Galaxies and the Universe - Environmental Effects on Galaxies

Galaxies and the Universe - Environmental Effects on Galaxies

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Unformatted text preview: 1/15/12 Gala ie and he Uni e e - En i onmen al Effec E on Gala ie E G G , ( , ). T .A , , , ( ). I , .T : (1) (2) (3) , M orphological t pe s .I " T : ", : D E+S0 S+I R 93 56 38 P 6 14 F E S0 , " 20 < 6 < 24 48 D .T , S .I ( S ( ) D , 1980 A J 236, 351). H 4 5( AAS) : .a . a.ed /keel/gala ie /en i onmen .h ml 1/11 1/15/12 Gala ie and he Uni e e - En i onmen al Effec on Gala ie O efe e fi d hi e a i i hi a i g e c e , i h ga a ie i he c e bei g E/S0. C ide a i f he g ibi i ha diffe e c e i g ca e a d de i ie g a diffe e a e c ica e he he edi e -e i e i e he e, i ha f ee i g he ( )ga a ai a e ea e ch, i i e f, ' gi e he b e ed c e a i . He e a e he h g - de i e a i f Ga a Z , fi f e i ica .a . a.ed /keel/gala ie /en i onmen .h ml 2/11 1/15/12 Gala ie and he Uni e e - En i onmen al Effec on Gala ie f ac ion , hen fo bl e ellip ical and ed pi al ( he e appea ed in Bamfo d e al. 2009 MNRAS 393, 1324). The e a e e e al po ibili ie fo hi , mo l conce ned i h ge ing id of ga - ich pi al . Pe hap (1) pi al gala ie co ldn' fo m in p o ocl e . Thi ha o ble if man cl e a e j no collap ing o of he H bble flo . (2) Spi al co ld n in o S0 if he a e ipped ei he b di ec colli ion o b am p e e of he in acl e ga , incl ding in bo h ca e "gala ha a men " (Moo e e al. 1996 Na e 379, 613). (3) Spi al co ld n in o ellip ical gala ie ia me ge . In all he e ca e , he p ope ie of S0 ma be c cial - do he ha e di ib ion of l mino i and di k/b lge ligh ha a e con i en i h o igin a pi al ? Thei pho ome ic p ope ie a e no con i en i h imple e pec a ion in he e ca e , ha i i h p e e ing he di k/b lge a io and di k geome (B ein 1979: ApJ S ppl 41,435; ApJ 234, 435, 234, 829, D e le 1980). Thi ma mean ha S0 eall a en' clo el ela ed o pi al , o i mo e likel mean ha (1) he imple e pec a ion a en' eali ic eno gh and (2) ha S0 a e no a homogeneo cla (a an den Be gh ha a g ed). Fo e ample, if he di k of an S0 i hea ed d ing emo al of he ga , a hicke di k ill e l han he o iginal pi al had. Thi i na oidable if .a . a.ed /keel/gala ie /en i onmen .h ml 3/11 1/15/12 Gala ie and he Uni e e - En i onmen al Effec on Gala ie he ga con ib e ignifican l o he di k ma den i , beca e he local ma den i con ol he e ical e en of a ella di k fo a gi en eloci di pe ion. The connec ion gi e he cla ical Oo limi (di c ed, fo e ample, in Binne and T emaine p. 199). Th , ei he a di ec colli ion be een ga - ich gala ie o am- p e e ipping ( ee belo ) co ld p ff p an ini iall hin di k. F he mo e, one ma b ild a b lge b ab o p ion of mall ga - ich companion and cce i e a b , hich migh ha e once been ea ie in p o ocl e (No man 1987, St arburst s and Gala Ev olut ion, Mo iond mee ing, p. 483). Finall , a ipped pi al di k ill fade i h ime, ini iall fa e han he b lge ince i con ain mo e ma i e a , o ha he di k/b lge a io ill dec ea e i h ime. The majo p oblem hen i ha man S0 ha e b lge ha a e picio l b igh compa ed o pi al . So ho man kind of S0 a e he e? Gas de ficie nc ha been infe ed f om H I mea emen fo pi al in cl e . Man e l a e mma i ed b Ha ne , Gio anelli, and Chinca ini 1984 (Ann Re A&A 22, 445). In a global en e, one ma define a ( a i ical) H I deficienc fac o gi en an a e age fo "no mal" gala ie of he ame mo phological pe < M >, ch ha fo ob e ed ma M he deficienc i (M- < M >)/< M > = 1 - M/< M >, occa ionall gi en in loga i hmic fo m. A ho n in hei Fig. 3 (f om NED/Le el 5), he mo deficien pi al a e fo nd in cl e co e ; he e A deno e he Abell adi fo cl e , abo 1.6 Mpc fo a Vi go di ance of 16 Mpc. Thi gge emo al of he ga fo ho e gala ie ha come clo e o he den e co e. A f he gge i e co ela ion e i be een he f ac ion of H I - deficien gala ie in a cl e and i ho ga con en , mea ed h o gh i X- a l mino i (Gio anelli and Ha ne 1985 ApJ 292, 404, ep od ced co e of he AAS): .a . a.ed /keel/gala ie /en i onmen .h ml 4/11 1/15/12 Gala ie and he Uni e e - En i onmen al Effec The e i he e i a e a big i he e a he he hi e a i i ece a i g c e a i be ee e a c e ich e a d L . S ch g ba e ec ac a e i H I - i i he ga a ha bee .a on Gala ie eig ab he a e f i i g, i ce d e h ga i e ed, he he a i d f ISM a e e a e ab e. A a b ai ed b Ca a e e a . 