DZ
DefZone.Net

Kien thuc cong nghe & giai tri

  1. Trang chủ
  2. Wiki

UGC 6541
A pale blue dwarf galaxy seen on the black backdrop of space with some faraway galaxies. The galaxy itself resembles a fuzzy cloud of tightly-packed stars, with a broad halo of stars dispersed around it. Several small, glowing patches of gas are spread across the galaxy’s core, where very hot stars are concentrated.
UGC 6541 imaged by the Hubble Space Telescope
Observation data (J2000 epoch)
ConstellationUrsa Major
Right ascension11h 33m 28.9488s[1]
Declination+49° 14′ 13.012″[1]
Redshift0.000833±0.00000200[1]
Heliocentric radial velocity250±1 km/s[1]
Distance15.15 ± 2.10 Mly (4.644 ± 0.644 Mpc)[1]
Apparent magnitude (V)14.50[1]
Characteristics
TypeIm[1]
Size~5,700 ly (1.76 kpc) (estimated)[1]
Apparent size (V)1.2′ × 0.7′[1]
Other designations
HOLM 263A, MCG +08-21-053, Mrk 178, PGC 035684, CGCG 242-046[1]

UGC 6541 (also known as Mrk 178) is a blue compact dwarf galaxy in the constellation of Ursa Major. Its velocity with respect to the cosmic microwave background is 455±14 km/s,[1] which is too small to use to obtain a distance using Hubble's law. However, 10 non-redshift measurements give a mean distance of 15.15 ± 2.10 Mly (4.644 ± 0.644 Mpc).[2] The first known reference to this galaxy comes from Erik Holmberg's A Study of Double and Multiple Galaxies Together with Inquiries into some General Metagalactic Problems, published in 1937, where UGC 6541 and UGC 6538 are listed together as Holm 263.[3] However, since UGC 6538 is about 10 times further away, at a distance of 158.3 ± 11.1 Mly (48.55 ± 3.41 Mpc),[4] the alignment is purely optical.

UGC 6541 imaged by Legacy Surveys

UGC 6541 has a possible active galactic nucleus, i.e. it has a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars.[5][6] UGC 6541 is a galaxy whose nucleus shines brightly in the ultraviolet and is listed in the Markarian catalogue as Mrk 178.[7]

The stellar and gas components of UGC 6541 have been extensively studied. An integrated H I intensity map shows a broken ring-like structure.[8] Other integrated H I intensity maps show that this galaxy has a highly irregular shape to its gaseous disk.[9] A detailed study of the Wolf-Rayet population revealed a large number of Wolf-Rayet stars in its brightest stellar component.[10] The stellar population has been studied in detail, indicating that this galaxy had a higher star formation rate 500 million years ago compared to its current rate, and that this galaxy has an old underlying stellar population.[11]

References

[edit]
  1. ^ a b c d e f g h i j k "Results for object UGC 06541". NASA/IPAC Extragalactic Database. NASA and Caltech. Retrieved 5 December 2025.
  2. ^ "Distance Results for UGC 06541". NASA/IPAC Extragalactic Database. NASA. Retrieved 5 December 2025.
  3. ^ Holmberg, Erik (1937). "A Study of Double and Multiple Galaxies Together with Inquiries into some General Metagalactic Problems". Annals of the Observatory of Lund. 6: 1. Bibcode:1937AnLun...6....1H.
  4. ^ "Results for object UGC 06538". NASA/IPAC Extragalactic Database. NASA and Caltech. Retrieved 5 December 2025.
  5. ^ Asmus, D.; Greenwell, C. L.; Gandhi, P.; Boorman, P. G.; Aird, J.; Alexander, D. M.; Assef, R. J.; Baldi, R. D.; Davies, R. I.; Hönig, S. F.; Ricci, C.; Rosario, D. J.; Salvato, M.; Shankar, F.; Stern, D. (2020). "Local AGN survey (LASr): I. Galaxy sample, infrared colour selection, and predictions for AGN within 100 MPC". Monthly Notices of the Royal Astronomical Society. 494 (2): 1784. arXiv:2003.05959. Bibcode:2020MNRAS.494.1784A. doi:10.1093/mnras/staa766.
  6. ^ "UGC 6541". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 5 December 2025.
  7. ^ Markaryan, B. E. (1969). "Galaxies with an ultraviolet continuum. II". Astrophysics. 5 (3): 206. Bibcode:1969Ap......5..206M. doi:10.1007/BF01004709.
  8. ^ Stil, J. M.; Israel, F. P. (2002). "Neutral hydrogen in dwarf galaxies. I. The spatial distribution of HI". Astronomy and Astrophysics. 389: 29. arXiv:astro-ph/0203128. Bibcode:2002A&A...389...29S. doi:10.1051/0004-6361:20020352.
  9. ^ Roychowdhury, Sambit; Chengalur, Jayaram N.; Begum, Ayesha; Karachentsev, Igor D. (2009). "Star formation in extremely faint dwarf galaxies". Monthly Notices of the Royal Astronomical Society. 397 (3): 1435. arXiv:0904.2748. Bibcode:2009MNRAS.397.1435R. doi:10.1111/j.1365-2966.2009.14931.x.
  10. ^ Kehrig, C.; Pérez-Montero, E.; Vílchez, J. M.; Brinchmann, J.; Kunth, D.; García-Benito, R.; Crowther, P. A.; Hernández-Fernández, J.; Durret, F.; Contini, T.; Fernández-Martín, A.; James, B. L. (2013). "Uncovering multiple Wolf-Rayet star clusters and the ionized ISM in MRK 178: The closest metal-poor Wolf-Rayet H II galaxy". Monthly Notices of the Royal Astronomical Society. 432 (4): 2731. arXiv:1304.5154. Bibcode:2013MNRAS.432.2731K. doi:10.1093/mnras/stt630.
  11. ^ Schulte-Ladbeck, Regina E.; Hopp, Ulrich; Greggio, Laura; Crone, Mary M. (2000). "A Near-Infrared Stellar Census of Blue Compact Dwarf Galaxies: NICMOS Detection of Red Giant Stars in the Wolf-Rayet Galaxy Markarian 178". The Astronomical Journal. 120 (4): 1713. arXiv:astro-ph/0007417. Bibcode:2000AJ....120.1713S. doi:10.1086/301547.
[edit]
  • Media related to UGC 6541 at Wikimedia Commons
  • UGC 6541 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images