NGC 4636

NGC 4636 is an elliptical galaxy located in the constellation Virgo. It is located at a distance of circa 55 million light years from Earth, which, given its apparent dimensions, means that NGC 4636 is about 105,000 light years across. It was discovered by William Herschel on February 23, 1784.[3] NGC 4636 lies one and a half degrees southwest of Delta Virginis. It can be viewed through a telescope at a ×23 magnification as a bright oval glow. It is part of the Herschel 400 Catalogue.[4]

NGC 4636
SDSS image of the elliptical galaxy NGC 4636.
Observation data (J2000 epoch)
ConstellationVirgo
Right ascension12h 42m 49.8s[1]
Declination+02° 41′ 16″[1]
Redshift0.003129 ± 0.000014 [1]
Helio radial velocity938 ± 4 km/s[1]
Distance53 ± 11 Mly (16.3 ± 3.4 Mpc)[1]
Apparent magnitude (V)9.4 [2]
Characteristics
TypeE/S0_1 [1]
Apparent size (V)6′.0 × 4′.7
Notable featuresStrong X-ray source
Other designations
UGC 7878, VCC 1939, CGCG 043-002, MCG +01-32-137, PGC 42734[1]

Characteristics

The central part of NGC 4636 is circular and is surrounded by an elongated fainter envelope, containing a large number of globular clusters.[5] The galaxy has an active galactic nucleus (AGN) that has been categorised as LINER or a type 1.9 Seyfert galaxy.[6] The source of nuclear activity in galaxies is suggested to be a supermassive black hole that accretes material. NGC 4636 harbors a relatively small supermassive black hole with mass 7.9×107 M☉, as inferred from the bulge velocity dispersion.[7]

Molecular gas
NGC 4636 by Hubble Space Telescope

When imaged in CO(2–1) there appear molecular clouds in NGC 4636. Cloud 1 is not associated with detectable optical emission and is out of the dust extinction map field of view, while cloud 2 is centered on a dust absorption knot and aligned with a ridge in the optical line emission map. The faint NGC 4636 ALMA continuum is in good agreement with the expected emission from cold dust, which would indicate that the dust content of NGC 4636 is fairly centrally located. The associated total molecular mass is 2.6×105 M☉.[8]

The ultraviolet emission of NGC 4636 exhibits O vi emission, which is a tracer of gas cooling. The measured emission indicates a cooling rate of 0.3 M⊙ yr−1.[9][10] Polycyclic aromatic hydrocarbons (PAH) emission was detected at 11.3 and 17 μm, as well as [Ne ii], [Ne iii], and [S iii] lines in the center of NGC 4636 (within re/8) using the Spitzer IRS.[11] The far infrared emission of the galaxy, as observed by the Infrared Space Observatory is 50 times more than expected based on stellar emission alone. This strongly suggests that there is dust, probably accreted in a recent merger with a gas-rich galaxy.[12] Hα observations reveal the presence of warm (T ~ 104 K) ionized gas in the inner kpc of NGC 4636. Spectra of this gas indicate irregular motion, with a typical velocity of 150–200 km/s. Hα maps of the galaxy core show the presence of a cavity in the distribution of the ionized gas encircled by a dense shell located at a distance of ~400 pc from the center. Again, the most plausible explanation is gas expansion caused by AGN activity.[8][13][14][15]

In NGC 4636, the [C ii] emission extends to a radius of ~1 kpc and is centrally peaked. The velocities inferred from the [C ii] line are consistent with those measured for the Hα line. Finally, NGC 4636 has an excess of cold dust, approximately cospatial with the ionized and molecular gas.[16][17] As above, this dust is expected be embedded in cold gas, to be protected against rapid sputtering. The extended dust distribution originates from the ejection of cold gas by AGN activity 10 Myr ago.[16]

Globular clusters

NGC 4636 is characterised by its large number of globular clusters, much larger than that of galaxies with similar size located not in the centre of galaxy clusters. The total number of globular clusters within a radius of 14 arcminutes is estimated to be 4,200 ± 120 and within 7 arcminutes is estimated to be 3,500 ± 170.[18] In comparison, 12,000 ± 800 globular clusters orbit around Messier 87, the giant elliptical galaxy at the centre of the Virgo Cluster, and 150–200 lie in and around the Milky Way. The number of globular clusters drops abruptly at 7 and 9 arcminutes, probably indicating the edge of the galaxy.[18]

