Sombrero Galaxy

The Sombrero Galaxy was discovered on May 11, 1781 by Pierre Méchain, who described the object in a May 1783 letter to J. Bernoulli that was later published in the Berliner Astronomisches Jahrbuch.{{cite book |author=G. R. Kepple |author2=G. W. Sanner |date=1998 |title=The Night Sky Observer's Guide |volume=2 |pages=451 |publisher=Willmann-Bell |isbn= 978-0-943396-60-6}}{{cite book |author=K. G. Jones |date=1991 |edition=2nd |title= Messier's Nebulae and Star Clusters |publisher=Cambridge University Press |isbn=978-0-521-37079-0}} Charles Messier made a handwritten note about this and five other objects (now collectively recognized as M104 – M109) to his personal list of objects now known as the Messier Catalogue, but it was not "officially" included until 1921. William Herschel independently discovered the object in 1784 and additionally noted the presence of a "dark stratum" in the galaxy's disc, what is now called a dust lane. Later astronomers were able to connect Méchain's and Herschel's observations.

In 1921, Camille Flammarion found Messier's personal list of the Messier objects including the hand-written notes about the Sombrero Galaxy. This was identified with object 4594 in the New General Catalogue, and Flammarion declared that it should be included in the Messier Catalogue. Since this time, the Sombrero Galaxy has been known as M104.

Image:Sombrero Galaxy (MIRI Image) (2024-137).png's Mid-Infrared Instrument in 2024.]]

As noted above, this galaxy's most striking feature is the dust lane that crosses in front of the bulge of the galaxy. This dust lane is actually a symmetrical ring that encloses the bulge of the galaxy.{{cite journal |author=G. J. Bendo |author2=B. A. Buckalew |author3=D. A. Dale |author4=B. T. Draine |author5=R. D. Joseph |author6=R. C. Kennicutt Jr. |author7=K. Sheth |author8=J.-D. T. Smith |author9=F. Walter | author10= D. Calzetti |author11=J. M. Cannon |author12=C. W. Engelbracht |author13=K. D. Gordon |author14=G. Helou |author15=D. Hollenbach |author16=E. J. Murphy |author17=H. Roussel |display-authors=6 |date=2006 |title=Spitzer and JCMT Observations of the Active Galactic Nucleus in the Sombrero Galaxy (NGC 4594) |journal=The Astrophysical Journal |volume=645 |issue=1 |pages=134–147 |bibcode=2006ApJ...645..134B |doi=10.1086/504033 |arxiv=astro-ph/0603160|s2cid=8027268 }} Most of the cold atomic hydrogen gas{{cite journal |last1=Bajaja |first1=E. |display-authors=4 |last2=Van Der Burg |first2=G. |last3=Faber |first3=S. M. |last4=Gallagher |first4=J. S. |last5=Knapp |first5=G. R. |last6=Shane |first6=W. W. |date=1984 |title=The distribution of neutral hydrogen in the Sombrero galaxy, NGC 4594 |journal=Astronomy & Astrophysics |volume=141 |pages=309–317 |bibcode=1984A&A...141..309B}} and the dust lie within this ring. The ring might also contain most of the Sombrero Galaxy's cold molecular gas, although this is an inference based on observations with low resolution and weak detections.{{cite journal |last1=Bajaja |first1=E. |last2=Dettmar |first2=R.-J. |last3=Hummel |first3=E. |last4=Wielebinski |first4=R. |date=1988 |title=The large-scale radio continuum structure of the Sombrero galaxy (NGC 4594) |journal=Astronomy & Astrophysics |volume=202 |pages=35–40 |bibcode=1988A&A...202...35B}}{{cite journal |author=J. S. Young |display-authors=4 |author2=S. Xie |author3=L. Tacconi |author4=P. Knezek |author5=P. Viscuso |author6=L. Tacconi-Garman |author7=N. Scoville |author8=S. Schneider |author9=F. P. Schloerb | author10= S. Lord |author11=A. Lesser |author12=J. Kenney |author13=Y.-L. Huang |author14=N. Devereux |author15=M. Claussen |author16=J. Case |author17=J. Carpenter |author18=M. Berry |author19=L. Allen |date=1995 |title=The FCRAO Extragalactic CO Survey. I. The Data |journal=The Astrophysical Journal |volume=98 |pages=219–257 |bibcode=1995ApJS...98..219Y |doi=10.1086/192159|doi-access=free }} Additional observations are needed to confirm that the Sombrero galaxy's molecular gas is constrained to the ring. Based on infrared spectroscopy, the dust ring is the primary site of star formation within this galaxy.

