NGC 541

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

{{Infobox galaxy

| name = NGC 541

| image = Hubble ngc541 new 2 gapsfilled flatcont final.jpg

| caption = NGC 541 imaged by the Hubble Space Telescope

| epoch = J2000

| type = cD;S0- {{cite web

| title=NASA/IPAC Extragalactic Database

| work=Results for NGC 541

| url=http://ned.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=NGC+541

| access-date=2016-01-18 }}

| ra = {{RA|01|25|44.3}}

| dec = {{DEC|-01|22|46}}

| dist_ly = 230 ± 60 Mly (70.6 ± 19.8 Mpc)

| z = 0.018086 +/- 0.000019

| h_radial_v = 5,422 ± 6 km/s

| appmag_v = 12.2

| size_v = 1.8{{prime}} × 1.7{{prime}}

| constellation name = Cetus

| notes =

| names = UGC 1004, Arp 133, CGCG 385-128, MCG +00-04-137, PGC 5305

}}

NGC 541 is a lenticular galaxy located in the constellation Cetus. It is located at a distance of about 230 million light years from Earth, which, given its apparent dimensions, means that NGC 541 is about 130,000 light years across. It was discovered by Heinrich d'Arrest on October 30, 1864.{{cite web |last1=Seligman |first1=Courtney |title=NGC 541 (= PGC 5305 = Arp 133) |url=https://cseligman.com/text/atlas/ngc5.htm#541 |website=Celestial Atlas |access-date=19 November 2018}} It is a member of the Abell 194 galaxy cluster and is included in the Atlas of Peculiar Galaxies in the category galaxies with nearby fragments. NGC 541 is a radio galaxy of Fanaroff–Riley class I, also known as 3C 40A (3C 40B is more prominent and is associated with the nearby galaxy NGC 547).{{cite journal |last1=Sakelliou |first1=Irini |last2=Hardcastle |first2=M. J. |last3=Jetha |first3=N. N. |title=3C 40 in Abell 194: can tail radio galaxies exist in a quiescent cluster? |journal=Monthly Notices of the Royal Astronomical Society |date=February 2008 |volume=384 |issue=1 |pages=87–93 |doi=10.1111/j.1365-2966.2007.12465.x|doi-access=free |arxiv=0709.2133|bibcode=2008MNRAS.384...87S |s2cid=16802624 }}

The galaxy was observed by the Hubble Space Telescope. It was found that it has a central disk seen nearly face-on with a diameter of 1".8. Inside the disk is an inner ring with a diameter of circa 0".44 arcseconds, which may be part of a hardly-visible spiral structure. There is also a linear dust feature sticking out of the disk with nearly the same axis as the radio jet. H-alpha and [N II] emission presented a peak at the centre of the dusk disk and also was found to form a ring around the peak, which had two brighter spots lying diametrically opposed.{{cite journal |last1=Verdoes Kleijn |first1=Gijs A. |last2=Baum |first2=Stefi A. |last3=de Zeeuw |first3=P. Tim |last4=O'Dea |first4=Chris P. |title=Hubble Space Telescope Observations of Nearby Radio-Loud Early-Type Galaxies |journal=The Astronomical Journal |date=December 1999 |volume=118 |issue=6 |pages=2592–2617 |doi=10.1086/301135|bibcode=1999AJ....118.2592V |arxiv=astro-ph/9909256 }} Observations in CO emission revealed the presence of molecular gas in NGC 541, with estimated mass of approximately 10⁸ {{solar mass|link=yes}}, and with a compact ring-like distribution with a radius of 1–2 kpc.{{cite journal |last1=Salomé |first1=Q. |last2=Salomé |first2=P. |last3=Combes |first3=F. |title=Jet-induced star formation in 3C 285 and Minkowski's Object |journal=Astronomy & Astrophysics |date=20 January 2015 |volume=574 |pages=A34 |doi=10.1051/0004-6361/201424932|bibcode=2015A&A...574A..34S |arxiv=1410.8367 |s2cid=119266072 }} In the centre of NGC 541 lies a supermassive black hole whose mass is estimated to be (1.9 – 9.2) × 10⁸ {{solar mass}}.{{cite journal |last1=Beifiori |first1=A. |last2=Sarzi |first2=M. |last3=Corsini |first3=E. M. |last4=Bontà |first4=E. Dalla |last5=Pizzella |first5=A. |last6=Coccato |first6=L. |last7=Bertola |first7=F. |title=UPPER LIMITS ON THE MASSES OF 105 SUPERMASSIVE BLACK HOLES FROM Hubble Space Telescope/SPACE TELESCOPE IMAGING SPECTROGRAPH ARCHIVAL DATA |journal=The Astrophysical Journal |date=10 February 2009 |volume=692 |issue=1 |pages=856–868 |doi=10.1088/0004-637X/692/1/856|bibcode=2009ApJ...692..856B |arxiv=0809.5103 |s2cid=54903233 }}