The color distribution of the globular clusters in the galaxy is bimodal, a distribution that has been observed in other galaxies too. The globular clusters are characterised based on their color as blue or red.[18] The population of red clusters is higher. Similarly with color, the metallicity distribution is bimodal, with two peaks at [Fe/H] = −1.23(σ = 0.32) and −0.35(σ = 0.19). The ages of the globular clusters in NGC 4636 vary from 2 to 15 billion years, with a bit more than a quarter of the clusters having ages less than 5 billion years. It has been suggested that the younger clusters were formed during the merging of smaller galaxies with the elliptical galaxy.[19]

The velocity dispersion of the clusters is 231+15
−17 km/s, with the velocity dispersion of the blue clusters being slightly larger.[20] This velocity dispersion is similar to that of Messier 60, which is, however, a brighter galaxy. Comparing the velocity dispersion of the globular clusters with the stellar one it is calculated that mass-to-light ratio is not constant, but should increase as the galactocentric distance increases, indicating the existence of an extended dark matter halo in NGC 4636.[21][22]

X-ray emission
Chandra image of the core of NGC 4636 with superimposed contours of Hα+[N ii] emission. White crosses mark the detected CO cloud positions.

NGC 4636 is one of the most luminous nearby elliptical galaxies when observed in X-rays, with estimated X-ray flux of 1.8×1041 erg/s. A hot gas corona around the galaxy was first detected by the Einstein Observatory.[23] Based on the hot interstellar medium temperature profile, the total mass of the halo was estimated to be 1.5×1012 M☉ within a radius of 35 kpc. The percentage of non-luminous matter mass is estimated to be between 50% and 80% of the total galactic mass, implying an exceptionally low baryon fraction in NGC 4636 and the presence of a large dark matter halo.[24]

The halo of NGC 4636 has some unique features. Observations by the Chandra X-ray Observatory revealed symmetric, 8 kpc long structures within the halo that look like spiral arms. The arms are about 30 percent hotter than the surrounding gas cloud.[25] The arms form the rim of two large ellipsoid bubbles of hot gas. One more bubble-like feature has been detected about 2 kpc south of the northeastern arm. A weak radio source, elongated in the NE–SW direction, connects the NE and SW bubbles. These large bubbles are likely the result of shocks generated by the AGN jets.[26] It is possible that the bubbles have different ages, generated by different AGN outbursts, as indicated by the presence of radio-emitting plasma in one cavity, while the others are radio-quiet.[27]

NGC 4636 has an X-ray-bright core, having a radius of ~1 kpc. The core shows a central cavity surrounded by a bright edge.[26] Interestingly, the small X-ray cavity surrounds the ~1 kpc radio jet detected at 1.4 GHz[28] and is likely generated by the jet. Thus, the X-ray and radio observations point to a scenario in which gas may be currently outflowing in the central kpc of NGC 4636.[8]

There are 318 point X-ray sources in the field of NGC 4636. About 25% of them are identified as background sources. 77 of the sources match the location of globular clusters. No correlation was found between the X-ray luminosities of the matched point sources and the luminosity or color of the host GC candidates. The other point sources are low-mass X-ray binaries.[29]

Supernovae

Two supernovae have been observed in NGC 4636, the first being SN 1939 A. It was a type Ia supernova whose maximum magnitude was estimated to be 11.9.[30][31] It was discovered by Fritz Zwicky.[32] In January 2020 another type Ia supernova, SN 2020ue, was discovered by Koichi Itagaki.[33]

Nearby galaxies

NGC 4636 is the foremost galaxy of the galaxy group known as the NGC 4636 group. Other members of the group include NGC 4457, NGC 4586, NGC 4587, NGC 4600, NGC 4665, and NGC 4688.[34] These galaxies, along with NGC 4753, Messier 61 and their groups form the southern boundary of the Virgo cluster. It can be difficult to determine which galaxies belong to which group especially around the southern edge of the Virgo cluster where there is a confusion of galaxies at different distances.[35] NGC 4636 has also been listed as a member of the Virgo Cluster.

