scholarly journals Tango for three: Sagittarius, LMC, and the Milky Way

2020 ◽  
Vol 501 (2) ◽  
pp. 2279-2304
Author(s):  
Eugene Vasiliev ◽  
Vasily Belokurov ◽  
Denis Erkal
Keyword(s):  
Milky Way ◽  
Galactic Halo ◽  
Large Magellanic Cloud ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Tentative Evidence ◽  
Virial Mass ◽  
Lyrae Stars ◽  
Astrometric Data ◽  
Gaia Dr2

ABSTRACT We assemble a catalogue of candidate Sagittarius stream members with 5D and 6D phase-space information, using astrometric data from Gaia DR2, distances estimated from RR Lyrae stars, and line-of-sight velocities from various spectroscopic surveys. We find a clear misalignment between the stream track and the direction of the reflex-corrected proper motions in the leading arm of the stream, which we interpret as a signature of a time-dependent perturbation of the gravitational potential. A likely cause of this perturbation is the recent passage of the most massive Milky Way satellite – the Large Magellanic Cloud (LMC). We develop novel methods for simulating the Sagittarius stream in the presence of the LMC, using specially tailored N-body simulations and a flexible parametrization of the Milky Way halo density profile. We find that while models without the LMC can fit most stream features rather well, they fail to reproduce the misalignment and overestimate the distance to the leading arm apocentre. On the other hand, models with an LMC mass in the range $(1.3\pm 0.3)\times 10^{11}\, \mathrm{M}_\odot$ rectify these deficiencies. We demonstrate that the stream can not be modelled adequately in a static Milky Way. Instead, our Galaxy is required to lurch toward the massive in-falling Cloud, giving the Sgr stream its peculiar shape and kinematics. By exploring the parameter space of Milky Way potentials, we determine the enclosed mass within 100 kpc to be $(5.6\pm 0.4)\times 10^{11}\, \mathrm{M}_\odot$, and the virial mass to be $(9.0\pm 1.3)\times 10^{11}\, \mathrm{M}_\odot$, and find tentative evidence for a radially-varying shape and orientation of the Galactic halo.

scholarly journals Detailed study of the Milky Way globular cluster Laevens 3

2019 ◽  
Vol 490 (2) ◽  
pp. 1498-1508
Author(s):  
Nicolas Longeard ◽  
Nicolas Martin ◽  
Rodrigo A Ibata ◽  
Michelle L M Collins ◽  
Benjamin P M Laevens ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Magnitude Diagram ◽  
Mass Segregation ◽  
Stellar Properties ◽  
Lyrae Stars ◽  
Gaia Dr2

ABSTRACT We present a photometric and spectroscopic study of the Milky Way satellite Laevens 3. Using MegaCam/Canada–France–Hawaii Telescope $g$ and $i$ photometry and Keck II/DEIMOS multi-object spectroscopy, we refine the structural and stellar properties of the system. The Laevens 3 colour–magnitude diagram shows that it is quite metal-poor, old ($13.0 \pm 1.0$ Gyr), and at a distance of $61.4 \pm 1.0$ kpc, partly based on two RR Lyrae stars. The system is faint ($M_V = -2.8^{+0.2}_{-0.3}$ mag) and compact ($r_h = 11.4 \pm 1.0$ pc). From the spectroscopy, we constrain the systemic metallicity (${\rm [Fe/H]}_\mathrm{spectro} = -1.8 \pm 0.1$ dex) but the metallicity and velocity dispersions are both unresolved. Using Gaia DR2, we infer a mean proper motion of $(\mu _\alpha ^*,\mu _\delta)=(0.51 \pm 0.28,-0.83 \pm 0.27)$ mas yr−1, which, combined with the system’s radial velocity ($\langle v_r\rangle = -70.2 \pm 0.5 {\rm \, km \,\, s^{-1}}$), translates into a halo orbit with a pericenter and apocenter of $40.7 ^{+5.6}_{-14.7}$ and $85.6^{+17.2}_{-5.9}$ kpc, respectively. Overall, Laevens 3 shares the typical properties of the Milky Way’s outer halo globular clusters. Furthermore, we find that this system shows signs of mass segregation that strengthens our conclusion that Laevens 3 is a globular cluster.

scholarly journals RR Lyrae to understand the Galactic halo

2015 ◽  
Vol 11 (S317) ◽  
pp. 77-82
Author(s):  
Giuliana Fiorentino
Keyword(s):  
Globular Clusters ◽  
Galactic Halo ◽  
Large Magellanic Cloud ◽  
Rr Lyrae Stars ◽  
Halo Structure ◽  
Intrinsic Nature ◽  
Rr Lyrae ◽  
Dwarf Spheroidals ◽  
Lyrae Stars

