View source for Dorado Group

{{Short description|Galaxy cluster in the constellation Dorado}}

{{Galaxy cluster
| name = Dorado Group
| image = [[Image:Sig05-013 small.jpg|300px]]
| caption = NGC 1566, one of the brightest members of the Dorado Group ([[Spitzer Space Telescope]] image)
| epoch = [[J2000]]
| ra = {{RA|04|17|03.9}}<ref name="ned">{{Citation
  | title=NASA/IPAC Extragalactic Database
  | work=Results for Dorado Group and various galaxies
  | url=http://nedwww.ipac.caltech.edu/
  | access-date=2008-06-26}}</ref>
| dec = {{DEC|-56|07|43}}<ref name="ned" />
| constellation = [[Dorado]]
| member_no = 46 plus 34 candidate members<ref name="Carrascoetal2001" />
| brightest_member = [[NGC 1566]]
| other_names = Shk 18,<ref name="Carrascoetal2001" /> G16,<ref name="Carrascoetal2001" /><ref name="Fergusonetal1990" /> HG3,<ref name="Carrascoetal2001">{{citation
 | title = The Dwarf Galaxy Population of the Dorado Group Down to M<sub>V</sub>~−11
 |author1=Carrasco, Eleazar R. |author2=Mendes de Oliveira, Cláudia |author3=Infante, Leopoldo |author4=Bolte, Michael | journal = The Astronomical Journal
 | volume = 121
 | issue = 1
 | pages = 148–168
 | date = January 2001
 | bibcode = 2001AJ....121..148C
 | doi = 10.1086/318035
|arxiv = astro-ph/0010076 |s2cid=1348985 }}</ref> MC13,<ref name="Maiaetal1989" /> and NGC 1566 Group<ref name="Kilbornetal2005" />
}}
The '''Dorado Group''' is a loose [[Galaxy groups and clusters|concentration of galaxies]]<ref name="Carrascoetal2001" /> containing both [[spiral galaxy|spiral]]s and [[elliptical galaxy|elliptical]]s.<ref name="Fergusonetal1990">{{citation | bibcode = 1990AJ....100....1F | title = Population studies in groups and clusters of galaxies. III – A catalog of galaxies in five nearby groups | date = July 1990 | last1 = Ferguson | first1 = Henry C. | last2 = Sandage | first2 = Allan | author-link2 = Allan Sandage | journal = Astronomical Journal | issn = 0004-6256 | volume = 100 | pages = 1–31 | doi = 10.1086/115486| doi-access = free }}</ref>  It is generally considered a 'galaxy group' but may approach the size of a 'galaxy cluster'.<ref name="Firthetal2006" /> It lies primarily in the southern constellation [[Dorado]] and is one of the richest galaxy groups of the [[Southern Hemisphere]].<ref name="Laurikainenetal2006">{{citation | bibcode = 2006AJ....132.2634L | title = The Near-infrared S0 Survey III: Morphology of 15 Southern Early-Type Disk Galaxies | date = December 2006 | journal = The Astronomical Journal | volume = 132 | issue = 6 | pages = 2634–2652 | doi = 10.1086/508810 |author1=Laurikainen, Eija |author2=Salo, Heikki |author3=Buta, Ronald |author4=Knapen, Johan |author5=Speltincx, Tom |author6=Block, David |arxiv = astro-ph/0609343 | s2cid = 16856632 }}</ref> [[Gérard de Vaucouleurs]] was the first to identify it in 1975 as a large complex nebulae II in the Dorado region,<ref name="Carrascoetal2001" /> designating it as G16.<ref name="Fergusonetal1990" />