1990 (AJ 100, 604), h a ed he h e Vi g C e c e e di ha a e i i g i i ed i a . Thei h e c e a i h he e, he e each ag ified 5 i e f ea e f c a i (c e AAS): . a.ed /keel/gala ie /en i onmen .h ml 5/11 1/15/12 Gala ie and he Uni e e - En i onmen al Effec on Gala ie Chung et al. have produced a higher- qualit version, with wider coverage as well: .a . a.ed /keel/gala ie /en i onmen .h ml 6/11 1/15/12 Gala ie and he Uni e e - En i onmen al Effec on Gala ie This strongly suggests a dominant role for ram- pressure stripping rather than collisions, since the ram pressure v2/2 (perhaps amplified by turbulence at the ISM- IGM interface) varies with location in the cluster. They do note that some stripped galaxies do seem to be undergoing tidal encounters, so that ram pressure isn't necessarily the whole story. One may also look for galaxies that are in the act of being stripped - galaxies in which we can see the gas being removed by no visible cause, so that direct tidal effects are ruled out (except for the tidal shock of the overall cluster field if the galaxy suddenly plunges into it, and that would affect stars and gas together). One such candidate is NGC 3312 in the Hydra I cluster (Abell 1060). As noted by Gallagher 1978 (ApJ 223, 386), this giant spiral shows diffuse matter that appears to be streaming away from part of the disk, and is projected quite close to the center of the cluster. NGC 2276 and NGC 1961 were once good candidates, but more detailed work showed that their oddities look more like weak tidal disturbances (in particular the stars and gas share the same disk geometry). Perhaps more convincing is the bizarre H I distribution in NGC 4438 (see Cayatte et al.), but a strong tidal encounter is also involved here so that the interpretation is not so clear- cut. Looking at nearby spirals claimed to show evidence for stripping, one usually finds that tidal effects are at least as likely to be involved, although the combination might make stripping work in places that it couldn't happen by itself. The most convincing evidence for ongoing ram- pressure effects has come in the form of soft X- ray and optical emission- line trails from galaxies moving rapidly through dense clusters. Two such are known in Abell 1367. At higher redshift, I'll point to the galaxy C153 in Abell 2125 (which was already shown but not marked below). (More information on C153). .a . a.ed /keel/gala ie /en i onmen .h ml 7/11 1/15/12 Gala ie and he Uni e e - En i onmen al Effec T K ,HIS ( HI Y (1989, A J 344, 171) CO ( H2) , HI HI NGC 3628, H . 1987 A J 229, 83; Y T C ; . , .T .a .S . (1986, A J 310, 660) CO HI .T CO CO . 1983 A J 269, 136). . .T =0.1-0.5 ( on Gala ie AAS) . a.ed /keel/gala ie /en i onmen .h ml B che r-Oe mle r e ffe c , .S B O 1978 (A J 219, 18). T : F . 13 8/11 1/15/12 Gala ie and he Uni e e - En i onmen al Effec on Gala ie La e die ha e c fi ed he e a e ce f ch ai i c e a de ed hif (f e a e, D e e e a . 1985, A J 288, 481) h gh he e i e e ide ce ha he b e ga a ie a e f e e i igh , e ha i e ac i g c (La e a d He 1988 A J 330, 596). HST i agi g (e.g. Oe e e a . 