NGC 3109

{{Infobox Galaxy

| name = NGC 3109

| image = NGC 3109 imaged by the Dark Energy Camera.jpg

| caption = NGC 3109 imaged by the Dark Energy Camera using the Víctor M. Blanco 4-meter Telescope

| epoch = J2000

| type = SB(s)m{{cite web

| website=NASA/IPAC Extragalactic Database

| publisher = NASA and Caltech

| title=Results for object NGC 3109

| url=https://ned.ipac.caltech.edu/byname?objname=NGC+3109

| access-date=2006-11-19 }}

| ra = {{RA|10|03|06.88}}

| dec = {{DEC|-26|09|34.5}}

| dist_ly = {{convert|1.333|+/-|0.19|Mpc|Mly|sigfig=4|abbr=on|lk=on}}

| z = 403 ± 1 km/s

| appmag_v = 10.4

| size = {{cvt|12.80|x|2.69|kpc|ly|sigfig=3|abbr=on|lk=on|disp=x|
(|)|order=flip}}
{{small|(diameter; ESO D_25.5 B-band isophote)}}{{efn|name=Scale}}
{{cvt|1.21|x|1.21|kpc|ly|sigfig=4|abbr=on|lk=on|disp=x|
(|)|order=flip}}
{{small|(diameter; 2MASS K-band total isophote)}}{{cite web |url=https://ned.ipac.caltech.edu/cgi-bin/objsearch?objname=NGC+3109&extend=no&hconst=67.74&omegam=0.3089&omegav=0.6911&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES |title=Detailed Information for Object NGC 3109 |work=NASA/IPAC Extragalactic Database |access-date=September 13, 2023}}{{efn|name=Scale|The quoted diameters in this infobox was based on NED's provided scale of 0.0065 kpc/arcsec multiplied with the given angular diameters.}}

| size_v = {{Val|19.1|×|3.7|u=arcminute}}

| constellation name = Hydra

| names = {{odlist | UGCA= 194 | PGC= 29128 | name= ESO 499- G 036 | MCG= -04-24-013 }}

}}

NGC 3109 is a small barred Magellanic type spiral or irregular galaxy around 4.35 Mly away in the direction of the constellation of Hydra. NGC 3109 is believed to be tidally interacting with the dwarf elliptical galaxy Antlia Dwarf.Grebel, Gallagher, Harbeck, p.7 It was discovered by John Herschel on March 24, 1835 while he was in what is now South Africa.[http://www.seds.org/~spider/spider/LG/n3109.html Irregular Galaxy NGC 3109] {{webarchive|url=https://web.archive.org/web/20071107164538/http://www.seds.org/~spider/spider/LG/n3109.html |date=2007-11-07 }}

Size and morphology

NGC 3109 is classified as a Magellanic type irregular galaxy,{{Cite book | last = Aparicio | first = Antonio |author2=Artemio Herrero |author3=F. Sánchez | title = Stellar astrophysics for the local group: VIII Canary Islands Winter School|

publisher = University of Cambridge | date = 1998 | page = 286 | url = https://books.google.com/books?id=3gn5hS2zIkcC&pg=PA286| isbn = 978-0-521-63255-3 }} but it may in fact be a small spiral galaxy. Based on the D_25.5 isophote at the B-band with an angular diameter of {{val|1980|fmt=commas}} arcseconds, it has an isophotal diameter approximately {{convert|12.80|kpc|ly|sigfig=3|abbr=off|lk=on}} across, slightly larger than the Large Magellanic Cloud but smaller than the Triangulum Galaxy. If it is a spiral galaxy, it would be the smallest in the Local Group.{{Cite book | last = Sauvage | first = Marc |author2=Grazyna Stasinska |author3=Daniel Schaerer | title =The evolution of galaxies: II—basic building blocks, Volume 2|publisher = Kluwer Academic Publishers | date = 2002 | pages = 123, 124 | url = https://books.google.com/books?id=xAPX8UfT6qAC&q=ngc+3109&pg=PA123 | isbn = 978-1-4020-0622-7}} NGC 3109 has a mass of about {{val|2.3|e=9}} times the mass of the Sun ({{solar mass|link=y}}), of which 20% is in the form of neutral hydrogen.{{Cite book | last = van den bergh | first = Sidney | title = The galaxies of the Local Group | publisher = University of Cambridge | date = 2000 | pages = 265 | url = https://books.google.com/books?id=NfOwG3cyAGIC&pg=PA265 | isbn = 978-0-521-65181-3}} It is oriented edge-on from our point of view, and may contain a disk and a halo. The disk appears to be composed of stars of all ages, whereas the halo contains only very old and metal-poor stars.{{Cite journal | doi = 10.1088/0004-6256/136/6/2332 | last = Hidalgo | first = Sebastian L. |display-authors=etal | title =The Disc-Halo Structure of NGC 3109|journal = The Astronomical Journal | volume = 136 | issue = 6 | pages = 2332–2342 | date = 2008 | bibcode=2008AJ....136.2332H| doi-access = free }} NGC 3109 does not appear to possess a galactic nucleus.

