Metal-poor globular clusters (GCs) show intriguing Al-Mg and Si-Al correlations, which are important clues to decipher the multiple population phenomenon. NGC 5053 is one of the most metal-poor GCs, and has been suggested to be associated with the Sagittarius dwarf galaxy (Sgr), due to its similar location and radial velocity with one of the Sgr arms. In this work, we simulate the orbit of NGC 5053, and argue against the connection between Sgr and NGC 5053. Meanwhile, Mg, Al, and Si spectral lines, which are difficult to detect in the optical spectra, have been detected in the near-infrared APOGEE spectra. We use three different sets of stellar parameters and codes to derive the Mg, Al, and Si abundances, and we always see a large Al variation, and a substantial Si enhancement. Comparing with other metal-poor GCs, we suggest metallicity may not be the only parameter that controls the multiple populations.
In this work a search was carried out for globular clusters belonging to the Sagittarius (Sgr) tidal stream using the analysis of spatial positions, radial velocities relative to the Galactic Standard of Rest (V_{GSR}),proper motions and ratio of "age -- metallicity" ([Fe/H]) for globular clusters and for stars in the tidal stream. As a result, three categories of globular clusters were obtained: A -- most certainly in the stream: Terzan 8, Whiting 1, Arp 2, NGC 6715, Terzan 7, Pal 12; B -- kinematic outliers: Pal 5, NGC 5904, NGC 5024, NGC 5053, NGC 5272, NGC 288; C -- lowest rank candidates:…
We use Gaia DR2 data to show that the globular cluster NGC5634 is physically associated with an arm of the Sagittarius Stream, the huge system of tidal tails created by the ongoing disruption of the Sagittarius dwarf spheroidal galaxy (Sgr dSph). Two additional arms of the Stream are also detected along the same line of sight, at different distances. We show that the Sgr Stream stars surrounding NGC5634 are more metal-poor, on average, than those found in the more distant Stream arm lying behind the cluster and in the main body of Sgr~dSph, confirming that a significant metallicity (and, presu…
Recently, new Sagittarius (Sgr) dwarf galaxy globular clusters were discovered, which opens the question on the actual size of the Sgr globular cluster population, and therefore on our understanding of the Sgr galaxy formation and accretion history onto the Milky Way. Based on Gaia EDR3 and SDSS IV DR16 (APOGEE-2) data sets, we performed an analysis of the color-magnitude diagrams (CMDs) of the eight new Sgr globular clusters found by from a sound cleaning of the contamination of Milky Way and Sgr field stars, complemented by Minniti et al. (2021b) available kinematic and metal abundance infor…
The cluster M54 lies at the centre of the Sagittarius dwarf spheroidal galaxy, and therefore may be the closest example of a nuclear star cluster. Either in-situ star formation, inspiralling globular clusters, or a combination have been invoked to explain the wide variety of stellar sub-populations in nuclear star clusters. Globular clusters are known to exhibit light element variations, which can be identified using the photometric construct called a chromosome map. In this letter, we create chromosome maps for three distinct age-metallicity sub-populations in the vicinity of M54. We find tha…
We present BV photometry of four Sagittarius dwarf spheroidal galaxy globular clusters: Arp 2, NGC 5634, Palomar 12, and Terzan 8, obtained with the Danish telescope at ESO-La Silla. We measure the structural parameters of the clusters using a King profile fitting, obtaining the first reliable measurements of the tidal radius of Arp 2 and Terzan 8. These two clusters are remarkably extended and with low concentrations; with a concentration of only c = 0.41 +/- 0.02, Terzan 8 is less concentrated than any cluster in our Galaxy. Blue stragglers are identified in the four clusters, and their spat…
We reconsider the case for the association of Galactic globular clusters (GCs) to the tidal stream of the Sagittarius dwarf spheroidal galaxy (Sgr dSph), using Gaia DR2 data. We use RR Lyrae to trace the stream in 6D and we select clusters matching the observed stream in position and velocity. In addition to the clusters residing in the main body of the galaxy (M 54, Ter 8, Ter 7, Arp 2) we confirm the membership of Pal 12 and Whiting 1 to the portion of the trailing arm populated by stars lost during recent perigalactic passages. NGC 2419, NGC 5634 and NGC 4147 are very interesting candidates…
