Optical observations of Dwingeloo 1, a nearby barred spiral galaxy behind the Milky Way

• Published in: Monthly notices of the Royal Astronomical Society 1996-05, Vol.280 (2), p.537-549
• Main Authors: Loan, A. J., Maddox, S. J., Lahav, O., Balcells, M., Kraan-Korteweg, R. C., Assendorp, R., Almoznino, E., Brosch, N., Goldberg, E., Ofek, E. O.
• Format: Article
• Language: English
• Subjects: galaxies: individual: Dwingeloo 1; galaxies: photometry; galaxies: spiral; Local Group
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/280.2.537

We present new optical observations of the nearby barred spiral galaxy Dwingeloo 1 (Dw1) obtained with the Isaac Newton, William Herschel and Wise telescopes. Dw1 lies at Galactic coordinates (l = 138###52, b= − 0### 11) and it is heavily obscured by dust and gas in the Milky Way. We infer that Dw1 is of morphological type SBb or SBc (T=4), has an inclination i≈50°, a position angle PA ≈110°, and a recession velocity relative to the Milky Way VMW= 256±9 km s−1. The measured total apparent magnitudes of Dw1 are V= 14.0 ±0.5, R = 12.2 ±0.2 and I=10.7 ±0.2. The extinction estimate towards Dw1 is highly uncertain. The extinction in the B band, derived from Galactic Hi column density measurements, is AB≈5.8. Estimated from Galactic 100-um emission, the extinction is AB≈4.3, while the reddened colours of Dwl yield an estimate of AB≈ 10.4. Assuming AB= 5.8, Tully-Fisher relations in the I and R bands lead to a distance estimate for Dw1 of D≈ 300 km s−1. However, for the derived range of extinction estimates 4.3≾AB≾ 10.4, the distance varies from 100 to 500 km s−1. We also report the detection of numerous H ii regions associated with Dw1, and present data from the Infrared Astronomical Satellite (IRAS) archive.