==Characteristics==
A rough distance estimate from NGC 1549 (using the [[Hubble constant]] as 70) put the cluster at 18.4 [[Megaparsec|megaparsecs (Mpc)]].<ref name="Carrascoetal2001" /> The [[Cepheid variable|Cepheid]] distance estimate from Freedman et al. 2001 is 15.3 Mpc.<ref name="Evstigneevaetal2007">{{citation | bibcode = 2007MNRAS.378.1036E | title = Searches for ultracompact dwarf galaxies in galaxy groups | doi = 10.1111/j.1365-2966.2007.11856.x | date = July 2007 | journal = [[Monthly Notices of the Royal Astronomical Society]] | volume = 378 | issue = 3 | pages = 1036–1042
 |author1=Evstigneeva, E. A. |author2=Drinkwater, M. J. |author3=Jurek, R. |author4=Firth, P. |author5=Jones, J. B. |author6=Gregg, M. D. |author7=Phillipps, S. | doi-access = free |arxiv = 0704.1750 | s2cid = 15880069 }}</ref> Based upon the 2001 work of Tonry et al.<ref name="tonryetal2001">{{Citation  |author1=J. L. Tonry |author2=A. Dressler |author3=J. P. Blakeslee |author4=E. A. Ajhar |author5=A. B. Fletcher |author6=G. A. Luppino |author7=M. R. Metzger |author8=C. B. Moore | title=The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances  | journal=Astrophysical Journal  | year=2001  | volume=546  | issue=2  | pages=681–693  | bibcode=2001ApJ...546..681T  | doi=10.1086/318301 |arxiv = astro-ph/0011223 |s2cid=17628238 }}</ref> the [[surface brightness fluctuation]] (SBF) of six member galaxies was averaged and adjusted to estimate the group's distance at {{val|19.1|0.8|u=Mpc}} in 2007.<ref name="DeGraaffetal2007" />

At the center of the cluster lie [[interacting galaxy|interacting galaxies]]<ref name="Bridgesetal1990">{{citation | bibcode = 1990AJ.....99.1100B | title = Globular clusters in the interacting galaxies NGC 1549 and NGC 1553 | date = April 1990 | journal = Astronomical Journal | issn = 0004-6256 | volume = 99 | pages = 1100–1107, 1340, 1341 | doi = 10.1086/115399 |author1=Bridges, Terry J. |author2=Hanes, David A. }}</ref> [[NGC 1549]] and [[NGC 1553]]. The dominant group members, ordered by luminosity, are: spiral [[NGC 1566]], [[lenticular galaxy|lenticular]] NGC 1553, and elliptical NGC 1549.<ref name="Firthetal2006">{{citation | bibcode = 2006MNRAS.372.1856F | date = November 2006 | title = Kinematics, substructure and luminosity-weighted dynamics of six nearby galaxy groups | journal = Monthly Notices of the Royal Astronomical Society | volume = 372 | issue = 4 | pages = 1856–1868 | doi = 10.1111/j.1365-2966.2006.10993.x |author1=Firth, P. |author2=Evstigneeva, E. A. |author3=Jones, J. B. |author4=Drinkwater, M. J. |author5=Phillipps, S. |author6=Gregg, M. D. | doi-access = free |arxiv = astro-ph/0608584 | s2cid = 18646500 }}</ref> The group spans an area of the sky 10° square, corresponding to an actual area of around 3 Mpc square.<ref name="Carrascoetal2001" /> The group exhibits a relatively small [[harmonic mean]] radius (230 ± 40 kpc) due to the concentration at its core of more luminous galaxies.<ref name="Firthetal2006" />  All together, the group has an overall luminosity of 7.8 ± 1.6 {{e|10}} [[solar luminosity|''L''<sub>⊙</sub>]].<ref name="Firthetal2006" />