We present a new spectroscopic study of the faint Milky Way satellite Sagittarius II. Using multi-object spectroscopy from the Fibre Large Array Multi Element Spectrograph, we supplement the dataset of Longeard et al. (2020) with 47 newly observed stars, 19 of which are identified as members of the satellite. These additional member stars are used to put tighter constraints on the dynamics and the metallicity properties of the system. We find a low velocity dispersion of SgrII v = 1.7 +/- 0.5 km s-1, in agreement with the dispersion of Milky Way globular clusters of similar luminosity. We conf…
We present a study of the kinematics of 101 stars observed with VIMOS around Whiting1, a globular cluster embedded in the Sagittarius tidal stream. The obtained velocity distribution shows the presence of two wraps of that halo substructure at the same heliocentric distance as that of the cluster and with well differentiated mean radial velocities. The most prominent velocity component seems to be associated with the trailing arm of Sagittarius with $<v_{\rm r}>$ ~ -130 km/s, which is consistent with the velocity of Whiting1. This result supports that this globular cluster was formed in Sagitt…
The Ophiuchus stream is a short arc-like stellar feature of uncertain origin located $\sim 5$ 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 the entire disrupted progenitor is visible in the observed stream today, and that little further tidal debris lies beyond the end…
We use the fundamental-mode RR Lyr-type variable stars (RRab) from OGLE-IV survey to draw a 3D picture of the central part of the tidally disrupted Sagittarius Dwarf Spheroidal (Sgr dSph) galaxy. We estimate the line-of-sight thickness of the Sgr dSph stream to be FWHM_cen=2.42 kpc. Based on OGLE-IV observations collected in seasons 2011-2014 we conduct a comprehensive study of stellar variability in the field of the globular cluster M54 (NGC 6715) residing in the core of this dwarf galaxy. Among the total number of 268 detected variable stars we report the identification of 174 RR Lyr stars, …
We have measured absolute proper motions for the three populations intercepted in the direction of the Galactic globular cluster NGC 6681: the cluster itself, the Sagittarius dwarf spheroidal galaxy and the field. For this we used Hubble Space Telescope ACS/WFC and WFC3/UVIS optical imaging data separated by a temporal baseline of 5.464 years. Five background galaxies were used to determine the zero point of the absolute-motion reference frame. The resulting absolute proper motion of NGC 6681 is ($μ_α\cosδ, μ_δ$)=($1.58\pm0.18, -4.57\pm0.16$) \masyr. This is the first estimate ever made for th…
Massive globular clusters (GCs) contain at least two generations of stars with slightly different ages and clearly distinct light elements abundances. The Na-O anticorrelation is the best studied chemical signature of multiple stellar generations. Low-mass clusters appear instead to be usually chemically homogeneous. We are investigating low-mass GCs to understand what is the lower mass limit where multiple populations can form, mainly using the Na and O abundance distribution. We used VLT/FLAMES spectra of giants in the low-mass, metal-poor GC Terzan 8, belonging to the Sagittarius dwarf gala…
We conducted a variable star search on the metal-rich Galactic globular cluster NGC 6652 using archival Gemini-S/GMOS data. We report the discovery of nine new variable stars in the NGC 6652 field, of which we classify six as eclipsing binaries and one as SX Phoenicis stars, leaving two variables without classification. Using proper motions from Gaia DR2 and HST, albeit with some uncertainties, we find that the cluster, the field, and the background Sagittarius stream, have 3 of these variables each. We also reassess the membership of known variables based on the Gaia proper motions, confirmin…
We use observations from the ACS study of Galactic globular clusters to investigate the spatial distribution of the inner regions of the disrupting Sagittarius dwarf spheroidal galaxy (Sgr). We combine previously published analyses of four Sgr member clusters located near or in the Sgr core (M54, Arp 2, Terzan 7 and Terzan 8) with a new analysis of diffuse Sgr material identified in the background of five low-latitude Galactic bulge clusters (NGC 6624, 6637, 6652, 6681 and 6809) observed as part of the ACS survey. By comparing the bulge cluster CMDs to our previous analysis of the M54/Sgr core…
