Mestnaya Gruppa Galaktik
Mestnaya Gruppa Galaktik
Igor' Drozdovskii
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"Obzory neba pokazyvayut, chto tumannosti razbrosany po odinochke i gruppami razlichnoi velichiny, vplot' do neozhidanno bol'shih skoplenii. Melkomasshtabnoe raspredelenie galaktik pohozhe na raspredelenie zvezd v zvezdnyh sistemah. [...] Nasha Galaktika yavlyaetsya chlenom tipichnoi nebol'shoi gruppy tumannostei, kotorye vydelyayutsya na obshem fone. Izvestnyi chleny "Mestnoi Gruppy" yavlyayutsya nasha Galaktika s Magellanovymi Oblakami -- dvumya ee sputnikami; M31 so sputnikami M32 i NGC205; M33, NGC6822 i IC1613. Tri tumannosti, NGC6946, IC10 i IC342, mogut byt' chlenami gruppy, no oni stol' slaby, chto rasstoyanie dr nih nevozmozhno opredelit'."
E.Habbl, "Carstvo Tumannostei" (1936)
[E.Hubble, "The Realm of the Nebulae" (1936)]. |
| Mestnaya Gruppa v cifrah |
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Chislo chlenov: okolo 40; Radius poloviny massy: Rh=350 kpk; Poverhnost' nulevoi skorosti, kotoraya otdelyaet MG ot polya, rasshiryayushegosya s "habblovskim potokom": Ro=1.18+-0.15 Mpk; Polnaya massa MG: MLG=(2.3+-0.6)x1012 Msun; Polnaya svetimost' MG: MV=-22.0: Massa/svetimost': M/LV=44+-12Msun/Lsun Skorost' Solnca po otnosheniyu k MG: 306+-18 km/s, po napravleniyu k apeksu: l=99o+-5o i b=-4o+-4o; Dispersiya skorostei ee chlenov: 61+-8 km/s Funkciya svetimostei v MG imeet naklon: -1.1+-0.1 Dannye vzyaty iz ... |
Mestnaya Gruppa (MG) - skoplenie galaktik (vsego bolee 40), k kotoromu prinadlezhit nasha Galaktika. Eti galaktiki raspredeleny v ob'eme diametrom okolo 3 Mpk Poskol'ku massa M31 v poltora raza bol'she massy nashei Galaktiki, centr mass MG nahoditsya v napravlenii M31 na 2/3 rasstoyaniya do nee, t.e. v 0.48 Mpk ot Galaktiki. Prinadlezhnost' k MG ochevidna ne dlya vseh galaktik, no v to zhe vremya nesomnenno sushestvuyut eshe ne obnaruzhennye chleny MG. Termin byl vpervye ispol'zovan Habblom, vo vremya pervyh opredelenii rasstoyanii do galaktik i ih krasnyh smeshenii.
Sredi chlenov MG Mlechnyi Put' i M31 -- naibolee massivnye, dominiruyushie chleny. Kazhdaya iz etih gigantskih spiralei sobrala vokrug sebya sistemy sputnikovyh galaktik. Rassmotrim ih.
Podgruppa nashei Galaktiki
Sistema Mlechnyi Put' soderzhit mnogo karlikovyh galaktik (62% iz kotoryh
E+Sph), raspredelennyh po vsemu nebu, a imenno:
Sag DEG,
LMC , SMC i
karlikovye galaktiki v sozvezdiyah Ursa Minor, Draco, Carina, Sextans (dwarf),
Sculptor,
Fornax,
Leo I i Leo II, i, vozmozhno,
Tucana dwarf.
V 1999 godu byla obnaruzhena novaya karlikovaya sferoidal'naya galaktika Cetus
(Whiting, Hau & Irwin).
Podgruppa MW imeet lineinyi razmer poryadka 140 kpk, dispersiya luchevyh skorostei galaktik v nei -- 68 km/s.
- Kak vidno iz Tablicy 1 karlikovye diffuznye (sferoidal'nye) galaktiki tipa Sculptor dSph sostavlyayut bolee poloviny ob'ektov podgruppy nashei Galaktiki.
- Za isklyucheniem naibolee dalekih karlikovyh galaktik NGC 6822+SagittariusDIG i Tucana (kotorye mogut byt' nesvyazannymi sputnikami Galaktiki) vse ostal'nye galaktiki imeyut prilivnoi indeks > 0, t.e. yavlyayutsya gravitacionno svyazannymi, tak chto podgruppa zanimaet v prostranstve ob'em, granicy kotorogo mozhno predstavit' ellipsoidom s sootnosheniem osei Z:Y:X=8:3:1. Vmeste s oblakami neitral'nogo vodoroda iz Magellanova Potoka etu strukturu sledovalo by nazyvat' polyarnym ellipsoidom, a ne polyarnym kol'com.
