J/AJ/150/77 Catalog of hypervelocity candidate stars (Vickers+, 2015)
Red runaways: hypervelocity stars, hills ejecta, and other outliers in the
F-to-M star regime.
Vickers J.J., Smith M.C., Grebel E.K.
<Astron. J., 150, 77 (2015)>
=2015AJ....150...77V 2015AJ....150...77V (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, F-type ; Stars, G-type ; Stars, K-type ;
Stars, M-type ; Proper motions ; Abundances, [Fe/H]
Keywords: Galaxy: kinematics and dynamics - Galaxy: stellar content -
stars: kinematics and dynamics - stars: peculiar - stars: statistics
Abstract:
In this paper we analyze a sample of metal-rich (>-0.8dex) main
sequence stars in the extended solar neighborhood, investigating
kinematic outliers from the background population. The data, which are
taken from the Sloan Digital Sky Survey, are kinematically profiled as
a function of distance from the Galactic plane using full
six-dimensional phase space information. Each star is examined in the
context of these kinematic profiles and likelihoods are assigned to
quantify whether a star matches the underlying profile. Since some of
these stars are likely to have been ejected from the disk, we trace
back their orbits in order to determine potential ejection radii. We
find that objects with low probability (i.e., "outliers") are
typically more metal-poor, faster and, most importantly, have a
tendency to originate from the inner Galaxy compared to the underlying
population. We also compose a sample of stars with velocities
exceeding the local escape velocity. Although we do not discount that
our sample could be contaminated by objects with spurious proper
motions, a number of stars appear to have been ejected from the disk
with exceptionally high velocities. Some of these are consistent with
being ejected from the spiral arms and hence are a rich resource for
further study. Finally we look at objects whose orbits are consistent
with them being ejected at high speeds from the Galactic center. Of
these objects we find that one, J135855.65+552538.19, is inconsistent
with halo, bulge and disk kinematics and could plausibly have been
ejected from the Galactic nucleus via a Hills mechanism.
Description:
We have collected a sample of high metallicity (>-0.8dex) main
sequence F-to-M type stars in the extended solar neighborhood. For our
object sample, we utilize SDSS Data Release 10 (Ahn et al.,
2014ApJS..211...17A 2014ApJS..211...17A; see cat. V/139 for the SDSS-DR9) objects with
high quality spectroscopic parameters.
The SDSS is a long-running survey (the first data release being more
than a decade ago) which, as of the tenth data release (Ahn et al.,
2014ApJS..211...17A 2014ApJS..211...17A), has imaged over a third of the sky in five
photometric bands (u, g, r, i, z). The SDSS 2.5m telescope is situated
at Apache Point Observatory in New Mexico.
The SDSS telescope is also outfitted with twin multifiber
spectrographs which can take up to 640 spectral readings
simultaneously on 3'' fibers. The spectrographs operate over the
visual range (3900-9000Å) at a moderate resolution (R∼1850-2200).
The SDSS offers a selection of stellar atmospheric parameters in its
Sloan Stellar Parameter Pipeline data product (SSPP; see Lee et al.,
2008AJ....136.2022L 2008AJ....136.2022L). In this work we limit our sample to spectra with
signal to noise ratios of 10 or higher-this corresponds to atmospheric
parameter estimate errors of about: ΔTeff∼103.9K,
Δlog(g)~.282dex and Δ[Fe/H]∼0.213dex.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 81 310 Hypervelocity candidates
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See also:
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
I/317 : The PPMXL Catalog (Roeser+ 2010)
J/ApJ/751/55 : MMT hypervelocity star survey. II. (Brown+, 2012)
J/ApJ/671/1708 : Hypervelocity stars. III (Brown+, 2007)
J/ApJ/660/311 : Hypervelocity stars. II. (Brown+, 2007)
J/ApJ/647/303 : Spectroscopic survey of hypervelocity stars (Brown+, 2006)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 I1 --- Nt [0/4] Number of tests in which the hypervelocity
star candidate failed (0=candidate that pass
our strict proper motion quality cut) (1)
3- 22 A20 --- Name IAU identifier (JHHMMSS.ss+DDMMSS.ss) (2)
23 A1 --- f_Name [*] Indicates an object independently noted
by Palladino et al. (2014ApJ...780....7P 2014ApJ...780....7P)
25- 31 F7.2 mas/yr Dpm [0.7/1412.37] Change in the proper motion (3)
33- 37 F5.2 arcsec Sep [1.16/28.7] Nearest neighbor separation (4)
39- 44 F6.2 mas/yr pmTot [4.93/707.65] Total proper motion (5)
46- 50 F5.2 mas/yr e_pmTot [3.2/15.5] The 1σ SDSS error in pmTot (6)
52- 56 F5.2 [-] [Fe/H] [-0.8/0.41] Metallicity (7)
58- 65 F8.2 km/s Vtotal [548.19/10628.51] Total velocity
67- 72 F6.2 km/s e_Vtotal [40.11/839.2] Uncertainty in Vtotal
74- 79 F6.2 km/s Vesc [463.76/603.49] Escape velocity
81 A1 --- Infall [X] Infalling candidate indicator (X=yes)
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Note (1): The four selection criteria provided in Section 4.2 (see more details
in the Appendix) are defined as below:
- SDSS proper motions differ from PPMXL (Roeser et al. 2010, cat. I/317)
proper motions by less than 12mas/yr;
- Absolute SDSS proper motions are less than 30mas/yr;
- Nearest observational (in projection) neighbor is more than 10'' away;
- SDSS proper motion errors are less than 5mas/yr.
Note (2): We identify hypervelocity star as star whose current kinetic energy
is greater than the gravitational potential (described in Section 2.2) at
its position. The star is traveling fast enough to escape the potential of
the Milky Way.
Note (3): The difference between the SDSS proper motions of Munn et al.
(2004AJ....127.3034M 2004AJ....127.3034M) and the PPMXL proper motions of Roeser et al. 2010,
cat. I/317).
Note (4): The distance on the sky to the nearest SDSS detection.
Note (5): Of the SDSS (Munn et al., 2004AJ....127.3034M 2004AJ....127.3034M).
Note (6): The pipeline reported error on the proper motions of the Munn et al.
(2004AJ....127.3034M 2004AJ....127.3034M) catalog.
Note (7): We wish to focus on disk-origin objects which have non-disk
kinematics. To weed out the halo, we investigate only objects with Sloan
Stellar Parameter Pipeline (SSPP; see Lee et al., 2008AJ....136.2022L 2008AJ....136.2022L)
metallicities greater than -0.8dex. An object with such a high metallicity,
which is found to be inconsistent in its kinematics with its neighboring
high metallicity stars, is a candidate runaway star.
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History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 14-Oct-2015