Messier 105

Messier 105 or M105, also known as NGC 3379, is an elliptical galaxy 36.6^[2] million light-years away in the equatorial constellation of Leo. It is the biggest elliptical galaxy in the Messier catalogue that is not in the Virgo cluster.^[8] It was discovered by Pierre Méchain in 1781, just a few days after he discovered the nearby galaxies Messier 95 and Messier 96.^[a][9] This galaxy is one of a few not object-verified by Messier so omitted in the editions of his Catalogue of his era. It was appended when Helen S. Hogg found a letter by Méchain locating and describing this object which matched those aspects under its first-published name, NGC 3379.^[9]

Messier 105
M105, as viewed by the HST; Credit: NASA/ESA
Observation data (J2000 epoch)
Constellation	Leo
Right ascension	10h 47m 49.600s[1]
Declination	+12° 34′ 53.87″[1]
Heliocentric radial velocity	908 km/s[2]
Distance	36.6 Mly (11.22 Mpc)[2]
Group or cluster	Leo I Group[3]
Apparent magnitude (V)	9.3[4]
Characteristics
Type	E1[5]
Apparent size (V)	5′.4 × 4′.8[6]
Other designations
M105, NGC 3379, PGC 32256, UGC 5902[7]

It has a morphological classification of E1,^[5] indicating a standard elliptical galaxy with a flattening of 10%. The major axis is aligned along a position angle of 71°. Isophotes of the galaxy are near perfect ellipses, twisting no more than 5° out of alignment, with changes in ellipticity of no more than 0.06. There is no fine structure apparent in the isophotes, such as ripples.^[10] Observation of giant stars in the halo indicate there are two general populations: a dominant metal-rich subpopulation and a weaker metal-poor group.^[3]

Messier 105 is known to have a supermassive black hole at its core whose mass is estimated to be between 1.4×10⁸ and 2×10⁸ M_☉.^[11] The galaxy has a weak active galactic nucleus of the LINER type with a spectral class of L2/T2, meaning no broad Hα line and intermediate emission line ratios between a LINER and a H II region.^[12] The galaxy also contains a few young stars and stellar clusters, suggesting some elliptical galaxies still form new stars, but very slowly.^[13]

This galaxy, along with its companion the barred lenticular galaxy NGC 3384, is surrounded by an enormous ring of neutral hydrogen with a radius of 200 kiloparsecs (650 kilolight-years) and a mass of 1.8×10⁹ M_☉ where star formation has been detected.^[14] Messier 105 is one of several galaxies within the M96 Group (also known as the Leo I Group), a group of galaxies in the constellation Leo, the other Messier objects of which are M95 and M96.^{[15][16][17][18]}