scholarly journals Field/isolated lenticular galaxies with high SN values: the case of NGC 4546 and its globular cluster system

2020 ◽  
Vol 493 (2) ◽  
pp. 2253-2270 ◽  
Author(s):  
Carlos G Escudero ◽  
Favio R Faifer ◽  
Analía V Smith Castelli ◽  
Mark A Norris ◽  
Juan C Forte
Keyword(s):  
Globular Cluster ◽  
Gaussian Mixture ◽  
Brightness Distribution ◽  
Galactic Centre ◽  
Distance Modulus ◽  
Lenticular Galaxies ◽  
Additional Group ◽  
The Galaxy ◽  
Colour Distribution ◽  
Specific Frequency

ABSTRACT We present a photometric study of the field lenticular galaxy NGC 4546 using Gemini/GMOS imaging in g′r′i′z′. We perform a 2D image decomposition of the surface brightness distribution of the galaxy using galfit, finding that four components adequately describe it. The subtraction of this model from our images and the construction of a colour map allow us to examine in great detail the asymmetric dust structures around the galactic centre. In addition, we perform a detailed analysis of the globular cluster (GC) system of NGC 4546. Using a Gaussian Mixture Model algorithm in the colour–colour plane, we detected hints of multiple groups of GC candidates: the classic blue and red subpopulations, a group with intermediate colours that present a concentrated spatial distribution towards the galaxy, and an additional group towards the red end of the colour distribution. We estimate a total GC population for NGC 4546 of 390 ± 60 members and specific frequency SN = 3.3 ± 0.7, which is relatively high compared to the typical value for galaxies of similar masses and environment. We suggest that the unusual GC population substructures were possibly formed during the interaction that led to the formation of the young ultra-compact dwarf (NGC 4546-UCD1) found in this system. Finally, we estimate the distance modulus of NGC 4546 by analysing its luminosity function, resulting in (m − M) = 30.75 ± 0.12 mag (14.1 Mpc).

scholarly journals Early-type galaxies in low-density environments: NGC 6876 explored through its globular cluster system

2019 ◽  
Vol 488 (1) ◽  
pp. 770-781 ◽  
Author(s):  
Ana I Ennis ◽  
Lilia P Bassino ◽  
Juan P Caso ◽  
Bruno J De Bórtoli
Keyword(s):  
Globular Cluster ◽  
Galaxy Cluster ◽  
Host Galaxy ◽  
Distance Modulus ◽  
Early Type ◽  
The Galaxy ◽  
Colour Distribution ◽  
Poor Group ◽  
Early Type Galaxy ◽  
Massive Galaxy

ABSTRACT We present the results of a photometric study of the early-type galaxy NGC 6876 and the surrounding globular cluster (GC) system. The host galaxy is a massive elliptical, the brightest of this type in the Pavo Group. According to its intrinsic brightness (Mv ∼ −22.7), it is expected to belong to a galaxy cluster instead of a poor group. Observational material consists of g′, r′, i′ images obtained with the Gemini/GMOS camera. The selected GC candidates present a clear bimodal colour distribution at different galactocentric radii, with mean colours and dispersions for the metal-poor (‘blue’) and metal-rich (‘red’) typical of old GCs. The red subpopulation dominates close to the galaxy centre, in addition to the radial projected distribution showing that they are more concentrated towards the galaxy centre. The azimuthal projected distribution shows an overdensity in the red subpopulation in the direction of a trail observed in X-ray that could be evidence of interactions with its spiral neighbour NGC 6872. The turnover of the luminosity function gives an estimated distance modulus (m − M) ≈ 33.5 and the total population amounts to 9400 GCs, i.e. a quite populous system. The halo mass obtained using the number ratio (i.e. the number of GCs with respect to the baryonic and dark mass) gives a total of ∼1013, meaning it is a very massive galaxy, given the environment.

