J/other/Sci/292.698 Candidate halo dark matter (Oppenheimer+, 2001)
Direct detection of Galactic halo dark matter Oppenheimer B.R., Hambly N.C., Digby A.P., Hodgkin S.T., Saumon D. <Science 292, 698 (2001)> =2001Sci...292..698O
ADC_Keywords: Stars, white dwarf ; Stars, dwarfs ; Stars, subdwarf ; Proper motions ; Positional data ; Photometry, photographic Abstract: The Milky Way galaxy contains a large, spherical component which is believed to harbor a substantial amount of unseen matter. Recent observations indirectly suggest that as much as half of this "dark matter" may be in the form of old, very cool white dwarfs, the remnants of an ancient population of stars as old as the galaxy itself. We conducted a survey to find faint, cool white dwarfs with large space velocities, indicative of their membership in the galaxy's spherical halo component. The survey reveals a substantial, directly observed population of old white dwarfs, too faint to be seen in previous surveys. This newly discovered population accounts for at least 2 percent of the halo dark matter. It provides a natural explanation for the indirect observations, and represents a direct detection of galactic halo dark matter. Description: Photographic astrometry and photometry is presented for all objects plotted in Figure 1. The first file gives data for all sources plotted in Figure 1 (small dots) while the second file lists the subset of those objects that where followed-up for low resolution spectra on the CTIO 4m telescope, along with a spectroscopic classification indicating the nature of each source (these are plotted as coloured symbols in Figure 1). At H_R>22.5, all objects in the first list were followed up at CTIO, and 15 objects were found to be spurious (mainly at very large HR and/or faint magnitudes - the second file gives details of which candidates are likely to be spurious. The first file also contains duplicate records in Schmidt field overlap regions - these are useful to assess the true external measurement errors on the photographic astrometry/photometry. Detailed analysis of the white dwarf subsample from these data is presented in Oppenheimer et al. (2001Sci...292..698O) and further analysis (including photometric transformations for WDs) is presented in Salim et al. (2004ApJ...601.1075S). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 83 38 Candidate Halo White Dwarfs ohdhsall.dat 310 1666 Complete dataset for Figure 1 ohdhsobs.dat 310 155 Data for coloured symbols in Figure 1
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 10 A10 --- Name Star name (1) 13 A1 --- n_Name [+ *] Spectral peculiarities (2) 15- 16 I2 h RAh Right ascension (J2000.00) 18- 19 I2 min RAm Right ascension (J2000.00) 21- 26 F6.3 s RAs Right ascension (J2000.00) 28 A1 --- DE- Declination sign (J2000.00) 29- 30 I2 deg DEd Declination (J2000.00) 32- 33 I2 arcmin DEm Declination (J2000.00) 35- 39 F5.2 arcsec DEs Declination (J2000.00) 41- 45 F5.3 arcsec/yr pm Total proper motion 47- 51 F5.3 arcsec/yr e_pm Error in total proper motion 53- 57 F5.1 deg pmPA Position angle of proper motion 59- 63 F5.2 mag BJmag BJ magnitude 65- 68 F4.2 mag BJ-R59F BJ-R59F colour index, with uncertainty of ±0.1mag on average 70- 74 F5.2 mag R59F-IN R59F-IN colour index, with uncertainty of ±0.1mag on average 75 A1 --- n_R59F-IN [+] +: calculated from spectrophotometry 77- 79 I3 km/s Vtan Estimated tangential velocity, based on photometric parallax 81- 83 I3 pc Dist Distance estimate based on a color-magnitude relation
Note (1): WD names are new discoveries; otherwise, Luyten LHS or LP names are given; note that * J0014-3937 was discovered by Scholz et al. (2000, Cat. J/A+A/353/958) who classify this object as "cool, no Halpha" * F351-50 was discovered by Ibata et al. (2000ApJ...532L..41I). Note (2): symbols with the following meaning: * = These stars have Hα features. All other stars have featureless spectra. + = This object is extremely cool but has a spectrum similar to the peculiar LHS 3250 (see Oppenheimer et al., 2001ApJ...550..448O).
