J/ApJ/721/369 PNe in the elliptical galaxy NGC 821 (Teodorescu+, 2010)
Planetary nebulae in the elliptical galaxy NGC 821: kinematics and distance
determination.
Teodorescu A.M., Mendez R.H., Bernardi F., Riffeser A., Kudritzki R.P.
<Astrophys. J., 721, 369-382 (2010)>
=2010ApJ...721..369T 2010ApJ...721..369T
ADC_Keywords: Galaxies, optical ; Planetary nebulae ; Radial velocities ;
Cross identifications ; Spectroscopy
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 the 8.2m Subaru telescope
and its FOCAS Cassegrain spectrograph, we have increased the number of
planetary nebula (PN) detections and PN velocity measurements in the
flattened elliptical galaxy NGC 821. A comparison with the detections
reported previously by the Planetary Nebulae Spectrograph group
indicates that we have confirmed most of their detections. The
velocities measured by the two groups, using different telescopes,
spectrographs, and slitless techniques, are in good agreement. We have
built a combined sample of 167 PNs and have confirmed the Keplerian
decline of the line-of-sight velocity dispersion reported previously.
We also confirm misaligned rotation from the combined sample. A dark
matter halo may exist around this galaxy, but it is not needed to keep
the PN velocities below the local escape velocity as calculated from
the visible mass. We have measured the m(5007) magnitudes of 145 PNs
and produced a statistically complete sample of 40 PNs in NGC 821. The
resulting PN luminosity function (PNLF) was used to estimate a
distance modulus of 31.4mag, equivalent to 19Mpc.
Description:
The observations were made by one of us (R.H.M.) with the Faint Object
Camera and Spectrograph (FOCAS) attached to the Cassegrain focus of
the 8.2m Subaru telescope, Mauna Kea, Hawaii, on three nights, 2004
November 7-9. The radial velocities were measured using a slitless
method (see Section 2.2) involving images taken through both the
on-band filter and an echelle grism. The on-band filter has a central
wavelength of 5025Å, an FWHM of 60Å, a peak transmission of
0.68, and an equivalent width of 40Å. We conservatively estimate
the calibration errors in FOCAS slitless radial velocities to be of
the order of 10km/s. We estimate an rms of about 0.3" for the
astrometry of our catalog of PNs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 43 155 Detected PN candidates in NGC 821
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See also:
I/284 : The USNO-B1.0 Catalog (Monet+ 2003)
J/MNRAS/394/1249 : New PNe in 6 early-type galaxies (Coccato+, 2009)
J/MNRAS/385/361 : BVRcIc photometry of NGC 821 globular clusters (Spitler+,
2008)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [101/280] FOCAS number
5- 7 I3 --- PNS ? PN.S number (<PNS-EPN NGC821-NNN> in Simbad)
9 I1 h RAh [2] Hour of right ascension (J2000)
11 I1 min RAm [8] Minute of right ascension (J2000)
13- 17 F5.2 s RAs Second of right ascension (J2000)
19 A1 --- DE- [+] Sign of declination (J2000)
20- 21 I2 deg DEd [10/11] Degree of declination (J2000)
23- 24 I2 arcmin DEm Arcminute of declination (J2000)
26- 30 F5.2 arcsec DEs Arcsecond of declination (J2000)
32- 36 F5.2 mag m5007 ? m(5007) magnitude (1)
38- 41 I4 km/s HRV ? Heliocentric radial velocity
43 A1 --- Note [ab] Notes (2)
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Note (1): The [OIII]5007Å fluxes measured through the on-band filter are
traditionally expressed in magnitudes m(5007), using the definition
introduced by Jacoby (1989ApJ...339...39J 1989ApJ...339...39J):
m(5007)=-2.5logI(5007)-13.74
Note (2): Flag as follows:
a = Rejected as PN: wrong velocity for NGC 821 if interpreted as 5007Å
emitter.
b = Velocity taken from the PN.S study (Planetary Nebulae Spectrograph group;
Coccato et al., 2009, Cat. J/MNRAS/394/1249).
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 06-Jul-2012