- Sferoidal'naya karlikovaya galaktika Lev-I na rasstoyanii 0.27 Mpk ( Lee et. al., 1993) imeet luchevuyu skorost' +176 km/s ( Zaritsky et. al., 1989) po otnosheniyu k centru Galaktiki, chto znachitel'no bol'she chem parabolicheskaya skorost' 118 km/s. V sootvetstvii so scenariem opisannym v rabote Byrd et.al. (1994) galaktika Lev-I byla vybroshena iz iz okrestnosti M31, kogda galaktiki M31 i Mlechnyi Put' otdalilis' drug ot druga.
- Raspredelenie sferoidal'nyh i irregulyarnyh sputnikov ne pokazyvaet zametnoi segregacii s rasstoyaniem ot nashei Galaktiki.
- Sudya po srednei luchevoi skorosti sputnikov +19±20 km/s, podgruppa Mlechnyi Put' ne ispytyvaet znachitel'nogo szhatiya ili rasshireniya.
Podgruppa M31
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| Podgruppy Mesnoi Gruppy |
Sistema galaktiki tumannost' Andromedy, vidimaya izvne, gruppiruetsya vokrug ee glavnoi
galaktiki M31, soderzhashaya blizhaishie k nei galaktiki
s bol'shoi poverhnostnoi yarkost'yu
M32 i M110,
a takzhe bolee slabye i bolee
dalekie NGC147 i NGC185, ochen' slabye sistemy
And I, And II, And III.
Letom 1998 goda dvumya gruppami nablyudatelei
(I.D.Karachencev i
V.E.Karachenceva;
T.Armandroff, J.Davies i G.Jacoby)
byli obnaruzheny
po krainei mere eshe 3 karlikovye
sferoidal'nye galaktiki -- vozmozhno, dalekie chleny podgruppy M31
( odna iz etih galaktik byla nezavisimo otkryta obeimi gruppami):
Pegasus DEG (And VI),
Cassiopea Dw i
And V.
Tret'yaya po velichine galaktika Mestnoi Gruppy
- M33 (Triangulum),
kotoraya mozhet byt', a mozhet i ne byt' dalekim
gravitacionno svyazannym kompan'onom
M31, sama imeet karlikovyi sputnik LGS 3.
- Sputniki galaktiki v Andromede formiruyut ploskuyu sistemu s sootnosheniem osei 5:2:1. Ee bol'shaya poluos' i bol'shaya (polyarnaya) os' podgruppy Mlechnyi Put' obrazuyut ugol okolo 57o.
- Morfologicheskaya segregaciya v podgruppe uverenno proslezhivaetsya. Vse sem' blizhaishih sputnikov M31 imeyut tipy E i Sph, v to vremya kak na periferii obnaruzheny tol'ko spiral'nye i irregulyarnye galaktiki.
- Kak bylo otmecheno Arpom (1982), raspredelenie luchevyh skorostei sputnikov M31 sil'no asimmetrichno. Pri ispol'zovanii nashego kriteriya chlenstva galaktik raznica luchevyh skorostei snizhaetsya po sravneniyu s Arpom do +46±29 km/s. Odnako, esli schitat' polnuyu massu M31 bol'she; skazhem k=3.0 vmesto 2.5, to to v zonu vliyaniya M31 popadut i dr. galaktiki (WLM, Pegasus i NGC 404), kotorye uvelichivayut asimmetriyu do +70 km/s.
- Assimetriya luchevyh skorostei znachitel'no umen'shaetsya, esli rassmatrivat' sistemu otnositel'no centra mass M31+M33. Eto mozhet sluzhit' dovodom v pol'zu togo, chto glavnaya massa etoi podgruppy zaklyuchena v ee chlenah, a ne raspredelena po vsemu ob'emu gruppy.
- Chislo sputnikov, nahodyashihsya na Severe i na Yuge ot M31 neskol'ko asimmetrichno. Esli eto vsledstvii poglosheniya izlucheniya nashei Galaktikoi, to sleduet zhdat' otkrytiya novyh chlenov podgruppy vblizi galaktiki IC 10. Spravedlivost' etogo predpolozheniya byla pokazana sovsem nedavno.
