English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Multiply gravitationally lensed objects with known time delays can lead todirect determinations of H$_0$ independent of the distance ladder if the massdistribution of the lens is known. Currently, the double QSO 0957+561 is theonly lensed object with a precisely known time delay. The largest remainingsource of systematic error in the H$_0$ determination results from uncertaintyin the mass distribution of the lens which is comprised of a massive galaxy(G1) and the cluster in which it resides.  We have obtained V-band CCD images from CFHT in order to measure the massdistribution in the cluster from its gravitional distorting effect on theappearance of background galaxes. We use this data to constuct atwo-dimensional mass map of the field. A mass peak is detected at the$4.5\sigma$ level, offset from, but consistent with, the position of G1. Simpletests reveal no significant substructure and the mass distribution isconsistent with a spherical cluster. The peak in the number density map ofbright galaxies is offset from G1 similarly to the mass peak.  We constructed an azimuthally averaged mass profile centered on G1 out to 2\arcmin ($400 h^{-1}$ kpc). It is consistent with an isothermal massdistribution with a small core ($r_c \approx 5 \arcsec = 17 h^{-1}$ kpc). Theinferred mass within 1 Mpc is consistent with the dynamical mass estimate but$2\sigma$ higher than the upper limits from a ROSAT X-ray study.  We discuss implications for H$_0$ in a future paper.

The Mass Distribution of the Cluster 0957+561 From Gravitational Lensing