scholarly journals Galactic structure studies with SCUSS and SDSS surveys

2012 ◽  
Vol 8 (S295) ◽  
pp. 309-310
Author(s):  
Cuihua Du ◽  
Xiyan Peng
Keyword(s):  
Galactic Halo ◽  
Galactic Structure ◽  
Scale Height ◽  
Thick Disk ◽  
Axis Ratio ◽  
Statistical Errors ◽  
Count Method ◽  
Sky Survey ◽  
Star Count ◽  
The Galaxy

AbstractBased on the South Galactic Cap U-band Sky Survey (SCUSS) and SDSS observations, we adopted the star-count method to analyze the stellar distribution in different directions of the Galaxy. We find that the scale height of the disk may be variable with the observed direction, which cannot simply be attributed to statistical errors. The main reason can be possibly attributed to the disk (mainly the thick disk) being flared, with a scale height increasing with radius. The axis ratio of the Galactic halo is in the range 0.4-0.6. This finding supports Galactic models with a flattened inner halo, partly formed through a merger early in the Galaxy's history.

scholarly journals Estimation of Galactic model parameters in high latitudes with the SDSS and SCUSS

2013 ◽  
Vol 9 (S298) ◽  
pp. 404-404
Author(s):  
Cuihua Du ◽  
Yunpeng Jia ◽  
Xiyan Peng
Keyword(s):  
Model Parameters ◽  
High Latitudes ◽  
The South ◽  
Statistical Errors ◽  
Count Method ◽  
Sky Survey ◽  
Star Count ◽  
The Galaxy ◽  
Galactic Model

AbstractBased on the South Galactic Cap U-band Sky Survey (SCUSS) and SDSS observation, we adopted the star-count method to analyze the stellar distribution in different directions of the Galaxy. We find that these model parameters may be variable with observed direction, which cannot simply be attributed to statistical errors.

scholarly journals Estimation of Galactic Model Parameters in High Latitudes with SDSS

2008 ◽  
Vol 25 (2) ◽  
pp. 69-84 ◽  
Author(s):  
S. Bilir ◽  
A. Cabrera-Lavers ◽  
S. Karaali ◽  
S. Ak ◽  
E. Yaz ◽  
...  
Keyword(s):  
Gravitational Effect ◽  
Mean Value ◽  
Sloan Digital Sky Survey ◽  
Asymmetric Structure ◽  
Model Parameters ◽  
Axis Ratio ◽  
Sky Survey ◽  
The Galaxy ◽  
Galactic Model ◽  
Galactic Longitude

AbstractWe estimated the Galactic model parameters for a set of 36 high-latitude fields included in the currently available Data Release 5 (DR 5) of the Sloan Digital Sky Survey (SDSS), to explore their possible variation with the Galactic longitude. The thick disc scaleheight moves from ∼550 pc at 120 < l < 150° to ∼720 pc at 250 < l < 290°, while the thin disc scaleheight is as large as ∼195 pc in the anticenter direction and ∼15% lower at |l| < 30°. Finally, the axis ratio (c/a) of the halo changes from a mean value of ∼0.55 in the two first quadrants of the Galaxy to ∼0.70 at 190 < l < 300°. For the halo, the reason for the dependence of the model parameters on the Galactic longitude arises from the well known asymmetric structure of this component. However, the variation of the model parameters of the thin and thick discs with Galactic longitude originates from the gravitational effect of the Galactic long bar. Moreover, the excess of stars in quadrant I (quadrant III) over quadrant IV (quadrant II) is in agreement with this scenario.

Kinematic and Chemical Analysis of AEGIS Survey Stars

2017 ◽  
Vol 13 (S334) ◽  
pp. 283-284
Author(s):  
Sarah Dietz ◽  
Timothy C. Beers ◽  
Vinicius M. Placco ◽  
Jinmi Yoon ◽  
Keyword(s):  
Chemical Analysis ◽  
Galactic Structure ◽  
Thick Disk ◽  
Spectroscopic Observations ◽  
Halo Stars ◽  
Medium Resolution ◽  
The Galaxy ◽  
History Of ◽  
Moderate Scale ◽  
Input Catalogue