Galaktiki NGC3109, Antlia,Sextans A i Sextans B, po-vidimomu, formiruyut, otdel'nuyu podgruppu s Vr=+114+-12 km/s, kotoraya raspolagaetsya vne tak nazyvaemogo "nulevogo rasstoyaniya Mestnoi Gruppy" 1.7 Mpk ot centroida Mestnoi Gruppy (van den Bergh, 1999).
Drugie chleny ne mogut byt' otneseny k kakoi-libo glavnoi podgruppe i dvigayutsya sovershenno izolirovanno v gravitacionnom pole chlenov gigantskih grupp. Podstruktury v gruppe veroyatno ne stabil'ny. Nablyudeniya i raschety dayut osnovaniya polagat', chto gruppy ochen' dinamichny i izmenyalis' v proshlom znachitel'no: galaktiki vokrug bol'shoi ellipticheskoi galaktiki Maffei 1 po vsei vidimosti byli kogda-to chlenami gruppy nashei galaktiki.
Vse vysheskazannoe pokazyvaet, chto MG ne izolirovana, a nahodit'sya v gravitacionnom vzaimodeistvii i obmene chlenami s blizhaishimi okruzhayushimi gruppami galaktik. Osobenno zametno vzaimodeistvie s:
- gruppoi IC342/Maffei, kotoraya krome gigantskoi ellipticheskoi galaktiki takzhe soderzhit men'shuyu po razmeram Maffei 2, i vzaimodeistvuet s kompleksom vokrug IC 342. Sil'no pogloshaetsya pyl'yu, tak kak nahoditsya vblizi ekvatorial'noi ploskosti Mlechnogo Puti.
- gruppa Sculptor'a ili gruppa Yuzhnogo Polyusa (s chlenami, nahodyashimisya vokrug Yuzhnogo Galakticheskogo Polyusa), v kotoroi dominiruet galaktika NGC 253
- gruppa M81
- gruppa M83
| Galaktika | Al't. imya | RA (2000.0) | Dec (2000.0) | Tip | V_r | Rasst. | Diam. | VBtot | AB |
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| WLM | DDO221 | 00:01:58 | -15:27:51 | IB(s)m IV-V | - 116 | 950 | 11.5x4.0 | 11.03 | 0.09 |
| IC 10 | UGC192 | 00:20:24 | +59:17:30 | IBm? | -344 | 660 | 6.3x5.1 | 11.80 | |
| Cetus | dSph | 775 | |||||||
| NGC 147 | DDO 3 | 00:33:12 | +48:30:29 | dE5 pec | -193 | 660 | 13.2x7.8 | 10.47 | 0.70 |
| And III | A0032+36 | 00:35:17 | +36:30:31 | dSph | 760 | 4.5x3.0 | 15.00 | 0.19 | |
| NGC 185 | UGC396 | 00:38:58 | +48:20:12 | dE3 pec + Sy | -202 | 620 | 11.7x10.0 | 10.10 | 0.78 |
| NGC205 | M 110 | 00:40:22 | +41:41:26 | E5 pec | - 241 | 725 | 21.9x11.0 | 8.92 | 0.14 |
| M32 | NGC 221 | 00:42:42 | +40:51:52 | E2 (cE2) | -205 | 725 | 8.7x6.5 | 9.03 | 0.31 |
| M31 | NGC 224 | 00:42:44 | +41:16:09 | SA(s)b Liner | -300 | 725 | 190x60 | 4.36 | 0.10 |
| And I | A0043+37 | 00:45:44 | +38:00:23 | dE3 pec ? | 810 | 2.5x2.5 | 13.6 | 0.20 | |
| SMC | NGC292 | 00:52:45 | -72:49:43 | SB(s)m pec | +158 | 58 | 320x185 | 2.7 | 0.17 |
| Scl dw Irr | E349-G31 | 00:08:13 | -34:34:42 | dIBm | +207 | 1.1x0.9 | 15.48 | ||
| Scl dSph | E351-G30 | 01:00:09 | -33:42:33 | dE3 pec | +110 | 84 | 39.8x30.9 | 10.50 | |
| LGS 3 | Psc dw | 01:03:53 | +21:53:05 | dIr/dSph | -277 | 810 | 2x2 | 18.00 | 0.10 |
| IC1613 | DDO 8 | 01:04:54 | +02:08:00 | IAB(s)m V | -234 | 720 | 16.2x14.5 | 9.88 | 0.02 |
