés Cristóbal; Blakeslee, John; Cote, Patrick; Ferrarese, Laura; Pattarakijwanich, Petchara
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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 Color Gradients of the Globular Cluster Systems in M87 and M49
    (2022) Wu, Yiming; Liu, Chengze; Peng, Eric W.; Ko, Youkyung; Cote, Patrick; Jain, Rashi; Ferrarese, Laura; Yang, Xiaohu; Lancon, Ariane; Puzia, Thomas; Lim, Sungsoon
    Combining data from the ACS Virgo Cluster Survey and the Next Generation Virgo cluster Survey, we extend previous studies of color gradients of the globular cluster (GC) systems of the two most massive galaxies in the Virgo cluster, M87 and M49, to radii of similar to 15 R (e) (similar to 200 kpc for M87 and similar to 250 kpc for M49, where R (e) is the effective radius). We find significant negative color gradients, i.e., becoming bluer with increasing distance, out to these large radii. The gradients are driven mainly by the outward decrease in the ratio of red to blue GC numbers. The color gradients are also detected out to similar to 15 R (e) in the red and blue subpopulations of GCs taken separately. In addition, we find a negative color gradient when we consider the satellite low-mass elliptical galaxies as a system, i.e., the satellite galaxies closer to the center of the host galaxy usually have redder color indices, for both their stars and their GCs. According to the "two phase" formation scenario of massive early-type galaxies, the host galaxy accretes stars and GCs from low-mass satellite galaxies in the second phase. So an accreted GC system naturally inherits the negative color gradient present in the satellite population. This can explain why the color gradient of the GC system can still be observed at large radii after multiple minor mergers.
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    The Next Generation Virgo Cluster Survey (NGVS). XXVI. The Issues of Photometric Age and Metallicity Estimates for Globular Clusters
    (2017) Powalka, Mathieu; Lançon, Ariane; Puzia, Thomas H.; Peng, Eric W.; Liu, Chengze; Muñoz, Roberto P.; Blakeslee, John P.; Côté, Patrick; Ferrarese, Laura; Zhang, Hongxin
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    The Next Generation Virgo Cluster Survey (NGVS). XXVII. The Size and Structure of Globular Cluster Systems and Their Connection to Dark Matter Halos
    (2024) Lim, Sungsoon; Peng, Eric W.; Cote, Patrick; Ferrarese, Laura; Roediger, Joel C.; Liu, Chengze; Spengler, Chelsea; Sola, Elisabeth; Duc, Pierre-Alain; Sales, Laura V.; Blakeslee, John P.; Cuillandre, Jean-Charles; Durrell, Patrick R.; Emsellem, Eric; Gwyn, Stephen D. J.; Lancon, Ariane; Marleau, Francine R.; Mihos, J. Christopher; Mueller, Oliver; Puzia, Thomas H.; Sanchez-Janssen, Ruben
    We study the size and structure of globular cluster (GC) systems of 118 early-type galaxies from the NGVS, MATLAS, and ACSVCS surveys. Fitting S & eacute;rsic profiles, we investigate the relationship between effective radii of GC systems (R-e,R-gc) and galaxy properties. GC systems are 2-4 times more extended than host galaxies across the entire stellar mass range of our sample (10(8.3)M(circle dot) < M-* < 10(11.6)M(circle dot)). The relationship between R-e,R-gc and galaxy stellar mass exhibits a characteristic "knee" at a stellar mass of M-p similar or equal to 10(10.8), similar to the galaxy R-e-stellar mass relationship. We present a new characterization of the traditional blue and red GC color subpopulations, describing them with respect to host galaxy color (Delta(gi)): GCs with similar colors to their hosts have a "red" Delta(gi), and those significantly bluer GCs have a "blue" Delta(gi). The GC populations with red Delta(gi), even in dwarf galaxies, are twice as extended as the stars, suggesting that formation or survival mechanisms favor the outer regions. We find a tight correlation between R-e,R-gc and the total number of GCs, with intrinsic scatter less than or similar to 0.1 dex spanning two and three orders of magnitude in size and number, respectively. This holds for both red and blue subpopulations, albeit with different slopes. Assuming that N-GC,N-Total correlates with M-200, we find that the red GC systems have effective radii of roughly 1%-5% R-200, while the blue GC systems in massive galaxies can have sizes as large as similar to 10% R-200. Environmental dependence on R-e,R-gc is also found, with lower-density environments exhibiting more extended GC systems at fixed mass.
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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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    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.
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    Virgo Redux: The Masses and Stellar Content of Nuclei in Early-type Galaxies from Multiband Photometry and Spectroscopy
    (2017) Spengler, Chelsea; Côté, Patrick; Roediger, Joel; Ferrarese, Laura; Sánchez Janssen, Rubén; Toloba, Elisa; Liu, Yiqing; Guhathakurta, Puragra; Muñoz, Roberto; Puzia, Thomas H.