The nucleus of the Sombrero Galaxy is classified as a low-ionization nuclear emission-line region (LINER).{{cite journal |author=L. C. Ho |author2=A. V. Filippenko |author3=W. L. W. Sargent |date=1997 |title=A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies |journal=The Astrophysical Journal |volume=112 |issue=2 |pages=315–390 |bibcode=1997ApJS..112..315H |doi=10.1086/313041 |arxiv=astro-ph/9704107|s2cid=17086638 }} These are nuclear regions where ionized gas is present, but the ions are only weakly ionized (i.e. the atoms are missing relatively few electrons). The source of energy for ionizing the gas in LINERs has been debated extensively. Some LINER nuclei may be powered by hot, young stars found in star formation regions, whereas other LINER nuclei may be powered by active galactic nuclei (highly energetic regions that contain supermassive black holes). Infrared spectroscopy observations have demonstrated that the nucleus of the Sombrero Galaxy is probably devoid of any significant star formation activity. However, a supermassive black hole has been identified in the nucleus (as discussed in the subsection below), so this active galactic nucleus is probably the energy source that weakly ionizes the gas in the Sombrero Galaxy.

In the 1990s, a research group led by John Kormendy demonstrated that a supermassive black hole is present within the Sombrero Galaxy.{{cite journal |author=J. Kormendy |display-authors=4 |author2=R. Bender |author3=E. A. Ajhar |author4=A.Dressler |author5=S. M. Faber |author6=K. Gebhardt |author7=C. Grillmair |author8=T. R. Lauer |author9=D. Richstone | author10=S. Tremaine |date=1996 |title=Hubble Space Telescope Spectroscopic Evidence for a 1 X 10 9 M☉ Black Hole in NGC 4594 |journal=The Astrophysical Journal |volume=473 |issue=2 |pages=L91–L94 |bibcode=1996ApJ...473L..91K |doi=10.1086/310399|doi-access=free }} Using spectroscopy data from both the CFHT and the Hubble Space Telescope, the group showed that the speed of revolution of the stars within the center of the galaxy could not be maintained unless a mass 1 billion times that of the Sun, {{solar mass|10⁹}}, is present in the center. This is among the most massive black holes measured in any nearby galaxy, and is the nearest billion-solar-mass black hole to Earth.

