NGC 5846

NGC 5846 is an elliptical galaxy located in the constellation Virgo. It is located at a distance of circa 90 million light years from Earth, which, given its apparent dimensions, means that NGC 5846 is about 110,000 light years across. It was discovered by William Herschel on February 24, 1786.[3] It lies near 110 Virginis and is part of the Herschel 400 Catalogue.[4]

NGC 5846
NGC 5846 (right) and NGC 5850 (left) by the Schulman Telescope at Mount Lemmon SkyCenter
Observation data (J2000 epoch)
ConstellationVirgo
Right ascension 15h 06m 29.3s[1]
Declination+01° 36′ 20″[1]
Redshift0.005711 ± 0.000017 [1]
Helio radial velocity1,712 ± 5 km/s[1]
Distance93 ± 32 Mly (28.5 ± 9.8 Mpc)[1]
Apparent magnitude (V)10.1 [2]
Characteristics
TypeE0-1 [1]
Apparent size (V)4′.1 × 3′.8
Notable featuresStrong X-ray source
Other designations
UGC 9706, CGCG 020-061, MCG +00-38-025, PGC 53932[1]

Characteristics

NGC 5846 is a giant elliptical galaxy with a round shape. It has a low luminosity active galactic nucleus, whose categorisation is ambiguous, having features that are observed both in LINER and HII regions.[5] The source of nuclear activity in galaxies is suggested to be a supermassive black hole that accretes material. NGC 5846 harbors a supermassive black hole with estimated mass (1.1±0.1)×109 M☉ based on the central velocity dispersion.[6][7]

NGC 5846 harbors a large number of globular clusters; over 1,200 have been detected in images by Hubble Space Telescope.[8] The specific frequency is similar to other elliptical galaxies in groups. As has been observed in other large elliptical galaxies, the metallicity has bimodial distribution, with metallicities roughly of [Fe/H]=-1.2 and -0.2.[9] Their typical effective radii are in the range of 3 - 5 pc, with the largest clusters located in the central regions. Seven of the globular clusters have X-ray counterparts, which are among the most luminous X-ray sources in NGC 5846. These clusters are mostly in the central region and they are optically luminous, compact and belong to the red subpopulation.[10]

Chandra image of NGC 5846 with superimposed contours of Hα+[N ii] emission. White crosses mark the detected CO cloud positions.[11]

The galaxy has complex X-ray morphology[12] that is considered to be the result of AGN outflows. Two inner bubbles in the hot gas, at a distance of 600 pc from the center and filled with radio emission, are clear indications of recent AGN feedback. A weak radio source, elongated in the NE–SW direction, connects the inner cavities. X-ray-bright rims surround the inner X-ray bubbles.[6] Many X-ray knots are visible, suggesting cooling sites. The scenario indicated by the Chandra observation is that of an AGN outflow, compressing and cooling the gas[13] in the central ~2 kpc (20" at the distance of NGC 5846).[11]

Hα observations[12][14][15] reveal the presence of warm ionized gas in the inner 2 kpc of NGC 5846. Spectra of this gas indicate irregular motion, with a typical velocity of 150–200 km s−1. The warm gas traces the X-ray-bright features, again suggesting a multiphase AGN outflow.[11] Using the Spitzer IRS[16] mid-infrared lines were detected (e.g., [Ne ii] 12.81 μm, [Ne iii] 15.55 μm) but no trace of polycyclic aromatic hydrocarbon (PAH) emission. Several sources are identified in the radio at 2.3, 5, and 15 GHz using VLBA data; these sources are aligned in the south–north direction.[17]

Recent Herschel PACS observations have detected the presence of [C ii]-emitting gas that extends to a radius of ~2 kpc and is centrally peaked. The [C ii] emission is almost exactly cospatial with the H-alpha +[N II] emission, and the total fluxes in [C ii] and H-alpha +[N II] have a ratio of 2.5, a very similar flux ratio value observed in other group-centered ellipticals.[15] Furthermore, the velocities inferred from the [C ii] line are consistent with those measured for the Hα line.[14] All of this evidence suggests that the [C ii] line is emitted by the warm gas, and it is not necessarily tracing the molecular phase.[11]

NGC 5846 has another indication that the cold gas is being disturbed by an AGN outburst. It has, in fact, an excess of cold (T ~ 30 K) dust approximately cospatial with the ionized and molecular gas. With a 70 μm luminosity of 3.5 × 1041 erg s−1[18], NGC 5846 shares the same dust properties as several giant ellipticals (e.g., NGC 4636 and NGC 5044[19]), which are best explained with the ejection of dusty gas from their centers by AGN activity that occurred ~107 yr ago.[11]

