gjdonatiello
Triangulum (M33)
Triangulum (M33) superstack
Credit: Giuseppe Donatiello
(J2000) RA: 01h 33m 50.02s Dec: +30° 39′ 36.7″
The gas-rich low-mass dwarf spiral galaxy Triangulum (Messier 33) at 3 million light-years. It is catalogued also as NGC 598 and known as Triangulum Galaxy. The galaxy is the smallest spiral galaxy in the Local Group and it is believed to be a big satellite of the Andromeda Galaxy.
M33 has two asymmetric faint arms, and an interstellar medium rich in gaseous filaments that extends for about 7 kpc. Although the inner disk is relatively undisturbed, the northern arm is less regular in shape than the southern one. M33, is a bulge-free galaxy with only two optically luminous dwarf galaxies believed to be its satellites: AndXXII (McConnachie et al., 2009; Martin et al., 2016) and Pisces VII (Martínez-Delgado et al., 2022) m discovered by me in 2020. However, given its mass, ΛCDM cosmological simulations predict that M33 should host a larger number of satellites, at least 10.
The neutral hydrogen (HI) disk is three times larger than the star-forming disk and is clearly warped. The outer disk has the same inclination as the inner one with respect to our line of sight but the position angle of the major axis changes by about 30 degrees compared to the inner disk and is more aligned with the M31 direction. While M33's undisturbed inner disk indicates that no major collisions between M31 and M33 or between M33 and a satellite have occurred in the past, the distortion could be the result of a flyby about 9 billion years ago. Timing assessments make this scenario unlikely and favor the hypothesis of a first fall of M33 in the region of influence of M31.
Triangulum (M33)
Triangulum (M33) superstack
Credit: Giuseppe Donatiello
(J2000) RA: 01h 33m 50.02s Dec: +30° 39′ 36.7″
The gas-rich low-mass dwarf spiral galaxy Triangulum (Messier 33) at 3 million light-years. It is catalogued also as NGC 598 and known as Triangulum Galaxy. The galaxy is the smallest spiral galaxy in the Local Group and it is believed to be a big satellite of the Andromeda Galaxy.
M33 has two asymmetric faint arms, and an interstellar medium rich in gaseous filaments that extends for about 7 kpc. Although the inner disk is relatively undisturbed, the northern arm is less regular in shape than the southern one. M33, is a bulge-free galaxy with only two optically luminous dwarf galaxies believed to be its satellites: AndXXII (McConnachie et al., 2009; Martin et al., 2016) and Pisces VII (Martínez-Delgado et al., 2022) m discovered by me in 2020. However, given its mass, ΛCDM cosmological simulations predict that M33 should host a larger number of satellites, at least 10.
The neutral hydrogen (HI) disk is three times larger than the star-forming disk and is clearly warped. The outer disk has the same inclination as the inner one with respect to our line of sight but the position angle of the major axis changes by about 30 degrees compared to the inner disk and is more aligned with the M31 direction. While M33's undisturbed inner disk indicates that no major collisions between M31 and M33 or between M33 and a satellite have occurred in the past, the distortion could be the result of a flyby about 9 billion years ago. Timing assessments make this scenario unlikely and favor the hypothesis of a first fall of M33 in the region of influence of M31.