| And V | 01:10:17 | +47:37:41 | dSph | 810 | |||||
| And II | 01:16:11 | +33:21:43 | E? | 680 | 3.6x2.52 | 13.5 | 0.14 | ||
| M33 | NGC 598 | 01:33:51 | +30:39:37 | SA(s)cd II-III | -179 | 795 | 70.8x41.7 | 6.27 | 0.18 |
| Phe dw | E245-G07 | 01:51:06 | -44:26:41 | IAm | +56 | 417 | 4.9x4.1 | 13.07 | |
| For dw | E356-G04 | 02:39:59 | -34:26:57 | dE4 | +53 | 140 | 17.0x12.6 | 9.04 | |
| LMC | E056-G115 | 05:23:34 | -69:45:22 | SB(s)m | +278 | 55 | 645x550 | 0.9 | 0.25 |
| Car dw | E206-G220 | 06:41:37 | -50:57:58 | dE3 | +229 | 100 | 23.4x15.5 | 22.14 | 0.10 |
| Leo A | DDO 69 | 09:59:24 | +30:44:42 | IBm V | +20 | 690 | 5.1x3.1 | 12.92 | 0.07 |
| Sex B | DDO 70 | 10:00:00 | +05:19:42 | Im+ IV-V | +301 | 1370 | 5.1x3.5 | 11.85 | 0.05 |
| NGC 3109 | DDO 236 | 10:03:07 | -26:09:32 | SB(s)m | +403 | 1260 | 19.1x3.7 | 10.39 | 0.14 |
| Antlia | A1001-27 | 10:01.8* | -27:05* | dE3 | +361 | 1320 | 1 | ||
| Leo I | Regulus G. | 10:08:27 | +12:18:27 | dE3 | +168 | 270 | 9.8x7.4 | 11.8 | 0.09 |
| Sex A | DDO 75 | 10:11:06 | -04:42:28 | IBm+ V | +324 | 1420 | 5.9x4.9 | 11.86 | 0.06 |
| Sex dw | 10:13:03 | -01:36:53 | dE3 | +230 | 87 | 0.07 | |||
| Leo II | DDO 93 | 11:13:29 | +22:09:17 | dE0 pec | +90 | 215 | 12.0x11.0 | 12.6 | 0.00 |
| GR 8 | DDO 155 | 12:58:39 | +14:13:02 | Im V | +214 | 1700 | 1.1x1.0 | 14.68 | 0.04 |
| E269-G70 | 13:10.6* | -43:07* | -8 | ||||||
| IC 4247 | 13:24.0* | -30:06* | +274 | ||||||
| UMi dw | DDO 199 | 15:09:11 | +67:12 :52 | dE4 | -209 | 60 | 30.2x19.1 | 11.9 | 0.04 |
| Dra dw | DDO 208 | 17:20:19 | +57:54:48 | dE0 pec | -281 | 76 | 35.5x24.4 | 10.9 | 0.08 |
| Mlechnyi Put' | 17:45.6 | -28:56 | SAB(s)bc I-II ? | 0 | 10 | 30 | |||
| SagDEG | 18:55 | -30:30 | dE7 | 24 | |||||
| Sgr dw | SagDIG | 19:29:59 | -17:40:41 | IB(s)m V | -77 | 1180 | 2.9x2.1 | 15.5 | 0.52 |
| NGC6822 | Barnard's | 19:44:56 | -14:48:05 | IB(s)m IV-V | -57 | 540 | 15.5x13.5 | 9.31 | 0.86 |
| Aqr dw | DDO 210 | 20:46:52 | -12:50:53 | Im V | -137 | 950 | 2.2x1.1 | 14.0 | 0.14 |
| IC5152 | 22:02:42 | -51:17:44 | IAB(s)m IV | +124 | 950 | 5.2x3.2 | 11.06 | 0.00 | |
| Tuc dw | 22:41:50 | -64:25:11 | dE5 | +130 | 830 | 2.9x1.2 | 15.7 | 0.00 | |
| Cass DEG | And VII | 23:26:31 | +50:41:31 | dSph | 690 | 2.5x2.0 | 12.9 | 0.84 | |
| Peg DIG | DDO 216 | 23:28:34 | +14:44:50 | Im V | -183 | 760 | 5.0x2.7 | 13.21 | 0.09 |
| Peg DEG | And VI | 23:51:46 | +24:34:57 | dSph | 780 | 4.0x2.0 | 14.5 |
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Zamechaniya k tablice:
- RA, Dec: Pryamoe voshozhdenie i sklonenie dlya epohi 2000.0 (* --dlya 1950.0)
- Tip: Klassifikaciya po tipam iz RC3
- V_r: Radial'naya geliocentricheskaya skorost' centra galaktiki
- Dist: Rasstoyanie (v kpk) do nas.
