EVIDENCE FOR WARPED DISKS OF YOUNG STARS IN THE GALACTIC CENTER

“The quantity p(χ2, 1) = 1 − Erf( √ χ2/2) denotes the probability to observe by chance a value of χ2 or larger, even for a correct model (Yao et al. 2006).”

“At a distance of about 8 kpc (Eisenhauer et al. 2003b; Gillessen et al. 2009; Ghez et al. 2008; Gronewegen et al. 2008; Trippe et al. 2008), processes in the GC can be studied at much higher resolution compared to any other galactic nucleus.”

“We define the significance for each bin of the sky map as (see Equation (10a) of Li & Ma 1983): significance = observed density − mean density of isotropic stars rms density of isotropic stars .”

“It is associated with the compact radio source Sgr A*, which must be a massive black hole, beyond any reasonable doubt (Schödel et al. 2002; Ghez et al. 2005; Gillessen et al. 2009).”

“It is also interesting to note a well known example of another warped nuclear disk surrounding a supermassive black hole in another galaxy; the maser disk observation of NGC 4258 (Miyoshi et al. 1995; Herrnstein et al. 1996).”

“For each star we assigned effective temperatures derived from spectral types using the effective temperature scales of Martins et al. (2005) for O stars and Crowther et al. (2006) for B supergiants.”

“The Galactic center (GC) is a uniquely accessible laboratory for studying the properties and evolution of galactic nuclei (for reviews, see, e.g., Genzel & Townes 1987; Morris & Serabyn 1996; Mezger et al. 1996; Alexander 2005).”

“R) stars (Forrest et al. 1987; Allen et al. 1990; Krabbe et al. 1991; Najarro et al. 1994; Krabbe et al. 1995; Blum et al. 1995; Tamblyn et al. 1996; Najarro et al. 1997; Genzel et al. 2003; Ghez et al. 2003; Paumard et al. 2006; Martins et al. 2007) with an estimated age of about 6×106 years.”

“Moreover, Figure 10 shows an extended Ushaped excess of counterclockwise orbits including the direction of the counterclockwise system of Paumard et al. (2006).”

“It is associated with the compact radio source Sgr A*, which must be a massive black hole, beyond any reasonable doubt (Schödel et al. 2002; Ghez et al. 2005; Gillessen et al. 2009).”

“All possible directions of the angular momentum lie on a onedimensional curve (see, e.g., Eisenhauer et al. 2005).”

“…low mass stars in a stellar disk, which grow, through accretion, into the more massive stars currently observed in the GC (Levin & Beloborodov 2003; Genzel et al. 2003; Goodman 2003; Milosavljević & Loeb 2004; Nayakshin & Cuadra 2005; Paumard et al. 2006; Bonnell & Rice 2008; Mapelli et al 2008;…”

“Genzel et al. (1996, 2000, 2003), Levin & Beloborodov (2003), Beloborodov et al. (2006), and Paumard et al. (2006) inferred that most of the dynamical properties of the W–”

“Genzel et al. (1996, 2000, 2003), Levin & Beloborodov (2003), Beloborodov et al. (2006), and Paumard et al. (2006) inferred that most of the dynamical properties of the W–”

“The tidal forces near the supermassive black hole Sgr A* are so strong that a cloud cannot be gravitationally bound unless its density exceeds 6 × 109MSgrA∗/(4 × 106 M )(R/7′′)−3 cm−3, where R is the distance to Sgr A*, orders of magnitude denser than currently observed (Morris 1993).”

“In addition, for all these early-type stars we derived proper motions from the NAOS/CONICA (Rousset et al. 2003; Hartung et al. 2003) imaging data set of the GC covering six epochs from May 2002 to March 2007 in the 27 mas pixel−1 scale (Trippe et al. 2008).”

“We motivate this choice as follows: for a power-law cusp the radial star number density is related to the surface number density Σ(rdisk) = dNstars/dAdisk ∝ r−βdisk (Schödel et al. 2003; Alexander 2005). rdisk denotes the three-dimensional distance in the plane of the disk.”

“′′5, the limit of the primary sample of Lu et al. (2009).”

“In the following, we present the results of new observations of the GC with the adaptive optics (AO) assisted near-infrared imager NACO and the integral field spectrograph SINFONI on the ESO/VLT.”

“Given the fact that the star formation event 6 Myr ago seems to be isolated, with no comparable activity for several tens of Myr before and not much after (Krabbe et al. 1995), Occam’s razor would suggest that only one disk of W–”

“R stars (e.g., Perets et al. 2007, but see Levin 2007 and Löckmann et al. 2008).”

“For each star we assigned effective temperatures derived from spectral types using the effective temperature scales of Martins et al. (2005) for O stars and Crowther et al. (2006) for B supergiants.”

“Genzel et al. (1996, 2000, 2003), Levin & Beloborodov (2003), Beloborodov et al. (2006), and Paumard et al. (2006) inferred that most of the dynamical properties of the W–”

“These errors propagate into the bolometric corrections, see Equation (3) and Table 1 of Martins & Plez (2006), and lead to the uncertainty in luminosities.”

