Dwingeloo 1 is a barred spiral galaxy about 10 million

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s away from the Earth, in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Cassiopeia. It lies in the Zone of Avoidance and is heavily obscured by the Milky Way. The size and mass of Dwingeloo 1 are comparable to those of Triangulum Galaxy. Dwingeloo 1 has two smaller satellite galaxies — Dwingeloo 2 and

MB 3 MB3 is a dwarf spheroidal galaxy discovered in 1997 and located about 10 million light-years away from the Earth. It was discovered during an optical survey of the IC 342/Maffei group to which the galaxy is a member. MB3 is a companion galaxy of ...

— and is a member of the IC 342/Maffei Group of galaxies.

Discovery

The Dwingeloo 1 galaxy was discovered in 1994 by the Dwingeloo Obscured Galaxy Survey (DOGS) using the

Dwingeloo Radio Observatory The Dwingeloo Radio Observatory is a single-dish radio telescope near the village of Dwingeloo () in the northeastern Netherlands. Construction started in 1954, and the telescope was completed in 1956. The radio telescope has a diameter of 25 ...

, which searched for neutral hydrogen (HI) radio emissions at the wavelength of 21 cm from objects in the Zone of Avoidance. In this zone gas and dust in the disk of the Milky Way galaxy block the light from the galaxies lying behind it. The galaxy was, however, first noted as an unremarkable feature on Palomar Sky Survey plates earlier in the same year, but was not recognized as such. It was also independently discovered a few weeks later by another team of astronomers working with Effelsberg 100-m Radio Telescope. Dwingeloo 1 was eventually named after the 25m radio telescope in the Netherlands that was used in the DOGS survey and first detected it.

Distance and group membership

Dwingeloo 1 is a highly obscured galaxy, which makes distance determination a difficult problem. The initial estimate, made soon after the discovery and based on the

Tully–Fisher relation In astronomy, the Tully–Fisher relation (TFR) is an empirical relationship between the mass or intrinsic luminosity of a spiral galaxy and its asymptotic rotation velocity or emission line width. It was first published in 1977 by astronomers ...

, was about 3 Mpc. Later, this value was slightly increased to 3.5–4 Mpc. In 1999 another estimate was published, claiming a distance of more than 5 Mpc. It was based on the infrared Tully–Fisher relation. As of 2011, the distance to Dwingeloo 1 is thought to be approximately 3 Mpc, based on its likely membership in the IC 342/Maffei group. Dwingeloo 1 has two smaller satellite galaxies. The first one, Dwingeloo 2, is an irregular galaxy, and the second,

, is likely a dwarf spheroidal galaxy.

Properties

After the discovery Dwingeloo 1 was classified as a barred spiral galaxy. It has a central bar and two distinct spiral arms beginning from the ends of the bar at nearly right angle and wound counterclockwise. The length of the arms is up to 180°. The disk of the galaxy is inclined with respect to the observer, with the inclination angle being 50°. The galaxy recedes from the Milky Way at a speed of about 256 km/s. The visible radius of Dwingeloo 1 is approximately 4.2', which at the distance of 3 Mpc corresponds to about 4 kpc. The neutral hydrogen is detected as far as 6 kpc (7.5') from the center. The total mass of the galaxy is about 1/4 that of the Milky Way out to the measured distance of 6 kpc or about 31 billion Solar masses. The distribution of the neutral hydrogen in Dwingeloo 1 is typical one for barred spiral galaxies—it is rather flat with a minimum in the center or along the bar. The total mass of the neutral hydrogen is estimated at 370–450 million

Solar mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

es. Dwingeloo 1 is a molecular gas-poor galaxy. The total mass of the molecular hydrogen does not exceed 10% of that of neutral hydrogen. Optical observations detected around 15 H II regions situated mainly along the spiral arms. In its overall size and mass, the galaxy is comparable to Triangulum Galaxy.

References

External links

* * {{Cassiopeia (constellation), state=collapsed Barred spiral galaxies IC 342/Maffei Group Cassiopeia (constellation) 100170 Astronomical objects discovered in 1994 100170

Discovery

Distance and group membership

Properties

See also

References

External links