J/AJ/154/41 Rotational velocities of M33 (Kam+, 2017)
H I kinematics and mass distribution of Messier 33.
Kam S.Z., Carignan C., Chemin L., Foster T., Elson E., Jarrett T.H.
<Astron. J., 154, 41-41 (2017)>
=2017AJ....154...41K 2017AJ....154...41K (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Galaxies, rotation ; Rotational velocities ;
H I data
Keywords: galaxies: individual: M33 - galaxies: kinematics and dynamics -
Local Group - techniques: interferometric
Abstract:
A new deep HI survey of the galaxy Messier 33 is presented, based on
observations obtained at the Dominion Radio Astrophysical Observatory.
We observe a perturbed outer gas distribution and kinematics in M33,
and confirm the disk warping as a significant twist of the major axis
of the velocity field, although no strong tilt is measured, in
agreement with previous work. Evidence for a new low-brightness HI
component with anomalous velocity is reported. It harbors a large
velocity scatter, as its kinematics both exceeds and lags the rotation
of the disk, and leaks in the forbidden velocity zone of apparent
counterrotation. The observations also reveal wide and multiple-peak
HI profiles that can be partly explained by crowded orbits in the
framework of the warp model. Asymmetric motions are identified in the
velocity field as possible signatures of a lopsided potential and the
warp. The mass distribution modeling of the hybrid Hα-HI
rotation curve favors a cuspy dark matter halo with a concentration in
disagreement with the ΛCDM dark halo mass-concentration
relationship. The total mass enclosed in 23kpc is 8,1010M☉, of
which 11% are stars and gas. At the virial radius of the cuspy halo,
the resulting total mass is 5,1011M☉, but with a baryonic mass
fraction of only 2%. This strongly suggests a more realistic radius
encompassing the total mass of M33 that is well smaller than the
virial radius of the halo, possibly comparable to the size of the HI
disk.
Description:
The primary observations for this study were made with the Synthesis
Telescope (ST) at the Dominion Radio Astrophysical Observatory (DRAO).
This telescope is an east-west interferometer consisting of seven
dishes (∼9m diameter) spaced variously across a baseline range of
13-617m. At 1420MHz, the longest baseline achieves a synthesized
half-power beam width of 49''(EW) by 49''/sinδ(NS) with uniform
weighting, although in the HI line we use a Gaussian taper in the u,v
plane to increase the sensitivity of each velocity channel at the
slight expense of resolution (58"*58"/sinδ).
Observations of M33 consist of Stokes I, Q, U, and V made in a 30MHz
continuum band centered at 1420MHz (λ21cm), Stokes I in a 2MHz
band at 408MHz (λ74cm), and 256 channels within a 2MHz band
centered on the HI line. For this study we use only the HI data
products; future studies will present the total power and polarized
radio emission from M33. The datacube velocity resolution is 2.64km/s
at 21cm, and each channel is ΔV=1.65km/s wide. The band was
centered on a heliocentric velocity of VHEL=-180km/s. The measured
noise per channel is ∼12-13mJy/beam or ΔTB∼1.1K in the
elliptical synthesized beam (58"*114"). To increase sensitivity to the
faint outermost HI disk of M33, a total of six full-synthesis
pointings on and around the galaxy were observed and mosaiced together
(on 09/29/08, 11/05/08, and 12/04/08).
To recover the large-scale HI structures in M33, we merge single-dish
(also known as "short-spacing") data obtained from the Turn-On GALFA
Survey (TOGS) portion of the GALFA-HI survey at Arecibo. These data
were previously published by Putman et al. (2009ApJ...703.1486P 2009ApJ...703.1486P).
Please refer to Section 2 in the paper for additional details about
the 21cm observations.
Objects:
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RA (ICRS) DE Designation(s)
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01 33 50.90 +30 39 35.8 M33 = LEDA 5818
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table9.dat 17 353 Hybrid Hα-HI rotation curve of M33
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See also:
J/A+A/552/A140 : SEDs of M33 HII regions (Relano+, 2013)
J/A+A/522/A3 : M33 CO(2-1) and HI integrated intensity maps (Gratier+, 2010)
Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1- 4 F4.2 [arcsec] lnR [1.61/8.64] Neperian logarithm of the radius ln(R)
6- 11 F6.2 km/s Vrot [6.2/125.49] Rotational velocity (Vrot)
13- 17 F5.2 km/s e_Vrot [0.5/39.13] Uncertainty in Vrot (ΔVrot)
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History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 12-Oct-2017