Continued photometric monitoring of the gravitational lens system 0957+561A,B in the g and r bands with the Apache Point Observatory (APO) 3.5 m telescope during 1996 shows a sharp g band event in the trailing (B) image light curve at the precise time predicted in an earlier paper. The prediction was using gravitational lenses and some other possible implications and uses of the 0957+561A,B light curves.

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A unique reconstruction of the image of a high redshift source galaxy responsible for multiple long arcs in the z = 0.4 cluster 0024+1654 is obtained by inverse lensing. Deep B and I imaging with the Hubble Space Telescope (Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, under NASA contract NAS 5-26555) enables high resolution of the arcs due to strong gravitational lensing of the background source. The gravitational lens in the foreground cluster is thus used to obtain a magnified view of the distant source. Four strongly lensed images of the source lead to a unique reconstruction. Each of the long arcs, when unlensed, leads to the same reconstructed source image exhibiting a beaded ring-like morphology. The U luminosity of the ring alone is equivalent to a normal galaxy. This is likely a galaxy in formation.Comment: 16 pages (aaspp.sty), full text & figures available at http://www.astro.princeton.edu/~library/prep.htm

We re-analyze brightness data sampled intensively over 5 nights at two epochs separated by the quasar lens time delay, to examine the nature of the observed microlensing. We find strong evidence for a microlensing event with an amplitude of 1% and a time scale of twelve hours. The existence of such rapid microlensing, albeit at low amplitude, imposes constraints on the nature of the quasar and of the baryonic dark matter.

We compute the two-point angular correlation function and number-magnitude relation of Hubble Deep Field sources in order to assess their nature. We find that the correlation peaks between 0.25 arcsec and 0.4 arcsec with amplitude of 2 or greater, and much more for the smallest objects. This angular scale corresponds to physical scales of order 1 kpc for redshifts z > 1. The correlation must therefore derive from objects with subgalaxian separations. At faint magnitudes, the counts satisfy the relation Number prop. to 1/flux, expected for images which are subdivisions of larger ones. A conservative conjecture may explain these results. Since high redshift space (z > 0.5) dominates the volume of the sample, observational redshift effects are important. The K-correction and surface brightness dimming of diffuse sources enhances the prominence of compact, unresolved, UV-bright objects, such as star-forming regions within normal gas-rich galaxies. If such regions appear as individual sources, they could explain the subgalaxian correlation.Comment: accepted by ApJL, AASTeX 4.0 preprint style, 2 PostScript figures, Replacing astro-ph/9603020 (major modification: improved detection alg.

We have independently measured the genus topology of the temperature fluctuations in the cosmic microwave background seen by the Wilkinson Microwave Anisotropy Probe (WMAP). A genus analysis of the WMAP data indicates consistency with Gaussian random‐phase initial conditions, as predicted by standard inflation.

We have measured the topology (genus) of the density distribution of large-scale structure observed in the Las Campanas Redshift Survey (LCRS). The LCRS is complete to magnitude 17.5 and contains nearly 24,000 galaxies with median redshift of 30,000 km s~1. The large volume and large number of galaxies permit sampling of nearly 100 independent structures with which to compute the genus topology, a vast improvement over previous studies. We Ðnd that the genus is consistent with a randomphase Gaussian distribution of initial density Ñuctuations, as would be produced naturally in inÑationary models. When we combine these results with the genus measurements of the COBE microwave background Ñuctuations, we Ðnd that two orthogonal projections of the three-dimensional distribution of initial density Ñuctuations are consistent with Gaussian random-phase behavior, in agreement with standard inÑationary models. Particular attention is given to statistical signiÐcance of the genus test.

We have continued our effort to re-reduce archival Q0957+561 brightness monitoring data and present results for 1629 R-band images using the methods for galaxy subtraction and seeing correction reported previously. The new dataset comes from 4 observing runs, several nights apiece, with sampling of typically 5 minutes, which allows the first measurement of the structure function for variations in the R-band from timescales of hours to years. Comparison of our reductions to previous reductions of the same data, and to r-band photometry produced at Apache Point Observatory shows good overall agreement. Two of the data runs, separated by 417 days, permit a sharpened value for the time delay of 417.4 days, valid only if the time delay is close to the now-fashionable 417-day value; our data do not constrain a delay if it is more than three days from this 417-day estimate. Our present results show no unambiguous signature of the daily microlensing, though a suggestive feature is found in the data. Both time delay measurement and microlensing searches suffer from from the lack of sampling at half-day offsets, inevitable at a single observatory, hence the need for round-the-clock monitoring with participation by multiple observatories.Comment: AASTeX 4.0 preprint style, 21 pages, 8 EPS figure