HSC Wide and Deep Imaging Survey for the Milky Way Satellite Galaxies

2017 ◽  
Vol 13 (S334) ◽  
pp. 319-320
Author(s):  
Yutaka Komiyama
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Milky Way ◽  
Local Group ◽  
Deep Imaging ◽  
Ursa Minor ◽  
Satellite Galaxies

AbstractWe have carried out an imaging survey for Local Group dwarf spheroidal galaxy Ursa Minor (UMi) using Hyper Suprime-Cam (HSC) on the 8.2m Subaru Telescope. Wide and deep data obtained by HSC enable us to investigate the extent of UMi which is revealed to extend out to twice the nominal tidal radius. The fraction of binary systems is also investigated from the morphology of the main sequence and estimated to be ~0.4.

Subaru Hyper Suprime-Cam Survey for the Local Group Dwarf Galaxies: Ursa Minor

2018 ◽  
Vol 14 (S344) ◽  
pp. 94-95
Author(s):  
Yutaka Komiyama
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Structural Parameters ◽  
Deep Imaging ◽  
Ursa Minor ◽  
Red Giant

AbstractWe have carried out a wide and deep imaging survey for the Local Group dwarf spheroidal galaxy Ursa Minor (UMi) using Hyper Suprime-Cam (HSC). The data cover out beyond the nominal tidal radius down to ~25 mag in i band, which is ~2 mag below the main sequence turn-off point. The structural parameters of UMi are derived using red giant branch (RGB) stars and sub-giant branch (SGB) stars, and the tidal radius is suggested to be larger than those estimated by the previous studies. It is also found that the distribution of bluer RGB/SGB stars is more extended than that of redder RGB/SGB stars. The fraction of binary systems is estimated to be ~0.4 from the morphology of the main sequences.

scholarly journals Evidence for Light-weight Local Group Dwarf Spheroidal Galaxies

2004 ◽  
Vol 220 ◽  
pp. 365-366
Author(s):  
J. R. Kuhn ◽  
D. Kocevski
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Local Group ◽  
Light Weight ◽  
Natural Explanation ◽  
Dwarf Spheroidal Galaxies ◽  
Ursa Minor ◽  
Matter Component ◽  
Morphological State ◽  
Spheroidal Galaxies

A simple and natural explanation for the dynamics and morphology of the Local Group Dwarf Spheroidal galaxies, Draco (Dra) and Ursa Minor (UMi), is that they are weakly unbound stellar systems with no significant dark matter component. A gentle, but persistent, Milky Way (MW) tide has left them in their current kinematic and morphological state (the “parametric tidal excitation”). A new test of a dark matter dominated dS potential follows from a careful observation of the “clumpiness” of the dS stellar surface density.

A whirling plane of satellite galaxies around Centaurus A challenges CDM cosmology

2018 ◽  
Vol 14 (S344) ◽  
pp. 473-476
Author(s):  
Oliver Müller
Keyword(s):  
Phase Space ◽  
Structure Formation ◽  
Milky Way ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Planar Structure ◽  
Space Correlation ◽  
Andromeda Galaxy ◽  
Satellite Galaxies ◽  
Centaurus A

AbstractThe phase-space correlation of dwarf galaxies around the Milky Way and the Andromeda galaxy pose a serious challenge to our understanding of structure formation. Recently, another planar structure was discovered around Cen A, the major galaxy of the Centaurus group. We have surveyed this galaxy group for new dwarf galaxies and presented the discovery of 57 new dwarf member candidates. Furthermore, we have studied the kinematics of previously known dwarfs and again found a kinematic coherence in their movement, similar to the Local Group satellites. In CDM simulations, such an alignment appears in less than 0.5 percent.

scholarly journals How galaxies form: Mass assembly from chemical abundances in the era of large surveys

2009 ◽  
Vol 5 (S265) ◽  
pp. 461-469
Author(s):  
Rosemary F.G. Wyse
Keyword(s):  
Mass Transfer ◽  
Large Scale ◽  
Binary Systems ◽  
Milky Way ◽  
Dynamical Evolution ◽  
Close Binary ◽  
Chemical Abundances ◽  
Milky Way Galaxy ◽  
Deep Imaging ◽  
Mass Assembly