Three CO clouds have been detected in NGC 5846. Clouds 1 and 3 are resolved in at least one direction by ALMA 12 m array observations and extend to 1"2 and 2"9, respectively, and are about 5"5 and 8"4 away (0.6 and 1.0 kpc) from the galaxy center, respectively. Cloud 3 is aligned almost exactly along a dust filament, while cloud 1 also coincides with small dust extinction structures. The elongation and potential bimodality of the surface brightness of cloud 3 of NGC 5846 could indicate that it might be composed of two nearby (in projection) clouds. Cloud 2 lies further away from the centre and is thought to originate from cooling in the wakes beneath buoyant X-ray cavities where compressions stimulate significant large-scale, coherent radiative cooling.[11]

Nearby galaxies

NGC 5846 forms a non-interacting pair with NGC 5846A, which lies 0.7 arcminutes from NGC 5846.[20] Its proximity to NGC 5846 and high surface brightness suggests it has been tidally stripped.[21] The barred spiral galaxy NGC 5850 lies at a projected distance of 10 arcminutes from NGC 5846 and may form an interacting pair with NGC 5846 based on its disturbed morphology. It is suggested that the two galaxies had a high speed encounter approximately 200 million years ago.[22]

NGC 5846 is the foremost galaxy of the large galaxy group known as the NGC 5846 group. Other members of the group include NGC 5813, NGC 5831, NGC 5845, and NGC 5854.[23] The group has two subgroups, one centered around the elliptical NGC 5813 and the other around NGC 5846, lying at a projected separation of 600 kpc.[21] The group is part of the Virgo III Groups, a very obvious chain of galaxy groups on the left side of the Virgo cluster, stretching across 40 million light years of space.[24]