AbstractWe present recent results obtained using old variable RR Lyrae stars on the Galactic halo structure and its connection with nearby dwarf galaxies. We compare the period and period-amplitude distributions for a sizeable sample of fundamental mode RR Lyrae stars (RRab) in dwarf spheroidals (~1300 stars) with those in the Galactic halo (~16'000 stars) and globular clusters (~1000 stars). RRab in dwarfs –as observed today– do not appear to follow the pulsation properties shown by those in the Galactic halo, nor they have the same properties as RRab in globulars. Thanks to the OGLE experiment we extended our comparison to massive metal–rich satellites like the dwarf irregular Large Magellanic Cloud (LMC) and the Sagittarius (Sgr) dwarf spheroidal. These massive and more metal–rich stellar systems likely have contributed to the Galactic halo formation more than classical dwarf spheroidals.Finally, exploiting the intrinsic nature of RR Lyrae as distance indicators we were able to study the period and period amplitude distributions of RRab within the Halo. It turned out that the inner and the outer Halo do show a difference that may suggest a different formation scenario (in situ vs accreted).

scholarly journals Local RR Lyrae stars: native and alien

2019 ◽  
Vol 492 (2) ◽  
pp. 2161-2176 ◽  
Author(s):  
R Zinn ◽  
X Chen ◽  
A C Layden ◽  
D I Casetti-Dinescu
Keyword(s):  
Milky Way ◽  
Large Magellanic Cloud ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Angular Momenta ◽  
Data Release ◽  
Total Energies ◽  
Using Data ◽  
Lyrae Stars ◽  
Existing Data

ABSTRACT Measurements of [Fe/H] and radial velocity are presented for 89 RR Lyrae (RRL) candidates within 6 kpc of the Sun. After the removal of two suspected non-RRLs, these stars were added to an existing data base, which yielded 464 RRLs with [Fe/H] on a homogeneous scale. Using data from the Gaia satellite (Data Release 2), we calculated the positions and space velocities for this sample. These data confirm the existence of a thin disc of RRL with [α/Fe] ∼ solar. The majority of the halo RRLs with large total energies have near-zero angular momenta about the Z-axis. Kinematically, these stars closely resemble the Gaia-Sausage/Gaia-Enceladus stars that others have proposed are debris from the merger of a large galaxy with the Milky Way. The metallicity and period distributions of the RRLs and their positions in the period–amplitude diagram suggest that this disrupted galaxy was as massive as the Large Magellanic Cloud and possibly greater.

scholarly journals The Pisces Plume and the Magellanic wake

2019 ◽  
Vol 488 (1) ◽  
pp. L47-L52 ◽  
Author(s):  
Vasily Belokurov ◽  
Alis J Deason ◽  
Denis Erkal ◽  
Sergey E Koposov ◽  
Julio A Carballo-Bello ◽  
...  
Keyword(s):  
Milky Way ◽  
Galactic Halo ◽  
Magellanic Clouds ◽  
Line Of Sight ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Data Release ◽  
Magellanic Stream ◽  
Lyrae Stars

ABSTRACT Using RR Lyrae stars in the Gaia Data Release 2 and Pan-STARRS1 we study the properties of the Pisces overdensity, a diffuse substructure in the outer halo of the Milky Way. We show that along the line of sight, Pisces appears as a broad and long plume of stars stretching from 40 to 110 kpc with a steep distance gradient. On the sky Pisces’s elongated shape is aligned with the Magellanic Stream. Using follow-up VLT FORS2 spectroscopy, we have measured the velocity distribution of the Pisces candidate member stars and have shown it to be as broad as that of the Galactic halo but offset to negative velocities. Using a suite of numerical simulations, we demonstrate that the structure has many properties in common with the predicted behaviour of the Magellanic wake, i.e. the Galactic halo overdensity induced by the infall of the Magellanic Clouds.

scholarly journals Reflex motion in the Milky Way stellar halo resulting from the Large Magellanic Cloud infall

2020 ◽  
Vol 494 (1) ◽  
pp. L11-L16 ◽  
Author(s):  
Michael S Petersen ◽  
Jorge Peñarrubia
Keyword(s):  
Milky Way ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Centre Of Mass ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Disc Centre ◽  
Stellar Streams ◽  
Stellar Halo ◽  
Lyrae Stars

ABSTRACT We present the results of N-body models of the Milky Way and Large Magellanic Cloud system and study the kinematic reflex motion in the stellar halo owing to the barycentre displacement of the disc. In agreement with previous studies, we find that the Milky Way disc may be moving at 40 $\, {\rm km~s^{-1}}$ relative to the barycentre prior to the Large Magellanic Cloud infall. The resulting reflex motion is visible in tangential velocities of the stellar halo as a simple dipole. The signal is strongest for stars with long dynamical times, identifiable in position-velocity data as stars with large apocentres, whose dynamical memory is still well represented by the unperturbed Milky Way potential. The signal varies across the sky depending on the stellar tracer and may be up to the same magnitude as the velocity of the disc centre of mass, making reflex motion a source of bias for Milky Way potential determinations based on the modelling of stellar streams and/or smooth halo tracers such as blue horizontal branch or RR Lyrae stars.

