Dorado Group

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Dorado Group
Sig05-013 small.jpg
NGC 1566, one of the brightest members of the Dorado Group (Spitzer Space Telescope image)
Observation data (Epoch J2000)
Constellation(s)Dorado
Right ascension04h 17m 03.9s[1]
Declination−56° 07′ 43″[1]
Brightest memberNGC 1566
Number of galaxies46 plus 34 candidate members[2]
Other designations
Shk 18,[2] G16,[2][3] HG3,[2] MC13,[4] and NGC 1566 Group[5]
See also: Galaxy group, Galaxy cluster, List of galaxy groups and clusters

The Dorado Group is a loose concentration of galaxies[2] containing both spirals and ellipticals.[3] It is generally considered a 'galaxy group' but may approach the size of a 'galaxy cluster'.[6] It lies primarily in the southern constellation Dorado and is one of the richest galaxy groups of the Southern Hemisphere.[7] Gérard de Vaucouleurs was the first to identify it in 1975 as a large complex nebulae II in the Dorado region,[2] designating it as G16.[3]

Characteristics[]

A rough distance estimate from NGC 1549 (using the Hubble constant as 70) put the cluster at 18.4 megaparsecs (Mpc).[2] The Cepheid distance estimate from Freedman et al. 2001 is 15.3 Mpc.[8] Based upon the 2001 work of Tonry et al.[9] the surface brightness fluctuation (SBF) of six member galaxies was averaged and adjusted to estimate the group's distance at 19.1 ± 0.8 Mpc in 2007.[10]

At the center of the cluster lie interacting galaxies[11] NGC 1549 and NGC 1553. The dominant group members, ordered by luminosity, are: spiral NGC 1566, lenticular NGC 1553, and elliptical NGC 1549.[6] The group spans an area of the sky 10° square, corresponding to an actual area of around 3 Mpc square.[2] The group exhibits a relatively small harmonic mean radius (230 ± 40 kpc) due to the concentration at its core of more luminous galaxies.[6] All together, the group has an overall luminosity of 7.8 ± 1.6 ×1010 L⊙.[6]

The Dorado Group contains three dominant smaller groups within itself, , NGC 1566 Group and the , as evidenced by the H I distribution of the region.[5] The Dorado Group is in the Fornax Wall that connects these three groups.[5] Due to its location in the Fornax Wall, the group is at a similar distance as the Fornax Cluster.[10] The Dorado Group is richer than the Local Group, while still being dominated by disk types of galaxies (i.e. its two brightest members are spiral NGC 1566 and lenticular NGC 1553) and its member galaxies have H I masses on par with non-interacting galaxies of the same morphological type.[10] With the group's apparent crossing time being 12.6 ± 0.6[6] % of the universe's age, recent analyses deduce that the group is unvirialized, and thus this may explain the abundance of spirals and H I.[10]

Members[]

The table below lists eighteen galaxies that were identified in 1982 as associated with the Dorado Group by John Peter Huchra and Margaret J. Geller with the ones later dropped stuck out.[12] In 1989, the list of members was expanded to 46 by Maia, da Costa, & Latham.[2] In 1990-1991, Henry C. Ferguson and Allan Sandage identified 34 other possible candidate members of the group with magnitudes greater than 19 and eliminated one member from Maia et al. putting the list at 79[6] galaxies.[2][3] Kilborn et al. 2005 confirmed 26 members from the list.[5] In 2006, the list was refined again by Firth et al.[6] Using redshift data, they excluded eleven (as being background galaxies or interloper) from the Ferguson et al. list, confirmed the membership of twenty on the list, and left 48 unconfirmed.[6]

Huchra et al. 1982 Members of the Dorado Group
(with strikeouts for ones dropped by Maia et al. in 1989)
Name Type[1] R.A. (J2000)[1] Dec. (J2000)[1] Redshift (km/s)[1] Apparent Magnitude[1]
NGC 2082 SAB(rs+)c 05h 41m 51.1s −64° 18′ 04″ 1184 ± 6 12.6
S0− pec 05h 26m 47.6s −63° 45′ 36″ 1100 ± 24 11.7
(R)SB(r)dm: 05h 02m 42.5s −61° 08′ 24″ 1014 ± 9 12.9
SB(rs)dm 04h 48m 23.8s −59° 48′ 01″ 1228 ± 6 12.6
NGC 1672 (R'_1:)SB(r)bc Sy2 04h 45m 42.5s −59° 14′ 50″ 1331 ± 3 10.3
SAB(r)b 04h 16m 24.5s −60° 12′ 25″ 1133 ± 10 12.5
NGC 1559 SB(s)cd 04h 17m 35.8s −62° 47′ 01″ 1304 ± 4 11.0
(R)SB(l)00 04h 12m 43.2s −57° 44′ 17″ 1176 ± 7 11.5
SA0− 04h 21m 58.8s −56° 58′ 29″ 1050 ± 25 11.4
NGC 1533 (L)SB(rs)00 04h 09m 51.8s −56° 07′ 06″ 790 ± 5 11.7
SA0+? 04h 14m 36.5s −56° 03′ 39″ 1284 ± 14 11.8
NGC 1553 SA(rl)00 04h 16m 10.5s −55° 46′ 49″ 1080 ± 11 10.3
NGC 1549 E0−1 04h 15m 45.1s −55° 35′ 32″ 1220 ± 15 10.7
NGC 1566 (R'_1)SAB(rs)bcSy1 04h 20m 00.4s −54° 56′ 16″ 1504 ± 2 10.3
(R')SAB(rs)a 04h 31m 39.5s −54° 36′ 08″ 1063 ± 21 11.4
SAB(s)bc 04h 04m 02.7s −54° 06′ 00″ 1175 ± 7 12.1
NGC 1705 SA0− pec 04h 54m 13.5s −53° 21′ 40″ 633 ± 6 12.8
SA0: sp 04h 27m 38.1s −55° 01′ 40″ 1510 ± 8 12.1
Peculiar galaxy NGC 1487 is located about 30 million light-years away in the constellation of Eridanus.[13]