From measurements of the neutral atomic hydrogen in the galaxy, it has been found that the disk of NGC 3109 is warped. The warp has the same radial velocity as gas in the Antlia Dwarf galaxy, indicating that the two galaxies had a close encounter approximately one billion years ago.{{Cite journal | doi = 10.1086/321170 | last1 = Barnes | first1 = D. G. | first2 = W. J. G. | last2 = de Blok | title = On the Neutral Gas Content and Environment of NGC 3109 and the Antlia Dwarf Galaxy | journal = The Astronomical Journal | volume = 122 | issue = 2 | pages = 825 | date = August 2001 | bibcode=2001AJ....122..825B|arxiv = astro-ph/0107474 | s2cid = 15734118 }}

Composition

Based on spectroscopy of blue supergiants in NGC 3109, it is known that the galaxy has a low metallicity, similar to that of the Small Magellanic Cloud. It is one of the most metal-poor star-forming galaxies in the Local group.{{Cite journal | last = Pena | first = M. | title = An interesting comparison between PNE and H II regions in NGC 3109 and NGC 6822 | journal = Revista Mexicana de Astronomía y Astrofísica|volume=35 | pages = 74–75 | url = http://www.astroscu.unam.mx/rmaa/RMxAC..35/PDF/RMxAC..35_mpena.pdf | access-date = 2010-09-24}}

NGC 3109 seems to contain an unusually large number of planetary nebulae for its luminosity.{{Cite journal | doi = 10.1086/116040 | last = Richer | first = Michael G. |author2=Marshall L. McCall | title = Planetary nebulae and H II regions in NGC 3109 | journal = The Astronomical Journal | volume = 103 | pages = 54–59 | date = 1992 | bibcode = 1992AJ....103...54R| doi-access = free }} It also contains a substantial amount of dark matter.

{{Cite journal | doi = 10.1086/115548 | last = Jobin | first = Marc |author2=Carignan, Claude | title = The dark side of NGC 3109 | journal = The Astronomical Journal | volume = 100 | issue = 3 | pages = 648–662 | date = 1990 | bibcode = 1990AJ....100..648J| doi-access = free }}

Location

NGC 3109 is located about {{convert|1.33|Mpc|Mly}} away, in the constellation Hydra. This puts it at the very outskirts of the Local Group.{{Cite journal | last = Evans | first = Chris|display-authors=etal | title = The ARAUCARIA Project – First Observations of Blue Supergiants in NGC 3109 | journal = The Messenger| volume = 126| pages = 5| url = http://www.eso.org/sci/publications/messenger/archive/no.126-dec06/messenger-no126-5-6.pdf | access-date = 2010-09-24| bibcode = 2006Msngr.126....5E| year = 2006}} Its membership of the Local Group has been questioned, because it seems to be receding faster than estimates of the Local Group's escape velocity.{{Cite web | last = Plotner | first = Tammy | title =Turning the Tides – NGC 3109 by Ken Crawford | publisher = Universe Today | date = 2009-05-18 | url = http://www.universetoday.com/27388/turning-the-tides-ngc-3109-by-ken-crawford/| access-date = 2010-09-24}} It is distant enough from the largest members of the Local Group that it has not been tidally influenced by them.

Luminous Blue Variable

Although no supernovae have been observed in NGC 3109 yet, a luminous blue variable, designated AT{{nbsp}}2018akx (type LBV, mag. 17.5), was discovered by the All Sky Automated Survey for SuperNovae on 22 March 2018.{{cite web | website=Transient Name Server | title=AT{{nbsp}}2018akx | url=https://www.wis-tns.org/object/2018akx | publisher = IAU | access-date=31 August 2024}}