J/ApJS/228/19 Exploring the SDSS data set. I. EMP & CV stars (Carbon+, 2017)
Exploring the SDSS data set with linked scatter plots. I. EMP, CEMP, and CV stars. Carbon D.F., Henze C., Nelson B.C. <Astrophys. J. Suppl. Ser., 228, 19-19 (2017)> =2017ApJS..228...19C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, metal-deficient ; Photometry, SDSS ; Spectroscopy ; Spectral types ; Stars, carbon Keywords: methods: data analysis; stars: abundances; stars: carbon; stars: emission line, Be; stars: Population II; surveys Abstract: We present the results of a search for extremely metal-poor (EMP), carbon-enhanced metal-poor (CEMP), and cataclysmic variable (CV) stars using a new exploration tool based on linked scatter plots (LSPs). Our approach is especially designed to work with very large spectrum data sets such as the SDSS, LAMOST, RAVE, and Gaia data sets, and it can be applied to stellar, galaxy, and quasar spectra. As a demonstration, we conduct our search using the SDSS DR10 data set. We first created a 3326-dimensional phase space containing nearly 2 billion measures of the strengths of over 1600 spectral features in 569738 SDSS stars. These measures capture essentially all the stellar atomic and molecular species visible at the resolution of SDSS spectra. We show how LSPs can be used to quickly isolate and examine interesting portions of this phase space. To illustrate, we use LSPs coupled with cuts in selected portions of phase space to extract EMP stars, CEMP stars, and CV stars. We present identifications for 59 previously unrecognized candidate EMP stars and 11 previously unrecognized candidate CEMP stars. We also call attention to 2 candidate He II emission CV stars found by the LSP approach that have not yet been discussed in the literature. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 96 57 Candidates likely to be extremely metal-poor (EMP) stars table2.dat 96 13 *Stars with "uncertain" classification table3.dat 96 2 Candidate cataclysmic variable (CV) stars
Note on table2.dat: Stars in table 2 had poor SED fits or poor Balmer line fits with known EMP stars, but showed weak CaII K absorption and CH absorption. These stars warrant some consideration since they may be EMP stars, or even carbon-enhanced metal-poor (CEMP) stars. However, the likelihood is not as high as for those in Table 1.
See also: V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015) J/ApJS/94/687 : Old stellar populations. V. (Worthey+, 1994) J/ApJS/111/377 : Hγ & Hδ absorption features (Worthey+ 1997) J/ApJS/116/1 : Old Stellar Populations. VI. Absorption-Line (Trager+ 1998) J/AJ/117/2308 : Spectroscopy of hot stars in the halo (Wilhelm+, 1999) J/AJ/125/1598 : New high PM stars in the northern sky (Lepine+, 2003) J/AJ/134/185 : Cataclysmic variables from SDSS-DR5 (Szkody+, 2007) J/AJ/134/2398 : Stellar SEDs in SDSS and 2MASS filters (Covey+, 2007) J/ApJ/725/L186 : Orbital eccentricities of 31535 G-dwarfs (Dierickx+, 2010) J/MNRAS/402/620 : SDSS WD main-sequence binaries (Rebassa-Mansergas+, 2010) J/MNRAS/402/436 : New Dwarf novae in SDSS, GALEX and astrom. cat. (Wils+, 2010) J/AJ/142/193 : RAVE stellar elemental abundances (DR1) (Boeche+, 2011) J/AJ/142/181 : CVs from SDSS. VIII. The final year (Szkody+, 2011) J/MNRAS/421/2414 : Faint cataclysmic variables from SDSS (Woudt+, 2012) J/AJ/145/13 : Metal-poor stars from SDSS/SEGUE. I. Abundances (Aoki+, 2013) J/A+A/579/A28 : Abundances of 3 CEMP stars (Bonifacio+, 2015) J/A+A/593/A28 : Halo metal-poor stars chemical data (Fernandez-Alvar+, 2016) http://www.sdss3.org/ : SDSS-III home page Byte-by-byte Description of file: table.dat
Bytes Format Units Label Explanations
1- 19 A19 --- SDSS Star name (JHHMMSS.ss+DDMMSS.s) 21- 24 I4 --- Plate SDSS plate 25 A1 --- --- [-] 26- 28 I3 --- Fiber SDSS fiber 29 A1 --- --- [-] 30- 34 I5 d MJD SDSS MJD 36- 40 F5.2 mag gmag [14.9/21] SDSS g-band magnitude 42- 45 F4.2 mag u-g [0.05/1] u-g color index 47- 51 F5.2 mag g-r [-0.1/0.4] g-r color index 53- 56 F4.2 --- SCaIIK [0.1/0.4]? S(Ca II K) value (1) 58- 62 F5.2 --- DCaIIK [3.2/27.2]? D(Ca II K) value (2) 64- 67 F4.2 --- SH [0.4/0.7]? S(Hε) value (1) 69- 73 F5.2 --- DH [16.2/60.2]? D(Hε) value (2) 75- 78 F4.2 --- SCH [0.01/0.3]? S(CH 4308) value (1) 80- 84 F5.2 --- DCH [0.2/14.7]? D(CH 4308) value (2) 86- 91 A6 --- SpT MK spectral type ("CV" for cataclysmic variable) 93- 94 A2 --- Notes Notes 96 A1 --- f_Notes Flag on Notes (3)
Note (1): We adopted the feature strength, S(λ_i), as our measure of the amount of absorption or emission at wavelength λi: S(λi)=[Fc(λi)-Fl(λi)]/Fc(λi) where Fc(λi) is the continuum flux and Fl(λi) is the observed spectrum's flux at feature wavelength λi. See Equation (2) in section 2.3. Note (2): We have adopted a second feature strength measure, D(λi), which we have often found helpful when searching for solid detections of weak features: D(λi)=|[Fc(λi)-Fl(λi)]/σ(λi)| where σ(λi) is an estimate of the noise level at λi determined from the interpolated pixel-by-pixel inverse-variance for each spectrum. See Equation (3) in section 2.3. Note (3): Flag as follows: a = Steepest SED slope of all candidate EMP stars, possible comparison spectra are quite noisy. b = Candidate has noisy SDSS spectrum. c = Very weak Ca II K line. d = Markedly weak Ca II K line.
History: From electronic version of the journal
(End) Emmanuelle Perret [CDS] 08-Aug-2017
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