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References
  1. "NASA/IPAC Extragalactic Database". Results for NGC 5846. Retrieved 2016-01-18.
  2. "Revised NGC Data for NGC 5846". spider.seds.org. Retrieved 25 November 2018.
  3. Seligman, Courtney. "NGC 5846 (= PGC 42734)". Celestial Atlas. Retrieved 19 November 2018.
  4. O'Meara, Steve (2007). Herschel 400 Observing Guide. Cambridge University Press. p. 205. ISBN 9780521858939.
  5. Ho, Luis C.; Filippenko, Alexei V.; Sargent, Wallace L. W.; Peng, Chien Y. (October 1997). "A Search for "Dwarf" Seyfert Nuclei. IV. Nuclei with Broad Hα Emission". The Astrophysical Journal Supplement Series. 112 (2): 391–414. arXiv:astro-ph/9704099. doi:10.1086/313042.
  6. Machacek, Marie E.; Jerius, Diab; Kraft, Ralph; Forman, William R.; Jones, Christine; Randall, Scott; Giacintucci, Simona; Sun, Ming (10 December 2011). "Deep Chandra Observations of Edges and Bubbles in the NGC 5846 Galaxy Group". The Astrophysical Journal. 743 (1): 15. arXiv:1108.5229. Bibcode:2011ApJ...743...15M. doi:10.1088/0004-637X/743/1/15.
  7. Hu, Jian (June 2008). "The black hole mass–stellar velocity dispersion correlation: bulges versus pseudo-bulges". Monthly Notices of the Royal Astronomical Society. 386 (4): 2242–2252. arXiv:0801.1481. Bibcode:2008MNRAS.386.2242H. doi:10.1111/j.1365-2966.2008.13195.x.
  8. Forbes, Duncan A.; Brodie, Jean P.; Huchra, John (December 1996). "Globular Cluster Luminosity Functions and the Hubble Constant from WFPC2 Imaging: The Dominant Group Elliptical NGC 5846". The Astronomical Journal. 112: 2448. arXiv:astro-ph/9611141. Bibcode:1996AJ....112.2448F. doi:10.1086/118194.
  9. Forbes, Duncan A.; Brodie, Jean P.; Huchra, John (March 1997). "Hubble Space Telescope Imaging of the Globular Cluster System Around NGC 5846". The Astronomical Journal. 113: 887. arXiv:astro-ph/9612172. Bibcode:1997AJ....113..887F. doi:10.1086/118308.
  10. Chies-Santos, A. L.; Pastoriza, M. G.; Santiago, B. X.; Forbes, D. A. (4 August 2006). "The globular cluster system of NGC 5846 revisited: colours, sizes and X-ray counterparts". Astronomy & Astrophysics. 455 (2): 453–459. arXiv:astro-ph/0604499. Bibcode:2006A&A...455..453C. doi:10.1051/0004-6361:20054212.
  11. Temi, Pasquale; Amblard, Alexandre; Gitti, Myriam; Brighenti, Fabrizio; Gaspari, Massimo; Mathews, William G.; David, Laurence (27 April 2018). "ALMA Observations of Molecular Clouds in Three Group-centered Elliptical Galaxies: NGC 5846, NGC 4636, and NGC 5044". The Astrophysical Journal. 858 (1): 17. arXiv:1711.10630. Bibcode:2018ApJ...858...17T. doi:10.3847/1538-4357/aab9b0. This article contains quotations from this source, which is available under the Creative Commons Attribution 3.0 Unported (CC BY 3.0) license.
  12. Trinchieri, G.; Goudfrooij, P. (15 May 2002). "The peculiar small-scale X-ray morphology of NGC 5846 observed with Chandra". Astronomy & Astrophysics. 386 (2): 472–486. arXiv:astro-ph/0202416. Bibcode:2002A&A...386..472T. doi:10.1051/0004-6361:20020311.
  13. Brighenti, Fabrizio; Mathews, William G.; Temi, Pasquale (1 April 2015). "Hot Gaseous Atmospheres in Galaxy Groups and Clusters Are Both Heated and Cooled by X-Ray Cavities". The Astrophysical Journal. 802 (2): 118. arXiv:1501.07647. Bibcode:2015ApJ...802..118B. doi:10.1088/0004-637X/802/2/118.
  14. Caon, Nicola; Macchetto, Duccio; Pastoriza, Miriani (March 2000). "A Survey of the Interstellar Medium in Early‐Type Galaxies. III. Stellar and Gas Kinematics". The Astrophysical Journal Supplement Series. 127 (1): 39–58. Bibcode:2000ApJS..127...39C. doi:10.1086/313315. hdl:10183/109051.
  15. Werner, N.; Oonk, J. B. R.; Sun, M.; Nulsen, P. E. J.; Allen, S. W.; Canning, R. E. A.; Simionescu, A.; Hoffer, A.; Connor, T.; Donahue, M.; Edge, A. C.; Fabian, A. C.; von der Linden, A.; Reynolds, C. S.; Ruszkowski, M. (11 April 2014). "The origin of cold gas in giant elliptical galaxies and its role in fuelling radio-mode AGN feedback". Monthly Notices of the Royal Astronomical Society. 439 (3): 2291–2306. arXiv:1310.5450. Bibcode:2014MNRAS.439.2291W. doi:10.1093/mnras/stu006.
  16. Rampazzo, R.; Panuzzo, P.; Vega, O.; Marino, A.; Bressan, A.; Clemens, M. S. (11 June 2013). "A Spitzer–IRS spectroscopic atlas of early-type galaxies in the Revised Shapley–Ames Catalog". Monthly Notices of the Royal Astronomical Society. 432 (1): 374–403. arXiv:1303.4584. doi:10.1093/mnras/stt475.
  17. Filho, M. E.; Fraternali, F.; Markoff, S.; Nagar, N. M.; Barthel, P. D.; Ho, L. C.; Yuan, F. (9 April 2004). "Further clues to the nature of composite LINER/H II galaxies". Astronomy & Astrophysics. 418 (2): 429–443. arXiv:astro-ph/0401593. Bibcode:2004A&A...418..429F. doi:10.1051/0004-6361:20034486.
  18. Mathews, William G.; Temi, Pasquale; Brighenti, Fabrizio; Amblard, Alexandre (11 April 2013). "Variations of Mid- and Far-Infrared Luminosities Among Early-Type Galaxies: Relation to Stellar Metallicity and Cold Dust". The Astrophysical Journal. 768 (1): 28. arXiv:1303.3350. Bibcode:2013ApJ...768...28M. doi:10.1088/0004-637X/768/1/28.
  19. Temi, Pasquale; Brighenti, Fabrizio; Mathews, William G. (September 2007). "Spitzer Observations of Transient, Extended Dust in Two Elliptical Galaxies: New Evidence of Recent Feedback Energy Release in Galactic Cores". The Astrophysical Journal. 666 (1): 222–230. arXiv:0705.3710. Bibcode:2007ApJ...666..222T. doi:10.1086/520123.
  20. Sandage, A., Bedke, J. (1994), The Carnegie Atlas of Galaxies. Volume I, Carnegie Institution of Washington
  21. Mahdavi, Andisheh; Trentham, Neil; Tully, R. Brent (October 2005). "The NGC 5846 Group: Dynamics and the Luminosity Function to MR = -12". The Astronomical Journal. 130 (4): 1502–1515. arXiv:astro-ph/0506737. doi:10.1086/444560.
  22. Higdon, James L.; Buta, Ronald J.; Purcell, Guy B. (January 1998). "An Optical and H [CSC]i[/CSC] Study of NGC 5850: Victim of a High-Speed Encounter?". The Astronomical Journal. 115 (1): 80–104. doi:10.1086/300193.
  23. Makarov, Dmitry; Karachentsev, Igor (21 April 2011). "Galaxy groups and clouds in the local (z∼ 0.01) Universe". Monthly Notices of the Royal Astronomical Society. 412 (4): 2498–2520. arXiv:1011.6277. Bibcode:2011MNRAS.412.2498M. doi:10.1111/j.1365-2966.2010.18071.x.
  24. "The Virgo III Groups". www.atlasoftheuniverse.com. Retrieved 9 January 2019.


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