J/ApJ/736/65 PNe in the Virgo elliptical galaxy NGC 4649 (Teodorescu+, 2011)
Planetary nebulae in the elliptical galaxy NGC 4649 (M60): kinematics and
distance redetermination.
Teodorescu A.M., Mendez R.H., Bernardi F., Thomas J., Das P., Gerhard O.
<Astrophys. J., 736, 65 (2011)>
=2011ApJ...736...65T 2011ApJ...736...65T
ADC_Keywords: Planetary nebulae ; Radial velocities ; Galaxies, spectra
Keywords: galaxies: distances and redshifts - techniques: radial velocities -
galaxies: elliptical and lenticular, cD - planetary nebulae: general -
galaxies: individual (NGC 821) - galaxies: kinematics and dynamics -
Abstract:
Using a slitless spectroscopy method with (1) the 8.2m Subaru
telescope and its FOCAS Cassegrain spectrograph and (2) the ESO Very
Large Telescope unit 1 (Antu) and its FORS2 Cassegrain spectrograph,
we have detected 326 planetary nebulae (PNs) in the giant Virgo
elliptical galaxy NGC 4649 (M60) and measured their radial
velocities. After rejecting some PNs more likely to belong to the
companion galaxy NGC 4647, we have built a catalog with kinematic
information for 298 PNs in M60. Using these radial velocities, we
have concluded that they support the presence of a dark matter halo
around M60. Based on an isotropic, two-component Hernquist model, we
estimate the dark matter halo mass within 3Re to be
4x1011M☉, which is almost one-half of the total mass of about
1012M☉ within 3Re. This total mass is similar to that
estimated from globular cluster, XMM-Newton, and Chandra observations.
The dark matter becomes dominant outside. More detailed dynamical
modeling of the PN data is being published in a companion paper. We
have also measured the m(5007) magnitudes of many of these PNs and
built a statistically complete sample of 218 PNs. The resulting PN
luminosity function (PNLF) was used to estimate a distance modulus of
30.7±0.2mag, equivalent to 14±1Mpc. This confirms an earlier PNLF
distance measurement based on a much smaller sample. The PNLF distance
modulus remains smaller than the surface brightness fluctuation
distance modulus by 0.4mag.
Description:
Figure 1 shows the fields of M60 we observed, using the ESO Very Large
Telescope (VLT) at the Cerro Paranal, Chile, and the Subaru telescope
at Mauna Kea, HI, USA. Chronologically, we first observed Field 1 in
2007 April with Subaru/FOCAS; because of poor seeing we reobserved
Field 1 and added Field 2, in 2007 June, with the VLT/FORS2; finally,
we reobserved Field 1 and added Field 3, in 2008 May, with Subaru.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 48 298 *PN candidates in M60 (NGC 4649)
table4.dat 48 28 PN candidates more likely to belong to NGC 4647
--------------------------------------------------------------------------------
Note on table3.dat: Table 3 lists the 298 PNs we have accepted as belonging to
M60. See section 4 for further explanations on the selection criteria.
--------------------------------------------------------------------------------
See also:
V/84 : Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (Acker+, 1992)
J/ApJS/182/216 : Surface photometry of Virgo ellipticals (Kormendy+, 2009)
J/ApJ/682/135 : CCD photometry of M60 (Lee+, 2008)
J/ApJ/356/332 : Planetary nebulae as standard candles. V. (Jacoby+, 1990)
Byte-by-byte Description of file: table[34].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [3/2042] Identification number
6- 7 I2 h RAh [12] Hour of right ascension (J2000)
9- 10 I2 min RAm [43/44] Minute of right ascension (J2000)
12- 16 F5.2 s RAs Second of right ascension (J2000)
18 A1 --- DE- [+] Sign of declination (J2000)
19- 20 I2 deg DEd [11] Degree of declination (J2000)
22- 23 I2 arcmin DEm [27/38] Arcminute of declination (J2000)
25- 28 F4.1 arcsec DEs Arcsecond of declination (J2000)
30- 33 I4 arcsec xG x, G coordinate from center of M60 (1)
35- 38 I4 arcsec yG y, G coordinate from center of M60 (1)
40- 43 I4 km/s HRV [279/1690] Heliocentric radial velocity (2)
45- 48 F4.1 mag m5007 [26.3/28.2]?=-1 magnitude m(5007) (3)
--------------------------------------------------------------------------------
Note (1): The x, y coordinates are measured in arcsec and are relative to the
center of M60. The x-coordinate runs in the direction of increasing
right ascension along the major axis of M60, defined to be at
PA=105° (from N through E). The y-coordinate runs in the direction
of increasing declination.
Note (2): We conservatively estimate the calibration errors in FOCAS slitless
radial velocities to be of the order of 10km/s. If we add
quadratically the uncertainties in velocity given by the calibration
errors (∼10km/s), the position errors (∼10km/s), and the errors from
image registration (∼10km/s), we get an overall error of about 17km/s.
Assuming that the spectrograph deformations and guiding errors have a
marginal contribution, we estimate the total uncertainty in the
velocities measured with Subaru and FOCAS to be at most 20km/s. The
expected errors in FORS2 velocities are a bit larger, around 25km/s,
because of the slightly lower spectral resolution after binning.
Note (3): Magnitude m(5007) as defined by Jacoby (1989ApJ...339...39J 1989ApJ...339...39J):
m(5007)=-2.5logI(5007)-13.74 where I(5007) is the [OIII]5007 flux
measured through the on-band filter.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 12-Dec-2012