Blue Horizontal-Branch Stars in the Sloan Digital Sky Survey. I. Sample Selection and Structure in the Galactic Halo

2004 ◽  
Vol 127 (2) ◽  
pp. 899-913 ◽  
Author(s):  
Edwin Sirko ◽  
Jeremy Goodman ◽  
Gillian R. Knapp ◽  
Jon Brinkmann ◽  
eljko Ivezi ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Sample Selection ◽  
Sloan Digital Sky Survey ◽  
Horizontal Branch ◽  
Horizontal Branch Stars ◽  
Sky Survey

scholarly journals The Pristine survey – VII. A cleaner view of the Galactic outer halo using blue horizontal branch stars

2019 ◽  
Vol 490 (4) ◽  
pp. 5757-5769 ◽  
Author(s):  
Else Starkenburg ◽  
Kris Youakim ◽  
Nicolas Martin ◽  
Guillaume Thomas ◽  
David S Aguado ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Narrow Band ◽  
Sloan Digital Sky Survey ◽  
Limiting Factor ◽  
Horizontal Branch ◽  
Complete Sample ◽  
Negative Power ◽  
Horizontal Branch Stars ◽  
Sky Survey ◽  
Clean Sample

ABSTRACT We use the Pristine survey CaHK narrow-band photometry, combined with the Sloan Digital Sky Survey (SDSS)ugr photometry, to provide a cleaner sample of blue horizontal branch stars in the Galactic halo out to large distances. We demonstrate a completeness of 91 per cent and a purity of 93 per cent with respect to available spectroscopic classifications. We subsequently use our new clean sample of these standard candles to investigate the substructure in the Galactic halo over the Pristine footprint. Among other features, this allows for a careful tracing of multiple parts of the Sagittarius stream, providing a measurement independent from other tracers used and reaching larger distances. Moreover, we demonstrate with this clean and complete sample that the halo follows a density profile with a negative power-law slope of 3.5–4.0. As the relatively shallow SDSS u band is the limiting factor in this technique, we foresee large potential for combining Pristine survey photometry with the much deeper u-band photometry from the Canada–France–Imaging Survey.

scholarly journals Blue Horizontal-Branch Stars in the Sloan Digital Sky Survey. II. Kinematics of the Galactic Halo

2004 ◽  
Vol 127 (2) ◽  
pp. 914-924 ◽  
Author(s):  
Edwin Sirko ◽  
Jeremy Goodman ◽  
Gillian R. Knapp ◽  
Jon Brinkmann ◽  
eljko Ivezi ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Sloan Digital Sky Survey ◽  
Horizontal Branch ◽  
Horizontal Branch Stars ◽  
Sky Survey

scholarly journals Contribution of Gaia Sausage to the Galactic Stellar Halo Revealed by K Giants and Blue Horizontal Branch Stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, Sloan Digital Sky Survey, and Gaia

2022 ◽  
Vol 924 (1) ◽  
pp. 23
Author(s):  
Wenbo Wu ◽  
Gang Zhao ◽  
Xiang-Xiang Xue ◽  
Sarah A. Bird ◽  
Chengqun Yang
Keyword(s):  
Gaussian Mixture ◽  
Sloan Digital Sky Survey ◽  
Horizontal Branch ◽  
Integrals Of Motion ◽  
Eccentric Orbits ◽  
Horizontal Branch Stars ◽  
Sky Survey ◽  
Stellar Halo ◽  
The Mean ◽  
K Giants