See also
  • NGC 720 – another elliptical galaxy with X-ray halo

References
  1. "NASA/IPAC Extragalactic Database". Results for NGC 4636. Retrieved 2016-01-18.
  2. "Revised NGC Data for NGC 4636". spider.seds.org. Retrieved 25 November 2018.
  3. Seligman, Courtney. "NGC 4636 (= PGC 42734)". Celestial Atlas. Retrieved 19 November 2018.
  4. O'Meara, Steve (2007). Herschel 400 Observing Guide. Cambridge University Press. p. 150. ISBN 9780521858939.
  5. Sandage, A., Bedke, J. (1994), The Carnegie Atlas of Galaxies. Volume I, Carnegie Institution of Washington
  6. 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. Bibcode:1997ApJS..112..391H. doi:10.1086/313042. S2CID 15256980.
  7. Merritt, D.; Ferrarese, L. (21 January 2001). "Black hole demographics from the M bullet - relation". Monthly Notices of the Royal Astronomical Society. 320 (3): L30–L34. doi:10.1046/j.1365-8711.2001.04165.x.
  8. 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. S2CID 54062372. This article contains quotations from this source, which is available under the Creative Commons Attribution 3.0 Unported (CC BY 3.0) license.
  9. Bregman, Joel N.; Miller, Eric D.; Irwin, Jimmy A. (1 June 2001). "The Detection of a Cooling Flow Elliptical Galaxy from O [CSC]vi[/CSC] Emission". The Astrophysical Journal. 553 (2): L125–L128. doi:10.1086/320675.
  10. Bregman, Joel N.; Miller, Eric D.; Athey, Alex E.; Irwin, Jimmy A. (20 December 2005). "O VI in Elliptical Galaxies: Indicators of Cooling Flows". The Astrophysical Journal. 635 (2): 1031–1043. arXiv:astro-ph/0511284. Bibcode:2005ApJ...635.1031B. doi:10.1086/497421. S2CID 5336177.
  11. 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. Bibcode:2013MNRAS.432..374R. doi:10.1093/mnras/stt475. S2CID 119266149.
  12. Temi, Pasquale; Mathews, William G.; Brighenti, Fabrizio; Bregman, Jesse D. (10 March 2003). "Dust in Hot Gas: Far-Infrared Emission from Three Local Elliptical Galaxies". The Astrophysical Journal. 585 (2): L121–L124. arXiv:astro-ph/0301452. Bibcode:2003ApJ...585L.121T. doi:10.1086/374326. S2CID 6175517.
  13. 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.
  14. 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. S2CID 53953986.
  15. Ahoranta, Jussi; Finoguenov, Alexis; Pinto, Ciro; Sanders, Jeremy; Kaastra, Jelle; de Plaa, Jelle; Fabian, Andrew (18 August 2016). "Observations of asymmetric velocity fields and gas cooling in the NGC 4636 galaxy group X-ray halo". Astronomy & Astrophysics. 592: A145. arXiv:1607.07444. Bibcode:2016A&A...592A.145A. doi:10.1051/0004-6361/201527523. S2CID 59029532.
  16. Temi, Pasquale; Brighenti, Fabrizio; Mathews, William G. (10 May 2007). "Far-Infrared Spitzer Observations of Elliptical Galaxies: Evidence for Extended Diffuse Dust". The Astrophysical Journal. 660 (2): 1215–1231. arXiv:astro-ph/0701431. Bibcode:2007ApJ...660.1215T. doi:10.1086/513690. S2CID 8819240.
  17. 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. S2CID 118646459.
  18. Dirsch, B.; Schuberth, Y.; Richtler, T. (14 March 2005). "A wide-field photometric study of the globular cluster system of NGC 4636". Astronomy & Astrophysics. 433 (1): 43–56. arXiv:astro-ph/0503283. Bibcode:2005A&A...433...43D. doi:10.1051/0004-6361:20035737. S2CID 14017938.
  19. Park, Hong Soo; Lee, Myung Gyoon; Hwang, Ho Seong; Kim, Sang Chul; Arimoto, Nobuo; Yamada, Yoshihiko; Tamura, Naoyuki; Onodera, Masato (10 November 2012). "The Globular Cluster System of NGC 4636 and Formation of Globular Clusters in Giant Elliptical Galaxies". The Astrophysical Journal. 759 (2): 116. arXiv:1209.3890. Bibcode:2012ApJ...759..116P. doi:10.1088/0004-637X/759/2/116. S2CID 118512169.
  20. Park, Hong Soo; Lee, Myung Gyoon; Hwang, Ho Seong; Arimoto, Nobuo; Tamura, Naoyuki; Onodera, Masato (20 January 2010). "The Globular Cluster System of the Virgo Giant Elliptical Galaxy NGC 4636. I. Subaru/Faint Object Camera and Spectrograph Spectroscopy and Database". The Astrophysical Journal. 709 (1): 377–385. arXiv:0912.0340. Bibcode:2010ApJ...709..377P. doi:10.1088/0004-637X/709/1/377. S2CID 119238390.