At radio and X-ray wavelengths, the nucleus is a strong source of synchrotron radiation.{{cite journal |last1=de Bruyn |first1=A. G. |last2=Crane |first2=P. C. |last3=Price |first3=R. M. |last4=Carlson |first4=J. B. |date=1976 |title=The radio sources in the nuclei of NGC 3031 and NGC 4594 |journal=Astronomy & Astrophysics |volume=46 |pages=243–251 |bibcode=1976A&A....46..243D}}{{cite journal |first1=E. |last1=Hummel |last2=van der Hulst |first2=J. M. |last3=Dickey |first3=J. M. |date=1984 |title=Central radio sources in spiral galaxies – Starburst or accretion |journal=Astronomy & Astrophysics |volume=134 |pages=207–221 |bibcode=1984A&A...134..207H}}{{cite journal |author=A. Thean |display-authors=4 |author2=A. Pedlar |author3=M. J. Kukula |author4=S. A. Baum |author5=C. P. O'Dea |date=2000 |title=High-resolution radio observations of Seyfert galaxies in the extended 12-μm sample - I. The observations |journal=Monthly Notices of the Royal Astronomical Society |volume=314 |issue=3 |pages=573–588 |bibcode=2000MNRAS.314..573T |doi=10.1046/j.1365-8711.2000.03401.x |doi-access=free |arxiv=astro-ph/0001459|s2cid=13990625 }}{{cite journal |author=T. Di Matteo |author2=C. L. Carilli |author3=A. C. Fabian |date=2001 |title=Limits on the Accretion Rates onto Massive Black Holes in Nearby Galaxies |journal=The Astrophysical Journal |volume=547 |issue=2 |pages=731–739 |bibcode=2001ApJ...547..731D |doi=10.1086/318405 |arxiv=astro-ph/0005516|s2cid=15963846 }}{{cite journal |author=S. Pellegrini |display-authors=4 |author2=G. Fabbiano |author3=F. Fiore |author4=G. Trinchieri |author5=A. Antonelli |date=2002 |title=Nuclear and global X-ray properties of LINER galaxies: Chandra and BeppoSAX results for Sombrero and NGC 4736 |journal=Astronomy & Astrophysics |volume=383 |issue=1 |pages=1–13 |bibcode=2002A&A...383....1P |doi=10.1051/0004-6361:20011482 |arxiv=astro-ph/0111353|s2cid=16321493 }}{{cite journal |author=S. Pellegrini |author2=A. Baldi |author3=G. Fabbiano |author4=D.-W. Kim |date=2003 |title=An XMM-Newton and Chandra Investigation of the Nuclear Accretion in the Sombrero Galaxy (NGC 4594) |journal=The Astrophysical Journal |volume=597 |issue=1 |pages=175–185 |bibcode=2003ApJ...597..175P |doi=10.1086/378235 |arxiv=astro-ph/0307142|s2cid=2372180 }}{{cite journal |author=M. Krause |author2=R. Wielebinski |author3=M. Dumke |date=2006 |title=Radio polarization and sub-millimeter observations of the Sombrero galaxy (NGC 4594). Large-scale magnetic field configuration and dust emission. |journal=Astronomy & Astrophysics |volume=448 |issue=1 |pages=133–142 |bibcode=2006A&A...448..133K |doi=10.1051/0004-6361:20053789 |arxiv=astro-ph/0510796|s2cid=204936461 }} Synchrotron radiation is produced when high-velocity electrons oscillate as they pass through regions with strong magnetic fields. This emission is quite common for active galactic nuclei. Although radio synchrotron radiation may vary over time for some active galactic nuclei, the luminosity of the radio emission from the Sombrero Galaxy varies only 10–20%.

In 2006, two groups published measurements of the terahertz radiation from the nucleus of the Sombrero Galaxy at a wavelength of {{val|850|ul=µm}}. This terahertz radiation was found not to originate from the thermal emission from dust (which is commonly seen at infrared and submillimeter wavelengths), synchrotron radiation (which is commonly seen at radio wavelengths), bremsstrahlung emission from hot gas (which is uncommonly seen at millimeter wavelengths), or molecular gas (which commonly produces submillimeter spectral lines). The source of the terahertz radiation remains unidentified.

