The Local Environment of HII Galaxies

We address the question of whether violent star formation in HII galaxies is induced by low mass companions by describing statistically their local environment as estimated by the correlation function. We argue that even if low mass companions were mainly intergalactic HI clouds, their optical counterparts should be detectable at faint limits of the Automatic Plate Measuring Machine scans. We then cross-correlate a large sample of HII galaxies with the APM faint field galaxy catalogue. The preliminary results are all consistent with HII galaxies being a randomly selected sample of normal faint field galaxy with no extra clustering. This suggests that at least in these dwarf starburst galaxies star formation is not triggered by tidal interactions and may have a different origin.Comment: 4 pages, 2 Postscript figures, uses moriond.sty. To appear in ``Dwarf Galaxies and Cosmology'', Eds. T.X. Thuan, C. Balkowski, V. Cayette, J. Tran Than Van, Editions Frontieres (Gyf-sur-Yvette, France

The APM Galaxy Survey:- V. Catalogues of Galaxy Clusters

We describe the construction of catalogues of galaxy clusters from the APM Galaxy survey using an automated algorithm based on Abell-like selection criteria. We investigate the effects of varying several parameters in our selection algorithm, including the magnitude range, and radius from the cluster centre used to estimate the cluster richnesses. We quantify the accuracy of the photometric distance estimates by comparing with measured redshifts, and we investigate the stability and completeness of the resulting catalogues. We find that the angular correlation functions for different cluster catalogues are in good agreement with one another, and are also consistent with the observed amplitude of the spatial correlation function of rich clusters.Comment: 14 pages, PostScript, including 15 figures, submitted to MNRAS. Also available from ftp://ftp-astro.physics.ox.ac.uk/pub/gbd/papers/apm5.ps.g

Weak Gravitational Lensing by a Sample of X-ray Luminous Clusters of Galaxies -- III. Serendipitous Weak Lensing Detections of Dark and Luminous Mass Concentrations

In the course of a weak gravitational lensing survey of 39 clusters of galaxies,covering a total sky area of ~1 square degree, we have serendipitously discovered mass concentrations in the fields of A1705 and A1722 which are most probably not associated with the main cluster target. By combining weak lensing information with two-color galaxy photometry in fields centered on our sample clusters, we identify a new cluster candidate at z~0.5 in the field of A1705. This cluster candidate also displays strong lensing in the form of a giant luminous arc. The new mass concentration in the field of A1722 also seems to be associated with an optically luminous cluster of galaxies at z~0.5, but in this case there is some evidence for additional structures along the line of sight that may contribute to the lensing signal. A third cluster, A959, has a dark sub-clump which shows interesting morphological evidence in the mass map for being associated with the main cluster. This is the first case where there is any significant evidence for a physical association between a dark sub-clump (discovered from weak lensing) and a normal cluster. Analysis of archival X-ray data shows that the three new mass concentrations are not firmly detected in X-rays and that they are X-ray underluminous.Comment: 14 pages, 10 figures, version accepted by ApJ. See http://www.nordita.dk/~dahle/paper3.ps.gz for a version with high-resolution figures and Fig.5 in colo

Teacher Candidate Success on State Mandated Professional Tests: One Predictive Measure

This article presents a predictive model using teacher candidates\u27 Grade Point Average (GPA) and its relationship to candidate success on two professional state mandated teaching exams. The 196 subjects for the study were traditional undergraduate teacher education candidates at a major university in Virginia. Specifically, the majority of courses were presented in the face-to-face setting, with a few online courses available. Subject selection was based upon completion of the Virginia Communication Literacy Assessment (VCLA) and the Virginia Reading Assessment (VRA). Data were collected for three consecutive years. Analysis of the relationship between GPA and scores on the VRA and VCLA demonstrated a statistically significant relationship between (a) GPA and mean score on the VRA, and (b) GPA and mean score on the VCLA. These results indicate that better overall performance in the classroom, as measured by grade point average (GPA), produces a higher mean score on both professional assessments

The Ha Luminosity Function and Star Formation Rate at z\sim 0.2

We have measured the Ha+[N II] fluxes of the I-selected Canada-France Redshift Survey (CFRS) galaxies lying at a redshift z below 0.3, and hence derived the Ha luminosity function. The magnitude limits of the CFRS mean that only the galaxies with M(B) > -21 mag were observed at these redshifts. We obtained a total Ha luminosity density of at least 10^{39.44\pm 0.04} erg/s/Mpc^{3} at a mean z=0.2 for galaxies with rest-fame EW(Ha+[N II]) > 10 Angs. This is twice the value found in the local universe by Gallego et al. 1995. Our Ha star formation rate, derived from Madau (1997) is higher than the UV observations at same z, implying a UV dust extinction of about 1 mag. We found a strong correlation between the Ha luminosity and the absolute magnitude in the B-band: M(B(AB)) = 46.7 - 1.6 log L(Ha). This work will serve as a basis of future studies of Ha luminosity distributions measured from optically-selected spectroscopic surveys of the distant universe, and it will provide a better understanding of the physical processes responsible for the observed galaxy evolution.Comment: Accepted for publication in ApJ, 14 pages, LaTeX (macro aas2pp4.sty), 6 figure