A DISK OF YOUNG STARS AT THE GALACTIC CENTER AS DETERMINED BY INDIVIDUAL STELLAR ORBITS

By Jessica R. Lu, A. Ghez, S. Hornstein, Mark R. Morris, E. Becklin, K. Matthews. 2008

235 citations recorded by the source corpus.

We present new proper motions from the 10 m Keck telescopes for a puzzling population of massive, young stars located within 3.″5 (0.14 pc) of the supermassive black hole at the Galactic center. Our proper motion measurements have uncertainties of only 0.07 mas yr−1 (3 km s−1), which is ≳ 7 times better than previous proper motion measurements for these stars, and enables us to measure accelerations as low as 0.2 mas yr−2 (7 km s−1 yr−1). Using these measurements, line-of-sight velocities from the literature, and three-dimensional velocities for additional young stars in the central parsec, we constrain the true orbit of each individual star and directly test the hypothesis that the massive stars reside in two stellar disks as has been previously proposed. Analysis of the stellar orbits reveals only one of the previously proposed disks of young stars using a method that is capable of detecting disks containing at least seven stars. The detected disk contains 50% of the young stars, is inclined by ∼115° from the plane of the sky, and is oriented at a position angle of ∼100° east of north. Additionally, the on-disk and off-disk populations have similar K-band luminosity functions and radial distributions that decrease at larger radii as ∝r−2. The disk has an out-of-the-disk velocity dispersion of 28 ± 6 km s−1, which corresponds to a half-opening angle of 7° ±  2°, and several candidate disk members have eccentricities greater than 0.2. Our findings suggest that the young stars may have formed in situ but in a more complex geometry than a simple, thin circular disk.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b61f9d2790531517d68a5c441233b30b18049460

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In Astronomy and Astrophysics

