IC 1816
{{Short description|Galaxy in the constellation Fornax}}
{{Infobox galaxy|name=IC 1816|epoch=J2000|constellation name=Fornax|ra={{RA|02|31|50.97}}|dec={{DEC|-36|40|19.64}}|z=0.016945 ± 0.000020|h_radial_v=5,080 km/s|dist_ly=245 Mly|type=SB(r)ab pec?|size=~{{convert|41.7|kpc|ly|abbr=on|lk=on|order=flip}} (estimated){{r|ned}}|names=ESO 355-G025, MCG -06-06-011, AM 0229-365, IRAS 02297-3653, 6dF J0231510-364019, PGC 9634|image=File:IC 1816 in DES color.png|caption=IC 1816 imaged by Dark Energy Survey.|appmag_v=13.1{{cite web |title=Revised NGC Data for IC 1816 |url=http://spider.seds.org/ngc/revngcic.cgi?IC+1816 |website=spider.seds.org}}}}
IC 1816 is a barred spiral galaxy located in the constellation of Fornax. The galaxy is located 245 million light-years from Earth and has a diameter of approximately 136,000 light-years across.{{Cite web |title=NED search results for IC 1816 |url=https://ned.ipac.caltech.edu/byname?objname=IC+1816&hconst=67.8&omegam=0.308&omegav=0.692&wmap=4&corr_z=1 |access-date=2025-06-21 |website=NASA/IPAC Extragalactic Database}} It was first discovered by Lewis Swift on 12 October 1896, who classified it as a small faint round object.{{Cite web |title=IC 1816 (= PGC 9634) |url=https://cseligman.com/text/atlas/ic18.htm#ic1816 |access-date=2025-06-21 |website=cseligman.com}}
Description
IC 1816 is an isolated face-on spiral galaxy.{{Cite journal |last1=Davies |first1=Rebecca L. |last2=Dopita |first2=Michael A. |last3=Kewley |first3=Lisa |last4=Groves |first4=Brent |last5=Sutherland |first5=Ralph |last6=Hampton |first6=Elise J. |last7=Shastri |first7=Prajval |last8=Kharb |first8=Preeti |last9=Bhatt |first9=Harish |last10=Scharwächter |first10=Julia |last11=Jin |first11=Chichuan |last12=Banfield |first12=Julie |last13=Zaw |first13=Ingyin |last14=James |first14=Bethan |last15=Juneau |first15=Stéphanie |date=2016-06-10 |title=The Role of Radiation Pressure in the Narrow Line Regions of Seyfert Host Galaxies |journal=The Astrophysical Journal |volume=824 |issue=1 |pages=50 |doi=10.3847/0004-637x/824/1/50 |doi-access=free |arxiv=1604.06104 |bibcode=2016ApJ...824...50D |issn=0004-637X}}{{Cite journal |last1=Márquez |first1=I. |last2=Durret |first2=F. |last3=González Delgado |first3=R. M. |last4=Marrero |first4=I. |last5=Masegosa |first5=J. |last6=Maza |first6=J. |last7=Moles |first7=M. |last8=Pérez |first8=E. |last9=Roth |first9=M. |date=November 1999 |title=Near-infrared photometry of isolated spirals with and without an AGN |journal=Astronomy and Astrophysics Supplement Series |volume=140 |issue=1 |pages=1–14 |doi=10.1051/aas:1999516 |arxiv=astro-ph/9909351 |issn=0365-0138}} It has three spiral arms with the northwest arm, the brightest and most detached. Two of the arms are distinctive and seem to open up as its spiral structure travels inwards. The galaxy also shows a prominent curved dust lane.{{Cite journal |last1=Deo |first1=R. P. |last2=Crenshaw |first2=D. M. |last3=Kraemer |first3=S. B. |date=2006-06-06 |title=The Host Galaxies of Narrow-Line Seyfert 1 Galaxies: Nuclear Dust Morphology and Starburst Rings |url=https://iopscience.iop.org/article/10.1086/504894/fulltext/ |journal=The Astronomical Journal |volume=132 |issue=1 |pages=321–346 |doi=10.1086/504894 |arxiv=astro-ph/0603806 |bibcode=2006AJ....132..321D |issn=0004-6256}} There is a clearly resolved ring and a smaller elongated structure interpreted as a nuclear bar. An inner bar might be present given the observation of a small counter-rotation located from its nucleus although a nuclear disk is suggested.{{Citation |last1=Marquez |first1=I. |title=Long slit spectroscopy of a sample of isolated spirals with and without an AGN |date=2003-11-28 |id=arXiv:astro-ph/0311616 |last2=Durret |first2=F. |last3=Masegosa |first3=J. |last4=Moles |first4=M. |last5=Varela |first5=J. |last6=Delgado |first6=R. M. Gonzalez |last7=Maza |first7=J. |last8=Perez |first8=E. |last9=Roth |first9=M.|journal=Astronomy & Astrophysics |volume=416 |issue=2 |pages=475–498 |doi=10.1051/0004-6361:20034108 |arxiv=astro-ph/0311616 }} The star formation rate for IC 1816 is estimated to be 0.74 Mʘ per year.