AbstractThe AAOmega Evolution of Galactic Structure (AEGIS) survey (P.I. Keller) was a moderate scale (45 nights) spectroscopic survey carried out with the AAOmega multi-fiber spectrograph at the Anglo-Australian Telescope. The input catalogue for the spectroscopic observations was derived from photometry of approximately 200 two-degree diameter fields obtained during the commissioning of the SkyMapper survey. The data consists of medium-resolution (R ~ 2,000) spectroscopy for approximately 70,000 thick disk and halo stars spanning a survey footprint of 4,900 square degrees. We plan to use the AEGIS data to further characterize the properties of the disk and halo systems and better constrain the assembly history of the Galaxy based on the behavior of the CEMP-no and CEMP-s stars in the sample.

scholarly journals Evolution of the Galactic Halo and Disk

1995 ◽  
Vol 164 ◽  
pp. 99-107
Author(s):  
Gerard Gilmore
Keyword(s):  
Angular Momentum ◽  
Galactic Halo ◽  
Evolutionary Model ◽  
Thick Disk ◽  
Structural Components ◽  
Stellar Kinematics ◽  
Chemical Abundances ◽  
The Galaxy ◽  
Stellar Halo ◽  
Discrete Populations

Correlations between stellar kinematics and chemical abundances are fossil evidence for evolutionary connections between Galactic structural components. Extensive stellar surveys show that the only tolerably clear distinction between galactic components appears in the distributions of specific angular momentum. Here the stellar metal-poor halo and the metal-rich bulge are indistinguishable from each other, as are the thick disk and the old disk. Each pair is very distinct from the other. This leads to an evolutionary model in which the metal-poor stellar halo evolves into the inner bulge, while the thick disk is a precursor to the thin disk. These evolutionary sequences are distinct. The galaxy is made of two discrete “populations”, one of low and one of high angular momentum. Some (minor?) complexity is added to this picture by the debris of late and continuing mergers, which will be especially important in the outer stellar halo.

scholarly journals A Survey of Surveys

1996 ◽  
Vol 169 ◽  
pp. 47-55
Author(s):  
S. M. Kent
Keyword(s):  
Near Infrared ◽  
Stellar Populations ◽  
Galactic Structure ◽  
Sloan Digital Sky Survey ◽  
New Era ◽  
Sky Surveys ◽  
Sky Survey ◽  
The Galaxy ◽  
The Status ◽  
Infrared Survey

A new era for the field of Galactic structure is about to be opened with the advent of wide-area digital sky surveys. In this article, I will review the status and prospects for research for 3 new ground-based surveys: the Sloan Digital Sky Survey (SDSS), the Deep Near-Infrared Survey of the Southern Sky (DENIS) and the Two Micron All Sky Survey (2MASS). These surveys will permit detailed studies of Galactic structure and stellar populations in the Galaxy with unprecedented detail. Extracting the information, however, will be challenging.

scholarly journals Structure and Kinematics of the Stellar Halos and Thick Disks of the Milky Way Based on Calibration Stars from SDSS DR7

2009 ◽  
Vol 5 (S265) ◽  
pp. 267-270
Author(s):  
D. Carollo ◽  
T. C. Beers ◽  
M. Chiba ◽  
J. E. Norris ◽  
K. C. Freeman ◽  
...  
Keyword(s):  
Milky Way ◽  
Thick Disk ◽  
Sloan Digital Sky Survey ◽  
Spatial Density ◽  
Density Profiles ◽  
Sky Survey ◽  
Likelihood Analysis ◽  
The Galaxy ◽  
Kinematic Information ◽  
Metallicity Distribution

AbstractThe structure and kinematics of the recognized stellar components of the Milky Way are explored, based on well-determined atmospheric parameters and kinematic quantities for 32360 “calibration stars” from the Sloan Digital Sky Survey (SDSS) and its first extension, (SDSS-II), which included the sub-survey SEGUE: Sloan Extension for Galactic Understanding and Exploration. Full space motions for a sub-sample of 16920 stars, exploring a local volume within 4 kpc of the Sun, are used to derive velocity ellipsoids for the inner- and outer-halo components of the Galaxy, as well as for the canonical thick-disk and proposed metal-weak thick-disk populations. This new sample of calibration stars represents an increase of 60% relative to the numbers used in a previous analysis. A Maximum Likelihood analysis of a local sub-sample of 16920 calibration stars has been developed in order to extract kinematic information for the major Galactic components (thick disk, inner halo, and outer halo), as well as for the elusive metal-weak thick disk (MWTD). We measure velocity ellipsoids for the thick disk, the MWTD, the inner halo, and the outer halo, demonstrate that the MWTD may be a component that is kinematically and chemically independent of the canonical thick disk (and put limits on the metallicity range of the MWTD), and derive the inferred spatial density profiles of the inner/outer halo components. We also present evidence for tilts in the velocity ellipsoids for stars in our sample as a function of height above the plane, for several ranges in metallicity, and confirm the shift of the observed metallicity distribution function (MDF) from the inner-halo to the outer-halo dominated sample.