1997 A J 474, 561) a e i c ea ha a f he a a b e ga a ie a e e ec ab a i a , i h he e c e bei g i e ich i i a . Whi e e e ge a d ida i e ac i a e ee , he ca be he h e , he e da a a e i c ea ha i c e , e a e dea i g i h he h e a e a f a i f i a i E/S0 9 ea . S d f a c e i hi he a fe 10 e a z=0.83 b a D e a . (2000 A J 541, 95) add he i e e i g i e ha he e ge e a hich a b ha e f ed e i ica ca be di i g i hed i c , a d ha he f ac i f i a ha eached 39% ( f d f a ich c e i eighb h d). The B che - Oe e effec i e ed hif de e de , a h gh i i ea i e a a z 0.4. The e a e a fe e ich c e f ed ga a ie a ab z=0.4 (C 0024+1654, f e a e, Sch eide , D e e , & G 1989 AJ 92, 523), a d ich c e i e Abe 2125 a z=0.25 (a HST de ai f a f hi c e i h be ) hich a e a ich i i a e be , ha he de i hi f a c e a be ei a ha ed hif per se. If , e ee he effec beca e ha e c ide ica c e d ' a a e a ge i he a e a hich i a a e a f ed. The e i a e c ea e ec i effec i ed i aci g hi he e , e a ed he Sc effec , ch ha a highe ed hif e a e e a ica iche (a d e Xa i ) c e (A d e & E i 1999 A J 516, 647, h gh I d ' ag ee i h a hei c c i ). .a . a.ed /keel/gala ie /en i onmen .h ml 9/11 1/15/12 Gala ie and he Uni e e - En i onmen al Effec S on Gala ie A2125- C153 .I ISM ( .E ), SFR. D , ( , V , B , / ). E S 0. A .C ?M ... G ( ), R .W HI - (1987 A J S 63, 265) H , 2 , . Tidal r nca ion , 2- .T , R ; , ,W .A , . , F (1988 A J 333, 522) W ,F , R , (1988 A J 333, 542) .I , , .T .A ca eat ; - .a . a.ed /keel/gala ie /en i onmen .h ml .T , , .B M 10/11 1/15/12 Gala ie and he Uni e e - En i onmen al Effec on Gala ie harassment simulation available. The overall effect of tidal stripping of stars has been sought in the form of diffuse cluster light, not associated with any single galaxy, which is a tough observational challenge. A remarkable step here was the discovery by Ferguson et al. (1998 Nature 391, 461) of an intergalactic population of red giants in the Virgo cluster, giving a direct measure of the density of intergalactic stars (which have, in only a few instances, been previously traced by supernovae). This was complemented by the ground- based detection of planetary nebulae in the Virgo cluster (Feldmeier, Ciardullo, & Jacoby 1998 ApJ 503, 109). The fraction of stars implied not to belong to individual galaxies is nontrivial, of order 1/3 the total in the cluster. Similar fractions, 0.1- 0.25 of the starlight, have come from analyzing intracluster light after very careful accounting for the light of galaxy outskirts and control of reflections within the telescope. See, for example, these colloquium slides from Chris Mihos. This population of loose stars can trace the recent dynamical history of the cluster. In contrast to the evidence above for spirals, e lliptical gala ie s , once produced, show little environmental influence. Their colors show a strikingly consistent color- absolute magnitude relation which is well accounted for just by metallicity changes, allowing very little (in fact, suspiciously little) recent star formation. Looking for these telltale signs of recent star formation in just- formed ellipticals in clusters is a popular sport; one often concentrates on spectral features such as H , as the last strong absorption line to disappear as a young population ages and fades. Somewhat younger systems, soon after cessation of star formation presumed to accompany gas removal, are the "E+A" systems, spectroscopically resembling a mix of E galaxy and A- star spectra. « Starburst galaxies | Dynamics in disk galaxies » Course Home | Bill Keel's Home Page | Image Usage and Copyright Info | UA Astronomy k eel@bildad.a Ls cags 920 at hne: /09 .a . a.ed /keel/gala ie /en i onmen .h ml . a.ed 20009 11/11 ...
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This note was uploaded on 01/15/2012 for the course AY 620 taught by Professor Williamkeel during the Fall '09 term at Alabama.

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