In our image on the right hand side, M95 is in the lower right corner, while M96 is in the lower middle, and M105 is the bright elliptical galaxy above and left of the picture's center, together with its fainter neighbors NGC 3384 and faint NGC 3889.
Nial R. Tanvir of the Cambridge Astronomy group has investigated this group of galaxies with the Hubble Space Telescope (Tanvir et.al. 1995, 1999). He and his coworkers found 8 Delta Cephei variable stars in the brightest galaxy of the group, M96, and were able to derive its distance from the Cepheid period-luminosity relation: M96 is 231+/-13 times more remote from us than the Large Magellanic Cloud, thus 12.7+/-0.8 Mpc (41+/-2 million light years).
An improvement of this value is hoped to be obtained from ongoing HST observations of Cepheid variables in the group galaxies M95 and UGC 5889 (both spirals). A first result was obtained for M95 in 1996-97 by the HST H0 Key Project Team (Graham et.al. 1997). They obtained a distance of 10.05+-0.88 Mpc (32.8+-2.9 million light years), which after correction for the new Cepheid distance scale becomes 10.90+-0.95 Mpc (35.5+-3.1 million light years). As a mean value of the two distances obtained in the work of Tanvir and the H0 key project team, we will use a distance of 38 million light years here.
From the distance derived here, it is possible to gauge a diameter-velocity dispersion-relation for elliptical galaxies, namely by using the galaxies M105 and NGC 3377. By the relation obtained for this, the distance of the Virgo and Coma clusters of galaxies could be estimated; one obtains a distance of 18.3+/-2.0 Mpc (60+/-6 million light years) for the Virgo cluster, and of 105+/-11 Mpc (~340 million light years) for the Coma cluster of galaxies. (The Virgo cluster distance may be estimated from that of the M96 group also by other methods, yielding about the same value).
The Coma distance then allows to estimate the value of the current Hubble constant (H0, "Hnaught") to be
The M96 group may be physically related to the M66 group which is roughly at the same distance and situated rather nearby in the sky.
The following table lists some data of the M96 or Leo I group members listed above (most data from the Sky Catalogue 2000.0):
Galaxy Name II RA (2000.0) Dec type m_v dim RVKey:
NGC 3299 H III.54 10:36.4 +12:42 SABdm 13.29p 2.1x1.7 465 M95 NGC 3351 10:44.0 +11:42 SBb 9.71 7.4x5.1 649 M96 NGC 3368 10:46.8 +11:49 Sbp 9.24 7.1x5.1 766 UGC 5889 NGC 3377A 10:47.4 +14:04 SABm 14.15p 2.0x1.9 449 NGC 3377 H II.99 10:47.7 +13:59 E5 10.21 4.4x2.7 595 M105 NGC 3379 10:47.8 +12:35 E1 9.26 4.5x4.0 752 NGC 3384 H I.18 10:48.3 +12:38 E7 9.96 5.9x2.6 641 NGC 3412 H I.27 10:50.9 +13:25 E5 10.55 3.6x2.0 737 NGC 3489 H II.101 11:00.3 +13:54 E6 10.33 3.7x2.1 576
Last Modification: September 5, 2005