Cosmic Flows: Green Bank Telescope and Parkes H i observations
H el e`ne M. Courtois
2
3
R. Brent Tully
2
D. I. Makarov
1
3
S. Mitronova
1
B. Koribalski
5
I. D. Karachentsev
1
3
J. Richard Fisher
4
0
520 Edgemont Road,
Charlottesville, VA 22903, USA
1
Special Astrophysical Observatory,
Russian Academy of Sciences
, N. Arkhyz, KChR, 369167,
Russia
2
Institute for Astronomy, University of Hawaii
, 2680 Woodlawn Drive, Honolulu,
HI 96822, USA
3
Universite Lyon 1
, CNRS/IN2P3/INSU,
Institut de Physique Nucleaire
,
Lyon, France
4
National Radio Astronomy Observatory
5
Australian Telescope National facility
, CSIRO, PO Box 76, Epping NSW 1710,
Australia
A B S T R A C T The neutral hydrogen properties of 1822 galaxies are being studied with the Green Bank 100-m and the Parkes 64-m telescopes as part of the 'Cosmic Flows' programme. Observed parameters include systemic velocities, profile linewidths and integrated fluxes. The linewidth information can be combined with the optical and infrared photometry to obtain distances. The 1822 H I observations complement an inventory of archives. All told, H I linewidth information is available for almost all of five samples: (i) luminosity-linewidth correlation calibrators; (ii) zero-point calibrators for the Type Ia supernova scale; (iii) a dense local sample of spiral galaxies with MKs < 21 within 3000 km s1; (iv) a sparser sample of 60-m selected galaxies within 6000 km s1 that provides an all-sky coverage of our extended supercluster complex; and (v) an even sparser sample of flat galaxies, extreme edge-on spirals, extending in a volume out to 12 000 km s1. The H I information for 13 941 galaxies, whether from the archives or acquired as part of the Cosmic Flows observational programme, is uniformly re-measured and made available through the Extragalactic Distance Database website.
1 I N T R O D U C T I O N
Cosmography is the study of the large-scale structure of the
universe. A complete analysis involves observational and interpretive
components. With spectroscopic information, a complete sample of
galaxies within specified limits describes the structure in the redshift
space. If distance measures are available for at least some fraction
of the spectroscopic sample, then steps can be taken to transform to
the physical space. Distance measures allow for the separation of
redshifts into cosmic expansion and deviant (or peculiar)
components. Cosmological simulations and orbit reconstructions provide
tools for the recovery of information about the underlying
distribution of matter from a map of peculiar velocities. The influence of
the dark sector on galaxy motions can be studied from 1 Mpc, the
scale of collapse, to 150 Mpc, the largest scale of useful peculiar
velocity measures.
After great enthusiasm for what could be learned from
peculiar velocity studies in the 1990s (Willick & Strauss 1998; Courteau
et al. 2000), progress slowed primarily because of the challenge
presented by the need for much more and better quality data. If the goal
is to have a dense grid of distance measures to a depth dominated
by the Hubble expansion, then most methodologies for
estimating distances have inadequacies. The Cepheid periodluminosity
(Freedman et al. 2001) and Tip of the Red Giant Branch (TRGB)
(Rizzi et al. 2007) methods have limited successes. The surface
brightness fluctuation (SBF) (Tonry et al. 2001) and Fundamental
Plane (Colless et al. 2001) methods apply to luminous early-type
galaxies that are poorly represented in low-density regions. The
Type Ia supernova (SNIa; Jha, Riess & Kirshner 2007) method
rests on the serendipity, resulting in an accurate but sparse map of
distances. The one well-established methodology that can provide
decent distances with high density over an appropriately large
volume is provided by the correlation between the galaxy luminosity
and rotation rate, the TullyFisher (TF) relation (Tully & Fisher
1977).
Two observations are needed to apply this method: a
spectroscopic measure of the rotation rate, most expeditiously
accomplished by observing the linewidth of a 21-cm neutral hydrogen
profile, and the surface photometry at optical or infrared bands that
monitor old star populations. New capabilities with the facilities
for both the spectroscopy and the photometry are revolutionizing
our capabilities. On the spectroscopic side, the new capabilities are
both realized and promised. We will describe observations with the
100-m Robert C Byrd Green Bank Telescope at the National Radio
Astronomy Observatory (NRAO-GBT) and with the 13-channel
multibeam receiver on the 64-m Parkes telescope. Our programme
also makes use of archival data from ongoing multibeam
observations with the Arecibo telescope (Giovanelli et al. 2005). The
promised capabilities are those that will accrue with the wide-field
interferometric surveys that will cover the entire Southern (ASKAP,
MeerKAT) and Northern hemispheres (Apertif, LOFAR) with
unprecedented sensitivities. As for the photometry, the ground
technology revolution comes from the (...truncated)