NGC 3672

Lore & Background

NGC 3672 has a small, bright nucleus. Spectral analysis of its nuclear region revealed large velocity gradients along the minor axis of the outer disk, interpreted as either excited nuclear gas rotating at a large angle relative to the rest of the galaxy or gas clouds collapsing toward the center. This was the first time such nuclear gas kinematics were observed in a spiral galaxy. Four well-defined arms with many knots emerge from the center in a grand design pattern. The galaxy's star formation rate is estimated at about 3.5 per year.

Two supernovae have been observed in NGC 3672. SN 2007bm, discovered by R. Martin of the Perth Observatory on April 20 and 21, 2007, was a type Ia supernova that reached a peak magnitude of 14.2. SN 2008gz, discovered by Koichi Itagaki on November 5, 2008, was a type IIP supernova about 80 days past explosion, located in the inner parts of a spiral arm next to an HII region; its progenitor star had an estimated main-sequence mass of 17 solar masses.

NGC 3672 is the foremost member of the NGC 3672 Group (LGG 235), which also includes NGC 3636, NGC 3637, and IC 688. IC 688 lies about 20 arcminutes away. The group lies in the same galaxy cloud as NGC 3730 and NGC 3779.

Reader's Guide

NGC 3672 holds significance as the first spiral galaxy where nuclear gas kinematics were observed, specifically large velocity gradients along the minor axis of the outer disk. This discovery provided new insight into the behavior of nuclear gas in spiral galaxies, suggesting either misaligned rotation or infalling gas clouds. The galaxy's grand design spiral structure, with four well-defined arms and many knots, contributes to its study as a site of ongoing star formation at a rate of about 3.5 solar masses per year. The two supernovae observed—SN 2007bm (type Ia) and SN 2008gz (type IIP)—offer additional data on stellar evolution and explosion mechanisms. As the leading member of the NGC 3672 Group, it serves as a reference point for studying galaxy groups and their interactions within the larger galaxy cloud containing NGC 3730 and NGC 3779. Its proximity at 80 million light years and well-documented characteristics make it a useful object for understanding spiral galaxy structure, nuclear dynamics, and supernova populations.