1. T. Alexander
2. R. Genzel
3. F. Antonini
4. F. Eisenhauer
5. B. Kocsis
6. A. Ghez
7. O. Gerhard
8. T. Ott

In Instrumentation

1. M. Cappellari
2. Roger Davies
3. T. Alexander
4. R. Genzel
5. R. McDermid
6. N. Neumayer
7. B. Kocsis
8. R. Schödel

Citations in the corpus

• AN IMPROVED DISTANCE AND MASS ESTIMATE FOR SGR A* FROM A MULTISTAR ORBIT ANALYSIS (2016, methodology): “The AO observations of this field from 2004 through 2011 have been previously reported (Ghez et al. 2005b; Ghez et al. 2008; Lu et al. 2009; Yelda et al. 2010; Yelda 2012; Yelda et al. 2014).”
• A New Distortion Solution for NIRC2 on the Keck II Telescope (2016, background): “…of the supermassive black hole and studies of its surrounding stellar population (e.g., Eckart & Genzel 1997; Ghez et al. 1998, 2005; Genzel et al. 2003; Paumard et al. 2006; Stolte et al. 2008; Bartko et al. 2009; Lu et al. 2009; Clarkson et al. 2012; Meyer et al. 2012; Yelda et al. 2014).”
• Stellar Dynamics and Stellar Phenomena Near a Massive Black Hole (2017, background): “(Bartko et al. 2009; Lu et al. 2009) provides compelling indications that star formation can occur in-situ in a circumnuclear disk.”
• Peering through the veil: near-infrared photometry and extinction for the Galactic nuclear star cluster (2009, background): “The young stars are arranged in a non-isotropic pattern and at least 50% of them are located in a rotating disk (see Bartko et al. 2009; Lu et al. 2009). ar X iv :0 91 2.”
• THE NGC 404 NUCLEUS: STAR CLUSTER AND POSSIBLE INTERMEDIATE-MASS BLACK HOLE (2010, background): “…al. 2008) and a nuclear star cluster (MNSC ∼ 3 × 107 M⊙ Genzel et al. 1996; Schödel et al. 2007; Trippe et al. 2008) that contains stars of many ages and in different substructures including disks of young stars in the immediate vicinity of the black hole (e.g. Lu et al. 2009; Bartko et al. 2009).”
• Adaptive Optics for Astronomy (2012, background): “…of stars in the central parsec are old and have randomly oriented orbits (Yelda et al. 2010), about half of the young stars in the central 10–15′′ are confined to a warped clockwise disk, while many of the remainder may be in a second counter-clockwise disk (Bartko et al. 2010, Lu et al. 2009).”
• NuSTAR DISCOVERY OF A 3.76 s TRANSIENT MAGNETAR NEAR SAGITTARIUS A* (2013, background): “′′5 outside a disk with mean eccentricity ∼0.3 (Beloborodov et al. 2006; Lu et al. 2009) of clockwise rotating, predominantly massive O-type and Wolf–Rayet (WR) stars with disk ages of ∼6 Myr (Genzel et al. 2010).”
• Nuclear star clusters (2009, background): “Mieske et al. (2013) proposed that the inflated dynamical mass estimates seen in many UCDs could be explained with black holes of order 10% of the total UCD mass.”
• On the rate of black hole binary mergers in galactic nuclei due to dynamical hardening (2017, background): “Within the core of the MW nuclear star cluster (NSC), of order a hundred OB stars rotate clockwise on the sky in a strongly warped disk ∼ 0.04- 0.6 pc from the SMBH (e.g. Levin & Beloborodov 2003; Lu et al. 2009; Bartko et al. 2010; Baruteau et al. 2011; Yelda et al. 2014; Chen & Amaro-Seoane 2015).”
• Surface brightness profile of the Milky Way’s nuclear star cluster (2014, background): “In fact, a disc of young stars is observed in the GC right now (e.g., Levin & Beloborodov 2003; Paumard et al. 2006; Lu et al. 2009).”
• HIGH ANGULAR RESOLUTION INTEGRAL-FIELD SPECTROSCOPY OF THE GALAXY'S NUCLEAR CLUSTER: A MISSING STELLAR CUSP? (2009, background): “The survey region is oriented at a position angle (PA) of ∼ 105 degrees, with the longer direction oriented along major axis of the disk of young stars rotating in the clockwise direction in the plane of the sky (Paumard et al. 2006; Lu et al. 2009).”
• Black Hole Mergers in Galactic Nuclei Induced by the Eccentric Kozai–Lidov Effect (2017, background): “Bottom panel: Distribution of EKL-induced mergers and GWonly mergers for merger time versus . the disk of massive stars (Bartko et al. 2009; Lu et al. 2009).”
• IMPROVING GALACTIC CENTER ASTROMETRY BY REDUCING THE EFFECTS OF GEOMETRIC DISTORTION (2010, methodology): “…more stable, and the exact advantage depends on the field coverage; for the Keck speckle and 10′′×10′′ AO data (see, e.g., Ghez et al. 2008; Lu et al. 2009), the translational stability is expected to be a factor of 17.5 and 12.5 times better, or 0.03 and 0.02 mas yr−1, respectively…”
• AN EXTREMELY TOP-HEAVY INITIAL MASS FUNCTION IN THE GALACTIC CENTER STELLAR DISKS (2009, background): “The difference compared to the R−2 power law suggested by earlier work (Paumard et al. 2006; Lu et al. 2009; Bartko et al. 2009) is due to the thorough completeness and coverage correction applied here.”
• STELLAR POPULATIONS IN THE CENTRAL 0.5 pc OF THE GALAXY. II. THE INITIAL MASS FUNCTION (2013, background): “…distances and also with moderate eccentricities, and (3) ∼10% cluster within 0.03 pc of the black hole with high eccentricities of ē = 0.8 (Genzel et al. 2000; Levin & Beloborodov 2003; Genzel et al. 2003; Paumard et al. 2006; Ghez et al. 2008; Lu et al. 2009; Gillessen et al. 2009b; Yelda 2012).”