704 research outputs found
Science Communication Versus Science Education: The Graduate Student Scientist As A K-12 Classroom Resource
Science literacy is a major goal of science educational reform (NRC, 1996; AAAS, 1998; NCLB Act, 2001). Some believe that teaching science only requires pedagogical content knowledge (PCK) (Shulman, 1987). Others believe doing science requires knowledge of the methodologies of scientific inquiry (NRC, 1996). With these two mindsets, the challenge for science educators is to create models that bring the two together. The common ground between those who teach science and those who do science is science communication, an interactive process that galvanizes dialogue among scientists, teachers, and learners in a rich ambience of mutual respect and a common, inclusive language of discourse (Stocklmayer, 2001). The dialogue between science and non-science is reflected in the polarization that separates those who do science and those who teach science, especially as it plays out everyday in the science classroom. You may be thinking, why is this important? It is vital because, although not all science learners become scientists, all K-12 students are expected to acquire science literacy, especially with the implementation of the No Child Left Behind Act of 2001 (NCLB). Students are expected to acquire the ability to follow the discourse of science as well as connect the world of science to the context of their everyday life if they plan on moving to the next grade level, and in some states, to graduate from high school. This paper posits that science communication is highly effective in providing the missing link for K-12 students’ cognition in science and their attainment of science literacy. This paper will focus on the “Science For Our Schools” (SFOS) model implemented at California State University, Los Angeles (CSULA) as a project of the National Science Foundation’s GK-12 program, (NSF 2001) which has been a huge success in bridging the gap between those who “know” science and those who “teach” science. The SFOS model makes clear the distinctions that identify science, science communication, science education, and science literacy in the midst of science learning by bringing together graduate student scientists and science teachers to engage students in the two world’s dialogue in the midst of the school science classroom. The graduate student scientists and the science teachers worked as a team throughout the school year and became effective science communicators as they narrowed the gulf between the two worlds
Gas dynamics of a luminous = 6.13 quasar ULAS J13190950 revealed by ALMA high resolution observations
We present new Atacama Large Millimeter/submillimeter Array (ALMA)
observations of the dust continuum and [C II] 158 m fine structure line
emission towards a far-infrared-luminous quasar, ULAS J131911.29095051.4 at
, and combine the new Cycle 1 data with ALMA Cycle 0 data. The combined
data have an angular resolution , and resolve both the dust
continuum and the [C II] line emission on few kpc scales. The [C II] line
emission is more irregular than the dust continuum emission which suggests
different distributions between the dust and [C II]-emitting gas. The combined
data confirm the [C II] velocity gradient that we previously detected in lower
resolution ALMA image from Cycle 0 data alone. We apply a tilted ring model to
the [C II] velocity map to obtain a rotation curve, and constrain the circular
velocity to be 427 55 km s at a radius of 3.2 kpc with an
inclination angle of 34. We measure the dynamical mass within the 3.2
kpc region to be 13.4 . This yields
a black hole and host galaxy mass ratio of 0.020, which is
about 4 times higher than the present-day / ratio. This suggests that the supermassive black hole grows the bulk of
its mass before the formation of the most of stellar mass in this quasar host
galaxy in the early universe.Comment: 24 pages, 5 figures, accepted for publication in Ap
Probing the interstellar medium and star formation of the Most Luminous Quasar at z=6.3
We report new IRAM/PdBI, JCMT/SCUBA-2, and VLA observations of the
ultraluminous quasar SDSSJ010013.02+280225.8 (hereafter, J0100+2802) at z=6.3,
which hosts the most massive supermassive black hole (SMBH) of 1.24x10^10 Msun
known at z>6. We detect the [C II] 158 m fine structure line and molecular
CO(6-5) line and continuum emission at 353 GHz, 260 GHz, and 3 GHz from this
quasar. The CO(2-1) line and the underlying continuum at 32 GHz are also
marginally detected. The [C II] and CO detections suggest active star formation
and highly excited molecular gas in the quasar host galaxy. The redshift
determined with the [C II] and CO lines shows a velocity offset of ~1000 km/s
from that measured with the quasar Mg II line. The CO (2-1) line luminosity
provides direct constraint on the molecular gas mass which is about
(1.0+/-0.3)x10^10 Msun. We estimate the FIR luminosity to be (3.5+/-0.7)x10^12
Lsun, and the UV-to-FIR spectral energy distribution of J0100+2802 is
