Anne’s Image of the Day: Galaxy Pair MRK 1034

April 9, 2014

MRK 1034, a galaxy pair in Triangulum

Image Credit: Judy Schmidt, ESA/Hubble & NASA

MRK 1034 (short for Markarian 1034) is an interacting galaxy pair that consists of two very similar spiral galaxies, named PGC 9071 (also known as Mrk 1034SW) and PGC 9074 (or Mrk 1034NE). The pair is located in the northern constellation of Triangulum (the Triangle).

The galaxies are close enough to one another to be bound together by gravity, although no gravitational disturbance can yet be seen in the image. These objects are probably only just beginning to interact gravitationally.

Because both galaxies are presented face-on to our eyes, we are able to see their distinctive shapes. The galaxy at the bottom in this image (PGC 9071) – although very similar and almost the same size as its neighbor – has a slightly different structure to its arms: its arms are further apart (a type Sb galaxy), and it has a fainter bulge than the galaxy at the top (PGC 9074), which has a bright bulge and two spiral arms tightly wound around the nucleus (a type Sa galaxy).

The spiral arms of both objects clearly show dark dust lanes that are obscuring the light of the stars lying behind, mixed with bright blue clusters of hot, recently-formed stars. Older, cooler stars can be found in the glowing, compact yellowish bulge towards the centers of the galaxies. The whole structure of each galaxy is surrounded by a much fainter round halo of old stars, some residing in globular clusters.

PGC 9074 is an active galaxy with an Active Galactic Nucleus (AGN), what means it has a compact region at the center of the galaxy that has a much higher than normal luminosity. The radiation from an AGN is believed to be a result of accretion of mass by a supermassive black hole at the center of its host galaxy.

PGC 9071 is a Seyfert I galaxy, what means it has an extremely bright nucleus that produces spectral line emission from highly ionized gas. The centers of Seyfert galaxies have Active Galactic Nuclei (AGN), and usually contain supermassive black holes with masses between 10 and 100 million solar masses. Seyferts are classified as Type I or II, depending upon whether the spectra show both narrow and broad emission lines (Type I), or only narrow lines (Type II).

Gradually, these two neighbors will attract each other, the process of star formation will be increased and tidal forces will throw out long tails of stars and gas. Eventually, after maybe hundreds of millions of years, the structures of the interacting galaxies will merge together into a new, larger galaxy.

The images combined to create this picture were captured by the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope, using an infrared and an optical filter. A version of this image was submitted to the Hubble’s Hidden Treasures image processing competition by Judy Schmidt.