Browsing by Author "Gwyn, Stephen"

Now showing 1 - 9 of 9
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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 large-scale structure of the halo of the andromeda galaxy. II. Hierarchical structure in the pan-andromeda archaeological survey
    (2018) McConnachie, Alan W.; Ibata, Rodrigo; Martin, Nicolas; Ferguson, Annette M.N.; Collins, Michelle; Gwyn, Stephen; Irwin, Mike; Lewis, Geraint F.; Dougal Mackey, A.; Puzia, Thomas H.
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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. XXXIII. Stellar Population Gradients in the Virgo Cluster Core Globular Cluster System
    (2022) Ko, Youkyung; Peng, Eric W.; Cote, Patrick; Ferrarese, Laura; Liu, Chengze; Longobardi, Alessia; Lancon, Ariane; Munoz, Roberto P.; Puzia, Thomas H.; Alamo-Martinez, Karla A.; Sales, Laura, V; Ramos-Almendares, Felipe; Abadi, Mario G.; Lee, Myung Gyoon; Hwang, Ho Seong; Caldwell, Nelson; Blakeslee, John P.; Boselli, Alessandro; Cuillandre, Jean-Charles; Duc, Pierre-Alain; Eyheramendy, Susana; Guhathakurta, Puragra; Gwyn, Stephen; Jordan, Andres; Lim, Sungsoon; Sanchez-Janssen, Ruben; Toloba, Elisa
    We present a study of the stellar populations of globular clusters (GCs) in the Virgo Cluster core with a homogeneous spectroscopic catalog of 692 GCs within a major-axis distance R (maj) = 840 kpc from M87. We investigate radial and azimuthal variations in the mean age, total metallicity, [Fe/H], and alpha-element abundance of blue (metal-poor) and red (metal-rich) GCs using their co-added spectra. We find that the blue GCs have a steep radial gradient in [Z/H] within R (maj) = 165 kpc, with roughly equal contributions from [Fe/H] and [alpha/Fe], and flat gradients beyond. By contrast, the red GCs show a much shallower gradient in [Z/H], which is entirely driven by [Fe/H]. We use GC-tagged Illustris simulations to demonstrate an accretion scenario where more massive satellites (with more metal- and alpha-rich GCs) sink further into the central galaxy than less massive ones, and where the gradient flattening occurs because of the low GC occupation fraction of low-mass dwarfs disrupted at larger distances. The dense environment around M87 may also cause the steep [alpha/Fe] gradient of the blue GCs, mirroring what is seen in the dwarf galaxy population. The progenitors of red GCs have a narrower mass range than those of blue GCs, which makes their gradients shallower. We also explore spatial inhomogeneity in GC abundances, finding that the red GCs to the northwest of M87 are slightly more metal-rich. Future observations of GC stellar population gradients will be useful diagnostics of halo merger histories.
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    The Relation between Globular Cluster Systems and Supermassive Black Holes in Spiral Galaxies. III. The Link to the M.-M * Correlation
    (2022) Gonzalez-Lopezlira, Rosa A.; Lomeli-Nunez, Luis; Ordenes-Briceno, Yasna; Loinard, Laurent; Gwyn, Stephen; Alamo-Martinez, Karla; Bruzual, Gustavo; Lancon, Ariane; Puzia, Thomas H.
    D We continue to explore the relationship between the total number of globular clusters (GCs), NGC, and the central black hole mass, M alpha, in spiral galaxies. We present here results for the Sab galaxies NGC 3368, NGC 4736 (M94), and NGC 4826 (M64), and the Sm galaxy NGC 4395. The GC candidate selection is based on the (u* - i cent) versus (i cent - Ks) color-color diagram, and i cent-band shape parameters. We determine the M alpha versus NGC correlation for these spirals, plus NGC 4258, NGC 253, M104, M81, M31, and the Milky Way. We also redetermine the correlation for the elliptical sample in Harris et al., with updated galaxy types from Sahu et al. Additionally, we derive the total stellar galaxy mass, M*, from its two-slope correlation with NGC, and fit M _ versus M* for both spirals and ellipticals. We obtain log M alpha. (1.01 +/- 0.13) log NGC for ellipticals, and log M alpha. (1.64 +/- 0.24) log NGC for latetype galaxies (LTGs). The linear M alpha versus NGC correlation in ellipticals could be due to statistical convergence through mergers, unlike the much steeper correlation for LTGs. However, in the M alpha versus total stellar mass (M*) parameter space, with M* derived from its correlation with NGC, M alpha. (1.48 +/- 0.18) log M* for ellipticals, and M alpha. (1.21 +/- 0.16) log M* for LTGs. The observed agreement between ellipticals and LTGs in this parameter space may imply that black holes and galaxies coevolve through calm accretion, active galactic nuclei feedback, and other secular processes.
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    The Relation Between Globular Cluster Systems and Supermassive Black Holes in Spiral Galaxies: The Case Study of NGC 4258
    (2017) González-Lópezlira, Rosa A.; Lomelí Núñez, Luis; Álamo Martínez, Karla; Órdenes Briceño, Yasna; Loinard, Laurent; Georgiev, Iskren Y.; Muñoz, Roberto P.; Puzia, Thomas H.; Bruzual, Gustavo A.; Gwyn, Stephen
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    THE. NEXT. GENERATION. VIRGO. CLUSTER. SURVEY. VII. THE. INTRINSIC. SHAPES. OF. LOW-LUMINOSITY. GALAXIES. IN. THE. CORE. OF. THE. VIRGO. CLUSTER, AND. A. COMPARISON. WITH. THE. LOCAL. GROUP
    (2016) Sánchez-Janssen, Rubén; Ferrarese, Laura; MacArthur, Lauren A.; Côté, Patrick; Blakeslee, John P.; Cuillandre, Jean-Charles; Duc, Pierre-Alain; Durrell, Patrick; Gwyn, Stephen; Puzia, Thomas H.
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    THE. NEXT. GENERATION. VIRGO. CLUSTER. SURVEY. XVI. : THE. ANGULAR. MOMENTUM. OF. DWARF. EARLY-TYPE. GALAXIES. FROM. GLOBULAR. CLUSTER. SATELLITES
    (2016) Toloba, Elisa; Biao, LI.; Guhathakur, Puragra; Peng, Eric W.; Ferrares, Laura; Côté, Patrick; Emsellem, Eric; Gwyn, Stephen; Hongxin, Zhan; Jordán Colzani, Andrés Cristóbal