scholarly journals The MACHO Project Large Magellanic Cloud Variable Star Inventory. XI. Frequency Analysis of the Fundamental‐Mode RR Lyrae Stars

2003 ◽  
Vol 598 (1) ◽  
pp. 597-609 ◽  
Author(s):  
C. Alcock ◽  
D. R. Alves ◽  
A. Becker ◽  
D. Bennett ◽  
K. H. Cook ◽  
...  
Keyword(s):  
Frequency Analysis ◽  
Fundamental Mode ◽  
Variable Star ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars

scholarly journals The Milky Way Revealed by Variable Stars. I. Sample Selection of RR Lyrae Stars and Evidence for Merger History

2022 ◽  
Vol 258 (1) ◽  
pp. 20
Author(s):  
Iminhaji Ablimit ◽  
Gang Zhao ◽  
Uy. Teklimakan ◽  
Jian-Rong Shi ◽  
Kunduz Abdusalam
Keyword(s):  
Milky Way ◽  
Sample Selection ◽  
Variable Stars ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Sky Survey ◽  
Spectroscopic Information ◽  
History Of ◽  
Dual Origin ◽  
Lyrae Stars

Abstract In order to study the Milky Way, RR Lyrae (RRL) variable stars identified by Gaia, ASAS-SN, and ZTF sky survey projects have been analyzed as tracers in this work. Photometric and spectroscopic information of 3417 RRLs including proper motions, radial velocity, and metallcity are obtained from observational data of Gaia, LAMOST, GALAH, APOGEE, and RAVE. Precise distances of RRLs with typical uncertainties less than 3% are derived by using a recent comprehensive period–luminosity–metallicity relation. Our results from kinematical and chemical analysis provide important clues for the assembly history of the Milky Way, especially for the Gaia–Sausage ancient merger. The kinematical and chemical trends found in this work are consistent with those of recent simulations that indicated that the Gaia–Sausage merger had a dual origin in the Galactic thick disk and halo. As recent similar works have found, the halo RRL sample in this work contains a subset of radially biased orbits besides a more isotropic component. This higher orbital anisotropy component amounts to β ≃ 0.8, and it contributes between 42% and 83% of the halo RRLs at 4 < R( kpc) < 20.

scholarly journals Light Curves and Metal Abundances of RR Lyrae Variables in the Bar of the Large Magellanic Cloud

2000 ◽  
Vol 176 ◽  
pp. 172-175 ◽  
Author(s):  
G. Clementini ◽  
A. Bragaglia ◽  
L. Di Fabrizio ◽  
E. Carretta ◽  
R. G. Gratton
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Photometric System ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Visual Magnitude ◽  
Metal Abundance ◽  
Definition Of ◽  
Lyrae Stars

AbstractThe Large Magellanic Cloud (LMC) is widely considered a corner-stone of the astronomical distance scale. However, a difference of 0.2−0.3 mag exists in its distance as predicted by the short and long distance scales. Distances to the LMC from Population II objects are founded on the RR Lyrae variables. We have undertaken an observational campaign devoted to the definition of the average apparent luminosity, and to the study of the mass–metallicity relation for RR Lyrae stars in the bar of the LMC. These are compared with analogous quantities for cluster RR Lyrae stars. The purpose is to see whether an intrinsic difference in luminosity, possibly due to a difference in mass, might exist between field and cluster RR Lyrae stars, which could be responsible for the well-known dichotomy between short and long distance scales. Preliminary results are presented on the V and B − V light curves, the average apparent visual magnitude, and the pulsational properties of 102 RR Lyrae stars in the bar of the LMC, observed at ESO in January 1999. The photometric data are accurately tied to the Johnson photometric system. Comparison is presented with the photometry of RR Lyrae stars in the bar of the LMC obtained by the MACHO collaboration (Alcock et al. 1996). Our sample includes 9 double-mode RR Lyrae stars selected from Alcock et al. (1997) for which an estimate of the metal abundance from the ΔS method is presented.

scholarly journals WEAK GALACTIC HALO-DWARF SPHEROIDAL CONNECTION FROM RR LYRAE STARS

2014 ◽  
Vol 798 (1) ◽  
pp. L12 ◽  
Author(s):  
Giuliana Fiorentino ◽  
Giuseppe Bono ◽  
Matteo Monelli ◽  
Peter B. Stetson ◽  
Eline Tolstoy ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars
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