“Such a scenario produces a surface number density of stars in the disk of Σ(r) ∝ r−2 (Lin & Pringle 1987; Hobbs & Nayakshin 2008), compatible with the observations.”

“R stars (e.g., Perets et al. 2007, but see Levin 2007 and Löckmann et al. 2008).”

“R) stars (Forrest et al. 1987; Allen et al. 1990; Krabbe et al. 1991; Najarro et al. 1994; Krabbe et al. 1995; Blum et al. 1995; Tamblyn et al. 1996; Najarro et al. 1997; Genzel et al. 2003; Ghez et al. 2003; Paumard et al. 2006; Martins et al. 2007) with an estimated age of about 6×106 years.”

“The Galactic center (GC) is a uniquely accessible laboratory for studying the properties and evolution of galactic nuclei (for reviews, see, e.g., Genzel & Townes 1987; Morris & Serabyn 1996; Mezger et al. 1996; Alexander 2005).”

“Other planar structures in the GC such as the minispiral and the CND have too low masses (Jackson et al. 1993; Liszt 2003) to cause significant warps.”

“The infalling cluster scenario predicts surface density profiles as shallow as Σ(r) ∝ r−0.75 (see, e.g., Hansen & Milosavljević 2003; Berukoff & Hansen 2006).”

“A significant average eccentricity of the disk stars of 0.36 ± 0.06 probably requires that the stars form on an orbital timescale, following the initial compression (Bonnell & Rice 2008).”

“Analytical studies suggest that the stellar cusp around the disks would quench their strong interaction and would not allow for the Kozai resonance to be effective (Ivanov et al. 2005; Karas & Šubr 2007; Chang 2009).”

“We assumed a distance of (8.0 ± 0.5) kpc and an extinction of AK = 2.8 ± 0.5 (Scoville et al. 2003; Schödel et al. 2007).”

“Thus the mass model of Trippe et al. (2008) provides a very good match to our data.”

“…the context of the two leading formation scenarios, the infalling cluster (Gerhard 2001; McMillan & Portegies Zwart 2003; Portegies Zwart et al. 2003; Kim & Morris 2003; Kim et al. 2004; Gürkan & Rasio 2005) and the in situ formation (Levin & Beloborodov 2003; Genzel et al. 2003; Goodman 2003;…”

“It is also interesting to note a well known example of another warped nuclear disk surrounding a supermassive black hole in another galaxy; the maser disk observation of NGC 4258 (Miyoshi et al. 1995; Herrnstein et al. 1996).”

“If IRS 13E is a star cluster at z ∼ 7′′ (Paumard et al. 2004, 2006), the stars IRS 13E2 and E4 would not be candidate members of a counterclockwise system.”

“…could be explained both by the in situ formation of eccentric disks/structures (Alexander et al. 2008; Bonnell & Rice 2008; Hobbs & Nayakshin 2008; Wardle & Yusef-Zadeh 2008) and/or through the dynamical heating of more circular configurations mainly by cusp stars and stellar mass black holes…”

“In addition, for all these early-type stars we derived proper motions from the NAOS/CONICA (Rousset et al. 2003; Hartung et al. 2003) imaging data set of the GC covering six epochs from May 2002 to March 2007 in the 27 mas pixel−1 scale (Trippe et al. 2008).”

“Nevertheless, observations of the GC Arches cluster show that it is on a noncircular orbit (Stolte et al. 2008), although at a large distance from the Sgr A*.”

“…disk, which grow, through accretion, into the more massive stars currently observed in the GC (Levin & Beloborodov 2003; Genzel et al. 2003; Goodman 2003; Milosavljević & Loeb 2004; Nayakshin & Cuadra 2005; Paumard et al. 2006; Bonnell & Rice 2008; Mapelli et al 2008; Hobbs & Nayakshin 2008).”

“…scenarios, the infalling cluster (Gerhard 2001; McMillan & Portegies Zwart 2003; Portegies Zwart et al. 2003; Kim & Morris 2003; Kim et al. 2004; Gürkan & Rasio 2005) and the in situ formation (Levin & Beloborodov 2003; Genzel et al. 2003; Goodman 2003; Milosavljević & Loeb 2004; Nayakshin…”

“…two leading formation scenarios, the infalling cluster (Gerhard 2001; McMillan & Portegies Zwart 2003; Portegies Zwart et al. 2003; Kim & Morris 2003; Kim et al. 2004; Gürkan & Rasio 2005) and the in situ formation (Levin & Beloborodov 2003; Genzel et al. 2003; Goodman 2003; Milosavljević & Loeb…”

“…interpret them in the context of the two leading formation scenarios, the infalling cluster (Gerhard 2001; McMillan & Portegies Zwart 2003; Portegies Zwart et al. 2003; Kim & Morris 2003; Kim et al. 2004; Gürkan & Rasio 2005) and the in situ formation (Levin & Beloborodov 2003; Genzel et al.…”

“R) stars (Forrest et al. 1987; Allen et al. 1990; Krabbe et al. 1991; Najarro et al. 1994; Krabbe et al. 1995; Blum et al. 1995; Tamblyn et al. 1996; Najarro et al. 1997; Genzel et al. 2003; Ghez et al. 2003; Paumard et al. 2006; Martins et al. 2007) with an estimated age of about 6×106 years.”