The Maia et al. 1989 thirty-four added members were: , , , , , , , , , , , , , , IC 2000, NGC 1483, NGC 1433, , , NGC 1510, NGC 1510, NGC 1512, , , NGC 1448, NGC 1487, , , , , , , , NGC 1249, and .[4] And the six dropped from the 1982 list were: NGC 2082, , , , NGC 1672, and NGC 1559.[4] In 2007, a study of ultracompact dwarfs (UCD) identified one definite and two possible UCD members of the group.[8] The thirty-four added by Ferguson et al. 1990 included and .[3]

The NGC 1566 Group of Dorado contains H I with MHI = 3.5×1010 M⊙ of which 40% alone comes from the NGC 1566 galaxy.[5] More than half of its members are outside its virial radius of 580 kpc which suggests this group is a young non-virialized group. The 2005 Kilborn et al. set of confirmed NGC 1566 Group members (within the Dorado Group) is:[5]

Kilborn et al. 2005 Members of the NGC 1566 Group
Name Type[1] R.A. (J2000)[1] Dec. (J2000)[1] Redshift (km/s)[1] Apparent Magnitude[1]
SAB(s)d? 04h 12m 04.3s −58° 33′ 25″ 1469 ± 7 14.5
SB(s)c pec 04h 10m 59.8s −56° 28′ 50″ 1217 ± 13 13.2
(R)SB(l)00 04h 12m 43.2s −57° 44′ 17″ 1176 ± 7 11.5
Irregular 04h 27m 13.7s −57° 25′ 42″ 1215 ± 7 16.7
NGC 1533 (L)SB(rs)00 04h 09m 51.8s −56° 07′ 06″ 790 ± 5 11.7
Sd pec 04h 08m 53.7s −55° 59′ 22″ 712 ± 52 15.5
Irregular 04h 22m 51.7s −56° 13′ 39″ 1350 ± 4 16.3
SA0+? 04h 14m 36.5s −56° 03′ 39″ 1284 ± 14 11.8
Sc 04h 17m 54.3s −55° 55′ 58″ 1379 ± 1 13.9
IAB(s)m pec 04h 07m 03.0s −55° 19′ 26″ 1068 ± 7 14.7
NGC 1566 (R'_1)SAB(rs)bcSy1 04h 20m 00.4s −54° 56′ 16″ 1504 ± 2 10.3
SA0: sp 04h 27m 38.1s −55° 01′ 40″ 1510 ± 8 12.1
IB(s)m pec 04h 27m 55.0s −55° 03′ 28″ 1568 ± 8 13.3
SAB(s)bc 04h 04m 02.7s −54° 06′ 00″ 1175 ± 7 12.1
(R')S00: pec 04h 06m 07.9s −52° 40′ 06″ 898 ± 7 13.9
S00 pec 04h 18m 59.5s −58° 15′ 27″ 1239 14.9
E4 04h 27m 32.6s −54° 11′ 48″ 1471 ± 28 14.7
S0/a? pec sp 04h 39m 19.1s −54° 12′ 41″ 1655 ± 10 15.5
S? 04h 39m 36.9s −53° 00′ 46″ 1678 ± 5 14.3
S00 pec sp 04h 31m 24.2s −54° 25′ 01″ 982 ± 10 13.9
NGC 1549 E0−1 04h 15m 45.1s −55° 35′ 32″ 1220 ± 15 10.7
NGC 1553 SA(rl)00 04h 16m 10.5s −55° 46′ 49″ 1080 ± 11 10.3
SA0− 04h 21m 58.8s −56° 58′ 29″ 1050 ± 25 11.4
S0− 04h 24m 44.9s −54° 56′ 31″ 1600 ± 27 13.6
(R')SAB(rs)a 04h 31m 39.5s −54° 36′ 08″ 1063 ± 21 11.4
Irregular 04h 01m 15.2s −53° 29′ 23″ 1135 ± 40 16.9