consistent with the templates of the local optically luminous quasars. The
derived [C II]-to-FIR luminosity ratio of J0100+2802 is 0.0010+/-0.0002, which
is slightly higher than the values of the most FIR luminous quasars at z~6. We
investigate the constraint on the host galaxy dynamical mass of J0100+2802
based on the [C II] line spectrum. It is likely that this ultraluminous quasar
lies above the local SMBH-galaxy mass relationship, unless we are viewing the
system at a small inclination angle.Comment: 19 pages, 4 figures, published by the Astrophysical Journal, minimal
changes in acknowledgement to match the published versio
Star Formation and Gas Kinematics of Quasar Host Galaxies at z~6: New insights from ALMA
We present ALMA observations of the [C II] 158 micron fine structure line and
dust continuum emission from the host galaxies of five redshift 6 quasars. We
also report complementary observations of 250 GHz dust continuum and CO (6-5)
line emission from the z=6.00 quasar SDSS J231038.88+185519.7. The ALMA
observations were carried out in the extended array at 0.7" resolution. We have
detected the line and dust continuum in all five objects. The derived [C II]
line luminosities are 1.6x10^{9} to 8.8x10^{9} Lsun and the [C II]-to-FIR
luminosity ratios are 3.0-5.6x10^{-4}, which is comparable to the values found
in other high-redshift quasar-starburst systems and local ultra-luminous
infrared galaxies. The sources are marginally resolved and the intrinsic source
sizes (major axis FWHM) are constrained to be 0.3" to 0.6" (i.e., 1.7 to 3.5
kpc) for the [C II] line emission and 0.2" to 0.4" (i.e., 1.2 to 2.3 kpc) for
the continuum. These measurements indicate that there is vigorous star
formation over the central few kpc in the quasar host galaxies. The ALMA
observations also constrain the dynamical properties of the atomic gas in the
starburst nuclei. The intensity-weighted velocity maps of three sources show
clear velocity gradients. Such velocity gradients are consistent with a
rotating, gravitationally bound gas component, although they are not uniquely
interpreted as such. Under the simplifying assumption of rotation, the implied
dynamical masses within the [C II]-emitting regions are of order 10^{10} to
10^{11} Msun. Given these estimates, the mass ratios between the SMBHs and the
spheroidal bulge are an order of magnitude higher than the mean value found in
local spheroidal galaxies, which is in agreement with results from previous CO
observations of high redshift quasars.Comment: 25 pages, 5 figures, accepted for publication in Ap
Thermal Emission from Warm Dust in the Most Distant Quasars
We report new continuum observations of fourteen z~6 quasars at 250 GHz and
fourteen quasars at 1.4 GHz. We summarize all recent millimeter and radio
observations of the sample of the thirty-three quasars known with
5.71<=z<=6.43, and present a study of the rest frame far-infrared (FIR)
properties of this sample. These quasars were observed with the Max Plank
Millimeter Bolometer Array (MAMBO) at 250 GHz with mJy sensitivity, and 30% of
them were detected. We also recover the average 250 GHz flux density of the
MAMBO undetected sources at 4 sigma, by stacking the on-source measurements.
The derived mean radio-to-UV spectral energy distributions (SEDs) of the full
sample and the 250 GHz non-detections show no significant difference from that
of lower-redshift optical quasars. Obvious FIR excesses are seen in the
individual SEDs of the strong 250 GHz detections, with FIR-to-radio emission
ratios consistent with that of typical star forming galaxies. Most 250
GHz-detected sources follow the L_{FIR}--L_{bol} relationship derived from a
sample of local IR luminous quasars (L_{IR}>10^{12}L_{\odot}), while the
average L_{FIR}/L_{bol} ratio of the non-detections is consistent with that of
the optically-selected PG quasars. The MAMBO detections also tend to have
weaker Ly\alpha emission than the non-detected sources. We discuss possible FIR
dust heating sources, and critically assess the possibility of active star
formation in the host galaxies of the z~6 quasars. The average star formation
rate of the MAMBO non-detections is likely to be less than a few hundred
M_{\odot} yr^{-1}, but in the strong detections, the host galaxy star formation
is probably at a rate of \gtrsim10^{3} M_{\odot} yr^{-1}, which dominates the
FIR dust heating.Comment: 32 pages with 6 figures; ApJ, in press; Added references; Corrected
typo
The interstellar medium distribution, gas kinematics, and system dynamics of the far-infrared luminous quasar SDSS J2310+1855 at
We present ALMA sub-kpc- to kpc-scale resolution observations of the [CII],
CO(9-8), and OH\,(--) lines along with their dust continuum
emission toward the FIR luminous quasar SDSS J231038.88+185519.7 at . The [CII] brightness follows a flat distribution with a Sersic index
of 0.59. The CO(9-8) line and the dust continuum can be fit with an unresolved
nuclear component and an extended Sersic component with a Sersic index of ~1.
