A STELLAR CENSUS OF THE TUCANA–HOROLOGIUM MOVING GROUP

By A. Kraus, E. Shkolnik, K. Allers, Michael C. Liu. 2014

155 citations recorded by the source corpus.

We report the selection and spectroscopic confirmation of 129 new late-type (SpT = K3–M6) members of the Tucana–Horologium moving group, a nearby (d ∼ 40 pc), young (τ ∼ 40 Myr) population of comoving stars. We also report observations for 13 of the 17 known Tuc–Hor members in this spectral type range, and that 62 additional candidates are likely to be unassociated field stars; the confirmation frequency for new candidates is therefore 129/191 = 67%. We have used radial velocities, Hα emission, and Li6708 absorption to distinguish between contaminants and bona fide members. Our expanded census of Tuc–Hor increases the known population by a factor of ∼3 in total and by a factor of ∼8 for members with SpT ⩾ K3, but even so, the K–M dwarf population of Tuc–Hor is still markedly incomplete. Our expanded census allows for a much more detailed study of Tuc–Hor than was previously feasible. The spatial distribution of members appears to trace a two-dimensional sheet, with a broad distribution in X and Y, but a very narrow distribution (±5 pc) in Z. The corresponding velocity distribution is very small, with a scatter of ±1.1 km s−1 about the mean UVW velocity for stars spanning the entire 50 pc extent of Tuc–Hor. We also show that the isochronal age (τ ∼ 20–30 Myr) and the lithium depletion boundary age (τ ∼ 40 Myr) disagree, following the trend in other pre-main-sequence populations for isochrones to yield systematically younger ages. The Hα emission line strength follows a trend of increasing equivalent width with later spectral type, as is seen for young clusters. We find that moving group members have been depleted of measurable lithium for spectral types of K7.0–M4.5. None of our targets have significant infrared excesses in the WISE W3 band, yielding an upper limit on warm debris disks of F < 0.7%. Finally, our purely kinematic and color–magnitude selection procedure allows us to test the efficiency and completeness for activity-based selection of young stars. We find that 60% of K–M dwarfs in Tuc–Hor do not have ROSAT counterparts and would have been omitted in X-ray-selected samples. In contrast, GALEX UV-selected samples using a previously suggested criterion for youth achieve completeness of 77% and purity of 78%, and we suggest new SpT-dependent selection criteria that will yield >95% completeness for τ ∼ 40 Myr populations with GALEX data available.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/93cf11c9cd2f24d8dcec8b04599703cd8f0fe2ff

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Instrumentation

Citations in the corpus

A self-consistent, absolute isochronal age scale for young moving groups in the solar neighbourhood (2015, methodology): “Not accounting for unresolved multiples, our sample includes a total of 89 members of the AB Dor moving group, 27 members of Argus, 97 members of the BPMG, 12 members of Carina, 50 members of Columba, 18 members of η Cha, 189 members of Tuc-Hor, 30 members of TWA, and 14 members of 32 Ori.”
BANYAN. VII. A NEW POPULATION OF YOUNG SUBSTELLAR CANDIDATE MEMBERS OF NEARBY MOVING GROUPS FROM THE BASS SURVEY (2015, methodology): “…2001a; Malo et al. 2014b; Binks & Jeffries 2014), Tucana-Horologium (THA; 20–40 Myr; Torres et al. 2000; Zuckerman & Webb 2000; Zuckerman et al. 2001b; Kraus et al. 2014b), Carina (CAR; 20–40 Myr; Torres et al. 2008), Columba (COL; 20–40 Myr; Torres et al. 2008), Argus (ARG; 30–50 Myr; Makarov…”
BANYAN. XI. The BANYAN Σ Multivariate Bayesian Algorithm to Identify Members of Young Associations with 150 pc (2018, methodology): “…et al. 2001; (35) Neuhäuser et al. 2003; (36) Zuckerman & Song 2004; (37) Gontcharov 2006; (38) Anderson & Francis 2012; (39) Bobylev et al. 2006; (40) Kraus et al. 2014; (41) Zuckerman & Webb 2000; (42) Grenier et al. 1999; (43) Pecaut & Mamajek 2013; (44) Elliott et al. 2014; (45) Webb et…”
HAZMAT. I. THE EVOLUTION OF FAR-UV AND NEAR-UV EMISSION FROM EARLY M STARS (2014, background): “…al. (2003), 10: Reid (2003), 11: Jayawardhana et al. (2006), 12: Zuckerman et al. (2001), 13: Looper et al. (2010), 14: Shkolnik et al. (2012), 15: Kraus et al. (2014), 16: Montes et al. (2001), 17: Zuckerman et al. (2004), 18: Malo et al. (2013), 19: López-Santiago et al. (2006), 20: Bowler et…”
THE HAWAII INFRARED PARALLAX PROGRAM. II. YOUNG ULTRACOOL FIELD DWARFS (2016, background): “…to find young ultracool dwarfs in the nearest young moving groups through kinematic and stellar-activity criteria (e.g., Shkolnik et al. 2009, 2011, 2012; Rodriguez et al. 2011; Schlieder et al. 2012; Malo et al. 2013; Gagné et al. 2014b; Kraus et al. 2014; Gagné et al. 2015b; Aller et al. 2016).”
PLANETS AROUND LOW-MASS STARS (PALMS). IV. THE OUTER ARCHITECTURE OF M DWARF PLANETARY SYSTEMS (2014, background): “Similarly, Kraus et al. (2014) infer a Li-depletion age of ≈40 Myr for the Tuc-Hor moving group, which is roughly 10 Myr older than its age from isochrone fitting.”
Imaging Extrasolar Giant Planets (2016, background): “Several planetary-mass companions have been imaged around binary stars on wide circumbinary orbits: ROXs 42B b (Kraus et al. 2014a; Currie et al. 2014b), Ross 458 c (Goldman et al. 2010; Scholz 2010), SR 12 C (Kuzuhara et al. 2011), HD 106906 b (Bailey et al. 2014; Lagrange et al. 2016), and VHS…”
THE IMPACT OF STELLAR MULTIPLICITY ON PLANETARY SYSTEMS. I. THE RUINOUS INFLUENCE OF CLOSE BINARY COMPANIONS (2016, background): “0 (Monet et al. 2003), as described in Kraus & Hillenbrand (2007) and Kraus et al. (2014), to estimate both parameters.”
Individual Dynamical Masses of Ultracool Dwarfs (2017, methodology): “Lithium Fusion Mass Limit Theoretical predictions of lithium depletion in ultracool dwarfs as a function of mass and age are thought to be one of the most reliable methods for age-dating young clusters (e.g., Chabrier et al. 1996; Bildsten et al. 1997; Binks & Jeffries 2014; Kraus et al. 2014).”