NGC 147

NGC 147
NGC 147
	Hubble Space Telescope image of NGC 147
Observation data (J2000 epoch)
Constellation	Cassiopeia
Right ascension	00h 33m 12.1s
Declination	48° 30′ 32″
Redshift	-193 ± 3 km/s
Distance	2.53 ± 0.11 Mly (780 ± 30 kpc)[a]
Apparent magnitude (V)	10.5
Characteristics
Type	dSph/dE5
Apparent size (V)	13.2′ × 7.8′
Notable features	satellite galaxy of M31
Other designations
	PGC 2004, UGC 326, DDO 3, LEDA 2004, Caldwell 17

NGC 147 (also known as DDO3 or Caldwell 17) is a dwarf spheroidal galaxy about 2.58 Mly away in the constellation Cassiopeia. NGC 147 is a member of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It forms a physical pair with the nearby galaxy NGC 185,^[5] another remote satellite of M31. It was discovered by John Herschel in September 1829. Visually it is both fainter and slightly larger than NGC 185 (and therefore has a considerably lower surface brightness). This means that NGC 147 is more difficult to see than NGC 185, which is visible in small telescopes. In the Webb Society Deep-Sky Observer's Handbook,^[6] the visual appearance of NGC 147 is described as follows:

Large, quite faint, irregularly round; it brightens in the middle to a stellar nucleus.

The membership of NGC 147 in the Local Group was confirmed by Walter Baade in 1944 when he was able to resolve the galaxy into individual stars with the 100-inch (2.5 m) telescope at Mount Wilson near Los Angeles.

Characteristics

A survey of the brightest asymptotic giant branch (AGB) stars in the area of radius 2′ from the center of NGC 147 shows that the last significant star-forming activity in NGC 147 occurred around 3 Gyr ago.^[7] NGC 147 contains a large population of older stars which show a spread in metallicity and age. The metallicity spread suggests that NGC 147 has had chemical enrichment. However, H I has not been observed and the interstellar medium (ISM) mass upper limit is much lower than expected had the material which is emitted from evolving stars been kept in the galaxy. This implies depletion of the ISM.^[7]

Distance measurements

At least two techniques have been used to measure distances to NGC 147. The surface brightness fluctuations distance measurement technique estimates distances to spiral galaxies based on the graininess of the appearance of their bulges. The distance measured to NGC 147 using this technique is 2.67 ± 0.18 Mly (870 ± 60 kpc).^[2] However, NGC 147 is close enough that the tip of the red giant branch (TRGB) method may be used to estimate its distance. The estimated distance to NGC 147 using this technique is 2.21 ± 0.09 Mly (680 ± 30 kpc).^[3] Averaged together, these distance measurements give a distance estimate of 2.53 ± 0.11 Mly (780 ± 30 kpc).^[a]

Notes

^{^} average(870 ± 60, 680 ± 30) = ((870 680) / 2) ± ((60² 30²)^0.5 / 2) = 780 ± 30

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ "NASA/IPAC Extragalactic Database". Results for NGC 147. Retrieved 2006-12-07.
^ ^a ^b J. L. Tonry; A. Dressler; J. P. Blakeslee; E. A. Ajhar; et al. (2001). "The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances". Astrophysical Journal. 546 (2): 681–693. arXiv:astro-ph/0011223. Bibcode:2001ApJ...546..681T. doi:10.1086/318301. S2CID 17628238.
^ ^a ^b McConnachie, A. W.; Irwin, M. J.; Ferguson, A. M. N.; Ibata, R. A.; et al. (2005). "Distances and metallicities for 17 Local Group galaxies". Monthly Notices of the Royal Astronomical Society. 356 (4): 979–997. arXiv:astro-ph/0410489. Bibcode:2005MNRAS.356..979M. doi:10.1111/j.1365-2966.2004.08514.x.
^ Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics. 49 (1): 3–18. Bibcode:2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6. S2CID 120973010.
^ "NGC 147". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-07.
^ Jones, K. G. (1981). Webb Society Deep-Sky Observer's Handbook. Enslow Publishers. ISBN 978-0-89490-134-8.
^ ^a ^b Davidge, T. J. (2005). "The Evolved Stellar Content of NGC 147, NGC 185, and NGC 205". The Astronomical Journal. 130 (5): 2087–2103. arXiv:astro-ph/0509612. Bibcode:2005AJ....130.2087D. doi:10.1086/491706. S2CID 17456987.