The dust temperature drops with distance from the center. The effective radius
of the dust continuum is smaller than that of the line emission and the dust
mass surface density, but is consistent with that of the star formation rate
surface density. The OH\,(--) line shows a P-Cygni profile
with an absorption, which may indicate an outflow with a neutral gas mass of
along the line of sight. We employed a 3D
tilted ring model to fit the [CII] and CO(9-8) data cubes. The two lines are
both rotation dominated and trace identical disk geometries and gas motions. We
decompose the circular rotation curve measured from the kinematic model fit to
the [CII] line into four matter components (black hole, stars, gas, and dark
matter). The quasar-starburst system is dominated by baryonic matter inside the
central few kiloparsecs. We constrain the black hole mass to be
; this is the first time that the
dynamical mass of a black hole has been measured at . A massive stellar
component (on the order of ) may have already existed when
the Universe was only ~0.93 Gyr old. The relations between the black hole mass
and the baryonic mass of this quasar indicate that the central supermassive
black hole may have formed before its host galaxy. [Abridged version. Please
see the full abstract in the manuscript.]Comment: Accepted for publication in A&
The Angular Correlation Function of Galaxies from Early SDSS Data
The Sloan Digital Sky Survey is one of the first multicolor photometric and
spectroscopic surveys designed to measure the statistical properties of
galaxies within the local Universe. In this Letter we present some of the
initial results on the angular 2-point correlation function measured from the
early SDSS galaxy data. The form of the correlation function, over the
magnitude interval 18<r*<22, is shown to be consistent with results from
existing wide-field, photographic-based surveys and narrower CCD galaxy
surveys. On scales between 1 arcminute and 1 degree the correlation function is
well described by a power-law with an exponent of ~ -0.7. The amplitude of the
correlation function, within this angular interval, decreases with fainter
magnitudes in good agreement with analyses from existing galaxy surveys. There
is a characteristic break in the correlation function on scales of
approximately 1-2 degrees. On small scales, < 1', the SDSS correlation function
does not appear to be consistent with the power-law form fitted to the 1'<
theta <0.5 deg data. With a data set that is less than 2% of the full SDSS
survey area, we have obtained high precision measurements of the power-law
angular correlation function on angular scales 1' < theta < 1 deg, which are
robust to systematic uncertainties. Because of the limited area and the highly
correlated nature of the error covariance matrix, these initial results do not
yet provide a definitive characterization of departures from the power-law form
at smaller and larger angles. In the near future, however, the area of the SDSS
imaging survey will be sufficient to allow detailed analysis of the small and
large scale regimes, measurements of higher-order correlations, and studies of
angular clustering as a function of redshift and galaxy type
Synthesis of freestanding HfO2 nanostructures
Two new methods for synthesizing nanostructured HfO2 have been developed. The first method entails exposing HfTe2 powders to air. This simple process resulted in the formation of nanometer scale crystallites of HfO2. The second method involved a two-step heating process by which macroscopic, freestanding nanosheets of HfO2 were formed as a byproduct during the synthesis of HfTe2. These highly two-dimensional sheets had side lengths measuring up to several millimeters and were stable enough to be manipulated with tweezers and other instruments. The thickness of the sheets ranged from a few to a few hundred nanometers. The thinnest sheets appeared transparent when viewed in a scanning electron microscope. It was found that the presence of Mn enhanced the formation of HfO2 by exposure to ambient conditions and was necessary for the formation of the large scale nanosheets. These results present new routes to create freestanding nanostructured hafnium dioxide
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