THE ASTROPHYSICAL JOURNAL, 442:523-537, 1995 April 1

   A MULTIPARAMETRIC ANALYSIS OF THE EINSTEIN SAMPLE OF EARLY-TYPE GALAXIES.
    II. GALAXY FORMATION HISTORY AND PROPERTIES OF THE INTERSTELLAR MEDIUM

                   PAUL B. ESKRIDGE AND GIUSEPPINA FABBIANO
        Harvard-Smithsonian Center for Astrophysics, 60 Garden Street,
                              Cambridge, MA 02138

                                      AND

                                 DONG-WOO KIM
 Harvard-Smithsonian Center for Astrophysics; and Department of Astronomy and
   Space Science, Chungnam National University, Taejon, 305-764, South Korea


                                   ABSTRACT

       We have conducted bivariate and multivariate statistical analysis of
    data measuring the integrated luminosity, shape, and potential depth of
    the Einstein sample of early-type galaxies (presented by Fabbiano et
    al. 1992, ApJS, 80, 531).  We find significant correlations between the
    X-ray properties and the axial ratios (a/b) of our sample, such that
    the roundest systems tend to have the highest L_X and L_X/L_B.  The
    most radio-loud objects are also the roundest.  We confirm the
    assertion of Bender et al. (1989, A&A, 217, 35) that galaxies with high
    L_X are boxy (have negative a_4).  Both a/b and a_4 are correlated with
    L_B, but not with IRAS 12 um and 100 um luminosities.  There are strong
    correlations between L_X, Mg_2 and sigma_v in the sense that those
    systems with the deepest potential wells have the highest L_X and Mg_2.
    Thus the depth of the potential well appears to govern both the ability
    to retain an ISM at the present epoch and to retain the enriched ejecta
    of early star formation bursts.  Both L_X/L_B and L_6 (the 6 cm radio
    luminosity) show threshold effects with sigma_v, exhibiting sharp
    increases at log(sigma_v) ~ 2.2.  Finally, there is clearly an
    interrelationship between the various stellar and structural
    parameters: The scatter in the bivariate relationships between the
    shape parameters (a/b and a_4) and the depth parameter (sigma_v) is a
    function of abundance in the sense that, for a given a_4 or a/b, the
    systems with the highest sigma_v also have the highest Mg_2.
    Furthermore, for a constant sigma_v, disky galaxies tend to have higher
    Mg_2 than boxy ones.  Alternatively, for a given abundance, boxy
    ellipticals tend to be more massive than disky ellipticals.  One
    possibility is that early-type galaxies of a given mass, originating
    from mergers (boxy ellipticals), have lower abundances than
    "primordial" (disky) early-type galaxies.  Another is that disky inner
    isophotes are due not to primordial dissipational collapse, but to
    either the self-gravitating inner disks of captured spirals or the
    dissipational collapse of new disk structures from the premerger ISM.
    The high measured nuclear Mg_2 values would thus be due to enrichment
    from secondary bursts of star formation triggered by the merging event.

    Subject headings: galaxies: elliptical and lenticular, cD -- galaxies:
                      ISM -- galaxies: structure -- X-rays: galaxies