- "WLM" - "Wolf-Lundmark-Melotte"
- "LGS" - "Local Group (suspected)" (LGS 3) - nazvanie, kotoroe uzhe sledovalo by peredelat' na "Local Group (member)" (LGM 3).
- "SagDEG" - "Sagittarius Dwarf Elliptical Galaxy" (otkryta v 1994, takzhe soderzhit M54)
- "SagDIG" - "Sagittarius Dwarf Irregular Galaxy"
| Galaktika | Al'tern.imya | RA | Dec | Tip | V_r | Rasst. | Diam. | VBtot |
|---|---|---|---|---|---|---|---|---|
| NGC 404 | 01:09.4 | +35:43 | S0 | +178 | 2000: | |||
| Argo dw | 07:04.5* | -58:27* | Irr | |||||
| 2318-42 | 23:18.1* | -42:00* | Irr | |||||
| UGCA438 | UKS2323-326 | 23:26.5 | -32:23 | dIr | +62 |
Tak kak nasha Galaktika pogloshaet izluchenie chasti neba, do sih por otkryvayut galaktiki, s koordinatami na nizkih galakticheskih shirotah (t.e. vblizi ekvatorial'noi ploskosti nashei Galaktiki, gde pogloshenie pyl'yu naibolee intensivno). Drugaya chast' otkryvaemyh galaktik imeyut ekstremal'no nizkuyu poverhnostnuyu yarkost' (Low Surface Brightness - LSB), tak chto tol'ko nedavno s vvedeniem v nablyudatel'nuyu astrofiziku novyh priborov stalo vozmozhno zaregistrirovat' ih. Poetomu mozhno ozhidat', chto sushestvuet bol'shee chislo galaktik prinadlezhashih k MG, svet kotoryh libo nastol'ko pogloshaetsya pyl'yu ili/i nastol'ko ekstremal'no slab, chto eshe ne podnimaetsya vyshe predela yarkosti, kotoryi mozhno zaregistrirovat' sovremennymi teleskopami.
Ssylki
- Sait "Dwarf Tales", posvyashennyi sboru informacii o karlikovyh galaktikah (novosti i rezyume rabot).
- Tablica Billa Arnetta (Bill Arnett) galaktik MG
- Dzheff Bondono (Jeff Bondono) sobral obshirnyi spisok galaktik chlenov MG i kandidatov v chleny.
- (Lengthy) stat'ya po MG George Lake [ kopiya v Koree]
- Izobrazheniya MG iz arhivov Astronomical Picture of the Day
Literatura
- Karachentsev, I.D., 1996, A&A, 305, p.33, 'The Local Group in comparison with other nearby groups of galaxies'
- van den Bergh, S., 1999, ApJL, 'The Nearest Group of Galaxies', v pechati.
- van den Bergh, S., 1999, ARA&A, 'The Local Group of Galaxies', v pechati.
- van den Bergh, S., 2000, astro-ph/0001040, 'Updated Information of the Local Group'.
- Whiting A.B., Hau G., Irwin M., 1999, AJ, v pechati.
- Tom Polakis opublikoval interesnuyu stat'yu dlya nablyudatelei MG galaktik Observing the Local Group, v zhurnale Deep Sky magazine (#36), kotoraya byla perepechatana v knige David Eicher'a "Galaxies and the Universe"
(Ispol'zovany materialy iz SEDS i NED.)
Vernut'sya v stat'yu "Mestnaya Gruppa galaktik".
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Publikacii s klyuchevymi slovami:
spiral'naya galaktika - ellipticheskaya galaktika - M 33 - Mestnaya gruppa galaktik - M 32 - MMO - BMO - Nepravil'naya galaktika - Maloe Magellanovo Oblako - Bol'shoe Magellanovo Oblako - Magellanovy Oblaka - LMC - SMC - Galaktika - M 110 - galaktika v Treugol'nike - katalog Mess'e - blizhaishie galaktiki
Publikacii so slovami: spiral'naya galaktika - ellipticheskaya galaktika - M 33 - Mestnaya gruppa galaktik - M 32 - MMO - BMO - Nepravil'naya galaktika - Maloe Magellanovo Oblako - Bol'shoe Magellanovo Oblako - Magellanovy Oblaka - LMC - SMC - Galaktika - M 110 - galaktika v Treugol'nike - katalog Mess'e - blizhaishie galaktiki | |
Sm. takzhe:
Vse publikacii na tu zhe temu >> | |