Context. Globular clusters (GCs) are witnesses of the past accretion events onto the Milky Way (MW). In particular, the GCs of the Sagittarius (Sgr) dwarf galaxy are important probes of an on-going merger. Aims. Our main goal is to search for new GC members of this dwarf galaxy using the VISTA Variables in the Via Lactea Extended Survey (VVVX) near-infrared database combined with the Gaia Early Data Release 3 (EDR3) optical database. Methods. We investigated all VVVX-enabled discoveries of GC candidates in a region covering about 180 sq. deg. toward the bulge and the Sgr dwarf galaxy. We used …
Context. The Sagittarius (Sgr) dwarf galaxy is merging with the Milky Way, and the study of its globular clusters (GCs) is important to understand the history and outcome of this ongoing process. Aims. Our main goal is to characterize the GC system of the Sgr dwarf galaxy. This task is hampered by high foreground stellar contamination, mostly from the Galactic bulge. Methods. We performed a GC search specifically tailored to find new GC members within the main body of this dwarf galaxy using the combined data of the VISTA Variables in the Via Lactea Extended Survey (VVVX) near-infrared survey …
Numerical models of the tidal disruption of the Sagittarius (Sgr) dwarf galaxy have recently been developed that for the first time simultaneously satisfy most observational constraints on the angular position, distance, and radial velocity trends of both leading and trailing tidal streams emanating from the dwarf. We use these dynamical models in combination with extant 3-D position and velocity data for Galactic globular clusters and dSph galaxies to identify those Milky Way satellites that are likely to have originally formed in Sgr and been stripped from it during its extended interaction …
We have derived from VIMOS spectroscopy the radial velocities for a sample of 71 stars selected from CFHT/Megacam photometry around the Galactic globular cluster NGC7492. In the resulting velocity distribution, it is possible to distinguish two relevant non-Galactic kinematic components along the same line of sight: a group of stars at $\langle{v_{\rm r}}\rangle \sim 125$km s$^{-1}$ which is compatible with the velocity of the old leading arm of the Sagittarius tidal stream, and a larger number of objects at $\langle{v_{\rm r}}\rangle \sim -110$km s$^{-1}$ that might be identified as members o…
We present the results of a spectroscopic survey of Red Giants in the globular cluster Terzan 8 with the aim of studying its kinematics. We derived accurate radial velocities for 82 stars located in the innermost 7 arcmin from the cluster center identifying 48 bona fide cluster members. The kinematics of the cluster have been compared with a set of dynamical models accounting for the effect of mass segregation and a variable fraction of binaries. The derived velocity dispersion appears to be larger than that predicted for mass-segregated stellar systems without binaries, indicating that either…
Passing through the Galactic disk, a massive object such as a globular cluster, can trigger star formation process leading to the birth of open clusters. Here, we analyze such possible evolutionary relationship between globular and open clusters. To search for the closest rapprochement between objects we computed backwards the orbits of 150 Galactic globular and 232 open clusters (younger than 100 Myr) with proper motions, derived from the Gaia DR2 Catalog. The orbits were computed using the recently modified three-component (disk, bulge and halo) axisymmetric Navarro-Frenk-White potential, wh…
Based on a large sample of 133 Galactic globular clusters we obtained a new estimate of the frequency of globular-cluster impacts onto the Galactic plane, which we found to be equal to three events per 1 Myr. Our computations involving new kinematical data do not support the well-known hypothesis about the possible origin of the open cluster Stephenson~2 as a result of the massive globular cluster $ω$ Cen crossing the Galactic disk. Our results also do not support the well-known hypothesis that the globular cluster NGC6397 could trigger the formation of the open cluster NGC6231. We found for t…
