Open AccessThe Hubble constant from the gravitational lens CLASS B0218+357 using the Advanced Camera for Surveys
Author(s) -
York T.,
Jackson N.,
Browne I. W. A.,
Wucknitz O.,
Skelton J. E.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.08618.x
Subject(s) - physics , gravitational lens , very long baseline interferometry , hubble's law , advanced camera for surveys , galaxy , spiral galaxy , astrophysics , lens (geology) , astronomy , hubble deep field , strong gravitational lensing , hubble space telescope , optics , redshift
We present deep optical observations of the gravitational lens system CLASS B0218+357, from which we derive an estimate for the Hubble constant ( H 0 ). Extensive radio observations using the VLA, MERLIN, the VLBA and VLBI have reduced the degeneracies between H 0 and the mass model parameters in this lens to one involving only the position of the radio‐quiet lensing galaxy with respect to the lensed images. B0218+357 has an image separation of only 334 mas, so optical observations have, up until now, been unable to resolve the lens galaxy from the bright lensed images. Using the new Advanced Camera for Surveys (ACS), installed on the Hubble Space Telescope in 2002, we have obtained deep optical images of the lens system and surrounding field. These observations have allowed us to determine the separation between the lens galaxy centre and the brightest image, and so estimate H 0 . We find an optical galaxy position, and hence an H 0 value, that varies depending on our approach to the spiral arms in B0218+357. If the most prominent spiral arms are left unmasked, we find H 0 = 70 ± 5 km s −1 Mpc −1 (95 per cent confidence). If the spiral arms are masked out, we find H 0 = 61 ± 7 km s −1 Mpc −1 (95 per cent confidence).