Abstract We explore the contribution of the Gaia Sausage to the stellar halo of the Milky Way by making use of a Gaussian mixture model (GMM) and applying it to halo star samples of Large Sky Area Multi-Object Fiber Spectroscopic Telescope K giants, Sloan Extension for Galactic Understanding and Exploration K giants, and Sloan Digital Sky Survey blue horizontal branch stars. The GMM divides the stellar halo into two parts, of which one represents a more metal-rich and highly radially biased component associated with an ancient, head-on collision referred to as the Gaia Sausage, and the other one is a more metal-poor and isotropic halo. A symmetric bimodal Gaussian is used to describe the distribution of spherical velocity of the Gaia Sausage, and we find that the mean absolute radial velocity of the two lobes decreases with the Galactocentric radius. We find that the Gaia Sausage contributes about 41%–74% of the inner (Galactocentric radius r gc < 30 kpc) stellar halo. The fraction of stars of the Gaia Sausage starts to decline beyond r gc ∼ 25–30 kpc, and the outer halo is found to be significantly less influenced by the Gaia Sausage than the inner halo. After the removal of halo substructures found by integrals of motion, the contribution of the Gaia Sausage falls slightly within r gc ∼ 25 kpc but is still as high as 30%–63%. Finally, we select several possible Sausage-related substructures consisting of stars on highly eccentric orbits. The GMM/Sausage component agrees well with the selected substructure stars in their chemodynamical properties, which increases our confidence in the reliability of the GMM fits.

scholarly journals Stars in the Galactic Halo

1995 ◽  
Vol 164 ◽  
pp. 75-83
Author(s):  
T.D. Kinman
Keyword(s):  
Globular Clusters ◽  
Galactic Halo ◽  
Horizontal Branch ◽  
Field Star ◽  
Horizontal Branch Stars

The field star halo is comprised of those field stars that are like the stars found in the halo globular clusters. We discuss the halo properties — in particular whether Vrot is a function of z. An analysis of recent surveys for blue horizontal branch stars is described; the halo that is defined by these stars is composite and contains both a spherical and flat component.

scholarly journals Compact galaxies and the size–mass galaxy distribution from a colour-selected sample at 0.04 < z < 0.15 supplemented by ugrizYJHK photometric redshifts

2020 ◽  
Vol 500 (2) ◽  
pp. 1557-1574
Author(s):  
Ivan K Baldry ◽  
Tricia Sullivan ◽  
Raffaele Rani ◽  
Sebastian Turner
Keyword(s):  
Galaxy Evolution ◽  
High Redshift ◽  
Sample Selection ◽  
Distribution Functions ◽  
Sloan Digital Sky Survey ◽  
Photometric Redshifts ◽  
Galaxy Distribution ◽  
Sky Survey ◽  
Galaxy Sample ◽  
Compact Galaxies

ABSTRACT The size–mass galaxy distribution is a key diagnostic for galaxy evolution. Massive compact galaxies are potential surviving relics of a high-redshift phase of star formation. Some of these could be nearly unresolved in Sloan Digital Sky Survey (SDSS) imaging and thus not included in galaxy samples. To overcome this, a sample was selected from the combination of SDSS and UKIRT Infrared Deep Sky Survey (UKIDSS) photometry to r &lt; 17.8. This was done using colour–colour selection, and then by obtaining accurate photometric redshifts (photo-z) using scaled flux matching (SFM). Compared to spectroscopic redshifts (spec-z), SFM obtained a 1σ scatter of 0.0125 with only 0.3 per cent outliers (|Δln (1 + z)| &gt; 0.06). A sample of 163 186 galaxies was obtained with 0.04 &lt; z &lt; 0.15 over $2300\, {\rm deg}^2$ using a combination of spec-z and photo-z. Following Barro et al. log Σ1.5 = log M* − 1.5log r50, maj was used to define compactness. The spectroscopic completeness was 76 per cent for compact galaxies (log Σ1.5 &gt; 10.5) compared to 92 per cent for normal-sized galaxies. This difference is primarily attributed to SDSS ‘fibre collisions’ and not the completeness of the main galaxy sample selection. Using environmental overdensities, this confirms that compact quiescent galaxies are significantly more likely to be found in high-density environments compared to normal-sized galaxies. By comparison with a high-redshift sample from 3D-HST, log Σ1.5 distribution functions show significant evolution, with this being a compelling way to compare with simulations such as EAGLE. The number density of compact quiescent galaxies drops by a factor of about 30 from z ∼ 2 to log (n/Mpc−3) = − 5.3 ± 0.4 in the SDSS–UKIDSS sample. The uncertainty is dominated by the steep cut off in log Σ1.5, which is demonstrated conclusively using this complete sample.

scholarly journals The Distribution of Field Horizontal–Branch Stars in the Galactic Halo

