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 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 2001Sci...292..698O) and further
analysis (including photometric transformations for WDs) is presented
in Salim et al. (2004ApJ...601.1075S 2004ApJ...601.1075S).
File Summary:
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FileName Lrecl Records Explanations
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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
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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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
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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 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 2001ApJ...550..448O).
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Byte-by-byte Description of file: ohdhsall.dat ohdhsobs.dat
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Bytes Format Units Label Explanations
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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 [0]? 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)
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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.
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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