The Friar Mercury - v.1 - n.3 - June 26, 1942

The Friar Mercury - student newspaper of Providence College. Volume 1, Number 3 - June 26, 1942. 8 pages

Spatially Resolved Star Formation History Along the Disk of M82 Using Multi-Band Photometric Data

We present the results on the star formation history and extinction in the disk of M82 over spatial scales of 10" (~180 pc). Multi-band photometric data covering from the far ultraviolet to the near infrared bands were fitted to a grid of synthetic spectral energy distributions. We obtained distribution functions of age and extinction for each of the 117 apertures analyzed, taking into account observational errors through Monte-Carlo simulations. These distribution functions were fitted with gaussian functions to obtain the mean ages and extinctions along with errors on them. The analyzed zones include the high surface brightness complexes defined by O'Connell & Mangano (1978). We found that these complexes share the same star formation history and extinction as the field stellar populations in the disk. There is an indication that the stellar populations are marginally older at the outer disk (450 Myr at ~3 kpc) as compared to the inner disk (100 Myr at 0.5 kpc). For the nuclear regions (radius less than 500 pc), we obtained an age of less than 10 Myr. The results obtained in this work are consistent with the idea that the 0.5-3 kpc part of the disk of M82 formed around 90% of the stellar mass in a star-forming episode that started around 450 Myr ago lasting for about 350 Myr. We found that field stars are the major contributors to the flux over the spatial scales analyzed in this study, with stellar cluster contribution being 7% in the nucleus and 0.7% in the disk.Comment: 19 pages, 14 figures. Accepted for publication in The Astrophysical Journa

Hubble Residuals of Nearby Type Ia Supernovae Are Correlated with Host Galaxy Masses

From Sloan Digital Sky Survey u'g'r'i'z' imaging, we estimate the stellar masses of the host galaxies of 70 low redshift SN Ia (0.015 < z < 0.08) from the hosts' absolute luminosities and mass-to-light ratios. These nearby SN were discovered largely by searches targeting luminous galaxies, and we find that their host galaxies are substantially more massive than the hosts of SN discovered by the flux-limited Supernova Legacy Survey. Testing four separate light curve fitters, we detect ~2.5{\sigma} correlations of Hubble residuals with both host galaxy size and stellar mass, such that SN Ia occurring in physically larger, more massive hosts are ~10% brighter after light curve correction. The Hubble residual is the deviation of the inferred distance modulus to the SN, calculated from its apparent luminosity and light curve properties, away from the expected value at the SN redshift. Marginalizing over linear trends in Hubble residuals with light curve parameters shows that the correlations cannot be attributed to a light curve-dependent calibration error. Combining 180 higher-redshift ESSENCE, SNLS, and HigherZ SN with 30 nearby SN whose host masses are less than 10^10.8 solar masses in a cosmology fit yields 1+w=0.22 +0.152/-0.143, while a combination where the 30 nearby SN instead have host masses greater than 10^10.8 solar masses yields 1+w=-0.03 +0.217/-0.108. Progenitor metallicity, stellar population age, and dust extinction correlate with galaxy mass and may be responsible for these systematic effects. Host galaxy measurements will yield improved distances to SN Ia.Comment: 16 pages, 6 figures, published in ApJ, minor change

Spartan Daily, March 17, 1961

Volume 48, Issue 87https://scholarworks.sjsu.edu/spartandaily/4141/thumbnail.jp

Spartan Daily, January 9, 1962

Volume 49, Issue 56https://scholarworks.sjsu.edu/spartandaily/4243/thumbnail.jp

Thickness dependence of magnetic properties of (Ga,Mn)As

We report on a monotonic reduction of Curie temperature in dilute ferromagnetic semiconductor (Ga,Mn)As upon a well controlled chemical-etching/oxidizing thinning from 15 nm down to complete removal of the ferro- magnetic response. The effect already starts at the very beginning of the thinning process and is accompanied by the spin reorientation transition of the in-plane uniaxial anisotropy. We postulate that a negative gradient along the growth direction of self-compensating defects (Mn interstitial) and the presence of surface donor traps gives quantitative account on these effects within the p-d mean field Zener model with adequate mod- ifications to take a nonuniform distribution of holes and Mn cations into account. The described here effects are of practical importance for employing thin and ultrathin layers of (Ga,Mn)As or relative compounds in concept spintronics devices, like resonant tunneling devices in particular.Comment: 4 pages, 4 figures and supplementary information 2 pages, 1 figur

Teacher education for effective technology integration

About a decade ago, several researchers used Shulman's (1986) framework about Pedagogical Content Knowledge (PCK) - a body of knowledge that constitutes a special amalgam of content, pedagogy, learners, and context - as a theoretical basis for developing TPCK or TPACK: a framework for guiding teachers' cognition about technology integration in teaching and learning (Angeli, Valanides, & Christodoulou, 2016). Different models of TPCK/TPACK are proposed in the literature, each with a different focus (on practice, instructional design, context, etc.) and with a different theoretical interpretation about the nature and development of the knowledge that teachers need to have to be able to teach with technology (e.g., Angeli & Valanides, 2005, 2009, 2013; Koehler & Mishra, 2008; Niess, 2005).In this direction, research is being carried out to identify TPCK design procedures for initial teacher education. In teaching, when transferring TPCK to design and methodological practices, there is a need to consider a number of factors, especially: the different modes of adopting technologies; the integration of tool affordances, content and pedagogy; the implementation of learning environments; the operationalization of knowledge; and detailed analysis of teaching models and approache

Molecular Beam Epitaxy of LiMnAs

We report on the molecular beam epitaxy (MBE) growth of high crystalline quality LiMnAs. The introduction of a group-I alkali metal element Li with flux comparable to fluxes of Mn and As has not caused any apparent damage to the MBE system after as many as fifteen growth cycles performed on the system to date.Comment: 8 pages, 5 figure