NGC 3995

{{Short description|Galaxy in the constellation Ursa Major}}

{{Infobox galaxy

| name = NGC 3995

| image = NGC3995 - SDSS DR14.jpg

| caption = NGC 3995 by Sloan Digital Sky Survey

| epoch = J2000

| type = SAm pec {{cite web

| title=NASA/IPAC Extragalactic Database

| work=Results for NGC 3995

| url=http://ned.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=NGC+3995

| access-date=2024-03-26 }}

| ra = {{RA|11|57|44.1}}

| dec = {{DEC|+32|17|39}}

| dist_ly = 102 Mly (31.2 Mpc)

| z = 0.010938 ± 0.000002

| h_radial_v = 3,279 ± 1 km/s

| appmag_v = 12.1{{cite web |title=Revised NGC Data for NGC 3995 |url=https://spider.seds.org/ngc/revngcic.cgi?NGC3995 |website=spider.seds.org |access-date=30 March 2024}}

| size_v = 1.89{{prime}} × 0.78{{prime}}

| constellation name = Ursa Major

| notes = Interacting galaxy

| names = {{odlist | UGC= 6944 | Arp= 313 | VV= 249a | MCG= +06-26-061 | PGC= 37624 | name= HOLM 309A | CGCG= 186-075}}

}}

NGC 3995 is a Magellanic spiral galaxy in the constellation Ursa Major. The galaxy lies about 100 million light years away from Earth based on the Tully–Fisher relation, which means, given its apparent dimensions, that NGC 3995 is approximately 80,000 light years across, while based on redshift it lies 170 million light years away. It was discovered by Heinrich d'Arrest on February 5, 1864.{{cite web |last1=Seligman |first1=Courtney |title=NGC 3995 (= Arp 24) |url=https://cseligman.com/text/atlas/ngc39a.htm#3995 |website=Celestial Atlas |access-date=19 November 2018}}

NGC 3995 forms a triplet of galaxies with NGC 3994, which lies 1.9 arcminutes, and NGC 3991, which lies 3.7 arcminutes away. The triplet has been included in Halton Arp's Atlas of Peculiar Galaxies as Arp 313. Both NGC 3995 and NGC 3991 have disturbed appearances while NGC 3994 does not.Sandage, A., Bedke, J. (1994), The Carnegie Atlas of Galaxies. Volume I, Carnegie Institution of Washington The triplet is part of the NGC 3966 Group or LGG 259. Other members include NGC 3966, NGC 3935, NGC 3986, IC 2973, UGC 6892, IC 2978, and IC 2979.{{cite journal |last1=Garcia |first1=A. M. |title=General study of group membership. II. Determination of nearby groups. |journal=Astronomy and Astrophysics Supplement Series |date=1 July 1993 |volume=100 |pages=47–90 |url=https://cdsarc.cds.unistra.fr/ftp/J/A+AS/100/47/table2.dat |bibcode= 1993A&AS..100...47G |issn=0365-0138}}{{cite journal|last1=Makarov|first1=Dmitry|last2=Karachentsev|first2=Igor|title=Galaxy groups and clouds in the local (z~ 0.01) Universe|journal=Monthly Notices of the Royal Astronomical Society|date=21 April 2011|volume=412|issue=4|pages=2498–2520|doi=10.1111/j.1365-2966.2010.18071.x|doi-access=free |bibcode=2011MNRAS.412.2498M|arxiv=1011.6277|s2cid=119194025}}

The star formation rate of NGC 3995 is estimated to be {{val|4.2|0.9|ul=M_solar}} per year, with higher rates observed near the centre of the galaxy.{{cite journal |last1=Logroño-García |first1=R. |last2=Vilella-Rojo |first2=G. |last3=López-Sanjuan |first3=C. |last4=Varela |first4=J. |last5=Viironen |first5=K. |last6=Muniesa |first6=D. J. |last7=Cenarro |first7=A. J. |last8=Cristóbal-Hornillos |first8=D. |last9=Ederoclite |first9=A. |last10=Marín-Franch |first10=A. |last11=Moles |first11=M. |last12=Vázquez Ramió |first12=H. |last13=Bonoli |first13=S. |last14=Díaz-García |first14=L. A. |last15=Orsi |first15=A. |last16=San Roman |first16=I. |last17=Akras |first17=S. |last18=Chies-Santos |first18=A. L. |last19=Coelho |first19=P. R. T. |last20=Daflon |first20=S. |last21=Costa-Duarte |first21=M. V. |last22=Dupke |first22=R. |last23=Galbany |first23=L. |last24=González Delgado |first24=R. M. |last25=Hernandez-Jimenez |first25=J. A. |last26=Lopes de Oliveira |first26=R. |last27=Mendes de Oliveira |first27=C. |last28=Oteo |first28=I. |last29=Gonçalves |first29=D. R. |last30=Sánchez-Portal |first30=M. |last31=Schmidtobreick |first31=L. |last32=Sodré |first32=L. |title=J-PLUS: Measuring H α emission line fluxes in the nearby universe |journal=Astronomy & Astrophysics |date=February 2019 |volume=622 |pages=A180 |doi=10.1051/0004-6361/201732487|arxiv=1804.04039 |bibcode=2019A&A...622A.180L }} The nucleus of the galaxy has emission that resembles an HII region.{{cite journal |last1=Kewley |first1=Lisa J. |last2=Rupke |first2=David |last3=Jabran Zahid |first3=H. |last4=Geller |first4=Margaret J. |last5=Barton |first5=Elizabeth J. |title=Metallicity Gradients and Gas Flows in Galaxy Pairs |journal=The Astrophysical Journal |date=20 September 2010 |volume=721 |issue=1 |pages=L48–L52 |doi=10.1088/2041-8205/721/1/L48|arxiv=1008.2204 |bibcode=2010ApJ...721L..48K }} The spectrum of the galaxy has Wolf-Rayet features, indicative of recent star formation.{{cite journal |last1=Schaerer |first1=D. |last2=Contini |first2=T. |last3=Pindao |first3=M. |title=New catalogue of Wolf-Rayet galaxies and high-excitation extra-galactic Hii regions |journal=Astronomy and Astrophysics Supplement Series |date=April 1999 |volume=136 |issue=1 |pages=35–52 |doi=10.1051/aas:1999197|arxiv=astro-ph/9812347 |bibcode=1999A&AS..136...35S }} Hubble Space Telescope detected 46 star formation knots in the galaxy, most of them having ages less than 20 million years.{{cite journal |last1=Eggers |first1=D. |last2=Weistrop |first2=D. |last3=Stone |first3=A. |last4=Nelson |first4=C. H. |last5=Hancock |first5=M. |title=Hubble Space Telescope Observations of Star-forming Regions in NGC 3994/3995 |journal=The Astronomical Journal |date=January 2005 |volume=129 |issue=1 |pages=136–147 |doi=10.1086/426358|bibcode=2005AJ....129..136E }}