Creative Learning: A Curriculum for Preprimary Children. Unit 8, Dinosaur Era and Fossils

DINOSAUR ERA AND FOSSILS is one resource unit. It is hoped to serve as a resource to others as they guide the learning of young children. It is not a cut-and-dried, how-to-do-it book. But it is a collection of numerous learning experiences within the context of a unit setting. The various disciplines are not, and cannot, be separated; learning overlaps. With a central theme, young children will have many opportunities to examine, investigate, explore, experience and discover concepts of meaning. As the children approach the same concept from a number of experiences, they will have opportunities to formulate ideas, to test these ideas for validity and meaning, and to draw conclusions relevant for them

Cold Dust in Kepler's Supernova Remnant

The timescales to replenish dust from the cool, dense winds of Asymptotic Giant Branch stars are believed to be greater than the timescales for dust destruction. In high redshift galaxies, this problem is further compounded as the stars take longer than the age of the Universe to evolve into the dust production stages. To explain these discrepancies, dust formation in supernovae (SNe) is required to be an important process but until very recently dust in supernova remnants has only been detected in very small quantities. We present the first submillimeter observations of cold dust in Kepler's supernova remnant (SNR) using SCUBA. A two component dust temperature model is required to fit the Spectral Energy Distribution (SED) with $T_{warm} \sim 102$K and $T_{cold} \sim 17$K. The total mass of dust implied for Kepler is $\sim 1M_{\odot}$ - 1000 times greater than previous estimates. Thus SNe, or their progenitors may be important dust formation sites.Comment: 12 pages, 2 figures, accepted to ApJL, corrected proof

The role of reproductive timing as a driver of genetic differentiation in populations of Pacific herring

There is growing recognition that maintaining diversity in life history traits contributes to the sustainable management of wild populations. One important life history characteristic is reproductive phenology, and it has been shown that differences in the timing of reproduction can act as a barrier to gene flow between populations. If the difference in reproductive timing determines the level of connectivity, one would expect that genetic differentiation between populations would increase as a function of difference in reproductive date. This pattern, known as “isolation by time” (IBT), has been observed in wild populations of salmonids containing early and late runs. Pacific herring in the Salish Sea also exhibit a wide diversity of spawn times; some populations start reproducing as early as January and reproductive activity in the region continues through May. Here, we test whether these temporal differences in reproduction influence the genetic population structure of herring. We collected adult herring from seven different locations in the Salish Sea during active spawning events (N = 48 per site). Samples were sequenced using a restriction site-associated (RAD) approach and approximately 3,000 polymorphic loci were genotyped in each sample. We found a positive correlation between genetic differentiation and difference in spawn date, with evidence of migration between populations with similar spawn timing. Several loci exhibited exceptionally steep gradients in allele frequencies, including one locus linked to the photoperiodic regulation of reproduction. Our discovery of IBT in Pacific herring support the adaptive significance of spawn timing and underscore the importance of conserving spawning time diversity in Puget Sound herring

An S-shaped outflow from IRAS 03256+3055 in NGC 1333

The IRAS source 03256+3055 in the NGC 1333 star forming region is associated with extended sub-millimeter emission of complex morphology, showing multiple clumps. One of these is found to coincide with the driving source of a bipolar jet of S-shaped morphology seen in the emission lines of H_alpha and [SII] as well as in the H2 emission lines in the K-band. Detailed images of the driving source at the wavelengths of H_alpha and [SII] and in the I, J, H, and K bands as well as a K-band spectrum and polarimetry are discussed. The near-infrared morphology is characterized by a combination of line emission from the jet and scattered light from a source with a steep continuum spectrum. The morphology and proper motion of the jet are discussed in the context of a binary system with a precessing disk. We conclude that the molecular core associated with IRAS 03256+3055 consists of several clumps, only one of which shows evidence of recent star formation at optical and near-infrared wavelengths.We also briefly discuss a second, newly found near-infrared source associated with a compact sub-millimeter continuum source near IRAS 03256+3055, and conclude that this source may be physically unrelated the cluster of molecular clumps.Comment: 25 pages, including 5 figures. Accepted for publication in The Astronomical Journa

A Submillimeter Study of the Star-Forming Region NGC7129

New molecular (13CO J=3-2) and dust continuum (450 and 850 micron) SCUBA maps of the NGC7129 star forming region are presented, complemented by C18O J=3-2 spectra at several positions within the mapped region. The maps include the Herbig Ae/Be star LkHalpha 234, the far-infrared source NGC 7129 FIRS2 and several other pre-stellar sources embedded within the molecular ridge. The SCUBA maps help us understand the nature of the pre-main sequence stars in this actively star forming region. A deeply embedded submillimeter source, SMM2, not clearly seen in any earlier data set, is shown to be a pre-stellar core or possibly a protostar. The highest continuum peak emission is identified with the deeply embedded source IRS6, a few arcseconds away from LkHalpha 234, and also responsible for both the optical jet and the molecular outflow. The gas and dust masses are found to be consistent, suggesting little or no CO depletion onto grains. The dust emissivity index is lower towards the dense compact sources, beta ~1 - 1.6, and higher, beta ~ 2.0, in the surrounding cloud, implying small size grains in the PDR ridge, whose mantles have been evaporated by the intense UV radiation.Comment: Accepted by Ap

The Hot Inner Disk of FU Ori

We have constructed a detailed radiative transfer disk model which reproduces the main features of the spectrum of the outbursting young stellar object FU Orionis from ~ 4000 angstrom, to ~ 8 micron. Using an estimated visual extinction Av~1.5, a steady disk model with a central star mass ~0.3 Msun and a mass accretion rate ~ 2e-4 Msun/yr, we can reproduce the spectral energy distribution of FU Ori quite well. With the mid-infrared spectrum obtained by the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope, we estimate that the outer radius of the hot, rapidly accreting inner disk is ~ 1 AU using disk models truncated at this outer radius. Inclusion of radiation from a cooler irradiated outer disk might reduce the outer limit of the hot inner disk to ~ 0.5 AU. In either case, the radius is inconsistent with a pure thermal instability model for the outburst. Our radiative transfer model implies that the central disk temperature Tc > 1000 K out to ~ 0.5 - 1 AU, suggesting that the magnetorotational instability (MRI) can be supported out to that distance. Assuming that the ~ 100 yr decay timescale in brightness of FU Ori represents the viscous timescale of the hot inner disk, we estimate the viscosity parameter (alpha) to be ~ 0.2 - 0.02 in the outburst state, consistent with numerical simulations of MRI in disks. The radial extent of the high mass accretion region is inconsistent with the model of Bell & Lin, but may be consistent with theories incorporating both gravitational instability and MRI.Comment: 32 pages, 10 figures, to appear in the Astrophysical Journa