  21. Lee, Myung Gyoon; Park, Hong Soo; Hwang, Ho Seong; Arimoto, Nobuo; Tamura, Naoyuki; Onodera, Masato (1 February 2010). "The Globular Cluster System of the Virgo Giant Elliptical Galaxy NGC 4636. Ii. Kinematics of the Globular Cluster System". The Astrophysical Journal. 709 (2): 1083–1099. arXiv:0912.1728. Bibcode:2010ApJ...709.1083L. doi:10.1088/0004-637X/709/2/1083. S2CID 118547886.
  22. Schuberth, Y.; Richtler, T.; Hilker, M.; Salinas, R.; Dirsch, B.; Larsen, S. S. (9 August 2012). "Dynamics of the NGC 4636 globular cluster system". Astronomy & Astrophysics. 544: A115. doi:10.1051/0004-6361/201015038.
  23. Forman, W.; Jones, C.; Tucker, W. (June 1985). "Hot coronae around early-type galaxies". The Astrophysical Journal. 293: 102. Bibcode:1985ApJ...293..102F. doi:10.1086/163218.
  24. Loewenstein, M.; Mushotzky, R. (July 2003). "The nature of dark matter in elliptical galaxies: Chandra observations of NGC 4636". Nuclear Physics B - Proceedings Supplements. 124: 91–94. arXiv:astro-ph/0205359. Bibcode:2003NuPhS.124...91L. doi:10.1016/S0920-5632(03)02085-1. S2CID 14616681.
  25. Jones, C.; Forman, W.; Vikhlinin, A.; Markevitch, M.; David, L.; Warmflash, A.; Murray, S.; Nulsen, P. E. J. (10 March 2002). "Chandra Observations of NGC 4636—an Elliptical Galaxy in Turmoil". The Astrophysical Journal. 567 (2): L115–L118. arXiv:astro-ph/0108114. Bibcode:2002ApJ...567L.115J. doi:10.1086/340114. S2CID 119463742.
  26. Baldi, A.; Forman, W.; Jones, C.; Kraft, R.; Nulsen, P.; Churazov, E.; David, L.; Giacintucci, S. (20 December 2009). "The Unusual X-Ray Morphology of NGC 4636 Revealed by Deep Chandra Observations: Cavities and Shocks Created by Past Active Galactic Nucleus Outbursts". The Astrophysical Journal. 707 (2): 1034–1043. arXiv:0904.2569. Bibcode:2009ApJ...707.1034B. doi:10.1088/0004-637X/707/2/1034. S2CID 119193902.
  27. Giacintucci, Simona; O’Sullivan, Ewan; Vrtilek, Jan; David, Laurence P.; Raychaudhury, Somak; Venturi, Tiziana; Athreya, Ramana M.; Clarke, Tracy E.; Murgia, Matteo; Mazzotta, Pasquale; Gitti, Myriam; Ponman, Trevor; Ishwara-Chandra, C. H.; Jones, Christine; Forman, William R. (10 May 2011). "A combined low-radio frequency/X-ray study of galaxy groups I. Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz". The Astrophysical Journal. 732 (2): 95. arXiv:1103.1364. Bibcode:2011ApJ...732...95G. doi:10.1088/0004-637X/732/2/95. S2CID 118449592.
  28. Allen, S. W.; Dunn, R. J. H.; Fabian, A. C.; Taylor, G. B.; Reynolds, C. S. (11 October 2006). "The relation between accretion rate and jet power in X-ray luminous elliptical galaxies". Monthly Notices of the Royal Astronomical Society. 372 (1): 21–30. arXiv:astro-ph/0602549. Bibcode:2006MNRAS.372...21A. doi:10.1111/j.1365-2966.2006.10778.x. S2CID 15313083.
  29. Posson-Brown, Jennifer; Raychaudhury, Somak; Forman, William; Donnelly, R. Hank; Jones, Christine (20 April 2009). "Chandra Observations of the X-Ray Point Source Population in NGC 4636". The Astrophysical Journal. 695 (2): 1094–1110. arXiv:astro-ph/0605308. Bibcode:2009ApJ...695.1094P. doi:10.1088/0004-637X/695/2/1094. S2CID 119360202.
  30. Kowal, C. T. (December 1968). "Absolute magnitudes of supernovae". The Astronomical Journal. 73: 1021. Bibcode:1968AJ.....73.1021K. doi:10.1086/110763.
  31. List of Supernovae IAU Central Bureau for Astronomical Telegrams. Retrieved 29 December 2015.
  32. Hoffleit, Dorrit (1 March 1939). "SN NGC 1003 and Other Supernovae". Harvard College Observatory Bulletin. 910: 1–11. Bibcode:1939BHarO.910....1H. ISSN 0891-3943.
  33. "Supernova 2020ue in NGC 4636". www.rochesterastronomy.org. Retrieved 2020-01-30.
  34. 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. S2CID 119194025.
  35. "The Virgo II Groups". www.atlasoftheuniverse.com. Retrieved 7 January 2019.


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