AbstractThe chemical abundances in the atmosphere of a star provide unique information about the gas from which that star formed, and, modulo processes that are not important for the vast majority of stars, such as mass transfer in close binary systems, are conserved through a star's life. Correlations between chemistry and kinematics have been used for decades to trace dynamical evolution of the Milky Way Galaxy. I discuss how it should be possible to refine and extend such analyses, provided planned large-scale deep imaging surveys have matched spectroscopic surveys.

scholarly journals The planes of satellite galaxies problem, suggested solutions, and open questions

2018 ◽  
Vol 33 (06) ◽  
pp. 1830004 ◽  
Author(s):  
Marcel S. Pawlowski
Keyword(s):  
Milky Way ◽  
Local Group ◽  
Small Scale ◽  
Velocity Measurements ◽  
Cosmological Simulations ◽  
Gravitational Effects ◽  
Open Questions ◽  
Andromeda Galaxy ◽  
Satellite Galaxies ◽  
Anisotropic Phase

Satellite galaxies of the Milky Way and of the Andromeda galaxy have been found to preferentially align in significantly flattened planes of satellite galaxies, and available velocity measurements are indicative of a preference of satellites in those structures to co-orbit. There is an increasing evidence that such kinematically correlated satellite planes are also present around more distant hosts. Detailed comparisons show that similarly anisotropic phase-space distributions of sub-halos are exceedingly rare in cosmological simulations based on the [Formula: see text]CDM paradigm. Analogs to the observed systems have frequencies of [Formula: see text] 0.5% in such simulations. In contrast to other small-scale problems, the satellite planes issue is not strongly affected by baryonic processes because the distribution of sub-halos on scales of hundreds of kpc is dominated by gravitational effects. This makes the satellite planes one of the most serious small-scale problems for [Formula: see text]CDM. This review summarizes the observational evidence for planes of satellite galaxies in the Local Group and beyond, and provides an overview of how they compare to cosmological simulations. It also discusses scenarios which aim at explaining the coherence of satellite positions and orbits, and why they all are currently unable to satisfactorily resolve the issue.

scholarly journals Stellar rotation bifurcation caused by tidal locking in the open cluster NGC 2287?

2019 ◽  
Vol 14 (S351) ◽  
pp. 228-232
Author(s):  
Weijia Sun ◽  
Chengyuan Li ◽  
Licai Deng ◽  
Richard de Grijs
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Milky Way ◽  
Open Cluster ◽  
Mass Ratio ◽  
Stellar Rotation ◽  
Rotation Rates ◽  
Short Period ◽  
Low Mass ◽  
Low Mass Ratio

AbstractWe present a detailed analysis of the projected stellar rotational velocities of the well-separated double main sequence (MS) in the young, ∼200 Myr-old Milky Way open cluster NGC 2287 and suggest that stellar rotation may drive the split MSs in NGC 2287. We find that the observed distribution of projected stellar rotation velocities could result from a dichotomous distribution of stellar rotation rates. We discuss whether our observations may reflect the effects of tidal locking affecting a fraction of the cluster’s member stars in stellar binary systems. The slow rotators are likely stars that initially rotated rapidly but subsequently slowed down through tidal locking induced by low-mass-ratio binary systems. However, the cluster may have a much larger population of short-period binaries than is usually seen in the literature, with relatively low secondary masses.

scholarly journals The Missing Satellite Problem Outside of the Local Group

2016 ◽  
Vol 11 (S321) ◽  
pp. 196-198
Author(s):  
Masayuki Tanaka ◽  
Masashi Chiba ◽  
Yutaka Komiyama ◽  
Mikito Tanaka ◽  
Sakurako Okamoto ◽  
...  
Keyword(s):  
Milky Way ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Milky Way Galaxy ◽  
Satellite Problem ◽  
Dynamical Simulations ◽  
First Results ◽  
Nearby Galaxies ◽  
Satellite Galaxies ◽  
Statistical Sample

AbstractWe report on the first results from our pilot observation of nearby galaxies with Hyper Suprime-Cam. We have observed two galaxies with mass similar to that of the Milky Way Galaxy and measured the abundance of their satellite galaxies in order to address the missing satellite problem outside of the Local Group. We find that (1) the abundance of dwarf galaxies is smaller by a factor of two than the prediction from one of the current hydro-dynamical simulations and (2) there is a large halo to halo scatter. Our results highlight the importance of a statistical sample of nearby galaxies to address the missing satellite problem.