The Dorado Group contains three dominant smaller groups within itself, [[NGC 1672 Group]], [[NGC 1566 Group]] and the [[NGC 1433 Group]], as evidenced by the [[H I region|H&nbsp;I]] distribution of the region.<ref name="Kilbornetal2005" /> The Dorado Group is in the [[Fornax Wall]] that connects these three groups.<ref name="Kilbornetal2005">{{citation | bibcode = 2005MNRAS.356...77K | title = A Wide-Field Hi Study of the NGC 1566 Group | date = January 2005 | journal = Monthly Notices of the Royal Astronomical Society | volume = 356 | issue = 1 | pages = 77–88 | doi = 10.1111/j.1365-2966.2004.08450.x |author1= Virginia A. Kilborn |author2=[[Bärbel Koribalski|Bärbel S. Koribalski]] |author3=Duncan A. Forbes |author4=David G. Barnes |author5=Ruth C. Musgrave
 | doi-access = free |arxiv = astro-ph/0409743 }}</ref> Due to its location in the Fornax Wall, the group is at a similar distance as the [[Fornax Cluster]].<ref name="DeGraaffetal2007">{{Citation |author1=DeGraaff, Regina Barber |author2=Blakeslee, John P. |author3=Meurer, Gerhardt R. |author4=Putman, Mary E. | title = A Galaxy in Transition: Structure, Globular Clusters, and Distance of the Star-Forming S0 Galaxy NGC 1533 in Dorado | journal = The Astrophysical Journal  | date = December 2007  | volume = 671  | issue = 2  | pages = 1624–1639  | bibcode = 2007ApJ...671.1624D  | doi = 10.1086/523640
 |arxiv=0710.0893|s2cid=14312626 }}</ref>  The Dorado Group is richer than the [[Local Group]], while still being dominated by disk [[Galaxy morphological classification|types of galaxies]] (i.e. its two brightest members are spiral NGC 1566 and lenticular NGC 1553) and its member galaxies have H&nbsp;I masses on par with [[interacting galaxy|non-interacting galaxies]] of the same morphological type.<ref name="DeGraaffetal2007" />  With the group's apparent crossing time being 12.6 ± 0.6 %<ref name="Firthetal2006" /> of the [[age of the universe|universe's age]], recent analyses deduce that the group is [[Virial theorem|unvirialized]], and thus this may explain the abundance of spirals and H&nbsp;I.<ref name="DeGraaffetal2007" />

==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 struck out.<ref name="Huchraetal1982">{{citation | bibcode = 1982ApJ...257..423H | title = Groups of galaxies. I – Nearby groups | last1 = Huchra | first1 = John Peter | author-link1 = John Peter Huchra | last2 = Geller | first2 = Margaret J. | author-link2 = Margaret J. Geller | doi = 10.1086/160000 | date = June 15, 1982 | journal = Astrophysical Journal | issue = Part 1 | volume = 257 | pages = 423–437}}</ref> In 1989, the list of members was expanded to 46 by Maia, da Costa, & Latham.<ref name="Carrascoetal2001" /> 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<ref name="Firthetal2006" /> galaxies.<ref name="Carrascoetal2001" /><ref name="Fergusonetal1990" /> Kilborn et al. 2005 confirmed 26 members from the list.<ref name="Kilbornetal2005" /> In 2006, the list was refined again by Firth et al.<ref name="Firthetal2006" /> 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.<ref name="Firthetal2006" />