We review our recent studies of the globular cluster system of NGC 5128. First, we have obtained low-resolution, high signal-to-noise spectroscopy of 72 globular clusters using Gemini-S/GMOS to obtain the ages, metallicities, and the level of alpha enrichment of the metal-poor and metal-rich globular cluster subpopulations. Second, we have explored the rotational signature and velocity dispersion of the galaxy's halo using over 560 globular clusters with radial velocity measurements. We have also compared the dependence of these properties on galactocentric distance and globular cluster age an…
As tracers of star formation, galaxy assembly and mass distribution, globular clusters have provided important clues to our understanding of early-type galaxies. But their study has been mostly constrained to galaxy groups and clusters where early-type galaxies dominate, leaving the properties of the globular cluster systems (GCSs) of isolated ellipticals as a mostly uncharted territory. We present Gemini-South/GMOS $g'i'$ observations of five isolated elliptical galaxies: NGC 3962, NGC 2865, IC 4889, NGC 2271 and NGC 4240. Photometry of their GCSs reveals clear color bimodality in three of th…
We present preliminary results of the variability survey in the field of the glo bular cluster NGC 4833. We observed all 34 variable stars known in the cluster. In add ition, we have found two new SX Phoenicis stars, one new RR Lyrae star, twelve new ecli psing systems mostly of the W Ursae Majoris type, nine new variable red giants, and ten new field-stars showing irregular variations. Properties of RR Lyrae stars indicate that NGC 4833 is an Oosterhoff's type II globular cluster.
As part of our on-going project on the homogeneous chemical characterization of multiple stellar populations in globular clusters (GCs), we studied NGC 5634, associated to the Sagittarius dwarf spheroidal galaxy, using high-resolution spectroscopy of red giant stars collected with FLAMES@VLT. We present here the radial velocity distribution of the 45 observed stars, 43 of which are member, the detailed chemical abundance of 22 species for the seven stars observed with UVES-FLAMES, and the abundance of six elements for stars observed with GIRAFFE. On our homogeneous UVES metallicity scale we de…
Even after decades of research, the origin of multiple stellar populations in globular clusters remains enigmatic. The question as to whether the galaxy environment plays a role in their formation remains unanswered. To that extent, we analysed two classical (> 10 Gyr old) Large Magellanic Cloud globular clusters namely, NGC 1786 and NGC 1898, using imaging data from Hubble Space Telescope to compare and contrast them with ancient Galactic globular clusters to assess systematic differences that might exist between their abundance variations. We calculated their Red Giant Branch width, subtract…
Globular clusters (GCs) are important tools to rebuild the accretion history of a galaxy. There are newly discovered GCs in the Sagittarius (Sgr) dwarf galaxy, that can be used as probes of the accretion event onto the Milky Way (MW). Our main aim is to characterize the Sgr GC system by measuring its main physical parameters. We build the optical and near-IR color-magnitude diagrams (CMDs) for 21 new Sgr GCs using the VISTA Variables in the Via Lactea Extended Survey (VVVX) near-IR database combined with the Gaia EDR3 optical database. We derive metallicities and ages for all targets, using th…
We present the discovery of three new Milky Way satellites from our search for compact stellar overdensities in the photometric catalog of the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS 1, or PS1) 3pi survey. The first satellite, Laevens 3, is located at a heliocentric distance of d=67+/-3 kpc. With a total magnitude of Mv=-4.4+/-0.3 and a half-light radius rh=7+/-2 pc, its properties resemble those of outer halo globular clusters. The second system, Draco II/Laevens 4 (Dra II), is a closer and fainter satellite (d~20 kpc, Mv =-2.9+/-0.8), whose uncertain size (rh = 19 …
We present new photometry for 323 of the globular clusters in NGC 5128 (Centaurus A), measured for the first time in the $g'r'i'z'$ filter system. The color indices are calibrated directly to standard stars in the $g'r'i'z'$ system and are used to establish the fiducial mean colors for the blue and red (low and high metallicity) globular cluster sequences. We also use spectroscopically measured abundances to establish the conversion between the most metallicity-sensitive colors ($(g'-r')_0$, $(g'-i')_0$) and metallicity, [Fe/H].