{{Cite journal |last1=Looze |first1=Ilse De |last2=Cormier |first2=Diane |last3=Lebouteiller |first3=Vianney |last4=Madden |first4=Suzanne |last5=Baes |first5=Maarten |last6=Bendo |first6=George J. |last7=Boquien |first7=Médéric |last8=Boselli |first8=Alessandro |last9=Clements |first9=David L. |last10=Cortese |first10=Luca |last11=Cooray |first11=Asantha |last12=Galametz |first12=Maud |last13=Galliano |first13=Frédéric |last14=Graciá-Carpio |first14=Javier |last15=Isaak |first15=Kate |date=2014-08-01 |title=The applicability of far-infrared fine-structure lines as star formation rate tracers over wide ranges of metallicities and galaxy types |url=https://www.aanda.org/articles/aa/pdf/2014/08/aa22489-13.pdf |journal=Astronomy & Astrophysics |language=en |volume=568 |pages=A62 |doi=10.1051/0004-6361/201322489 |arxiv=1402.4075 |bibcode=2014A&A...568A..62D |issn=0004-6361}}
The nucleus of IC 1816 is active. It was originally classified as a type 1 Seyfert galaxy{{Cite journal |last1=Maia |first1=M. a. G. |last2=da Costa |first2=L. N. |last3=Willmer |first3=C. |last4=Pellegrini |first4=P. S. |last5=Rite |first5=C. |date=March 1987 |title=New Southern Galaxies with Active Nuclei |url=https://articles.adsabs.harvard.edu/pdf/1987AJ.....93..546M |journal=The Astronomical Journal |language=en |volume=93 |pages=546 |doi=10.1086/114336 |bibcode=1987AJ.....93..546M |issn=0004-6256}} but later reclassified as a type 2 Seyfert galaxy due to it lacking broad emission lines.{{Cite journal |last1=Cid Fernandes |first1=Roberto |last2=Storchi-Bergmann |first2=Thaisa |last3=Schmitt |first3=Henrique R. |date=June 1998 |title=The Stellar Content of Active Galaxies |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=297 |issue=2 |pages=579–616 |doi=10.1046/j.1365-8711.1998.01519.x |doi-access=free |arxiv=astro-ph/9801309 |bibcode=1998MNRAS.297..579C |issn=0035-8711}} The Seyfert spectrum of the galaxy is found extending as far as 3.4 arcseconds east from the nucleus.{{Cite journal |last1=Fehmers |first1=G. C. |last2=de Grijp |first2=M. H. K. |last3=Miley |first3=G. K. |last4=Keel |first4=W. C. |date=November 1994 |title=Warm IRAS sources from the point source catalog. IV. Extended optical line emission. |url=https://articles.adsabs.harvard.edu/pdf/1994A%26AS..108...61F |journal=Astronomy and Astrophysics Supplement Series |language=en |volume=108 |pages=61–67 |issn=0365-0138}} A hydrogen alpha component is seen broadening, likely caused by the blending of nitrogen lines.{{Cite journal |last=Winkler |first=H. |date=August 1992 |title=Variability studies of Seyfert galaxies - II. Spectroscopy. |url=https://articles.adsabs.harvard.edu/pdf/1992MNRAS.257..677W |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=257 |issue=4 |pages=677–688 |doi=10.1093/mnras/257.4.677 |doi-access=free |issn=0035-8711}}
IC 1816 has an extended narrow line region showing highly ionized gas, indicated by the presence of coronal line emission, with the region mainly centering in its star-forming ring.{{Cite journal |last1=Dopita |first1=Michael A. |last2=Shastri |first2=Prajval |last3=Davies |first3=Rebecca |last4=Kewley |first4=Lisa |last5=Hampton |first5=Elise |last6=Scharwächter |first6=Julia |last7=Sutherland |first7=Ralph |last8=Kharb |first8=Preeti |last9=Jose |first9=Jessy |last10=Bhatt |first10=Harish |last11=Ramya |first11=S. |last12=Jin |first12=Chichuan |last13=Banfield |first13=Julie |last14=Zaw |first14=Ingyin |last15=Juneau |first15=Stéphanie |date=March 2015 |title=Probing the Physics of Narrow Line Regions in Active Galaxies. II. The Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7) |journal=The Astrophysical Journal Supplement Series |language=en |volume=217 |issue=1 |pages=12 |doi=10.1088/0067-0049/217/1/12 |arxiv=1501.02022 |bibcode=2015ApJS..217...12D |issn=0067-0049}} The gas located in its nuclear region is mainly blueshifted with a peak velocity dispersion of 320 kilometers per second, suggesting the active galactic nucleus of the galaxy is powered through outflows.