Gender and Overconfidence

Do males differ from females in terms of self-confidence? The structure of the Economics I exam at Stockholm University provides an opportunity to shed some light on this question. By answering an extra, optional question, the students can aim for a higher mark. We find a clear gender difference in that male students are more inclined than female students to take this opportunity. This difference in selfassessment is more pronounced among younger than among older students.Overconfidence; gender differences; exam behavior; exam results

Detection of isolated population III stars with the James Webb Space Telescope

The first population III stars are predicted to form in minihalos at a redshift of approximately 10-30. The James Webb Space Telescope (JWST), tentatively scheduled for launch in 2018, will probably be able to detect some of the first galaxies, but whether it will also be able to detect the first stars remains more doubtful. Here, we explore the prospects of detecting an isolated population III star or a small cluster of population III stars down to redshift 2 in either lensed or unlensed fields. Our calculations are based on realistic stellar atmospheres and take into account the potential flux contribution from the surrounding HII region. We find that unlensed population III stars are beyond the reach of JWST, and that even lensed population III stars will be extremely difficult to detect. However, the main problem with the latter approach is not necessarily that the lensed stars are too faint, but that their surface number densities are too low. To detect even one population III star of 60 solar masses when pointing JWST through the galaxy cluster MACS J0717.5+3745, the lensing cluster with the largest Einstein radius detected so far, the cosmic star formation rate of population III stars would need to be approximately an order of magnitude higher than predicted by the most optimistic current models.Comment: 8 pages, 6 figures, 1 table, published in MNRAS. The main change in version 2 is the inclusion of lower redshifts, down to 2. There was also one more SFR comparison model (Tornatore 2007) adde