Globular cluster system of NGC 3613, a massive elliptical galaxy in a poor environment

2019 ◽  
Vol 14 (S351) ◽  
pp. 84-88
Author(s):  
Bruno J. De Bórtoli ◽  
Lilia P. Bassino ◽  
Juan P. Caso ◽  
Ana I. Ennis
Keyword(s):  
Globular Cluster ◽  
Elliptical Galaxy ◽  
Cluster System ◽  
Host Galaxy ◽  
Low Density ◽  
Stellar Component ◽  
Magnitude Diagram ◽  
The Galaxy ◽  
Colour Distribution ◽  
Globular Cluster System

AbstractWe present an analysis of the globular cluster system (GCS) of the galaxy NGC 3613, an intrinsically bright elliptical galaxy (MV = −21.5) in a low density environment (it is the central galaxy of a group of a dozen galaxies). Based on Gemini/GMOS photometry of NGC 3613 we obtained the following properties for this GCS. A ‘blue tilt’ is detected in the colour-magnitude diagram. The colour distribution is bimodal, presenting the two classical globular cluster (GC) sub-populations. The spatial and azimuthal projected distributions show that red sub-population correlates with the stellar component of the host galaxy.

scholarly journals The Outer Halo Cluster System of NGC 1399

2002 ◽  
Vol 207 ◽  
pp. 324-326 ◽  
Author(s):  
B. Dirsch ◽  
D. Geisler ◽  
T. Richtler ◽  
J.C. Forte
Keyword(s):  
Globular Cluster ◽  
Cluster System ◽  
Wide Field ◽  
Ccd Photometry ◽  
The Galaxy ◽  
Specific Frequency ◽  
Field Imaging ◽  
Wide Field Imaging

We investigate the outer halo globular cluster population of NGC 1399. This study uses wide-field imaging of this cluster system, which covers the largest area studied with CCD photometry until now. The cluster system of NGC 1399 is found to extend further than 100 kpc from the galaxy. A population of metal-rich, as well as metal-poor clusters has been identified at these large radii. At radii smaller than 55 kpc the specific frequency of the red cluster system remains constant, while that of the blue clusters increases proportional tor0.8±0.2. For larger radii, the uncertainty of the galaxy light profile does not permit any reliable statement.

scholarly journals Globular cluster systems of relic galaxies

2021 ◽  
Vol 503 (2) ◽  
pp. 2406-2422
Author(s):  
Karla A Alamo-Martínez ◽  
Ana L Chies-Santos ◽  
Michael A Beasley ◽  
Rodrigo Flores-Freitas ◽  
Cristina Furlanetto ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Host Galaxy ◽  
Stellar Kinematics ◽  
Distribution Width ◽  
Colour Distribution ◽  
Specific Frequency ◽  
Low Mass ◽  
Comparable Mass

ABSTRACT We analyse the globular cluster (GC) systems of a sample of 15 massive, compact early-type galaxies (ETGs), 13 of which have already been identified as good relic galaxy candidates on the basis of their compact morphologies, old stellar populations and stellar kinematics. These relic galaxy candidates are likely the nearby counterparts of high-redshift red nugget galaxies. Using F814W (≈I) and F160W (≈H) data from the WFC3 camara onboard the Hubble Space Telescope, we determine the total number, luminosity function, specific frequency, colour, and spatial distribution of the GC systems (GCSs). We find lower specific frequencies (SN < 2.5 with a median of SN = 1) than ETGs of comparable mass. This is consistent with a scenario of rapid, early dissipative formation, with relatively low levels of accretion of low-mass, high-SN satellites. The GC half-number radii are compact, but follow the relations found in normal ETGs. We identify an anticorrelation between the specific angular momentum (λR) of the host galaxy and the (I − H) colour distribution width of their GCSs. Assuming that λR provides a measure of the degree of dissipation in massive ETGs, we suggest that the (I − H) colour distribution width can be used as a proxy for the degree of complexity of the accretion histories in these systems.

scholarly journals The Globular Cluster Specific Frequency in NGC 1399 and 4486: A Comparative Study

