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RE: NGC 4254
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Messier 99 was discovered by Pierre Méchain on March 17, 1781.
Messier 99 was one of the first galaxies in which a spiral pattern was first seen. The spiral pattern was first identified by Lord Rosse in the spring of 1846.

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Messier 99
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Messier 99 (also M99, NGC 4254, MCG 3-31-99 and PGC 39578) is a magnitude +10.4 face-on spiral galaxy located 50 million light-years away in the constellation Coma Berenices.

The galaxy was discovered by French astronomer Pierre François André Méchain using a 15.24 cm (6 inch) speculum newtonian reflector on the 17th March 1781.

Right Ascension 12h 18m 49.6s, Declination Dec +14° 24 59"



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NGC 4254
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Title: NGC 4254: An Act of Harassment Uncovered by the Arecibo Legacy Fast ALFA Survey
Authors: Martha P. Haynes, Riccardo Giovanelli, Brian R. Kent

We present an HI map constructed from the Arecibo Legacy Fast ALFA (ALFALFA) survey of the surroundings of the strongly asymmetric Virgo cluster Sc galaxy NGC 4254. Noted previously for its lopsided appearance, rich interstellar medium, and extradisk HI emission, NGC 4254 is believed to be entering the Virgo environment for the first time and at high speed. The ALFALFA map clearly shows a long HI tail extending ~250 kpc northward from the galaxy. Embedded as one condensation within this HI structure is the object previously identified as a "dark galaxy": Virgo HI21 (Davies et al. 2004). A body of evidence including its location within and velocity with respect to the cluster and the appearance and kinematics of its strong spiral pattern, extra-disk HI and lengthy HI tail is consistent with a picture of "galaxy harassment" as proposed by Moore et al. (1996a,b; 1998). The smoothly varying radial velocity field along the tail as it emerges from NGC 4254 can be used as a timing tool, if interpreted as resulting from the coupling of the rotation of the disk and the collective gravitational forces associated with the harassment mechanism.

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