We present a new photometric study of NGC 3258 and NGC 3268 globular cluster systems (GCSs), using images in filters $B,C,V,R,I$ and $z'$, obtained from four different telescopes. The wide spatial coverage allow us to estimate the whole extension of both GCSs more precisely than in previous works, and new values for the richness of GCs subpopulations. We find differences in the azimuthal distribution between blue (metal-poor) and red (metal-rich) globular clusters (GCs), and confirm that radial profiles flatten towards the centre of the galaxies. In both cases we detected a radial gradient in …
Most globular clusters (GCs) are now known to host multiple stellar populations with different light element abundances. Here we use narrow-band photometry and low-resolution spectroscopy for NGC 362 and NGC 6723 to investigate their chemical properties and radial distributions of subpopulations. We confirm that NGC 362 and NGC 6723 are among the GCs with multiple populations showing bimodal CN distribution and CN-CH anti-correlation without a significant spread in calcium abundance. These two GCs show more centrally concentrated CN-weak earlier generation stars compared to the later generatio…
We report the discovery of tidal tails around the Galactic globular cluster NGC 7492, based on the Data Release 1 of the Pan-STARRS 1 survey. The tails were detected with a version of the matched filter technique applied to the $(g-r,r)$ and $(g-i,i)$ color-magnitude diagrams. Tidal tails emerging from the cluster extend at least $\sim$3.5 degrees in the North-East to South-East direction, equivalent to $\sim1.5$ kpc in projected length.
We study the radial distribution of stars of different stellar generations in the globular cluster NGC 3201. From recently published multicolour photometry, a radial dependence of the location of stars on the giant branch was found. We coupled the photometric information to our sample of 100 red giants with Na, O abundances and known classification as first or second-generation stars. We find that giants stars of the second generation in NGC 3201 show a tendency to be more centrally concentrated than stars of the first generation, supporting less robust results from our spectroscopic analysis.
The giant elliptical galaxy NGC 1316 is the brightest galaxy in the Fornax cluster, and displays a number of morphological features that might be interpreted as an intermediate age merger remanent ($\sim$3 Gyr). Based on the idea that globular clusters systems (GCS) constitute genuine tracers of the formation and evolution of their host galaxies, we conducted a spectroscopic study of approximately 40 globular clusters (GCs) candidates associated with this interesting galaxy. We determined ages, metallicities, and $α$-element abundances for each GC present in the sample, through the measurement…
Metal-poor globular clusters (GCs) exhibit intriguing Al-Mg anti-correlations and possible Si-Al correlations, which are important clues to decipher the multiple-population phenomenon. NGC 5053 is one of the most metal-poor GCs in the nearby Universe, and has been suggested to be associated with the Sagittarius (Sgr) dwarf galaxy, due to its similarity in location and radial velocity with one of the Sgr arms. In this work, we simulate the orbit of NGC 5053, and argue against a physical connection between Sgr and NGC 5053. On the other hand, the Mg, Al, and Si spectral lines, which are difficul…
We discuss the chemical composition of six giant stars of the outer Halo globular cluster NGC5694, through the analysis of UVES@FLAMES high-resolution spectra. The cluster has an average iron content [Fe/H]=--1.83+-0.01, solar-scaled [alpha/Fe] ratios and a very low Ba abundance ([Ba/Fe]=--0.71+-0.06). These anomalous abundance patterns are different from those observed in other Halo globular clusters but similar to those of the metal-poor stars in typical dwarf spheroidal galaxies. These findings suggest an extra-galactic origin for NGC5694, likely from a dwarf spheroidal galaxy.
