2005/04/30 by James Pizagno, Francisco Prada, David H. Weinberg +13 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics #Context (archaeology) #Disc galaxy #Fundamental plane (elliptical galaxies) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Galaxy rotation curve #Halo #Mass ratio #Physics #Scale height #Star formation #Stellar mass #Stellar, planetary, and galactic studies #Thick disk #Thin disk #astro-ph
paper · pdf · doi:10.1086/491614
published as Astrophys.J. 633 (2005) 844-856 · 18 pages, 2 tables, 7 figures, Accepted to ApJ, Table 1 updated, otherwise minor changes
arxiv created 2005/11/02 · openalex publication_date 2005/11/07 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We investigate the correlations among stellar mass ( M * ), disk scale length ( R d ), and rotation velocity at 2.2 disk scale lengths ( V 2.2 ) for a sample of 81 disk-dominated galaxies (disk/total ≥ 0.9) selected from the SDSS. We measure V 2.2 from long-slit Hα rotation curves and infer M * from galaxy i -band luminosities ( L i ) and g - r colors. We find logarithmic slopes of 2.60 ± 0.13 and 3.05 ± 0.12 for the (forward fit) L i - V 2.2 and M * - V 2.2 relations, somewhat shallower than most previous studies, with intrinsic scatter of 0.13 and 0.16 dex, respectively. Our direct estimates of the total-to-stellar mass ratio within 2.2 R d , assuming a Kroupa IMF, yield a median ratio of 2.4 for M * > 10 10 M ☉ and 4.4 for M * = 10 9 -10 10 M ☉ , with large scatter at a given M * and R d . The typical ratio of the rotation speed predicted for the stellar disk alone to the observed rotation speed at 2.2 R d is ~0.65. The distribution of scale lengths at fixed M * is broad, but we find no correlation between disk size and the residual from the M * - V 2.2 relation, implying that the M * - V 2.2 relation is an approximately edge-on view of the disk galaxy fundamental plane. Independent of the assumed IMF, this result implies that stellar disks do not, on average, dominate the mass within 2.2 R d . We discuss our results in the context of infall models where disks form in adiabatically contracted cold dark matter halos. A model with a disk-to-halo mass ratio m d = 0.05 provides a reasonable match to the R d - M * distribution for spin parameters λ ranging from ~0.04 to 0.08, and it yields a reasonable match to the mean M * - V 2.2 relation. A model with m d = 0.1 predicts overly strong correlations between disk size and M * - V 2.2 residual. Explaining the wide range of halo-to-disk mass ratios within 2.2 R d requires significant scatter in m d values, with systematically lower m d for galaxies with lower M * or lower stellar surface density Σ * .