The Sombrero Galaxy has a relatively large number of globular clusters, observational studies of which have produced population estimates in the range of 1,200 to 2,000.{{cite journal |author=K.-I. Wakamatsu |date=1977 |title=Radial distribution and total number of globular clusters in M104 |journal=Publications of the Astronomical Society of the Pacific |volume=89 |pages=267–270 |bibcode=1977PASP...89..267W |doi=10.1086/130114|s2cid=121568307 |doi-access=free }}{{cite journal |author=W. E. Harris |author2=H. C. Harris |author3=G. L. H. Harris |date=1984 |title=Globular clusters in galaxies beyond the local group. III NGC 4594 (the Sombrero) |journal=The Astronomical Journal |volume=89 |pages=216–223 |bibcode=1984AJ.....89..216H |doi=10.1086/113504|doi-access=free }}{{cite journal |author=T. J. Bridges |author2=D. A. Hanes |date=1992 |title=The globular cluster system of NGC 4594 (the Sombrero) |journal=The Astronomical Journal |volume=103 |pages=800–814 |bibcode=1992AJ....103..800B |doi=10.1086/116102|doi-access=free }} The ratio of globular clusters to the galaxy's total luminosity is high compared to the Milky Way and similar galaxies with small bulges, but comparable to other galaxies with large bulges. These results have often been used to demonstrate that the number of a galaxy's globular clusters is thought to be related to the size of its bulge. The surface density of the globular clusters generally follows the bulge's light profile, except near the galaxy's center.{{cite journal |author=S. S. Larsen |author2=D. A. Forbes |author3=J. P. Brodie |date=2001 |title=Hubble Space Telescope photometry of globular clusters in the Sombrero galaxy |journal=Monthly Notices of the Royal Astronomical Society |volume=327 |issue=4 |pages=1116–1126 |bibcode=2001MNRAS.327.1116L |doi=10.1046/j.1365-8711.2001.04797.x |doi-access=free |arxiv=astro-ph/0107082|s2cid=15369293 |url=https://researchbank.swinburne.edu.au/file/930d5c03-c31e-437b-8475-b9496b44f13a/1/PDF%20(Accepted%20manuscript).pdf }}

At least two methods have been used to measure the distance to the Sombrero Galaxy.

The first method relies on comparing the measured fluxes from the galaxy's planetary nebulae to the known luminosity of planetary nebulae in the Milky Way. This method gave the distance to the Sombrero Galaxy as {{cvt|29|±|2|Mly|lk=on}}.{{cite journal |author=H. C. Ford |author2=X. Hui |author3=R. Ciardullo |author4=G. H. Jacoby |author5=K. C. Freeman |date=1996 |title=The Stellar Halo of M104. I. A Survey for Planetary Nebulae and the Planetary Nebula Luminosity Function Distance |journal=The Astrophysical Journal |volume=458 |pages=455–466 |bibcode=1996ApJ...458..455F |doi=10.1086/176828|doi-access=free }}

The second method is the surface brightness fluctuations method, which uses the grainy appearance of the galaxy's bulge to estimate the distance to it. Nearby galaxy bulges appear very grainy, while more distant bulges appear smooth. Early measurements using this technique gave distances of {{cvt|30.6|±|1.3|Mly}}.{{cite journal |author=E. A. Ajhar |display-authors=4 |author2=T. R. Lauer |author3=J. L. Tonry |author4=J. P. Blakeslee |author5=A. Dressler |author6=J. A. Holtzman |author7=M. Postman |date=1997 |title=Calibration of the Surface Brightness Fluctution Method for use with the Hubble Space Telescope |journal=The Astronomical Journal |volume=114 |pages=626–634 |bibcode=1997AJ....114..626A |doi=10.1086/118498}} Later, after some refinement of the technique, a distance of {{cvt|32|±|3|Mly}} was measured.{{cite journal |author=J. L. Tonry |display-authors=4 |author2=A. Dressler |author3=J. P. Blakeslee |author4=E. A. Ajhar |author5=A. B. Fletcher |author6=G. A. Luppino |author7=M. R. Metzger |author8=C. B. Moore |date=2001 |title=The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances |journal=The Astrophysical Journal |volume=546 |issue=2 |pages=681–693 |bibcode=2001ApJ...546..681T |doi=10.1086/318301 |arxiv=astro-ph/0011223|s2cid=17628238 }} This was even further refined in 2003 to {{cvt|29.6|±|2.5|Mly}}.{{cite journal |author=Jensen, Joseph B. |display-authors=4 |author2=Tonry, John L. |author3=Barris, Brian J. |author4=Thompson, Rodger I. |author5=Liu, Michael C. |author6=Rieke, Marcia J. |author7=Ajhar, Edward A. |author8=Blakeslee, John P. |date=2003 |title=Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations |journal=The Astrophysical Journal |volume=583 |issue=2 |pages=712–726 |bibcode=2003ApJ...583..712J |doi=10.1086/345430 |arxiv=astro-ph/0210129|s2cid=551714 }}

