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J/ApJ/681/1254   Radial velocities of stars in the Galactic Center (Zhu+, 2008)
Radial velocities of stars in the Galactic center.
    Zhu Q., Kudritzki R.P., Figer D.F., Najarro F., Merritt D.
   <Astrophys. J., 681, 1254-1278 (2008)>
   =2008ApJ...681.1254Z    (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type ; Radial velocities ; Spectral types ;
              Spectroscopy ; Stars, early-type ; Equivalent widths ;
              Stars, nearby
Keywords: Galaxy: center - stars: kinematics - techniques: spectroscopic


Abstract:
    We present results from K-band slit scan observations of a ∼20"x20"
    region of the Galactic center (GC) in two separate epochs more than 5
    years apart. The high-resolution (R={lamda}/Δλ≥14000)
    observations allow the most accurate radial velocity and acceleration
    measurements of the stars in the central parsec of the Galaxy.
    Detected stars can be divided into three groups based on the CO
    absorption band heads at ∼2.2935um and the HeII lines at ∼2.0581 and
    ∼2.112, 2.113um: cool, narrow-line hot, and broad-line hot. The radial
    velocities of the cool, late-type stars have approximately a
    symmetrical distribution with its center at ~-7.8±10.3km/s and a
    standard deviation ∼113.7±10.3km/s. Although our statistics are
    dominated by the brightest stars, we estimate a central black hole
    mass of (3.9±1.1)x106M☉, consistent with current estimates
    from complete orbits of individual stars. Our surface density profile
    and the velocity dispersion of the late-type stars support the
    existence of a low-density region at the Galactic center suggested by
    earlier observations.

Description:
    Four slit scan observations were conducted over a ∼20"x20" region in
    the GC with the near-infrared spectrometer (NIRSPEC) on the Keck II
    Telescope during 1999 June 4, 1999 July 4, 2005 April 13, and 2005
    April 14.
Objects:
    ----------------------------------------------------------
          RA   (2000)   DE         Designation(s)
    ----------------------------------------------------------
       17 45 40.04  -29 00 28.11   NAME Sgr A*
    ----------------------------------------------------------

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table3.dat        81      123   Cool star velocity
table5.dat       119       20   Radial velocities of narrow HeI line stars
table6.dat       119        9   Radial velocities of broad HeI line stars


See also:
   J/A+A/499/483  : NIR observations of sources in galactic center (Buchholz+,
                    2009)
   J/ApJ/670/1115 : IRS spectra at 38 positions in Galactic center (Simpson+,
                    2007)
   J/A+A/426/81   : Kinematic analysis of the Minispiral (Paumard+, 2004)
   J/ApJ/597/323  : Cool stars at the Galactic Center (Blum+, 2003)
   J/ApJ/523/248  : Variable stars in the Galactic center (Ott+, 1999)


Byte-by-byte Description of file: table3.dat

   Bytes Format Units   Label   Explanations

   1- 10  A10   ---     Name    Source identification (1)
  12- 17  F6.2  arcsec  oRA     Right ascension offset from Sagittarius A*
  19- 24  F6.2  arcsec  oDE     Declination offset from Sagittarius A*
  26- 31  F6.1  km/s    RV99    ? Radial velocity; epoch 1999 (2)
  33- 35  F3.1  km/s    e_RV99  ? RV99 uncertainty
  37- 42  F6.1  km/s    RV05    ? Radial velocity; epoch 2005 (2)
  44- 46  F3.1  km/s    e_RV05  ? RV05 uncertainty
  48- 53  F6.1  km/s    <RV>    Mean radial velocity
  55- 57  F3.1  km/s    e_<RV>  <RV> uncertainty
  59- 62  I4    K       Teff    Effective temperature (3)
      64  A1    ---     l_SpT   Limit flag on SpType
  65- 70  A6    ---     SpT     MK spectral type (3)
  72- 77  F6.1  km/s    RVf     ? Radial velocity from Figer et al.
                                (2003ApJ...599.1139F) (4)
  79- 81  F3.1  km/s    e_RVf   ? RVFig uncertainty (4)