Byte-by-byte Description of file: ohdhsall.dat ohdhsobs.dat
Bytes Format Units Label Explanations
1- 3 I3 --- F1 ESO/SRC Schmidt field no. of master plate containing this object (ESO-R or UK Schmidt J plate) 5- 8 I4 --- F2 ESO/SRC (3 digit) or POSS-I (4 digit) field no. of second R plate (UK Schmidt R or POSS-I E plate) 10- 11 I2 h RAh Right ascension (J2000.0) 13- 14 I2 min RAm Right ascension (J2000.0) 16- 22 F7.4 s RAs Right ascension (J2000.0) 24 A1 --- DE- Declination sign (J2000.0) 25- 26 I2 deg DEd Declination (J2000.0) 28- 29 I2 arcmin DEm Declination (J2000.0) 31- 36 F6.3 arcsec DEs Declination (J2000.0) 38- 45 F8.3 yr Epoch Epoch of position 48- 60 E13.6 arcsec/yr pmX Proper motion in X plate co-ordinate 63- 75 E13.6 arcsec/yr pmY Proper motion in Y plate co-ordinate 78- 90 E13.6 arcsec/yr e_pmX Error in proper motion in X 93-105 E13.6 arcsec/yr e_pmY Error in proper motion in Y 108-120 E13.6 arcsec/yr pm Total proper motion 123-135 E13.6 arcsec/yr e_pm Error in total proper motion 138-150 E13.6 deg pmPA Celestial position angle of proper motion measured east of north 153-165 E13.6 --- Nstars No. of reference stars in local linear plate model of two-plate proper motion solution 168-172 F5.2 mag Bjmag Magnitude of star in photographic Bj (GG395/IIIaJ filter/emulsion combo) 175-179 F5.2 mag R1mag Magnitude of star in photographic R from first red plate (RG630/IIIaF or 2444-plexiglass/103aE combo) 182-186 F5.2 mag R2mag Magnitude of star in photographic R from second red plate (OG590/IIIaF combo) 189-193 F5.2 mag Imag ?=99.99 Magnitude of star in photographic I (RG715/IV-N combo) 195-201 I7 --- p1 1st rec pointer to original SSS file (1) 203-209 I7 --- p2 2nd rec pointer to original SSS file (1) 211-217 I7 --- p3 3rd rec pointer to original SSS file (1) 219-225 I7 --- p4 4th rec pointer to original SSS file (1) 243-247 F5.2 mag H Reduced proper motion (2) 250-254 F5.2 mag Bj-R2 B-R photographic colour of star 256 I1 --- Flg ? Visual inspection flag (3) 258-259 I2 --- Symb ? PGPLOT symbol type for star category (4) 263-275 E13.6 arcsec/yr pmX3 3-plate proper motion in X (5) 278-290 E13.6 arcsec/yr pmY3 3-plate proper motion in Y (5) 292-300 F9.5 --- chi2X chi-squared statistic for X (5) 302-310 F9.5 --- chi2Y chi-squared statistic for Y (5)
Note (1): Internal record numbers for raw binary object catalogues of each plate; peculiar values are: -1 indicates no plate available, 0 indicates plate is available for this field but no pair was found (usually because the object in question is too faint) Note (2): HR = R2mag + 5log(pm) + 5 Note (3): Flag present only in ohdhsall.dat. All objects in this list having HR>22 were inspected on ellipse plots from all plates and were found to have no indication of problems; objects having HR<22 are all assumed to be OK. Note (4): Symbol present only in ohdhsobs.dat. The nature of each target is coded as follows: -2 = Target is a duplicate that appears earlier in the list. -1 = Target could not be found at the telescope and is assumed non-existent. 18 = The star has a spectrum (CTIO or previously published) showing it to be a white dwarf 12 = The star was not observed, but is assumed to be a WD (from reduced pm & photometry) 13 = The star has a spectrum (CTIO or previously published) showing it to be dM 7 = The star was not observed, but is assumed to be dM 17 = The star has a spectrum (CTIO or previously published) showing it to be sdM 21 = The star was not observed, but is assumed to be sdM Note (5): As a sanity check, 3-plate proper motion solutions were carried out for all stars incorporating the two red and one blue plates. Goodness-of-fit chi-squared statistics are available indicating the quality of the 3-plate astrometric solutions.
Acknowledgements: We thank Hugh Harris, James Liebert and Samir Salim for encouraging us to archive these data for community use. Nigel Hambly (nch(at)roe.ac.uk)
(End) Nigel Hambly [ROE, UK], Patricia Bauer, [CDS] 29-Oct-2003
|The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line|