M101 Group

Dave Riebel & Justice Bruursema

12 Februrary 2007

Basic Info Located in the Ursa Major

constellation Part of the Virgo supercluster Brightest member, M101 is the

pinwheel galaxy Main members consist of

about 5-8 companion galaxies as defined by

NGC Fouque et al. survey Lyons Groups of Galaxies Catalog Giuricin et al. Nearby Optical Galaxy

survey

Group MembersName Type Redshift* (km/s) mV*

M101 SAB(rs)cd 241 2 8.3

NGC 5204 SA(s)m 201 1 11.7

NGC 5474 SA(s)cd pec 273 9 11.3

NGC 5477 SA(s)m 304 5 14.4

NGC 5585 SAB(s)d 305 3 11.2

UGC 8837 IB(s)m 144 3 13.8

UGC 9405 Im 222 6 17

*data gathered from NED **other possible members are NGC 5238 & UGC 8508

Image from www.nightsky.at/Photo/Gal/M101_wide_APO.html

Comparing Galaxy Groups

Table from Karachentsev 1996

There have been no dwarf spheroidal galaxies with a diameter larger than 1 kpc detected in the NGC 5236 & M101 groups

M101 or NGC 5457 Very large, bright, nearly face on late-type spiral

Bulgeless, extremely thin disk 28.8 arcmin x 26.9 arcmin = 1/5 the area of a full moon ~52 kpc = 2X the size of the Milky Way about 7.7 Mpc away, as determined by:

Cepheid distances (Kelson et al. 1996) Planetary Nebulae distances (Feldmeier et al. 1996) Red Supergiant Var Stars (Jurcevic 2006)

Mass is uncertain, often cited as 1.1·1011 Mo Problem is probably due to low surface brightness Studying dynamics of HII regions should help, although Puerari et

al. only got 9.8·1010 within 10kpc in 2004

More on M101 Gyser in nucleus (Moody et al. 1995)

Intermediate mass black hole HII Regions – GHRs

Home of SSCs ~1000 O stars, M101 has GHRs 2 orders of magnitude bigger than Milky Way’s

X-ray binaries (recently found a 32.69hr eclipsing binary) ULX sources and UL-SSS (Also found in NGC 5204)

possible intermediate mass black holes Hypernova – NGC 5471B, 5·1052 ergs (Chen, R. et al., 2002)

Super Novae observed (1909, 1951, 1970*) Not symmetric (in outer regions), core displaced from center

of disk Perhaps distorted by near collision (NGC 5474)

NGC 5474 2nd closest companion

to M 101 Z velocity consistent

with other studies (6-9 km/s)

Bulge not coincident with kinematic center – Background?

Unanswered Questions Better mass estimates for M101 Photometry for NGC 5474 to understand star

formation history What is the mechanism for the formation of

GHR’s? (related to efficiency of molecular gas clouds to make new stars?)

Can we use M101 and NGC 5204 to put better mass constraints on the BH’s of ULXs? (Vierdayanti et al. 2006)

References Chen, R., et al., 2002, A Critical Examination of Hypernova Remnant Candidates in

M101, AJ, 123, 2462. Feldmeier, J., et al., 1996, The Planetary Nebulae Distance to M101 ,ApJ, 461, L25. Kelson, DD, et al., 1996, The Extragalactic Distance Scale Key Project. III…, ApJ,

463, 26. Karachentsev, I., 1996, The Local Group in comparison with other nearby groups of

galaxies, A&A, 305, 33. Kong, A., Di Stefano, R., 2006, Ultra Luminous Supersoft X-Ray Sources in Nearby

Galaxies. Liu, J., et al., 2006, Discovery of an eclipsing binary with a 32.69hr period in M101…,

ApJ, 653, 602. Moody, J., et al., 1995, Evidence for mass outflow from the nucleus of M101: Knots,

Rings and a Geyser, AJ 110, 2088. Rownd B. K., et al. H I distribution and kinematics in the peculiar spiral galaxy NGC

5474, AJ 108, 1638. Vierdayanti, K., et al., 2006, Do ULX Sources Really Contain Intermediate-Mass

Black Holes?, PASJ, 58, 915. Thanks to http://hubblesite.org/newscenter/archive/releases/2006/10/ for the M101

picture and current distance/ size info.