We investigate radial and vertical metallicity gradients for a sample of red clump stars from the RAdial Velocity Experiment (RAVE) Data Release 3. We select a total of 6781 stars, using a selection of colour, surface gravity and uncertainty in the derived space motion, and calculate for each star a probabilistic (kinematic) population assignment to a thin or thick disc using space motion and additionally another (dynamical) assignment using stellar vertical orbital eccentricity. We derive almost equal metallicity gradients as a function of the Galactocentric distance for the high‐probability thin‐disc stars and for stars with vertical orbital eccentricities consistent with being dynamically young, ev≤ 0.07, i.e. d[M/H]/dRm=−0.041 ± 0.003 and d[M/H]/dRm=−0.041 ± 0.007 dex kpc−1. Metallicity gradients as a function of the distance from the Galactic plane for the same populations are steeper, i.e. d[M/H]/dzmax=−0.109 ± 0.008 and d[M/H]/dzmax=−0.260 ± 0.031 dex kpc−1, respectively. Rm and zmax are the arithmetic mean of the perigalactic and apogalactic distances, and the maximum distance to the Galactic plane, respectively. Samples including more thick‐disc red clump giant stars show systematically shallower abundance gradients. These findings can be used to distinguish between different formation scenarios of the thick and thin discs.
We present colour transformations for the conversion of the W1 and W2 magnitudes of the Wide‐field Infrared Survey Explorer (WISE) photometric system to the Johnson–Cousins BVRI, Sloan Digital Sky Survey gri and Two‐Micron All‐Sky Survey JHKs photometric systems, for dwarfs. The W3 and W4 magnitudes were not considered due to their insufficient signal‐to‐noise ratio (S/N). The coordinates of 825 dwarfs along with their BVRI, gri and JHKs data taken from Bilir et al. were matched with the coordinates of stars in the preliminary data release of the WISE, and a homogeneous dwarf sample with high S/N had been obtained using the following constraints: (1) the data were dereddened; (2) giants were identified and excluded from the sample; (3) sample stars were selected according to data quality; (4) transformations were derived for subsamples of different metallicity ranges; and (5) transformations were two‐colour‐dependent. These colour transformations, coupled with known absolute magnitudes at shorter wavelengths, can be used in space‐density evaluation for the Galactic (thin and thick) discs, at distances larger than the ones evaluated with JHKs photometry.
Abstract:We present colour transformations for the conversion of Wide-Field Survey Explorer W1, W2, and W3 magnitudes to the Johnson-Cousins BVI c , Sloan Digital Sky Survey gri, and Two Micron All Sky Survey JHK s photometric systems, for red clump (RC) stars. RC stars were selected from the Third Radial Velocity Experiment Data Release. The apparent magnitudes were collected by matching the coordinates of this sample with different photometric catalogues. The final sample (355 RC stars) was used to obtain metallicitydependent and free-of-metallicity transformations. These transformations combined with known absolute magnitudes at shorter wavelengths can be used in space density determinations for the Galactic (thin and thick) discs at distances larger than the ones evaluated with JHK s photometry alone, hence providing a powerful tool in the analysis of Galactic structure.
Selecting the future site for a large Turkish radio telescope is a key issue. The National Radio Astronomy Observatory is now in the stage of construction at a site near Karaman City, in Turkey. A single-dish parabolic radio antenna of 30-40 m will be installed near a building that will contain offices, laboratories, and living accommodations. After a systematic survey of atmospheric, meteorological, and radio frequency interference (RFI) analyses,
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.