NGC 4818

{{Short description|Galaxy in the constellation Virgo}}

{{Infobox galaxy

| name = NGC 4818

| image = NGC 4818 hst 05446 606.png

| caption = NGC 4818 imaged by Hubble Space Telescope

| epoch = J2000

| type = SAB(rs)ab pec {{cite web

| website=NASA/IPAC Extragalactic Database

| publisher = NASA and Caltech

| title=Results for object NGC 4818

| url=https://ned.ipac.caltech.edu/byname?objname=NGC+4818

| access-date=25 February 2025 }}

| ra = {{RA|12|56|48.8829}}

| dec = {{DEC|-08|31|30.906}}

| dist_ly = 45.2 ± 14.2 Mly (13.9 ± 4.4 Mpc)

| z = 0.003552 ± 0.000103

| h_radial_v = 1,065 ± 31 km/s

| appmag_v = 11.1{{cite web |title=Revised NGC Data for NGC 4818 |url=https://spider.seds.org/ngc/revngcic.cgi?NGC4818 |website=spider.seds.org |access-date=30 March 2024}}

| size_v = 4.3{{prime}} × 1.5{{prime}}

| size = ~{{convert|17.3|kpc|ly|abbr=on|lk=on|order=flip}} (estimated){{r|ned}}

| constellation name = Virgo

| group_cluster = Virgo II Groups

| notes =

| names = {{odlist | MRK = 9022 | MCG= -01-33-057 | IRAS= 12542-0815 | PGC= 44191 }}{{r|ned}}

}}

NGC 4818 is a spiral galaxy in the constellation Virgo. The galaxy lies about 45 million light years away from Earth, which means, given its apparent dimensions, that NGC 4818 is approximately 55,000 light years across. It was discovered by William Herschel on March 3, 1786.{{cite web |last1=Seligman |first1=Courtney |title=NGC 4818 (= PGC 44191) |url=https://cseligman.com/text/atlas/ngc48.htm#4818 |website=Celestial Atlas |access-date=19 November 2018}}

NGC 4818 has an elliptical bulge with a bright nucleus. The galaxy has a bar which appears about 30 degrees offset from the major axis of the bulge. Some loosely wrapped spiral arms emerge from the bulge. A faint disk with a low contrast broad spiral pattern is seen surrounding the bulge, aligned with the major axis of the elliptical bulge.{{cite journal |last1=Eskridge |first1=Paul B. |last2=Frogel |first2=Jay A. |last3=Pogge |first3=Richard W. |last4=Quillen |first4=Alice C. |last5=Berlind |first5=Andreas A. |last6=Davies |first6=Roger L. |last7=DePoy |first7=D. L. |last8=Gilbert |first8=Karoline M. |last9=Houdashelt |first9=Mark L. |last10=Kuchinski |first10=Leslie E. |last11=Ramirez |first11=Solange V. |last12=Sellgren |first12=K. |last13=Stutz |first13=Amelia |last14=Terndrup |first14=Donald M. |last15=Tiede |first15=Glenn P. |title=Near-Infrared and Optical Morphology of Spiral Galaxies |journal=The Astrophysical Journal Supplement Series |date=November 2002 |volume=143 |issue=1 |pages=73–111 |doi=10.1086/342340|arxiv=astro-ph/0206320 |bibcode=2002ApJS..143...73E }} The spectrum of the nucleus is similar to that of an HII region.{{cite journal |last1=Goulding |first1=A. D. |last2=Alexander |first2=D. M. |title=Towards a complete census of AGN in nearby Galaxies: a large population of optically unidentified AGN |journal=Monthly Notices of the Royal Astronomical Society |date=21 September 2009 |volume=398 |issue=3 |pages=1165–1193 |doi=10.1111/j.1365-2966.2009.15194.x|doi-access=free |arxiv=0906.0772 |bibcode=2009MNRAS.398.1165G }} The total star formation rate is estimated to be 0.7 {{solar mass}} per year. The total gas mass is estimated to be {{val|e=9.77|u=M_solar}} while the total star mass is about {{val|e=10.2|u=M_solar}}.{{cite journal |last1=Ramos Padilla |first1=Andrés F |last2=Ashby |first2=M L N |last3=Smith |first3=Howard A |last4=Martínez-Galarza |first4=Juan R |last5=Beverage |first5=Aliza G |last6=Dietrich |first6=Jamie |last7=Higuera-G. |first7=Mario-A |last8=Weiner |first8=Aaron S |title=The AGN contribution to the UV–FIR luminosities of interacting galaxies and its role in identifying the main sequence |journal=Monthly Notices of the Royal Astronomical Society |date=31 October 2020 |volume=499 |issue=3 |pages=4325–4369 |doi=10.1093/mnras/staa2813|doi-access=free |arxiv=2009.05614 }}

A. M. Garcia considers the galaxy to be a member of the NGC 4699 Group, or LGG 307. Other members of that group include NGC 4699, NGC 4700, NGC 4722, NGC 4742, NGC 4781, NGC 4790, and NGC 4802.{{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|bibcode-access=free}} Makarov et al consider the galaxy to be a member of the Messier 104 Group, along with NGC 4802 and the Sombrero Galaxy among other members.{{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 |url=http://www.sao.ru/hq/dim/groups/galaxies.dat|bibcode=2011MNRAS.412.2498M|arxiv=1011.6277|s2cid=119194025|access-date=1 February 2025}} It is part of a Virgo II Groups, a chain of groups extending from the Virgo Cluster.{{cite web |title=The Virgo II Groups |url=http://www.atlasoftheuniverse.com/galgrps/virii.html |website=www.atlasoftheuniverse.com |access-date=25 February 2025}}