Note (1): Designations of the stars are taken from Figer et al.,
          2003ApJ...599.1139F and Tanner et al., 2006ApJ...641..891T. For those
          objects which were not included in the previous works, we use their
          coordinates as the designation (they are <[ZKF2008] +XX.xx+YY.yy> in
          Simbad).
Note (2): Radial velocity of individual cool stars derived from the Dopplor
          shift of the CO(2-1) band-head feature. Velocity measurements in two
          epochs 1999 and 2005 are listed when available.
Note (3): The temperatures and spectral types are calculated with measured
          average equivalent widths of the CO feature using the method describe
          in Tanner et al. (2006ApJ...641..891T).
Note (4): Values are taken from Figer et al. (2003ApJ...599.1139F), which was
          based on the same two data sets obtained in 1999.


Byte-by-byte Description of file: table5.dat table6.dat

   Bytes Format Units    Label    Explanations

   1- 14  A14   ---      Name     Star designation
      15  A1    ---      r_Name   [ab] Name reference (1)
  17- 21  F5.2  arcsec   oRA      Right ascension offset from Sagittarius A*
  23- 27  F5.2  arcsec   oDE      Declination offset from Sagittarius A*
  29- 34  F6.1  km/s     RV1      ? Radial velocity 1 (2)
  36- 40  F5.1  km/s     e_RV1    ? RV1 uncertainty
  42- 47  F6.1  km/s     RV2      ? Radial velocity 2 (2)
  49- 53  F5.1  km/s     e_RV2    ? RV2 uncertainty
  55- 60  F6.1  km/s     RV3      ? Radial velocity 3 (2)
  62- 66  F5.1  km/s     e_RV3    ? RV3 uncertainty
  68- 73  F6.1  km/s     RV4      ? Radial velocity 4 (2)
  75- 78  F4.1  km/s     e_RV4    ? RV4 uncertainty
  80- 85  F6.1  km/s     <RV>     Mean radial velocity
  87- 91  F5.1  km/s     e_<RV>   <RV> uncertainty
  93- 97  F5.1  km/s     DRV      ? Radial velocity difference between 1999 and
                                  2005
  99-102  F4.1  km/s     e_DRV    ? DRV uncertainty
 104-109  F6.2  0.1nm    EW       Equivalent width (3)
 111-119  A9    ---      Ref      Previous reference(s) (4)

Note (1): Source name as follows:
   a = Figer et al. (2003ApJ...599.1139F, <[FGK2003] NNN> or 
       <[GPE2000] NN.NNA> in Simbad.)
   b = Ott et al. (1999, Cat. J/ApJ/523/248, <[OEG99] NNN> in Simbad)
   IRS sources are <GCIRS NNWWN> in Simbad.
Note (2): Radial velocity measurements of narrow or broad type HeI stars
     from four data sets. Unlike the cool star cases, radial velocities of
     some hot stars are quite uncertain due to the variation of extracted
     line profiles from night to night within one epoch. Big uncertainties
     are expected for the measurements.
Note (3): The equivalent width for each narrow type HeI star is calculated
     from the average width of the fitted Gaussian components. The
     equivalent width for each broad type HeI star is calculated by
     integrating the area below the normalized spectrum within the
     ±1000km/s wavelength range of the corresponding spectral line
     emission peak.
Note (4): References as follows:
   1 = Genzel et al., 2000MNRAS.317..348G
   2 = Paumard et al., 2001A&A...366..466P
   3 = Tanner et al., 2006ApJ...641..891T
   4 = Paumard et al., 2006ApJ...643.1011P
   5 = Paumard et al., 2003ANS...324..303P
   6 = Paumard et al., 2004, Cat. J/A+A/426/81


History:
    From electronic version of the journal
(End)                                     Emmanuelle Perret [CDS]    28-Oct-2010