The average distance measured through these two techniques is {{cvt|29.3|±|1.6|Mly}}.{{efn|name=average|reference= average(29.6 ± 2.5, 29 ± 2) = ((29.6 + 29) / 2) ± ((2.5² + 2²)^0.5 / 2) = 29.3 ± 1.6}}

The mass of M104 is estimated to be 800 billions solar masseshttps://science.nasa.gov/mission/hubble/science/explore-the-night-sky/hubble-messier-catalog/messier-104/

The galaxy's absolute magnitude (in the blue) is estimated as −21.9 at {{cvt|30.6|Mly}} (−21.8 at the average distance of above)—which, as stated above, makes it the brightest galaxy in a radius of {{cvt|32.6|Mly}} around the Milky Way.

A 2016 report used the Hubble Space Telescope to measure the distance to M104 based on the tip of the red-giant branch method, yielding 9.55 ± 0.13 ± 0.31 Mpc.

The Sombrero Galaxy lies within a complex, filament-like cloud of galaxies that extends to the south of the Virgo Cluster.{{cite book |first=R. B. | last= Tully |date=1988 |title=Nearby Galaxies Catalog |publisher=Cambridge University Press |isbn=978-0-521-35299-4}} However, it is unclear whether it is part of a formal galaxy group. Hierarchical methods for identifying groups, which determine group membership by considering whether individual galaxies belong to a larger aggregate of galaxies, typically produce results showing that the Sombrero Galaxy is part of a group that includes NGC 4487, NGC 4504, NGC 4802, UGCA 289, and possibly a few other galaxies.{{cite journal |first1=P. | last1= Fouque | first2=E. | last2= Gourgoulhon | first3=P. | last3= Chamaraux |first4=G. | last4=Paturel |date=1992 |title=Groups of galaxies within 80 Mpc. II – The catalogue of groups and group members |journal=Astronomy & Astrophysics |volume=93 |pages=211–233 |bibcode=1992A&AS...93..211F}}{{cite journal |first1= G. |last1= Giuricin |first2= C. |last2= Marinoni |first3= L. |last3= Ceriani |first4= A. |last4= Pisani |date=2000 |title= Nearby Optical Galaxies: Selection of the Sample and Identification of Groups |journal=The Astrophysical Journal |volume=543 |issue=1 |pages=178–194 |bibcode= 2000ApJ...543..178G |doi=10.1086/317070 |arxiv=astro-ph/0001140|s2cid= 9618325 }} However, results that rely on the percolation method (also known as the friends-of-friends method), which links individual galaxies together to determine group membership, indicate that either the Sombrero Galaxy is not in a group{{cite journal |first=A. | last= Garcia |date=1993 |title=General study of group membership. II – Determination of nearby groups |journal= Astronomy & Astrophysics |volume=100 |pages=47–90 |bibcode= 1993A&AS..100...47G}} or that it may be only part of a galaxy pair with UGCA 287.

Besides that, M104 is also accompanied by an ultra-compact dwarf galaxy, discovered in 2009, with an absolute magnitude of −12.3, an effective radius of just {{convert|47.9|ly|abbr=in|e6AU|lk=out}}, and a mass of 3.3×{{solar mass|10⁷|link=on}}{{cite journal | display-authors = 3| author1=Hau, George K. T. |author2=Spitler, Lee R. |author3=Forbes, Duncan A. |author4=Proctor, Robert N. |author5=Strader, Jay |author6=Mendel, J. Trevor |author7=Brodie, Jean P. |author8= Harris, William E. |title=An ultra-compact dwarf around the Sombrero galaxy (M104): the nearest massive UCD |journal=Monthly Notices of the Royal Astronomical Society: Letters |date=2009 |volume=394 |issue=1 |pages=L97–L101 |bibcode= 2009MNRAS.394L..97H |doi=10.1111/j.1745-3933.2009.00618.x | doi-access=free |arxiv= 0901.1693|s2cid=17015063 }}

The Sombrero Galaxy is 11.5° west of Spica and 5.5° north-east of Eta Corvi.{{cite book |author=S. J. O'Meara |date=1998 |title=The Messier Objects |publisher=Cambridge University Press |isbn=978-0-521-55332-2 |url-access=registration |url=https://archive.org/details/messierobjectsfi00omea }} Although it is visible with 7×35 binoculars or a {{convert|4|in|adj=on}} amateur telescope, an {{convert|8|in|adj=on}} telescope is needed to distinguish the bulge from the disk, and a 10- or 12-inch (250 or 300 mm) telescope to see the dark dust lane.