“Analytical studies suggest that the stellar cusp around the disks would quench their strong interaction and would not allow for the Kozai resonance to be effective (Ivanov et al. 2005; Karas & Šubr 2007; Chang 2009).”

“Moreover, even more massive and less likely perturbers such as in-spiraling intermediate mass black holes (Yu et al 2007; Löckmann & Baumgardt 2008a) have difficulties explaining both the clockwise and the inclined counterclockwise systems.”

“The evolution and the star formation history in the central pc of the Galaxy may also be used as a probe of star formation processes near supermassive black holes in general, also relevant to other galactic nuclei (Collin & Zahn 2008; Levin 2007).”

“The gaseous disk then fragments to form new low mass stars in a stellar disk, which grow, through accretion, into the more massive stars currently observed in the GC (Levin & Beloborodov 2003; Genzel et al. 2003; Goodman 2003; Milosavljević & Loeb 2004; Nayakshin & Cuadra 2005; Paumard et al. 2006; Bonnell & Rice 200…”

“R stars (e.g., Perets et al. 2007, but see Levin 2007 and Löckmann et al. 2008).”

“The 10◦ sigma thickness of the clockwise system may be explained by disk heating due to interactions with cusp stars (Perets et al. 2008a), massive disk stars (Alexander et al. 2007; Cuadra et al. 2008) and binaries (Perets et al. 2008b).”

“But such heating cannot excite and explain the large fraction of young stars at very high inclinations from the main clockwise disk structure, and/or the coherent counterclockwise structure (Cuadra et al. 2008).”

“In most scenarios for the infall of a cluster, the stars remain close to the in-spiral plane (Berukoff & Hansen 2006) and form a single flat star distribution with a thickness comparable to or larger than the original cluster.”

“However, Tanner et al. (2006) were only able to assign 15 out of 30 early-type stars near the GC as disk members.”

“Levin et al. (2005) have shown that after the infall of a cluster of young stars around an intermediate mass black hole on an initially eccentric orbit a significant fraction of stars get pushed out of the in-spiral plane and end up with large inclinations.”

“Moreover, even more massive and less likely perturbers such as in-spiraling intermediate mass black holes (Yu et al 2007; Löckmann & Baumgardt 2008) have difficulties explaining both the clockwise and the inclined counter-clockwise systems.”

“For our further analysis, we use a cylindrical equal area projection (Gall 1885; Peters 1983) of this sphere: (cos θJ versus φJ ).”

“Analytical studies suggest that the stellar cusp around the disks would quench their strong interaction and would not allow for the Kozai resonance to be effective (Ivanov et al. 2005; Karas & Šubr 2007; Chang 2009).”

“Moreover, even more massive and less likely perturbers such as in-spiraling intermediate mass black holes (Yu et al 2007; Löckmann & Baumgardt 2008a) have difficulties explaining both the clockwise and the inclined counterclockwise systems.”

“Other planar structures in the GC such as the minispiral and the CND have too low masses (Jackson et al. 1993; Liszt 2003) to cause significant warps.”

“It is likely to be of a different origin of the GC disk, and various suggestions have been discussed in the literature (e.g., Binney 1992; Arnaboldi & Galletta 1993; Caproni et al. 2006; Ferreira & Ogilvie 2009).”

“…g obeys Poisson statistics: it has a flat probability distribution between 0 and 1 with the mean expectation value g = 0.5 and the standard deviation Δg = 12−1/2 ≈ 0.29. g → 0 for small assumed masses and g → 1 for too large assumed masses (Beloborodov & Levin 2004; Beloborodov et al. 2006).”

“For some of the fields we used the laser guide star facility (Rabien et al. 2003; Bonaccini Calia et al. 2006).”

“…(Krabbe et al. 1995), including massive young stars in one and possibly two disks with diameters of 1– 2 arcmin rotating around the SMBH (Paumard et al. 2006, Bartko et al. 2009) and a remarkable concentration of B stars within 1 arcsec of the SMBH, the so-called S stars (Eckart et al. 1995).”

“In situ star formation from dense gas accretion disks is favored over the inspiraling star cluster scenario (see e.g. Bartko et al. 2009).”

“…both observations and theory suggest that it is top-heavy in extreme environments like the Galactic Centre and starburst galaxies (e.g. Padoan, Nordlund & Jones 1997; Baugh et al. 2005; Klessen, Spaans & Jappsen 2007; Maness et al. 2007; Bartko et al. 2009; Dabringhausen, Kroupa & Baumgardt 2009).”