2002 ◽  
Vol 207 ◽  
pp. 251-255 ◽  
Author(s):  
Juan C. Forte ◽  
Doug Geisler ◽  
E. Kim ◽  
Myung Gyoon Lee ◽  
Pablo Ostrov
Keyword(s):  
Comparative Study ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Surface Brightness ◽  
Two Systems ◽  
The Galaxy ◽  
Long Time ◽  
Specific Frequency

A two color CCD survey for globular clusters in the galactocentric range from 2 to 7 arcmin from the galaxy centers is presented for NGC 1399 and NGC 4486 (M87), two systems that, for a long time, have been considered as class archetypes of the so called “high specific frequency phenomenon”. The new results, combined with previously published HST data for the inner 2 arcmin, and with a re-discussion of the surface brightness profiles, allow a new estimate of the globular cluster specific frequencies. The resulting SN values cannot be considered as anomalously large and, rather, they are consistent with values obtained for other galaxies with similar morphologies.

scholarly journals VEGAS-SSS. II. Comparing the globular cluster systems in NGC 3115 and NGC 1399 using VEGAS and FDS survey data

2018 ◽  
Vol 611 ◽  
pp. A93 ◽  
Author(s):  
Michele Cantiello ◽  
Raffaele D’Abrusco ◽  
Marilena Spavone ◽  
Maurizio Paolillo ◽  
Massimo Capaccioli ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Radial Density ◽  
Density Profiles ◽  
Density Maps ◽  
Radial Profiles ◽  
Wide Range ◽  
Significant Difference ◽  
The Galaxy ◽  
Deep Survey ◽  
Specific Frequency

We analyze the globular cluster (GC) systems in two very different galaxies, NGC 3115 and NGC 1399. With the papers of this series, we aim at highlighting common and different properties in the GC systems in galaxies covering a wide range of parameter space. We compare the GCs in NGC 3115 and NGC 1399 as derived from the analysis of one square degree u-, g-, and i-band images taken with the VST telescope as part of the VST early-type galaxy survey (VEGAS) and Fornax deep survey (FDS). We selected GC candidates using as reference the morpho-photometric and color properties of confirmed GCs. The surface density maps of GCs in NGC 3115 reveal a morphology similar to the light profile of field stars; the same is true when blue and red GCs are taken separately. The GC maps for NGC 1399 are richer in structure and confirm the existence of an intra-cluster GC component. We confirm the presence of a spatial offset in the NGC 1399 GC centroid and find that the centroid of the GCs for NGC 3115 coincides well with the galaxy center. Both GC systems show unambiguous color bimodality in (g − i) and (u − i); the color–color relations of the two GC systems are slightly different with NGC 3115 appearing more linear than NGC 1399. The azimuthal average of the radial density profiles in both galaxies reveals a larger spatial extent for the total GCs population with respect to the galaxy surface brightness profile. For both galaxies, the red GCs have radial density profiles compatible with the galaxy light profile, while the radial profiles for blue GCs are shallower. As for the specific frequency of GCs, SN, we find it is a factor of two higher in NGC 1399 than for NGC 3115; this is mainly the result of extra blue GCs. By inspecting the radial behavior of the specific frequency, SN(<r), for the total, blue, and red GCs, we find notable similarities between the trends for red GCs in the two targets. In spite of extremely different host environments, the red GCs in both cases appear closely linked to the light distribution of field stars. Blue GCs extend to larger galactocentric scales than red GCs, marking a significant difference between the two galaxies: the blue/red GCs and field stellar components of NGC 3115 appear well thermalized with each other and the blue GCs in NGC 1399 appear to fade into an unrelaxed intra-cluster GC population.

scholarly journals The Ophiuchus stream progenitor: a new type of globular cluster and its possible Sagittarius connection

