Young and Intermediate-age Distance Indicators

Distance measurements beyond geometrical and semi-geometrical methods, rely mainly on standard candles. As the name suggests, these objects have known luminosities by virtue of their intrinsic proprieties and play a major role in our understanding of modern cosmology. The main caveats associated with standard candles are their absolute calibration, contamination of the sample from other sources and systematic uncertainties. The absolute calibration mainly depends on their chemical composition and age. To understand the impact of these effects on the distance scale, it is essential to develop methods based on different sample of standard candles. Here we review the fundamental properties of young and intermediate-age distance indicators such as Cepheids, Mira variables and Red Clump stars and the recent developments in their application as distance indicators.Comment: Review article, 63 pages (28 figures), Accepted for publication in Space Science Reviews (Chapter 3 of a special collection resulting from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in the Space Age

Young and intermediate-age massive star clusters

An overview of our current understanding of the formation and evolution of star clusters is given, with main emphasis on high-mass clusters. Clusters form deeply embedded within dense clouds of molecular gas. Left-over gas is cleared within a few million years and, depending on the efficiency of star formation, the clusters may disperse almost immediately or remain gravitationally bound. Current evidence suggests that a few percent of star formation occurs in clusters that remain bound, although it is not yet clear if this fraction is truly universal. Internal two-body relaxation and external shocks will lead to further, gradual dissolution on timescales of up to a few hundred million years for low-mass open clusters in the Milky Way, while the most massive clusters (> 10^5 Msun) have lifetimes comparable to or exceeding the age of the Universe. The low-mass end of the initial cluster mass function is well approximated by a power-law distribution, dN/dM ~ M^{-2}, but there is mounting evidence that quiescent spiral discs form relatively few clusters with masses M > 2 x 10^5 Msun. In starburst galaxies and old globular cluster systems, this limit appears to be higher, at least several x 10^6 Msun. The difference is likely related to the higher gas densities and pressures in starburst galaxies, which allow denser, more massive giant molecular clouds to form. Low-mass clusters may thus trace star formation quite universally, while the more long-lived, massive clusters appear to form preferentially in the context of violent star formation.Comment: 21 pages, 3 figures. To appear as invited review article in a special issue of the Phil. Trans. Royal Soc. A: Ch. 9 "Star clusters as tracers of galactic star-formation histories" (ed. R. de Grijs). Fully peer reviewed. PDFLaTeX, requires rspublic.cls style fil

Chart of head length of pouch young tammar wallabies (Macropus eugenii) of known age

This is a chart of the head lengths of pouch young tammar wallabies (Macropus eugenii)of known age, enabling the ages of pouch young of unknown age to be determined by their head lengt

Ages and Age Spreads in Young Stellar Clusters

I review progress towards understanding the time-scales of star and cluster formation and of the absolute ages of young stars. I focus in particular on the areas in which Francesco Palla made highly significant contributions - interpretation of the Hertzsprung-Russell diagrams of young clusters and the role of photospheric lithium as an age diagnostic.Comment: To appear in "Francesco's Legacy: Star Formation in Space and Time", Memorie della SAIt, in press. Eds. R. Cesaroni, E. Corbelli and D. Galli. 5p

The Impact of Homophobia and Racism on GLBTQ Youth of Color

As members of more than one minority group, GLBTQ youth of color face special challenges in a society which often presents heterosexuality as the only acceptable orientation and in which nonwhites have disproportionately higher rates of negative sexual outcomes. Economic and cultural disparities, as well as sexual risk taking and other risk-taking behavior, make these youth vulnerable to HIV, pregnancy, and sexual violence. Holistic, culturally competent health care is essential to their well being. Sexual identity formation is not significantly influenced by cultural factors; that is, studies have shown no significant differences between white youth and youth of color in mean age of being "out to self" (16 for young women, 15 for young men); age coming out to others (17 for young women and young men), or age of first homosexual sexual experience (17 for young women, 16 for young men). Black and Latino youth also did not differ from white youth in acceptance of their own sexuality. But while GLBTQ youth of color develop similarly to white youth, they must bear the twin burdens of racism and homophobia

Where do I go and what should I do? Routes through further education

This paper investigates the educational attainment of young people between the ages of sixteen and eighteen after having entered full-time post-compulsory education. In particular we focus on the educational attainment and labour market trajectory of `underachievers´: young people who have chosen to remain in full-time education at age sixteen, despite not gaining the widely recognised U.K. academic benchmark of five GCSE grades A*-C. Our results suggest that the best route to educational success for young people considered as of lower ability at age 16 is through the FE college where they catch-up with their `more able´ counterparts by age 18

Self-Perceived Health and Outlook Among the Rural Elderly

Differences in life outlook and self-perceived health often attributed to age differences among the elderly were found to be more accurately explained by education. The young-old (62-74 years) and the old-old (75 years and older) were compared among 495 elderly in two rural counties in western Arkansas. The old-old were more likely than the young-old to perceive their health as better than that of others their age. But when six variables including age were entered into a predictive model for self-perceived health, differences were explained by education. That is, those with better educations rated their health more positively. There was no difference between the two age groups in sick days, although the old-old reported more days hospitalized and trips to the doctor. However, no predictive model for health status measured was statistically significant. On measures of life satisfaction, the old-old were slightly more pessimistic than the young-old. But the age difference in life outlook was explained by education when the data were controlled for other variables. The customary division of the elderly into young-old and old-old is questioned, and policy implications of the findings are discussed