The tidal disruption of the Sagittarius dwarf Spheroidal galaxy (Sgr dSph) is producing the most prominent substructure in the Milky Way (MW) halo, the Sagittarius Stream. Aside from field stars, the Sgr dSph is suspected to have lost a number of globular clusters (GC). Many Galactic GC are suspected to have originated in the Sgr dSph. While for some candidates an origin in the Sgr dSph has been confirmed due to chemical similarities, others exist whose chemical composition has never been investigated. NGC 5053 and NGC 5634 are two among these scarcely studied Sgr dSph candidate-member cluster…
The dynamical evolution of a single globular cluster and also of the entire Galactic globular cluster system has been studied theoretically in detail. In particular, simulations show how the 'lost' stars are distributed in tidal tails emerging from the clusters. We investigate the distribution of Galactic globular cluster stars on the sky to identify such features like tidal tails. The Sloan Digital Sky Survey provides consistent photometry of a large part of the sky to study the projected two dimensional structure of the 17 globular clusters in its survey area. We use a color-magnitude weight…
Globular clusters are prone to lose stars while moving around the Milky Way. These stars escape the clusters and are distributed throughout extended envelopes or tidal tails. However, such extra-tidal structures are not observed in all globular clusters, and yet there is no structural or dynamical parameters that can predict their presence or absence. NGC\,6864 is an outer halo globular cluster with reported no observed tidal tails. We used Dark Energy Camera (DECam) photometry reaching $\sim$ 4 mag underneath its main sequence turnoff to confidently detect an extra-tidal envelope, and stellar…
We present high-quality BVRI photometric data in the field of globular cluster NGC 6496 obtained with the SOAR Telescope Adaptive Module (SAM). Our observations were collected as part of the ongoing SAM commissioning. The distance modulus and cluster color excess as found from the red clump is $\mMv = 15.71 \pm 0.02$\,mag and $\EVI = 0.28 \pm 0.02$\,mag. An age of $10.5 \pm 0.5$\,Gyr is determined from the difference in magnitude between the red clump and the subgiant branch. These parameters are in excellent agreement with the values derived from isochrone fitting. From the color-magnitude di…
We present an abundance analysis of eight potential member stars of the old Galactic bulge globular cluster NGC6522. The same stars have previously been studied by Chiappini et al. (2011), who found very high abundances of the slow neutron capture elements compared with other clusters and field stars of similar metallicity, which they interpreted as reflecting nucleosynthesis in rapidly rotating, massive Population III stars. In contrast to their analysis, we do not find any unusual enhancements of the neutron capture elements Sr, Y, Ba and Eu and conclude that previous claims result mainly fr…
We present new photometry and analysis of the twelve variable stars (nine RR Lyrae, three SX Phoenicis) belonging to the Sagittarius globular cluster Arp 2. Of the nine RR Lyrae stars in the cluster, eight are RRab and one is RRc. From the RRab stars, we determined a mean period of $\langle P_{ab}\rangle=0.581\pm0.047$ days, where the error is the standard error of the mean. This places Arp 2 at the border between the Oosterhoff I and Oosterhoff-Int clusters. Using the $V$-band data from the RR Lyrae stars, a distance modulus of $(m-M)_0=17.24\pm0.17$ was determined. From the $I$-band data, we…
