Integrated magnitudes and mean colors of DDO dwarf galaxies in the UBV system. II. Distances, luminosities, and H I properties

Journal Article · Wed Jun 01 00:00:00 EDT 1983 · Astron. J.; (United States)

DOI:https://doi.org/10.1086/113365· OSTI ID:5895175

de Vaucouleurs, G; de Vaucouleurs, A; Buta, R

An analysis of the properties of the DDO magellanic irregular ''dwarf'' galaxies concludes: (1) The mean effective surface brightness varies with zenith distance as expected from the dependence on sec z of atmospheric extinction and sky brightness. (2) The mean surface brightness is independent of distance modulus (25<..mu../sub 0/<33). (3) The mean absolute magnitude is brighter than average south of +10/sup 0/ declination and fainter near the zenith at Palomar. (4) The mean corrected effective color index is independent of absolute magnitude at M/sup 0//sub T/ <-15, but fainter systems tend to be bluer. (5) The mean absolute magnitude M/sup 0//sub T/ is correlated with distance modulus at ..mu../sub 0/>28; we confirm that the DDO sample is not tricted to dwarf systems and includes galaxies as bright as M/sup 0//sub T/ < or approx. =-18 at ..mu../sub 0/>30. (6) We confirm also that the luminosity class L and luminosity index ..lambda.. are not valid indicators of absolute magnitude for late-type systems beyond ..mu../sub 0/approx. =28 (..delta.. = 4 Mpc). (7) Effective linear diameter and absolute magnitude are highly correlated. (8) Apparent magnitude and 21-cm line flux are loosely correlated, but there is a large range of HI index (hydrogen/luminosity ratio) among the DDO objects at a given Hubble type (Sd to Im). (9) The relative excess or deficiency in hydrogen/luminosity ratio is uncorrelated with mean effective surface brightness. (10) The hydrogen/luminosity ratio residuals are loosely correlated with color residuals. (11) The necessity of correcting H I linewidths for velocity dispersion is once again demonstrated by the conspicuous departure from linearity of the Tully-Fisher relation based on raw linewidths. (12) The derived T-F relation for the DDO sample of late-type systems is in near perfect agreement in slope and zero point with the relation adopted by Bottinelli et al. for normal spiral galaxies of earlier types.

• Research Organization: Department of Astronomy and McDonald Observatory, The University of Texas at Austin, Austin, Texas 78712
• OSTI ID: 5895175
• Journal Information: Astron. J.; (United States), Vol. 88:6
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
GALAXIES
DISTANCE
H1 REGIONS
LUMINOSITY
BRIGHTNESS
COLOR
HYDROGEN
MAGELLANIC CLOUDS
PHOTOMETRY
RADIOWAVE RADIATION
SIZE
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
ELEMENTS
NONMETALS
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
640105* - Astrophysics &amp; Cosmology- Galaxies