External links

SEDS – NGC 147
NGC 147 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

[ned-1] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ "NASA/IPAC Extragalactic Database". Results for NGC 147. Retrieved 2006-12-07.

[tonryetal2001-2] J. L. Tonry; A. Dressler; J. P. Blakeslee; E. A. Ajhar; et al. (2001). "The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances". Astrophysical Journal. 546 (2): 681–693. arXiv:astro-ph/0011223. Bibcode:2001ApJ...546..681T. doi:10.1086/318301. S2CID 17628238.

[McConnachie2005-3] McConnachie, A. W.; Irwin, M. J.; Ferguson, A. M. N.; Ibata, R. A.; et al. (2005). "Distances and metallicities for 17 Local Group galaxies". Monthly Notices of the Royal Astronomical Society. 356 (4): 979–997. arXiv:astro-ph/0410489. Bibcode:2005MNRAS.356..979M. doi:10.1111/j.1365-2966.2004.08514.x.

[Karachentsevetal2006-4] Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics. 49 (1): 3–18. Bibcode:2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6. S2CID 120973010.

[simbad-5] "NGC 147". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-07.

[Webb-6] Jones, K. G. (1981). Webb Society Deep-Sky Observer's Handbook. Enslow Publishers. ISBN 978-0-89490-134-8.

[Davidge2005-7] Davidge, T. J. (2005). "The Evolved Stellar Content of NGC 147, NGC 185, and NGC 205". The Astronomical Journal. 130 (5): 2087–2103. arXiv:astro-ph/0509612. Bibcode:2005AJ....130.2087D. doi:10.1086/491706. S2CID 17456987.

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v t e Astronomical catalogs
NGC	NGC 142 NGC 143 NGC 144 NGC 145 NGC 146 NGC 147 NGC 148 NGC 149 NGC 150 NGC 151 NGC 152
PGC	PGC 2000 PGC 2001 PGC 2002 PGC 2003 PGC 2004 PGC 2005 PGC 2006 PGC 2007 PGC 2008
UGC	UGC 322 UGC 323 UGC 324 UGC 325 UGC 326 UGC 327 UGC 328 UGC 329 UGC 330
Caldwell	C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19 C20 C21 C22 C23 C24 C25 C26

v t e Andromeda Galaxy
Location	Andromeda Galaxy → Andromeda subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Local Hole → Observable universe → Universe Each → may be read as "within" or "part of".	Andromeda Galaxy
Satellite galaxies	M32 M110 NGC 185 NGC 147 Andromeda I Andromeda II Andromeda III Andromeda IV* Andromeda V Andromeda VI Andromeda VII Andromeda VIII Andromeda IX Andromeda X Andromeda XI Andromeda XII Andromeda XIII Andromeda XIV Andromeda XV Andromeda XVI Andromeda XVII Andromeda XVIII Andromeda XIX Andromeda XX Andromeda XXI Andromeda XXII Andromeda XXIII Andromeda XXIV Andromeda XXV Andromeda XXVI Andromeda XXVII Andromeda XXVIII Andromeda XXIX Triangulum subgroup* *It is uncertain whether these are companion galaxies of the Andromeda Galaxy
Catalogued stars	AE Andromedae AF Andromedae M31-RV
Other	Andromeda–Milky Way collision S Andromedae Mayall II M32p NGC 206 3XMM J004232.1 411314
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See also	Messier Catalogue Catalogue of Nebulae and Clusters of Stars New General Catalogue Index Catalogue Revised New General Catalogue Herschel 400 Catalogue
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Characteristics

Distance measurements

See also

Notes

References

External links