Aims. We present a new technique to estimate the relative ages of multiple stellar populations hosted by five globular clusters: NGC 104 (47 Tuc), NGC 6121 (M4), NGC 6352, NGC 6362 and NGC 6723. Methods. We used the catalogs of the database "HST UV Globular cluster Survey (HUGS)" to create color-magnitude and two-color diagrams of the Globular Clusters. We identified the multiple populations within each globular cluster, and we divided them into two main stellar populations: POPa or first generation (1G) and POPb, composed of all the successive generations of stars. The new technique allows us…
What is the mass of the progenitor of the Sagittarius (Sgr) dwarf galaxy? Here, we reassemble the stellar debris using SDSS and 2MASS data to find the total luminosity and likely mass. We find that the luminosity is in the range 9.6-13.2 x10^7 solar luminosities or M_V ~ -15.1 - 15.5, with 70% of the light residing in the debris streams. The progenitor is somewhat fainter than the present-day Small Magellanic Cloud, and comparable in brightness to the M31 dwarf spheroidals NGC 147 and NGC 185. Using cosmologically motivated models, we estimate that the mass of Sgr's dark matter halo prior to t…
We present DECam imaging for the peculiar Galactic globular clusters NGC1851, NGC1904 (M79), NGC2298 and NGC2808. Our deep photometry reveals that all the clusters have an important contribution of stars beyond their King tidal radii and present tails with different morphologies. We have also explored the surroundings of the clusters where the presence of the Canis Major overdensity and/or the low Galactic latitude Monoceros ring at d~8kpc is evident. A second stellar system is found at d~17kpc and spans at least 18deg x 15deg in the sky. As one of the possible scenarios to explain that featur…
We derived Potassium abundances in red giant branch stars in the Galactic globular clusters NGC104 (144 stars), NGC6752 (134 stars) and NGC6809 (151 stars) using high-resolution spectra collected with FLAMES at the ESO - Very Large Telescope. In the considered samples we do not find significant intrinsic spreads in [K/Fe] (confirming the previous findings by Carretta et al.), at variance with the cases of the massive clusters NGC2419 and NGC2808. Additionally, marginally significant [K/Fe]-[O/Fe] anti-correlations are found in NGC104 and NGC6809, and [K/Fe]-[Na/Fe] correlations are found in NG…
Globular clusters (GCs) associated with the Sagittarius dwarf spheroidal galaxy (Sgr dSph) have evolved under the gravitational potential of both Sgr dSph and the Milky Way. The effects of these potentials are most pronounced in the extra-tidal regions as compared to the central regions of the GCs.We aim to study the extra-tidal regions of the GCs that are possibly associated with Sgr dSph, namely Arp 2, Terzan 8, NGC 5634, NGC 6284, Terzan 7, NGC 2419, NGC 4147, M 54 and Pal 12, using data from the {\it Gaia} early data release 3. We selected the extra-tidal candidates based on their angular …
We explore the possibility of searching for extratidal features around the Galactic globular cluster NGC362 using the Gaia DR2 together with a modified version of a classical statistical decontamination algorithm. Our results suggest that an important stellar component is associated with this globular cluster, which is perfectly distinguishable from the populations in the Small Magellanic Cloud and that of the nearby NGC104 (47 Tucanae). We thus confirm once again the power of Gaia to disentangle different stellar components along the same line-of-sight.