{| class="wikitable" style="text-align:center;border-collapse:collapse;" cellpadding="2"
|+'''Huchra et al. 1982 Members of the Dorado Group<br>(with strikeouts for ones dropped by Maia et al. in 1989)'''
|-
! style="background:#efefef;" | Name
! style="background:#efefef;" | [[Galaxy morphological classification|Type]]<ref name="ned" />
! style="background:#efefef;" | [[Right Ascension|R.A.]] ([[J2000]])<ref name="ned" />
! style="background:#efefef;" | [[Declination|Dec.]] ([[J2000]])<ref name="ned" />
! style="background:#efefef;" | [[Redshift]] (km/[[second|s]])<ref name="ned" />
! style="background:#efefef;" | [[Apparent Magnitude]]<ref name="ned" />
|-
| <s>[[NGC 2082]]</s>
| SAB(rs+)c
| {{RA|05|41|51.1}}
| {{DEC|-64|18|04}}
| 1184 ± 6
| 12.6
|-
| <s>[[NGC 1947]]</s>
| S0<sup>−</sup> pec
| {{RA|05|26|47.6}}
| {{DEC|-63|45|36}}
| 1100 ± 24
| 11.7
|-
| <s>[[NGC 1796]]</s>
| (R)SB(r)dm:
| {{RA|05|02|42.5}}
| {{DEC|-61|08|24}}
| 1014 ± 9
| 12.9
|-
| <s>[[NGC 1688]]</s>
| SB(rs)dm
| {{RA|04|48|23.8}}
| {{DEC|-59|48|01}}
| 1228 ± 6
| 12.6
|-
| <s>[[NGC 1672]]</s>
| (R'_1:)SB(r)bc Sy2
| {{RA|04|45|42.5}}
| {{DEC|-59|14|50}}
| 1331 ± 3
| 10.3
|-
| [[IC 2056]]
| SAB(r)b
| {{RA|04|16|24.5}}
| {{DEC|-60|12|25}}
| 1133 ± 10
| 12.5
|-
| <s>[[NGC 1559]]</s>
| SB(s)cd
| {{RA|04|17|35.8}}
| {{DEC|-62|47|01}}
| 1304 ± 4
| 11.0
|-
| [[NGC 1543]]
| (R)SB(l)0<sup>0</sup>
| {{RA|04|12|43.2}}
| {{DEC|-57|44|17}}
| 1176 ± 7
| 11.5
|-
| [[NGC 1574]]
| SA0<sup>−</sup>
| {{RA|04|21|58.8}}
| {{DEC|-56|58|29}}
| 1050 ± 25
| 11.4
|-
| [[NGC 1533]]
| (L)SB(rs)0<sup>0</sup>
| {{RA|04|09|51.8}}
| {{DEC|-56|07|06}}
| 790 ± 5
| 11.7
|-
| [[NGC 1546]]
| SA0<sup>+?</sup>
| {{RA|04|14|36.5}}
| {{DEC|-56|03|39}}
| 1284 ± 14
| 11.8
|-
| [[NGC 1553]]
| SA(rl)0<sup>0</sup>
| {{RA|04|16|10.5}}
| {{DEC|-55|46|49}}
| 1080 ± 11
| 10.3
|-
| [[NGC 1549]]
| E0<sup>−1</sup>
| {{RA|04|15|45.1}}
| {{DEC|-55|35|32}}
| 1220 ± 15
| 10.7
|-
| [[NGC 1566]]
| (R'_1)SAB(rs)bcSy1
| {{RA|04|20|00.4}}
| {{DEC|-54|56|16}}
| 1504 ± 2
| 10.3
|-
| [[NGC 1617]]
| (R')SAB(rs)a
| {{RA|04|31|39.5}}
| {{DEC|-54|36|08}}
| 1063 ± 21
| 11.4
|-
| [[NGC 1515]]
| SAB(s)bc
| {{RA|04|04|02.7}}
| {{DEC|-54|06|00}}
| 1175 ± 7
| 12.1
|-
| [[NGC 1705]]
| SA0<sup>−</sup> pec
| {{RA|04|54|13.5}}
| {{DEC|-53|21|40}}
| 633 ± 6
| 12.8
|-
| [[NGC 1596]]
| SA0: sp
| {{RA|04|27|38.1}}
| {{DEC|-55|01|40}}
| 1510 ± 8
| 12.1
|-
|}

[[File:NGC 1487 HST.jpg|thumb|Peculiar galaxy [[NGC 1487]] is located about 30 million light-years away in the constellation of [[Eridanus (constellation)|Eridanus]].<ref>{{cite web|title=One from many|url=http://www.spacetelescope.org/images/potw1605a/|access-date=1 February 2016}}</ref>]]