External links[]

References[]

  1. ^ a b c d e f g h i j k l "NASA/IPAC Extragalactic Database", Results for Dorado Group and various galaxies, retrieved 2008-06-26
  2. ^ a b c d e f g h i j Carrasco, Eleazar R.; Mendes de Oliveira, Cláudia; Infante, Leopoldo; Bolte, Michael (January 2001), "The Dwarf Galaxy Population of the Dorado Group Down to MV~-11", The Astronomical Journal, 121 (1): 148–168, arXiv:astro-ph/0010076, Bibcode:2001AJ....121..148C, doi:10.1086/318035
  3. ^ a b c d e Ferguson, Henry C.; Sandage, Allan (July 1990), "Population studies in groups and clusters of galaxies. III - A catalog of galaxies in five nearby groups", Astronomical Journal, 100: 1–31, Bibcode:1990AJ....100....1F, doi:10.1086/115486, ISSN 0004-6256
  4. ^ a b c Maia, M. A. G.; da Costa, L. N.; Latham, David W. (April 1989), "A catalog of southern groups of galaxies", Astrophysical Journal Supplement Series, 69: 809–829, Bibcode:1989ApJS...69..809M, doi:10.1086/191328, ISSN 0067-0049
  5. ^ a b c d e f Virginia A. Kilborn; Bärbel S. Koribalski; Duncan A. Forbes; David G. Barnes; Ruth C. Musgrave (January 2005), "A Wide-Field Hi Study of the NGC 1566 Group", Monthly Notices of the Royal Astronomical Society, 356 (1): 77–88, arXiv:astro-ph/0409743, Bibcode:2005MNRAS.356...77K, doi:10.1111/j.1365-2966.2004.08450.x
  6. ^ a b c d e f g h Firth, P.; Evstigneeva, E. A.; Jones, J. B.; Drinkwater, M. J.; Phillipps, S.; Gregg, M. D. (November 2006), "Kinematics, substructure and luminosity-weighted dynamics of six nearby galaxy groups", Monthly Notices of the Royal Astronomical Society, 372 (4): 1856–1868, arXiv:astro-ph/0608584, Bibcode:2006MNRAS.372.1856F, doi:10.1111/j.1365-2966.2006.10993.x
  7. ^ Laurikainen, Eija; Salo, Heikki; Buta, Ronald; Knapen, Johan; Speltincx, Tom; Block, David (December 2006), "The Near-infrared S0 Survey III: Morphology of 15 Southern Early-Type Disk Galaxies", The Astronomical Journal, 132 (6): 2634–2652, arXiv:astro-ph/0609343, Bibcode:2006AJ....132.2634L, doi:10.1086/508810
  8. ^ a b Evstigneeva, E. A.; Drinkwater, M. J.; Jurek, R.; Firth, P.; Jones, J. B.; Gregg, M. D.; Phillipps, S. (July 2007), "Searches for ultracompact dwarf galaxies in galaxy groups", Monthly Notices of the Royal Astronomical Society, 378 (3): 1036–1042, arXiv:0704.1750, Bibcode:2007MNRAS.378.1036E, doi:10.1111/j.1365-2966.2007.11856.x
  9. ^ J. L. Tonry; A. Dressler; J. P. Blakeslee; E. A. Ajhar; A. B. Fletcher; G. A. Luppino; M. R. Metzger; C. B. Moore (2001), "The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances", Astrophysical Journal, 546 (2): 681–693, arXiv:astro-ph/0011223, Bibcode:2001ApJ...546..681T, doi:10.1086/318301
  10. ^ a b c d DeGraaff, Regina Barber; Blakeslee, John P.; Meurer, Gerhardt R.; Putman, Mary E. (December 2007), "A Galaxy in Transition: Structure, Globular Clusters, and Distance of the Star-Forming S0 Galaxy NGC 1533 in Dorado", The Astrophysical Journal, 671 (2): 1624–1639, arXiv:0710.0893, Bibcode:2007ApJ...671.1624D, doi:10.1086/523640
  11. ^ Bridges, Terry J.; Hanes, David A. (April 1990), "Globular clusters in the interacting galaxies NGC 1549 and NGC 1553", Astronomical Journal, 99: 1100–1107, 1340, 1341, Bibcode:1990AJ.....99.1100B, doi:10.1086/115399, ISSN 0004-6256
  12. ^ Huchra, John Peter; Geller, Margaret J. (June 15, 1982), "Groups of galaxies. I - Nearby groups", Astrophysical Journal, 257 (Part 1): 423–437, Bibcode:1982ApJ...257..423H, doi:10.1086/160000
  13. ^ "One from many". Retrieved 1 February 2016.

Coordinates: Sky map 04h 17m 03.9s, −56° 07′ 43″

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