scholarly journals Constraining the Variability and Binary Fraction of Galactic Center Young Stars

2016 ◽  
Vol 11 (S322) ◽  
pp. 237-238
Author(s):  
Abhimat K. Gautam ◽  
Tuan Do ◽  
Andrea M. Ghez ◽  
Jessica R. Lu ◽  
Mark R. Morris ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Adaptive Optics ◽  
Binary Systems ◽  
Main Sequence ◽  
Milky Way ◽  
Galactic Center ◽  
Young Stars ◽  
Early Type ◽  
Eclipsing Binary ◽  
Early Type Stars

AbstractWe present constraints on the variability and binarity of young stars in the central 10 arcseconds (~ 0.4 pc) of the Milky Way Galactic Center (GC) using Keck Adaptive Optics data over a 12 year baseline. Given our experiment’s photometric uncertainties, at least 36% of our sample’s known early-type stars are variable. We identified eclipsing binary systems by searching for periodic variability. In our sample of spectroscopically confirmed and likely early-type stars, we detected the two previously discovered GC eclipsing binary systems. We derived the likely binary fraction of main sequence, early-type stars at the GC via Monte Carlo simulations of eclipsing binary systems, and find that it is at least 32% with 90% confidence.

scholarly journals On the origin of the helium-rich population in the peculiar globular cluster Omega Centauri

2009 ◽  
Vol 5 (S268) ◽  
pp. 187-188
Author(s):  
Donatella Romano ◽  
M. Tosi ◽  
M. Cignoni ◽  
F. Matteucci ◽  
E. Pancino ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Globular Cluster ◽  
Main Sequence ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Potential Well ◽  
Galactic Winds ◽  
Supernova Explosions

AbstractIn this contribution we discuss the origin of the extreme helium-rich stars which inhabit the blue main sequence (bMS) of the Galactic globular cluster Omega Centauri. In a scenario where the cluster is the surviving remnant of a dwarf galaxy ingested by the Milky Way many Gyr ago, the peculiar chemical composition of the bMS stars can be naturally explained by considering the effects of strong differential galactic winds, which develop owing to multiple supernova explosions in a shallow potential well.

scholarly journals Pushing back the limits: detailed properties of dwarf galaxies in a ΛCDM universe

2018 ◽  
Vol 616 ◽  
pp. A96 ◽  
Author(s):  
Yves Revaz ◽  
Pascale Jablonka
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Mass Scale ◽  
Dwarf Spheroidal Galaxies ◽  
The Galaxy ◽  
Dynamical Simulations ◽  
Ursa Minor ◽  
Stellar Properties ◽  
Star Formation Histories

We present the results of a set of high-resolution chemo-dynamical simulations of dwarf galaxies in a ΛCDM cosmology. Out of an original (3.4 Mpc/h)3 cosmological box, a sample of 27 systems are re-simulated from z = 70 to z = 0 using a zoom-in technique. Gas and stellar properties are confronted to the observations in the greatest details: in addition to the galaxy global properties, we investigated the model galaxy velocity dispersion profiles, half-light radii, star formation histories, stellar metallicity distributions, and [Mg/Fe] abundance ratios. The formation and sustainability of the metallicity gradients and kinematically distinct stellar populations are also tackled. We show how the properties of six Local Group dwarf galaxies, NGC 6622, Andromeda II, Sculptor, Sextans, Ursa Minor and Draco are reproduced, and how they pertain to three main galaxy build-up modes. Our results indicate that the interaction with a massive central galaxy could be needed for a handful of Local Group dwarf spheroidal galaxies only, the vast majority of the systems and their variety of star formation histories arising naturally from a ΛCDM framework. We find that models fitting well the local Group dwarf galaxies are embedded in dark haloes of mass between 5 × 108 to a few 109 M⊙, without any missing satellite problem. We confirm the failure of the abundance matching approach at the mass scale of dwarf galaxies. Some of the observed faint however gas-rich galaxies with residual star formation, such as Leo T and Leo P, remain challenging. They point out the need of a better understanding of the UV-background heating.

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