2020 ◽  
Vol 492 (3) ◽  
pp. 4164-4174 ◽  
Author(s):  
James M M Lane ◽  
Julio F Navarro ◽  
Azadeh Fattahi ◽  
Kyle A Oman ◽  
Jo Bovy
Keyword(s):  
Globular Cluster ◽  
Surface Brightness ◽  
Lower Surface ◽  
Galactic Centre ◽  
Proper Motions ◽  
Weakly Bound ◽  
The Galaxy ◽  
Length Width ◽  
New Type ◽  
Short Arc

ABSTRACT The Ophiuchus stream is a short arc-like stellar feature of uncertain origin located ∼5 kpc North of the Galactic centre. New proper motions from the second Gaia data release reconcile the direction of motion of stream members with the stream arc, resolving a puzzling mismatch reported in earlier work. We use N-body simulations to show that the stream is likely only on its second pericentric passage, and thus was formed recently. The simulations suggest that most of the disrupted progenitor is visible in the observed stream today, and that little further tidal debris is expected to lie beyond the ends of the stream. The luminosity, length, width, and velocity dispersion of the stream suggest a globular cluster (GC) progenitor substantially fainter and of lower surface brightness than estimated in previous work, and unlike any other known globulars in the Galaxy. This result suggests the existence of clusters that would extend the known GC population to fainter and more weakly bound systems than hitherto known. How such a weakly bound cluster of old stars survived until it was disrupted so recently, however, remains a mystery. Integrating backwards in time, we find that the orbits of Sagittarius and Ophiuchus passed within ∼5 kpc of each other about ∼100 Myr ago, an interaction that might help resolve this puzzle.

scholarly journals The Globular Cluster System of NGC 1316

2002 ◽  
Vol 207 ◽  
pp. 321-323
Author(s):  
Matías Gómez ◽  
Tom Richtler ◽  
Leopoldo Infante ◽  
Georg Drenkhahn
Keyword(s):  
Globular Cluster ◽  
Stellar Population ◽  
Cluster System ◽  
Angular Distributions ◽  
Population Synthesis ◽  
Stellar Population Synthesis ◽  
The Galaxy ◽  
Specific Frequency ◽  
Globular Cluster System ◽  
Fornax Cluster

We have studied the Globular Cluster System of the merger galaxy NGC 1316 in Fornax, using CCD BV I photometry. Dividing the sample into red (presumably metal-rich) and blue (metal-poor) subpopulations at B - I = 1.75, we find that they follow strikingly different angular distributions. The red clusters show a strong correlation with the galaxy elongation, but the blue ones are circularly distributed. An astonishingly low specific frequency for NGC 1316 of only SN = 0.9±0.2 is derived, which confirms with a larger field a previous finding by Grillmair et al. (1999). Assuming a “normal” SN of ∼ 4 for early-type galaxies, we use stellar population synthesis models to estimate the merger age to about 2 Gyr, if an intermediate-age population were to explain the low SN we observe. By fitting t5 functions to the Globular Cluster Luminosity Function (GCLF), we derive the following turnover magnitudes: and . They support that NGC 1316, in spite of its outlying location, is at the same distance as the core of the Fornax cluster.

Interstellar gas in the central region of the Galaxy

1967 ◽  
Vol 31 ◽  
pp. 239-251 ◽  
Author(s):  
F. J. Kerr
Keyword(s):  
Central Region ◽  
Galactic Plane ◽  
Neutral Hydrogen ◽  
Continuum Emission ◽  
Galactic Centre ◽  
Interstellar Gas ◽  
Hydrogen Recombination ◽  
The Galaxy ◽  
Centre Region ◽  
The Relationship

A review is given of information on the galactic-centre region obtained from recent observations of the 21-cm line from neutral hydrogen, the 18-cm group of OH lines, a hydrogen recombination line at 6 cm wavelength, and the continuum emission from ionized hydrogen.Both inward and outward motions are important in this region, in addition to rotation. Several types of observation indicate the presence of material in features inclined to the galactic plane. The relationship between the H and OH concentrations is not yet clear, but a rough picture of the central region can be proposed.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

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