1977 ◽  
Vol 4 (2) ◽  
pp. 73-74
Author(s):  
A. G. Davis Philip
Keyword(s):  
Density Distribution ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Horizontal Branch ◽  
Schmidt Telescope ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Horizontal Branch Stars ◽  
General Program ◽  
Objective Prism

Since the time allowed per paper at this joint discussion is short only one aspect of the stellar distribution at high galactic latitudes will be presented here, namely the distribution of field horizontal-branch stars (FHB) in the galactic halo. First, the method by which FHB stars are found will be described. Second, the density distribution of FHB stars will be compared with that of the RR Lyrae stars.As part of a general program to study the stellar density distribution perpendicular to the galactic plane a number of possible FHB stars has been discovered. In each survey area objective prism plates (at a dispersion of 280 Å/mm. to a limiting magnitude of V = 14) are taken with the Michigan Curtis Schmidt telescope at Cerro Tololo Inter-American Observatory or the Schmidt telescope at the Warner and Swasey Observatory. A set of direct plates are taken also to obtain photographic magnitudes for the stars with spectral classifications.

scholarly journals Probing star formation and ISM properties using galaxy disk inclination

2018 ◽  
Vol 615 ◽  
pp. A7 ◽  
Author(s):  
S. K. Leslie ◽  
M. T. Sargent ◽  
E. Schinnerer ◽  
B. Groves ◽  
A. van der Wel ◽  
...  
Keyword(s):  
Sample Selection ◽  
Ultra Violet ◽  
Far Infrared ◽  
Sloan Digital Sky Survey ◽  
Star Forming ◽  
Star Forming Regions ◽  
Sky Survey ◽  
Dust Fraction ◽  
Galaxy Disk ◽  
Intermediate Redshift

Disk galaxies at intermediate redshift (z ~ 0.7) have been found in previous work to display more optically thick behaviour than their local counterparts in the rest-frame B-band surface brightness, suggesting an evolution in dust properties over the past ~6 Gyr. We compare the measured luminosities of face-on and edge-on star-forming galaxies at different wavelengths (Ultraviolet (UV), mid-infrared (MIR), far-infrared (FIR), and radio) for two well-matched samples of disk-dominated galaxies: a local Sloan Digital Sky Survey (SDSS)-selected sample at z ~ 0.07 and a sample of disks at z ~ 0.7 drawn from Cosmic Evolution Survey (COSMOS). We have derived correction factors to account for the inclination dependence of the parameters used for sample selection. We find that typical galaxies are transparent at MIR wavelengths at both redshifts, and that the FIR and radio emission is also transparent as expected. However, reduced sensitivity at these wavelengths limits our analysis; we cannot rule out opacity in the FIR or radio. Ultra-violet attenuation has increased between z ~ 0 and z ~ 0.7, with the z ~ 0.7 sample being a factor of ~3.4 more attenuated. The larger UV attenuation at z ~ 0.7 can be explained by more clumpy dust around nascent star-forming regions. There is good agreement between the fitted evolution of the normalisation of the SFRUV versus 1 − cos(i) trend (interpreted as the clumpiness fraction) and the molecular gas fraction/dust fraction evolution of galaxies found out to z < 1.

scholarly journals Spectral Characteristics of A-Type Stars in the Galactic Halo

1993 ◽  
Vol 138 ◽  
pp. 432-436
Author(s):  
C.J. Corbally ◽  
R.O. Gray
Keyword(s):  
Galactic Halo ◽  
Spectral Characteristics ◽  
Horizontal Branch ◽  
Dwarf Stars ◽  
Horizontal Branch Stars

AbstractAmong 67 early A-type stars at high galactic latitudes, selected to have both small m1 and large c1 Strömgren photometric indices, we find about one third to have quite normal dwarf or subgiant spectra at MK classification dispersion. Those stars with peculiarities included 10 new λ Bootis stars, though none of these appeared significantly evolved. We wonder whether some of the metal-weak dwarf stars in our set may be field horizontal-branch equivalents of the blue, downward-curving, low-luminosity end of the blue horizontal-branch stars.

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