4,824 research outputs found
Optical and infrared spectrophotometry of 18 Markarian galaxies
Slit spectra, spectrophotometric scans and infrared broad band observations are presented. Eight of the program galaxies can be classified as Seyfert galaxies. Arguments are given that thermal, nonthermal and stellar radiation components were present. One group of Seyfert galaxies was characterized both by the presence of a high density region of gas and by a continuum dominated by nonthermal radiation. The continua of the remaining program Seyferts, which did not have a high density region of gas, were dominated by thermal radiation from dust and a stellar continuum. Ten of the galaxies, which are not Seyfert galaxies, are shown to be examples of extragalactic H 2 regions
The clusters of M33
A selection of clusters in M33 is studied using three different observational techniques which give consistent quantitative results. M33 contains clusters which resemble galactic globular clusters as well as clusters as young as 10^8 years; the luminous clusters thus have an age range similar to those of the Magellanic Clouds rather than those of our Galaxy or M31. The four true globular clusters in our sample are all more metal poor than 47 Tuc. Based on limited data, the carbon star contribution to the integrated infrared light of the intermediate age clusters in M33 is approximately the same as in the intermediate age clusters in the Magellanic Clouds
Real Time Relativity: exploration learning of special relativity
Real Time Relativity is a computer program that lets students fly at
relativistic speeds though a simulated world populated with planets, clocks,
and buildings. The counterintuitive and spectacular optical effects of
relativity are prominent, while systematic exploration of the simulation allows
the user to discover relativistic effects such as length contraction and the
relativity of simultaneity. We report on the physics and technology
underpinning the simulation, and our experience using it for teaching special
relativity to first year university students
Atomic Beams
Contains reports on two research projects.Lincoln Laboratory, Purchase Order DDL-B158Department of the ArmyDepartment of the NavyDepartment of the Air Force under Contract AF 19(122)-45
Understanding the truth about subjectivity
Results of two experiments show childrenâs understanding of diversity in personal preference is incomplete. Despite acknowledging diversity, in Experiment 1(N=108), 6-
and 8-year-old children were less likely than adults to see preference as a legitimate basis for personal tastes and more likely to say a single truth could be found about a matter of taste. In Experiment 2 (N=96), 7- and 9-year-olds were less likely than 11- and 13-yearolds to say a dispute about a matter of preference might not be resolved. These data suggest that acceptance of the possibility of diversity does not indicate an adult-like understanding of subjectivity. An understanding of the relative emphasis placed on objective and subjective factors in different contexts continues to develop into adolescence
Very Luminous Carbon Stars in the Outer Disk of the Triangulum Spiral Galaxy
Stars with masses in the range from about 1.3 to 3.5 Mo pass through an
evolutionary stage where they become carbon stars. In this stage, which lasts a
few Myr, these stars are extremely luminous pulsating giants. They are so
luminous in the near-infrared that just a few of them can double the integrated
luminosity of intermediate-age (0.6 to 2 Gyr) Magellanic Cloud clusters at 2.2
microns. Astronomers routinely use such near-infrared observations to minimize
the effects of dust extinction, but it is precisely in this band that carbon
stars can contribute hugely. The actual contribution of carbon stars to the
outer disk light of evolving spiral galaxies has not previously been
morphologically investigated. Here we report new and very deep near-IR images
of the Triangulum spiral galaxy M33=NGC 598, delineating spectacular arcs of
carbon stars in its outer regions. It is these arcs which dominate the
near-infrared m=2 Fourier spectra of M33. We present near-infrared photometry
with the Hale 5-m reflector, and propose that the arcs are the signature of
accretion of low metallicity gas in the outer disk of M33.Comment: 4 pages, 4 figures. Revised version submitted to A&A Letter
Star counts in NGC 6397
I-band CCD images of a large area of the nearby globular cluster NGC~6397
have been used to construct a surface density profile and two luminosity and
mass functions. The surface density profile extends out to 14\arcm from the
cluster center and shows no sign of a tidal cutoff. The inner profile is a
power-law with slope -0.8 steepening to -1.7 outside of 1\arcm. The mass
functions are for fields at 4\arcm\ and 11\arcm from the cluster center and
confirm the upturn in the mass function for stars less massive than about 0.4
M\solar. There appears to be an excess of low-mass stars over higher-mass stars
in the outer field with respect to the inner, in qualitative agreement with
expectations for mass segregation.Comment: 16 pages + 7 pages of tables, LaTeX using AASTeX macros, 11 figures
available by request, IoA preprin
Comparison of data on Mutation Frequencies of Mice Caused by Radiation - Low Dose Model -
We propose LD(Low Dose) model, the extension of LDM model which was proposed
in the previous paper [Y. Manabe et al.: J. Phys. Soc. Jpn. 81 (2012) 104004]
to estimate biological damage caused by irradiation. LD model takes account of
all the considerable effects including cell death effect as well as
proliferation, apoptosis, repair. As a typical example of estimation, we apply
LD model to the experiment of mutation frequency on the responses induced by
the exposure to low levels of ionizing radiation. The most famous and extensive
experiments are those summarized by Russell and Kelly [Russell, W. L. & Kelly,
E. M: Proc. Natl Acad. Sci. USA 79 (1982) 539-541], which are known as
'Mega-mouse project'. This provides us with important information of the
frequencies of transmitted specific-locus mutations induced in mouse
spermatogonia stem-cells. It is found that the numerical results of the
mutation frequency of mice are in reasonable agreement with the experimental
data: the LD model reproduces the total dose and dose rate dependence of data
reasonably. In order to see such dose-rate dependence more explicitly, we
introduce the dose-rate effectiveness factor (DREF). This represents a sort of
preventable effects such as repair, apoptosis and death of broken cells, which
are to be competitive with proliferation effect of broken cells induced by
irradiation.Comment: subimitting to J. Phys. Soc. Jpn, 32 pages, 8 figure
Molecular Beams
Contains research objectives and reports on two research projects.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 36-039-AMC-03200(E)Sloan Fund for Basic Research (M. I. T. Grant 99
Combined color indexes and photometric structure of galaxies NGC 834 and NGC 1134
We present the results of BVRI photometry of two galaxies with active star
formation: NGC 834 and NGC 1134. Combined color index Q_{BVI} was used to
investigate the photometrical structure of the galaxies. Index Q_{BVI} is not
affected by internal extinction and is sensitive to the presence of blue stars.
Ring-like region with active star formation at 15" from the center reveals
itself in the Q_{BVI} map of NGC 834. Three-arm spiral structure is well-seen
on the Q_{BVI} map of NGC 1134.
We propose to use the combined indexes Q_{BVI} and similarly defined indices
as a tracers of Star Formation activity and structure of dusty galaxies.Comment: 3 pages, 4 embedded figures, LaTeX2e, using the EslabStyle.cls file,
presented as a poster in the 33rd ESLAB Symp. "Star formation from the small
to the large scale", Noordwijk, The Netherlands, 2-5 November 1999, (F.
Favata, A.A. Kaas & A. Wilson eds, ESA SP-445
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