The Milky Way, Local Galaxies, and the Infrared Tully-Fisher Relation
Abstract
Using the near-infrared fluxes of local galaxies derived from Cosmic Background Explorer (COBE)/Diffuse Infrared Background Experiment (DIRBE)^5^ J-(1.25 micron) K- (2.2 micron), and L-band (3.5 micron) maps and published Cepheid distances, we construct Tully-Fisher (TF) diagrams for nearby galaxies. The measured dispersions in these luminosity-line width diagrams are remarkably small: σ_J_ = 0.09 mag, σ_K_ = 0.13 mag, and σ_L_ = 0.20 mag. These dispersions include contributions from the intrinsic TF relation scatter and the errors in estimated galaxy distances, fluxes, inclination angles, extinction corrections, and circular speeds. For the J and K bands, Monte Carlo simulations give a 95% confidence interval upper limit on the true scatter in the TF diagram of σ_J_ <= 0.35 and σ_K_ <- 0.45. We determine the Milky Way's luminosity and place it in the TF diagram by fitting a bar plus exponential disk model of the Milky Way to the all- sky DIRBE maps. For "standard" values of its size and circular speed (Sun-Galactic center distance R_0_ = 8.5 kpc and {THETA}_0_ = 220 km s^- 1^), the Milky Way lies within 1.5 σ of the TF relations. We can use the TF relation and the Cepheid distances to nearby bright galaxies to constrain R_0_ and {THETA}_0_: 1.63 log ({THETA}_0_/220 km s^-1^) - log (R_0_/8.5 kpc) = 0.08 +/- 0.03. Alternatively, we can fix the parameters of the Galaxy to their standard values, ignore the Cepheid zero point, and use the TF relation to determine the Hubble constant directly: H_0_ = 72 +/- 12 km s^-1^ Mpc^-1^. We have also tested the TF relation at longer wavelengths, where the emission is dominated by dust. We find no evidence for a TF relation at wavelengths beyond 10 microns. The tight correlation seen in the L band suggests that stellar emission dominates over the 3.3 micron polycyclic aromatic hydrocarbon emission.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1996
- DOI:
- 10.1086/178181
- arXiv:
- arXiv:astro-ph/9604151
- Bibcode:
- 1996ApJ...473..687M
- Keywords:
-
- GALAXIES: DISTANCES AND REDSHIFTS;
- GALAXIES: FUNDAMENTAL PARAMETERS;
- GALAXIES: PHOTOMETRY;
- Astrophysics
- E-Print:
- 11 pages, aaspp macro, 3 figures, submitted to the Astrophysical Journal. Also available at http://www.astro.princeton.edu/~san/gal.html