At 45 arcseconds northeast of NGC 541 lies an irregular dwarf galaxy known as Minkowski's object. It is located in the path of the radio jet of NGC 541 and there is strong evidence that the jet has caused a starburst in Minkowski's object. There is a HI region downstream from the Minkowski's object with {{val|4.9|e=8}} {{solar mass}} that straddles the jet at the point where the jet changes direction. At least 20 regions with star clusters and associated HII regions have been detected in Minkowski's object. The stellar population in Minkowski's object is dominated by stars formed in a single event 7.5 million years ago. The current starbirth rate is 0.52 {{solar mass}} per year.{{cite journal |last1=Croft |first1=Steve |last2=van Breugel |first2=Wil |last3=de Vries |first3=Wim |last4=Dopita |first4=Mike |last5=Martin |first5=Chris |last6=Morganti |first6=Raffaella|author6-link=Raffaella Morganti |last7=Neff |first7=Susan |last8=Oosterloo |first8=Tom |last9=Schiminovich |first9=David |last10=Stanford |first10=S. A. |last11=van Gorkom |first11=Jacqueline |title=Minkowski's Object: A Starburst Triggered by a Radio Jet, Revisited |journal=The Astrophysical Journal |date=20 August 2006 |volume=647 |issue=2 |pages=1040–1055 |doi=10.1086/505526|bibcode=2006ApJ...647.1040C |arxiv=astro-ph/0604557 |s2cid=119331218 }} Although it has been proposed that Minkowski's object was a dwarf galaxy that happened to pass through the radio jet of NGC 541, it is more probable that the HI region was warm intergalactic gas that was cooled by the jet, resulting in star formation,{{cite journal |last1=Lacy |first1=Mark |last2=Croft |first2=Steve |last3=Fragile |first3=Chris |last4=Wood |first4=Sarah |last5=Nyland |first5=Kristina |title=ALMA Observations of the Interaction of a Radio Jet with Molecular Gas in Minkowski's Object |journal=The Astrophysical Journal |date=4 April 2017 |volume=838 |issue=2 |pages=146 |doi=10.3847/1538-4357/aa65d7|bibcode=2017ApJ...838..146L |arxiv=1703.03006 |s2cid=119525917 |doi-access=free }} a model that has been reproduced by computer stimulations.{{cite journal |last1=Fragile |first1=P. Chris |last2=Anninos |first2=Peter |last3=Croft |first3=Steve |last4=Lacy |first4=Mark |last5=Witry |first5=Jason W. L. |title=Numerical Simulations of a Jet–Cloud Collision and Starburst: Application to Minkowski's Object |journal=The Astrophysical Journal |date=30 November 2017 |volume=850 |issue=2 |pages=171 |doi=10.3847/1538-4357/aa95c6|bibcode=2017ApJ...850..171F |arxiv=1701.00024 |s2cid=118932503 |doi-access=free }}

A stellar bridge has been detected between NGC 541 and the galaxy pair NGC 545/547, which lies 4.5 arcminutes to the northeast (projected distance circa 100 kpc).