Browsing by Author "Lancon, Ariane"

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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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    Spectroscopy of NGC 4258 Globular Cluster Candidates: Membership Confirmation and Kinematics
    (2019) Gonzalez-Lopezlira, Rosa A.; Mayya, Y. D.; Loinard, Laurent; Alamo-Martinez, Karla; Heald, George; Georgiev, Iskren Y.; Ordenes-Briceno, Yasna; Lancon, Ariane; Lara-Lopez, Maritza A.; Lomeli-Nunez, Luis; Bruzual, Gustavo; Puzia, Thomas H.
    We present multiobject spectroscopic observations of 23 globular cluster candidates (GCCs) in the prototypical megamaser galaxy NGC 4258, carried out with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy instrument at the 10.4 m Gran Telescopio Canarias. The candidates have been selected based on the (u* - i') versus (i' - K-s) diagram, in the first application of the u*i'K-s, method to a spiral galaxy. In the spectroscopy presented here, 70% of the candidates are confirmed as globular clusters (GCs). Our results validate the efficiency of the u*i'K-s, method in the sparser GC systems of spirals, and given the downward correction to the total number of GCs, the agreement of the galaxy with the correlations between black hole mass and the total number and mass of GCs is actually improved. We find that the GCs, mostly metal-poor, corotate with the H I disk, even at large galactocentric distances.
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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 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.