Aj. Loan et al., OPTICAL OBSERVATIONS OF DWINGELOO-1, A NEARBY BARRED SPIRAL GALAXY BEHIND THE MILKY-WAY, Monthly Notices of the Royal Astronomical Society, 280(2), 1996, pp. 537-549
We present new optical observations of the nearby barred spiral galaxy
Dwingeloo 1 (Dw1) obtained with the Isaac Newton, William Herschel an
d Wise telescopes. Dw1 lies at Galactic coordinates (l=138.degrees 52,
b=-0.degrees 11) and it is heavily obscured by dust and gas in the Mi
lky Way. We infer that Dw1 is of morphological type SBb or SBc (T=4),
has an inclination i approximate to 50 degrees, a position angle PA ap
proximate to 110 degrees, and a recession velocity relative to the Mil
ky Way V-MW=256+/-9 km s(-1). The measured total apparent magnitudes o
f 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 H I column density measurements, is A(B) appro
ximate to 5.8. Estimated from Galactic 100-mu m emission, the extincti
on is A(B) approximate to 4.3, while the reddened colours of Dw1 yield
an estimate of A(B) approximate to 10.4. Assuming A(B)=-5.8, Tully-Fi
sher relations in the I and R bands lead to a distance estimate for Dw
1 of D approximate to 300 km s(-1). However, for the derived range of
extinction estimates 4.3 less than or similar to A(B) less than or sim
ilar to 10.4, the distance varies from 100 to 500 km s(-1). We also re
port the detection of numerous H II regions associated with Dw1, and p
resent data from the Infrared Astronomical Satellite (IRAS) archive.