J/MNRAS/490/2905 Andromeda XXVII and the North West Stream (Preston+, 2019)
A dwarf disrupting - Andromeda XXVII and the North West Stream.
Preston J., Collins M.L.M., Ibata R.A., Tollerud E.J., Rich R.M.,
Bonaca A., McConnachie A.W., Mackey D., Lewis G.F., Martin N.F.,
Penarrubia J., Chapman S.C., Delorme M.
<Mon. Not. R. Astron. Soc., 490, 2905-2917 (2019)>
=2019MNRAS.490.2905P 2019MNRAS.490.2905P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Galaxies, nearby ; Stellar distribution ;
Radial velocities ; Photometry ; Spectroscopy ; Optical
Keywords: galaxies: dwarf - galaxies: fundamental parameters -
galaxies: kinematics and dynamics - Local Group
Abstract:
We present a kinematic and spectroscopic analysis of 38 red giant
branch stars, in seven fields, spanning the dwarf spheroidal galaxy
Andromeda XXVII and the upper segment of the North West Stream. Both
features are located in the outer halo of the Andromeda galaxy at a
projected radius of 50-80kpc, with the stream extending for ∼3° on
the sky. Our data are obtained as part of the PAndAS survey and
enables us to confirm that Andromeda XXVII's heliocentric distance is
827±47kpc and spectroscopic metallicity is -2.1+0.4-0.5. We also
re-derive Andromeda XXVII's kinematic properties, measuring a systemic
velocity =-526.1+10.0-11.0km/s and a velocity dispersion that we
find to be non-Gaussian but for which we derive a formal value of
27.0+2.2-3.9km/s. In the upper segment of the North West Stream we
measure mean values for the metallicity =-1.8±0.4, systemic velocity
=-519.4±4.0km/s, and velocity dispersion =10.0±4.0km/s. We also
detect a velocity gradient of 1.7±0.3km/s/kpc on an infall
trajectory towards M31. With a similar gradient, acting in the same
direction, in the lower segment we suggest that the North West Stream
is not a single structure. As the properties of the upper segment of
the North West Stream and Andromeda XXVII are consistent within 90 per
cent confidence limits, it is likely that the two are related and
plausible that Andromeda XXVII is the progenitor of this stream.
Description:
Data for the initial observations were obtained as part of the PAndAS
survey. PAndAS used the 3.6m CFHT with the MegaPrime/MegaCam camera,
comprising 36, 2048x4612, CCDs with a pixel scale of
0.185arcsec/pixel, delivering an almost 1deg2 field of view
(McConnachie et al. 2009Natur.461...66M 2009Natur.461...66M). To enable good colour
discrimination of Red Giant Branch (RGB) stars, g-band (4140-5600Å)
and i-band (7020-8530Å) filters were used.
Spectroscopic data was obtained from seven masks spanning a distance
of ∼120arcmin (∼30kpc) of NW-K1 and crossing the centre of And XXVII.
Three of the masks were observed in 2010 and 2011 (603HaS, 604HaS, and
7And27) and may have been analysed by Collins et al.
(2013ApJ...768..172C 2013ApJ...768..172C, Cat. J/ApJ/768/172) and Martin et al.
(2016ApJ...833..167M 2016ApJ...833..167M, Cat. J/ApJ/833/167), though they are not
explicitly named in either work. The remaining four masks, A27sf1,
A27sf2, A27sf3, and A27sf4, provide us with additional spectroscopic
data obtained using the DEep-Imaging Multi-Object Spectrograph
(DEIMOS) on the Keck II Telescope. Our observations use the OG550
filter with the 1200 lines/mm grating with a resolution of
∼1.1-1.6Å at FWHM. Each mask/site is observed for 1h, split into
3x20min integrations. Observations focus on the Calcium Triplet (CaT)
region located between wavelengths 8400 and 8700Å.
Table A1 contains the details of the observed stars from the masks
across the centre of And XXVII and along NW-K1 with velocities in the
range -650=<v=<50km/s and verr=<20km/s.
Objects:
------------------------------------------------------------------------
RA (ICRS) DE Designation(s)
------------------------------------------------------------------------
00 37 27.09 +45 23 13.0 AndromedaXXVII = And XXVII = LEDA 5057230
------------------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 72 544 Properties of observed stars from the masks
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Loc Location of the star (And XXVII or NW-K1)
11- 16 A6 --- Mask Mask used for the observation
18- 20 I3 --- ID Internal object identifier
22- 23 I2 h RAh Right ascension (J2000)
25- 26 I2 min RAm Right ascension (J2000)
28- 32 F5.2 s RAs Right ascension (J2000)
34 A1 --- DE- Declination sign (J2000)
35- 36 I2 deg DEd Declination (J2000)
38- 39 I2 arcmin DEm Declination (J2000)
41- 44 F4.1 arcsec DEs [] Declination (J2000)
46- 49 F4.1 mag imag CFHT MegaCam i-band magnitude
51- 54 F4.1 mag gmag CFHT MegaCam g-band magnitude
56- 59 F4.1 10nm-1 S/N Sinal to noise ratio
61- 67 F7.1 km/s vLOS Line of sight velocity
69- 72 F4.1 km/s e_vLOS Error on vLOS
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 31-Jan-2023