One artistic work referencing the Sombrero Galaxy is the song South of the Sombrero Galaxy by St. Louis folk metal band Ars Arcanum. The gritty sci-fi Western piece is told from the perspective of a man on the run, from both the law and his own troubled past. The Sombrero Galaxy serves as a backdrop for the song’s narrative, blending cosmic imagery with themes of pursuit and regret.{{cite web | title=South of the Sombrero Galaxy | url=https://arsarcanum.bandcamp.com/track/south-of-the-sombrero-galaxy | website=Ars Arcanum's South of the Sombrero Galaxy on Bandcamp | access-date=October 3, 2024}}

File:Sombrero Galaxy in infrared (Ssc2005-11a3).jpg|M104 in infrared by the Spitzer Space Telescope

• List of Messier objects
• Lists of astronomical objects
• NGC 1167, another LINER galaxy
• NGC 1291, a galaxy with an outer dust ring
• NGC 4725, a similar galaxy with an extended dust ring
• NGC 6027a, a member of Seyfert's Sextet with a very similar dust ring structure
• NGC 7742, a spiral galaxy with a similar dust ring
• NGC 7814, a galaxy sometimes referred to as "the little sombrero"
• Ring galaxy
• Messier object
• New General Catalogue

{{Notelist}}

{{Reflist}}

{{Commons category|Sombrero Galaxy}}

• {{WikiSky|name=The Sombrero Galaxy}}
• [https://web.archive.org/web/20070117183138/http://www.spacetelescope.org/images/html/opo0328a.html Hubble Mosaic of the Majestic Sombrero Galaxy (ESA)]
• [http://hubblesite.org/newscenter/newsdesk/archive/releases/2003/28/image/a HubbleSite: The Majestic Sombrero Galaxy (M104)] {{Webarchive|url=https://web.archive.org/web/20080516051640/http://hubblesite.org/newscenter/newsdesk/archive/releases/2003/28/image/a |date=2008-05-16 }}
• [http://www.nightskyinfo.com/archive/m104_galaxy/ M104, the Sombrero Galaxy (NightSkyInfo.com)]
• [http://messier.seds.org/m/m104.html Messier 104 (SEDS)]
• [http://chandra.harvard.edu/photo/2007/sombrero/ Sombrero Galaxy: A Great Observatories View]
• [http://www.dsi-astronomie.de/M104.htm M104 The Sombrero Galaxy]
• {{cite web |last=Bauer |first=Amanda |title=M104 – Sombrero Galaxy |url=http://www.deepskyvideos.com/videos/messier/M104_sombrero_galaxy.html |work=Deep Sky Videos |publisher=Brady Haran |author2=Merrifield, Michael}}
• [http://www.constellation-guide.com/sombrero-galaxy-messier-104/ Sombrero Galaxy (Messier 104) at Constellation Guide]
• [https://www.youtube.com/watch?v=8zOtfrVpDpk South of the Sombrero Galaxy On YouTube]

{{Messier objects}}

{{Astronomical catalogs|M=104|NGC=4594|PGC=42407|UGC=293|GC=3132}}

{{Ngc50}}

{{Virgo (constellation)}}

{{Portal bar|Astronomy|Stars|Outer space}}

{{Authority control}}

{{Sky|12|39|59.4314|-|11|37|23.118|29300000}}

{{DEFAULTSORT:Sombrero Galaxy}}

Category:Elliptical galaxies

Category:Spiral galaxies

Category:LINER galaxies

Category:Virgo (constellation)

Category:Messier objects

Category:NGC objects

042407

17810511

Category:Discoveries by Pierre Méchain

Category:Peculiar galaxies

293

12373-1120

-02-32-020