J/AJ/164/20 RGB radial velocities in M31 northeast shelf fields (Escala+, 2022)
Kinematics and Metallicity of Red Giant Branch Stars in the Northeast Shelf of
M31.
Escala I., Gilbert K.M., Fardal M., Guhathakurta P., Sanderson R.E.,
Kalirai J.S., Mobasher B.
<Astron. J., 164, 20 (2022)>
=2022AJ....164...20E 2022AJ....164...20E
ADC_Keywords: Stars, giant; Spectra, optical; Radial velocities
Keywords: Galaxy structure ; Andromeda Galaxy ; Galaxy mergers ; Galaxy
dynamics
Abstract:
We obtained Keck/DEIMOS spectra of 556 individual red giant branch
stars in four spectroscopic fields spanning 13-31 projected kpc along
the northeast (NE) shelf of M31. We present the first detection of a
complete wedge pattern in the space of projected M31-centric radial
distance versus line-of-sight velocity for this feature, which
includes the returning stream component of the shelf. This wedge
pattern agrees with expectations of a tidal shell formed in a radial
merger and provides strong evidence in favor of predictions of Giant
Stellar Stream (GSS) formation models in which the NE shelf originates
from the second orbital wrap of the tidal debris. The observed
concentric wedge patterns of the NE, west (W), and southeast (SE)
shelves corroborate this interpretation independently of the models.
We do not detect a kinematical signature in the NE shelf region
corresponding to an intact progenitor core, favoring GSS formation
models in which the progenitor is completely disrupted. The shelf's
photometric metallicity ([Fe/H]phot) distribution implies that it is
dominated by tidal material, as opposed to the phase-mixed stellar
halo or the disk. The metallicity distribution
([Fe/H]phot=-0.42±0.01) also matches the GSS, and consequently
the W and SE shelves, further supporting a direct physical association
between the tidal features.
Description:
We observed five slit masks targeting M31's northeast (NE) shelf with
the DEep Imaging Multi-Object Spectrograph (DEIMOS) instrument on Keck
II as part of the Spectroscopic and Photometric Landscape of
Andromeda's Stellar Halo (SPLASH) survey. We utilized the 1200line/mm
grating, which has a spectral dispersion of 0.33Å/pixel, with the
OG550 order-blocking filter and a central wavelength of 7800Å for
our science configuration. The spectroscopic fields were observed in
fall 2011 with ∼1hr exposures.
Objects:
----------------------------------------
RA (2000) DE Designation(s)
----------------------------------------
00 42 44.33 +41 16 07.5 M 31 = M 31
----------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 64 556 Catalog of velocity measurements for M31 RGB stars
in the northeast shelf fields
--------------------------------------------------------------------------------
See also:
J/MNRAS/369/120 : Kinematic survey of planetary nebulae in M31 (Merrett+, 2006)
J/ApJ/663/960 : Radial velocities of Leo I stars (Sohn+, 2007)
J/ApJ/748/29 : Spectroscopy of M87 globular clusters (Romanowsky+, 2012)
J/ApJ/752/45 : SPLASH Stellar spectroscopy of M31 satellites (Tollerud+, 2012)
J/ApJ/765/28 : CFHTLS galaxies with faint tidal features (Atkinson+, 2013)
J/MNRAS/442/3544 : Kinematic tracers in Umbrella galaxy (Foster+, 2014)
J/ApJS/215/9 : PHAT X. UV-IR photometry of M31 stars (Williams+, 2014)
J/ApJ/868/55 : Large-scale structure M31 halo. II. PAndAS (McConnachie+, 2018)
J/ApJ/883/128 : alpha & Fe abundances in giant stellar stream (Gilbert+, 2019)
J/ApJ/889/177 : RGB abundances in disk, stream & halo of M31 (Escala+, 2020)
J/ApJ/902/51 : Abundances for M31 RGB stars from Keck/DEIMOS (Escala+, 2020)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- ID Object identifier
8- 9 I2 h RAh [00] Hour of Right Ascension (J2000)
11- 12 I2 min RAm [47/53] Minute of Right Ascension (J2000)
14- 18 F5.2 s RAs Second of Right Ascension (J2000)
20 A1 --- DE- [+] Sign of the Declination (J2000)
21- 22 I2 deg DEd [41/42] Degree of Declination (J2000)
24- 25 I2 arcmin DEm Arcminute of Declination (J2000)
27- 30 F4.1 arcsec DEs Arcsecond of Declination (J2000)
32- 36 F5.2 mag Vmag [22.1/24.4] Extinction-corrected V-band Vega
magnitude
38- 42 F5.2 mag Imag [20.1/22.4] Extinction-corrected I-band Vega
magnitude
44- 47 F4.2 mag e_Vmag [0.01/0.2] Uncertainty in Vmag
49- 52 F4.2 mag e_Imag [0.01/0.2] Uncertainty in Imag
54- 59 F6.1 km/s RVel [-541/-100] Heliocentric velocity (1)
61- 64 F4.1 km/s e_RVel [2/21] Uncertainty in RVel
--------------------------------------------------------------------------------
Note (1): The velocity uncertainty is determined from the scaled
cross-correlation based error (Howley+, 2013ApJ...765...65H 2013ApJ...765...65H) and a
systematic error component (Simon & Geha, 2007ApJ...670..313S 2007ApJ...670..313S), but
does not include statistical uncertainties on the A-band correction
(Section 2.1).
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 21-Oct-2022