scholarly journals Abundances in the Gaseous Galactic Halo

1998 ◽  
Vol 11 (1) ◽  
pp. 86-89
Author(s):  
Ulysses J. Sofia
Keyword(s):  
Interstellar Medium ◽  
Gas Phase ◽  
High Velocity ◽  
Galactic Halo ◽  
Solar Neighborhood ◽  
Local Interstellar Medium ◽  
The Galaxy ◽  
Metal Abundances ◽  
High Velocity Clouds

Abstract The well measured gas-phase abundances in the low halo suggest that this region of the Galaxy has total (gas plus dust) metal abundances which are close to those in the solar neighborhood. The gas-phase abundances in the halo are generally higher than those seen in the disk, however, this affect is likely due to the destruction of dust in the halo clouds. Observations of high velocity clouds (HVCs) in the halo suggest that these clouds have metal abundances which are substantially lower than those measured for the local interstellar medium. These determinations, however, are often of lower quality than those for the low halo because of uncertainties in the hydrogen abundances along the sightlines, in the incorporation of elements into dust, and in the partial ionization of the clouds.

scholarly journals The Age of Old Galactic Populations

1998 ◽  
Vol 11 (1) ◽  
pp. 560-561
Author(s):  
M. Grenon
Keyword(s):  
High Velocity ◽  
Radial Velocities ◽  
Thick Disk ◽  
Early Evolution ◽  
Galactic Bulge ◽  
Colour Class ◽  
The Galaxy ◽  
Nearby Stars

As a preparation to the HIPPARCOS mission, a large observing programme on NLTT stars (propermotion > 0.18 ″/yr) was started in Genevaphotometry. The original programme consists of 10047 stars brighter than mR = 11.5, or mR = 12.5 if of colour class m. Among them, 7813 targets could be included in the HIPPARCOS programme, selected according to their observability and internal priorities in favour of large parallaxe stars (photometric distances < 100 pc) and high-velocity stars. The bulk of new nearby, halo, mild-metal poor and SMR stars in the HIP Catalogue originates from this proposal (N° 139). No less than 208 new nearby stars with π ≥ 40 mas were discovered south of δ +10°, the closest has π(HIP)= 182 mas. Radial velocities were obtained with CORAVEL at OHP and ESO. Most aspects of the early evolution of the Galaxy may be addressed with this sample. Here we discuss, as examples, the ages of the thick disk and of the galactic bulge.

scholarly journals Searching for Mg ii absorbers in and around galaxy clusters

2021 ◽  
Vol 503 (3) ◽  
pp. 4309-4319
Author(s):  
Jong Chul Lee ◽  
Ho Seong Hwang ◽  
Hyunmi Song
Keyword(s):  
Galaxy Clusters ◽  
Detection Rate ◽  
Massive Star ◽  
Sloan Digital Sky Survey ◽  
Number Density ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Quasar Spectra ◽  
Sky Survey ◽  
The Galaxy

ABSTRACT To study environmental effects on the circumgalactic medium (CGM), we use the samples of redMaPPer galaxy clusters, background quasars, and cluster galaxies from the Sloan Digital Sky Survey (SDSS). With ∼82 000 quasar spectra, we detect 197 Mg ii absorbers in and around the clusters. The detection rate per quasar is 2.7 ± 0.7 times higher inside the clusters than outside the clusters, indicating that Mg ii absorbers are relatively abundant in clusters. However, when considering the galaxy number density, the absorber-to-galaxy ratio is rather low inside the clusters. If we assume that Mg ii absorbers are mainly contributed by the CGM of massive star-forming galaxies, a typical halo size of cluster galaxies is smaller than that of field galaxies by 30 ± 10 per cent. This finding supports that galaxy haloes can be truncated by interaction with the host cluster.

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