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J/MNRAS/462/3376    Radial velocities of NGC 6822 carbon stars (Thompson+, 2016)

The rotation of the halo of NGC 6822 from the radial velocities of carbon stars. Thompson G.P., Ryan S.G., Sibbons L.F. <Mon. Not. R. Astron. Soc., 462, 3376-3385 (2016)> =2016MNRAS.462.3376T (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, carbon ; Stars, giant ; Radial velocities Keywords: techniques: radial velocities - stars: AGB and post-AGB - galaxies: individual: NGC 6822 - galaxies: kinematics and dynamics - Local Group - infrared: stars Abstract: Using spectra taken with the AAOmega spectrograph, we measure the radial velocities of over 100 stars, many of which are intermediate age carbon stars, in the direction of the dwarf irregular galaxy NGC 6822. Kinematic analysis suggests that the carbon stars in the sample are associated with NGC 6822, and estimates of its radial velocity and galactic rotation are made from a star-by-star analysis of its carbon star population. We calculate a heliocentric radial velocity for NGC 6822 of -51±3km/s and show that the population rotates with a mean rotation speed of 11.2±2.1km/s at a mean distance of 1.1kpc from the galactic centre, about a rotation axis with a position angle of 26°±13°, as projected on the sky. This is close to the rotation axis of the HI gas disc and suggests that NGC 6822 is not a polar ring galaxy, but is dynamically closer to a late-type galaxy. However, the rotation axis is not aligned with the minor axis of the AGB isodensity profiles and this remains a mystery. Description: Wide band, low-resolution spectra for 323 target objects, out to ∼8kpc from the galactic centre, were obtained using the AAOmega multifibre spectrograph on 2011 August 30 and 31 (Sibbons et al., 2015, Cat. J/A+A/574/A102). An optical fibre was placed over each target object position on the field plate of the spectrograph and throughout this paper, objects are referred to by their fibre number. Wide band gratings 385R and 580V were used in the spectroscopy but this study uses only the spectra from grating 385R, which has a bandpass from 5687 to 8856Å, covering the CaII triplet, dispersed at 1.6Å/pix. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 83 282 Individual results for objects meeting the criteria (hght≥0.2, -200km/s≤HV≤+200km/s)
See also: J/AJ/123/832 : C star population in NGC 6822 (Letarte+, 2002) J/A+A/540/A135 : AGB population of NGC 6822 (Sibbons+, 2012) J/A+A/574/A102 : AGB candidates in NGC 6822 (Sibbons+, 2015) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Fibre Fibre number (1) 5- 10 I6 --- ID Target identifier (1) 12- 17 F6.2 deg RAdeg Right ascension (J2000) (1) 19- 24 F6.2 deg DEdeg Declination (J2000) (1) 26- 29 F4.1 mag Imag ? I-band magnitude of C-type AGBs in the inner region from the catalogue of Letarte et al. (2002, Cat. J/AJ/123/832) 31- 34 F4.2 kpc Dist Distance of the object from the putative galactic centre (2) 36- 40 A5 --- PClass Photometric classification (3) 42- 45 A4 ---- SClass Spectroscopic classification (1) 47- 48 I2 --- SNR1 ? SNR in the band 8560-8650Å for the night of 2011 August 30 51- 54 F4.2 --- hght1 [0.2/0.84]? Strength of the cross-correlation function for the night of 2011 August 30 56- 59 I4 km/s HV1 ? Heliocentric radial velocity returned from fxcor for the night of 2011 August 30 61- 63 I3 km/s e_HV1 ? rms uncertainty on HV1 66- 67 I2 --- SNR2 ? NR in the band 8560-8650Å for the night of 2011 August 31 69- 72 F4.2 --- hght2 [0.21/0.89]? Strength of the cross-correlation function for the night of 2011 August 31 74- 77 I4 km/s HV2 ? Heliocentric radial velocity returned from fxcor for the night of 2011 August 31 79- 81 I3 km/s e_HV2 ? rms uncertainty on HV2 83 A1 --- Flag [CM] flag showing which objects were used in the composite templates (4)
Note (1): from Sibbons et al. (2015, Cat. J/A+A/574/A102) Note (2): Distance of the object from the putative galactic centre (RA=19:44:56 (296.2333°), DE=-14:48:0.6 (-14.8017°), J2000, centred on the optical co-ordinates of NGC 6822 adopted by Sibbons et al. (2012, Cat. J/A+A/540/A135 and 2015, Cat. J/A+A/574/A102) and a galactic distance of 490kpc (Mateo, 1998ARA&A..36..435M). Note (3): from Sibbons et al. (2012, Cat. J/A+A/540/A135) Note (4): Flag as follows: C = C-type composite M = M-type composite
History: From electronic version of the journal
(End) Patricia Vannier [CDS] 23-Mar-2018
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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