Recently, Kundu et al (2019) reported that the globular cluster NGC 5024 (M53) possesses five extra-tidal RR Lyrae. In fact, four of them were instead known members of a nearby globular cluster NGC 5053. The status of the remaining extra-tidal RR Lyrae is controversial depending on the adopted tidal radius of NGC 5024. We have also searched for additional extra-tidal RR Lyrae within an area of $\sim8$~deg$^2$ covering both globular clusters. This includes other known RR Lyrae within the search area, as well as stars that fall within the expected range of magnitudes and colors for RR Lyrae (and…
The study of dynamical properties of Galactic open clusters is a fundamental prerequisite for the comprehension of their dissolution processes. In this work, we characterized 12 open clusters, namely: Collinder 258, NGC 6756, Czernik 37, NGC 5381, Ruprecht 111, Ruprecht 102, NGC 6249, Basel 5, Ruprecht 97, Trumpler 25, ESO 129-SC32 and BH 150, projected against dense stellar fields. In order to do that, we employed Washington $CT_{1}$ photometry and GAIA DR2 astrometry, combined with a decontamination algorithm applied to the three-dimensional astrometric space of proper motions and parallaxes…
NGC 2419 is a massive outer halo Galactic globular cluster whose stars have previously been shown to have somewhat peculiar abundance patterns. We have observed seven luminous giants that are members of NGC 2419 with Keck/HIRES at reasonable SNR. One of these giants is very peculiar, with an extremely low [Mg/Fe] and high [K/Fe] but normal abundances of most other elements. The abundance pattern does not match the nucleosynthetic yields of any supernova model. The other six stars show abundance ratios typical of inner halo Galactic globular clusters, represented here by a sample of giants in t…
In this paper we present photometric CCD observations of the globular cluster NGC 6093 (M80) in filters B, V , R and I. We produce the colour-magnitude diagrams for this object and obtain values for its metallicity [Fe/H], reddening E(V-B), E(V-I) and distance modulus (m - M)_0.
We present metallicities for red giant stars in the globular cluster NGC 6273 based on intermediate resolution GMOS-S spectra of the calcium triplet region. For the 42 radial velocity members with reliable calcium triplet line strength measurements, we obtain metallicities, [Fe/H], using calibrations established from standard globular clusters. We confirm the presence of an intrinsic abundance dispersion identified by Johnson et al. (2015). The total range in [Fe/H] is ~1.0 dex and after taking into account the measurement errors, the intrinsic abundance dispersion is σ[Fe/H] = 0.17 dex. Among…
We present radial velocities and chemical abundances for red giant branch stars in the Galactic bulge globular clusters NGC 6342 and NGC 6366. The velocities and abundances are based on measurements of high resolution (R > 20,000) spectra obtained with the MMT-Hectochelle and WIYN-Hydra spectrographs. We find that NGC 6342 has a heliocentric radial velocity of +112.5 km/s (sigma = 8.6 km/s), NGC 6366 has a heliocentric radial velocity of -122.3 km/s (sigma = 1.5 km/s), and that both clusters have nearly identical metallicities ([Fe/H] ~ -0.55). NGC 6366 shows evidence of a moderately extended …
We present results of time series photometry to search for variable stars in the field of metal-poor globular cluster NGC 4590 (M68). Periods have been revised for 40 known variables and no significant changes were found. A considerable change in Blazhko effect for V25 has been detected. Among nine newly discovered variable candidates, 5 stars are of RRc Bailey type variables while 4 stars are unclassified. The variable stars V10, V21, V50 and V51 are found to be cluster members based on the radial velocity data taken from literature.
We use Hubble Space Telescope imaging to show that the nearby dwarf starburst galaxy NGC 4449 has an unusual abundance of luminous red star clusters. Joint constraints from integrated photometry, low-resolution spectroscopy, dynamical mass-to-light ratios, and resolved color-magnitude diagrams provide evidence that some of these clusters are old globular clusters. Spectroscopic data for two massive clusters suggest intermediate metallicities ([Fe/H] ~ -1) and subsolar Mg enhancement ([Mg/Fe] ~ -0.1 to -0.2). One of these clusters may be the nucleus of a tidally disrupting dwarf galaxy; the oth…
Using parallaxes from Gaia DR2, we estimate the distance to the globular clusters 47 Tuc and NGC 362, taking advantage of the background stars in the Small Magellanic Cloud and quasars to account for various parallax systematics. We found the parallax to be dependent on the Gaia DR2 G apparent magnitude for stars with $13<\textrm{G}<18$ , where brighter stars have a lower parallax zero point than fainter stars. The distance to 47 Tuc was found to be $4.45\pm0.01\pm0.12$ kpc, and for NGC 362 $8.54\pm0.20\pm0.44$ kpc with random and systematic errors listed respectively. This is the first time a…