The Maia et al. 1989 thirty-four added members were: [[IC 2049]], [[NGC 1536]], [[IC 2058]], [[IC 2032]], [[NGC 1602]], [[NGC 1581]], [[IC 2085]], [[NGC 1522]], [[PGC 15149]], [[NGC 1556]], [[NGC 1527]], [[NGC 1494]], [[NGC 1493]], [[PGC 14416]], IC 2000, [[NGC 1483]], [[NGC 1433]], [[PGC 14078]], [[NGC 1495]], [[NGC 1510]], [[NGC 1512]], [[IC 1959]], [[IC 1986]], [[NGC 1448]], [[NGC 1487]], [[IC 1933]], [[NGC 1311]], [[IC 1954]], [[IC 1914]], [[NGC 1411]], [[IC 1970]], [[PGC 13818]], [[NGC 1249]], and [[PGC 11139]].<ref name="Maiaetal1989">{{citation | bibcode = 1989ApJS...69..809M | date = April 1989 | journal = Astrophysical Journal Supplement Series | issn = 0067-0049 | volume = 69 | pages = 809–829 | doi = 10.1086/191328 | title = A catalog of southern groups of galaxies |author1=Maia, M. A. G. |author2=da Costa, L. N. |author3=Latham, David W. | doi-access = free }}</ref> And the six dropped from the 1982 list were: [[NGC 2082]], [[NGC 1947]], [[NGC 1796]], [[NGC 1688]], [[NGC 1672]], and [[NGC 1559]].<ref name="Maiaetal1989" />  In 2007, a study of [[ultracompact dwarf]]s (UCD) identified one definite and two possible UCD members of the group.<ref name="Evstigneevaetal2007" /> The thirty-four added by Ferguson et al. 1990 included [[IC 2038]] and [[IC 2039]].<ref name="Fergusonetal1990" />

