Stellar Masses of High-Redshift Galaxies

We present constraints on the stellar-mass distribution of distant galaxies. These stellar-mass estimates derive from fitting population-synthesis models to the galaxies' observed multi-band spectrophotometry. We discuss the complex uncertainties (both statistical and systematic) that are inherent to this method, and offer future prospects to improve the constraints. Typical uncertainties for galaxies at z ~ 2.5 are ~ 0.3 dex (statistical), and factors of ~ 3 (systematic). By applying this method to a catalog of NICMOS-selected galaxies in the Hubble Deep Field North, we generally find a lack of high-redshift galaxies (z > 2) with masses comparable to those of present-day ``L*'' galaxies. At z < 1.8, galaxies with L*-sized masses do emerge, but with a number density below that at the present epoch. Thus, it seems massive, present-day galaxies were not fully assembled by z ~ 2.5, and that further star formation and/or merging are required to assemble them from these high-redshift progenitors. Future progress on this subject will greatly benefit from upcoming surveys such as those planned with HST/ACS and SIRTF.Comment: 7 pages, 5 figures. To appear in The Mass of Galaxies at Low and High Redshift, eds. R. Bender & A. Renzini (ESO Astrophysics Symposia, Springer-Verlag), Venice, 24-26 Oct 200

The WFPC2 Archival Parallels Project

We describe the methods and procedures developed to obtain a near-automatic combination of WFPC2 images obtained as part of the WFPC2 Archival Pure Parallels program. Several techniques have been developed or refined to ensure proper alignment, registration, and combination of overlapping images that can be obtained at different times and with different orientations. We quantify the success rate and the accuracy of the registration of images of different types, and we develop techniques suitable to equalize the sky background without unduly affecting extended emission. About 600 combined images of the 1,500 eventually planned have already been publicly released through the STScI Archive. The images released to date are especially suited to study star formation in the Magellanic Clouds, the stellar population in the halo of nearby galaxies, and the properties of star-forming galaxies at $z \sim 3$.Comment: 12 pages, 7 figures, to appear in the PAS

The Burglar Rag

Illustration of a boyin a newsboy cap shining a flashlight that reveals the title of the piece.https://scholarsjunction.msstate.edu/cht-sheet-music/4361/thumbnail.jp

Photoelectron Spectroscopy of ClH2 - and ClD2 -: A Probe of the Cl+H2 Van Der Waals Well and Spin-Orbit Excited States

Photoelectron (PE) spectra of ClH−2 and ClD−2 were measured at 299 nm (4.154 eV). Photodetachment of these anions accesses the prereactive van der Waals well on the ground stateCl+H2potential energy surface, as well as the low-lying spin–orbit excited states resulting from the interaction of Cl and Cl* with H2. The PE spectra are dominated by two relatively narrow peaks corresponding to transitions to the neutral Cl⋅H2 and Cl*⋅H2 complexes. The energetics and widths of these features are interpreted in terms of the properties of the anion and neutral potential energy surfaces

How children become invisible in child protection work: findings from research into day to day social work practice

It is well known that in cases in which abused children have died, social workers and other professionals did not relate to them effectively—the phenomenon now known as the ‘invisible child’. Much less well understood is how often and why such invisibility occurs where there has not been a major inquiry or scandal and this paper draws on research which observed day-to-day encounters between social workers, children and families. In most of the practice, children were seen and related to but, in a small number of home visits, social workers were not child-focused. The paper provides a detailed analysis of those cases and shows how social workers were overcome by the emotional intensity of the work and complex interactions with angry, resistant parents and family friends. Workers were also affected by organisational culture, time limits on their work and insufficient support to enable them to contain their feelings and think clearly. The powerful impact of unbearable levels of complexity and anxiety on social workers requires much greater recognition. Sociological, psycho-dynamic and systemic theories are drawn upon to establish how workers need to be helped to think clearly about children and relate to them in the close, intimate ways that are required to keep them safe