The NGC 1566 Group of Dorado contains [[H I region|H&nbsp;I]] with ''M''<sub>HI</sub> = 3.5{{e|10}} ''M''<sub>⊙</sub> of which 40% alone comes from the NGC 1566 galaxy.<ref name="Kilbornetal2005" /> 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:<ref name="Kilbornetal2005" />
{{clear}}
{| class="wikitable sortable" style="text-align:center;border-collapse:collapse;" cellpadding="2"
|+'''Kilborn et al. 2005 Members of the NGC 1566 Group'''
|-
! style="background:#efefef;" | Name
! style="background:#efefef;" | [[Galaxy morphological classification|Type]]<ref name="ned" />
! style="background:#efefef;" | [[Right Ascension|R.A.]] ([[J2000]])<ref name="ned" />
! style="background:#efefef;" | [[Declination|Dec.]] ([[J2000]])<ref name="ned" />
! style="background:#efefef;" | [[Redshift]] (km/[[second|s]])<ref name="ned" />
! style="background:#efefef;" | [[Apparent Magnitude]]<ref name="ned" />
|-
| [[IC 2049]]
| SAB(s)d?
| {{RA|04|12|04.3}}
| {{DEC|-58|33|25}}
| 1469 ± 7
| 14.5
|-
| [[NGC 1536]]
| SB(s)c pec
| {{RA|04|10|59.8}}
| {{DEC|-56|28|50}}
| 1217 ± 13
| 13.2
|-
| [[NGC 1543]]
| (R)SB(l)0<sup>0</sup>
| {{RA|04|12|43.2}}
| {{DEC|-57|44|17}}
| 1176 ± 7
| 11.5
|-
| [[LSBG F157-081]]
| Irregular
| {{RA|04|27|13.7}}
| {{DEC|-57|25|42}}
| 1215 ± 7
| 16.7
|-
| [[NGC 1533]]
| (L)SB(rs)0<sup>0</sup>
| {{RA|04|09|51.8}}
| {{DEC|-56|07|06}}
| 790 ± 5
| 11.7
|-
| [[IC 2038]]
| Sd pec
| {{RA|04|08|53.7}}
| {{DEC|-55|59|22}}
| 712 ± 52
| 15.5
|-
| [[APMBGC 157+016+068]]
| Irregular
| {{RA|04|22|51.7}}
| {{DEC|-56|13|39}}
| 1350 ± 4
| 16.3
|-
| [[NGC 1546]]
| SA0<sup>+?</sup>
| {{RA|04|14|36.5}}
| {{DEC|-56|03|39}}
| 1284 ± 14
| 11.8
|-
| [[IC 2058]]
| Sc
| {{RA|04|17|54.3}}
| {{DEC|-55|55|58}}
| 1379 ± 1
| 13.9
|-
| [[IC 2032]]
| IAB(s)m pec
| {{RA|04|07|03.0}}
| {{DEC|-55|19|26}}
| 1068 ± 7
| 14.7
|-
| [[NGC 1566]]
| (R'_1)SAB(rs)bcSy1
| {{RA|04|20|00.4}}
| {{DEC|-54|56|16}}
| 1504 ± 2
| 10.3
|-
| [[NGC 1596]]
| SA0: sp
| {{RA|04|27|38.1}}
| {{DEC|-55|01|40}}
| 1510 ± 8
| 12.1
|-
| [[NGC 1602]]
| IB(s)m pec
| {{RA|04|27|55.0}}
| {{DEC|-55|03|28}}
| 1568 ± 8
| 13.3
|-
| [[NGC 1515]]
| SAB(s)bc
| {{RA|04|04|02.7}}
| {{DEC|-54|06|00}}
| 1175 ± 7
| 12.1
|-
| [[NGC 1522]]
| (R')S0<sup>0</sup>: pec
| {{RA|04|06|07.9}}
| {{DEC|-52|40|06}}
| 898 ± 7
| 13.9
|-
| [[ESO 118-019]]
| S0<sup>0</sup> pec
| {{RA|04|18|59.5}}
| {{DEC|-58|15|27}}
| 1239
| 14.9
|-
| [[ESO 157-030]]
| E4
| {{RA|04|27|32.6}}
| {{DEC|-54|11|48}}
| 1471 ± 28
| 14.7
|-
| [[ESO 157-047]]
| S0/a? pec sp
| {{RA|04|39|19.1}}
| {{DEC|-54|12|41}}
| 1655 ± 10
| 15.5
|-
| [[ESO 157-049]]
| S?
| {{RA|04|39|36.9}}
| {{DEC|-53|00|46}}
| 1678 ± 5
| 14.3
|-
| [[IC 2085]]
| S0<sup>0</sup> pec sp
| {{RA|04|31|24.2}}
| {{DEC|-54|25|01}}
| 982 ± 10
| 13.9
|-
| [[NGC 1549]]
| E0<sup>−1</sup>
| {{RA|04|15|45.1}}
| {{DEC|-55|35|32}}
| 1220 ± 15
| 10.7
|-
| [[NGC 1553]]
| SA(rl)0<sup>0</sup>
| {{RA|04|16|10.5}}
| {{DEC|-55|46|49}}
| 1080 ± 11
| 10.3
|-
| [[NGC 1574]]
| SA0<sup>−</sup>
| {{RA|04|21|58.8}}
| {{DEC|-56|58|29}}
| 1050 ± 25
| 11.4
|-
| [[NGC 1581]]
| S0<sup>−</sup>
| {{RA|04|24|44.9}}
| {{DEC|-54|56|31}}
| 1600 ± 27
| 13.6
|-
| [[NGC 1617]]
| (R')SAB(rs)a
| {{RA|04|31|39.5}}
| {{DEC|-54|36|08}}
| 1063 ± 21
| 11.4
|-
| [[Abell 3202]]
| Irregular
| {{RA|04|01|15.2}}
| {{DEC|-53|29|23}}
| 1135 ± 40
| 16.9
|-
|}

==External links==
* {{WikiSky|name=The Dorado Group|z=9}}

==References==
{{Reflist}}

{{Stars of Dorado}}

{{Authority control}}

{{Sky|04|17|03.9|-|56|07|43|60000000}}

{{DEFAULTSORT:Dorado Group}}
[[Category:Dorado Group| ]]
[[Category:Dorado]]
[[Category:Southern Supercluster]]