48 research outputs found
A Letter of E. Ravenshorst, Ommen, to Rev. Albertus C. Van Raalte
A letter of E. Ravenshorst, Ommen, to Rev. Albertus C. Van Raalte, about many people and news items which he considers would be of interest to A.C.V.R.. Two people mentioned are Blikman and Bolckel. Ravenshorst is reporting on a Mr. Mansier, Van Raalte\u27s brother-in-law. The letter is a mine of information about family and business matters.https://digitalcommons.hope.edu/vrp_1860s/1027/thumbnail.jp
Black Hole Mass Estimates from Reverberation Mapping and from Spatially Resolved Kinematics
Black hole (BH) masses that have been measured by reverberation mapping in
active galaxies fall significantly below the correlation between bulge
luminosity and BH mass determined from spatially resolved kinematics of nearby
normal galaxies. This discrepancy has created concern that one or both
techniques suffer from systematic errors. We show that BH masses from
reverberation mapping are consistent with the recently discovered relationship
between BH mass and galaxy velocity dispersion. Therefore the bulge
luminosities are the probable source of the disagreement, not problems with
either method of mass measurement. This result underscores the utility of the
BH mass -- velocity dispersion relationship. Reverberation mapping can now be
applied with increased confidence to galaxies whose active nuclei are too
bright or whose distances are too large for BH searches based on spatially
resolved kinematics.Comment: 4 pages, 1 figure, ApJ Letters accepted, minor revision
The Updated Zwicky Catalog (UZC)
The Zwicky Catalog of galaxies (ZC), with m_Zw<=15.5mag, has been the basis
for the Center for Astrophysics (CfA) redshift surveys. To date, analyses of
the ZC and redshift surveys based on it have relied on heterogeneous sets of
galaxy coordinates and redshifts. Here we correct some of the inadequacies of
previous catalogs by providing: (1) coordinates with <~2 arcsec errors for all
of the Nuzc catalog galaxies, (2) homogeneously estimated redshifts for the
majority (98%) of the data taken at the CfA (14,632 spectra), and (3) an
estimate of the remaining "blunder" rate for both the CfA redshifts and for
those compiled from the literature. For the reanalyzed CfA data we include a
calibrated, uniformly determined error and an indication of the presence of
emission lines in each spectrum. We provide redshifts for 7,257 galaxies in the
CfA2 redshift survey not previously published; for another 5,625 CfA redshifts
we list the remeasured or uniformly re-reduced value. Among our new
measurements, Nmul are members of UZC "multiplets" associated with the original
Zwicky catalog position in the coordinate range where the catalog is 98%
complete. These multiplets provide new candidates for examination of tidal
interactions among galaxies. All of the new redshifts correspond to UZC
galaxies with properties recorded in the CfA redshift compilation known as
ZCAT. About 1,000 of our new measurements were motivated either by inadequate
signal-to-noise in the original spectrum or by an ambiguous identification of
the galaxy associated with a ZCAT redshift. The redshift catalog we include
here is ~96% complete to m_Zw<=15.5, and ~98% complete (12,925 galaxies out of
a total of 13,150) for the RA(1950) ranges [20h--4h] and [8h--17h] and
DEC(1950) range [-2.5d--50d]. (abridged)Comment: 34 pp, 7 figs, PASP 1999, 111, 43
The 2MASS Redshift Survey - Description and Data Release
We present the results of the 2MASS Redshift Survey (2MRS), a ten-year
project to map the full three-dimensional distribution of galaxies in the
nearby Universe. The 2 Micron All-Sky Survey (2MASS) was completed in 2003 and
its final data products, including an extended source catalog (XSC), are
available on-line. The 2MASS XSC contains nearly a million galaxies with Ks <=
13.5 mag and is essentially complete and mostly unaffected by interstellar
extinction and stellar confusion down to a galactic latitude of |b|=5 deg for
bright galaxies. Near-infrared wavelengths are sensitive to the old stellar
populations that dominate galaxy masses, making 2MASS an excellent starting
point to study the distribution of matter in the nearby Universe.
We selected a sample of 44,599 2MASS galaxies with Ks =5
deg (>= 8 deg towards the Galactic bulge) as the input catalog for our survey.
We obtained spectroscopic observations for 11,000 galaxies and used
previously-obtained velocities for the remainder of the sample to generate a
redshift catalog that is 97.6% complete to well-defined limits and covers 91%
of the sky. This provides an unprecedented census of galaxy (baryonic mass)
concentrations within 300 Mpc.
Earlier versions of our survey have been used in a number of publications
that have studied the bulk motion of the Local Group, mapped the density and
peculiar velocity fields out to 50 Mpc, detected galaxy groups, and estimated
the values of several cosmological parameters.
Additionally, we present morphological types for a nearly-complete sub-sample
of 20,860 galaxies with Ks = 10 deg.Comment: Accepted for publication in The Astrophysical Journal Supplement
Series. The 2MRS catalogs and a version of the paper with higher-resolution
figures can be found at http://tdc-www.harvard.edu/2mrs
The James Webb Space Telescope
The James Webb Space Telescope (JWST) is a large (6.6m), cold (50K),
infrared-optimized space observatory that will be launched early in the next
decade. The observatory will have four instruments: a near-infrared camera, a
near-infrared multi-object spectrograph, and a tunable filter imager will cover
the wavelength range, 0.6 to 5.0 microns, while the mid-infrared instrument
will do both imaging and spectroscopy from 5.0 to 29 microns. The JWST science
goals are divided into four themes. The End of the Dark Ages: First Light and
Reionization theme seeks to identify the first luminous sources to form and to
determine the ionization history of the early universe. The Assembly of
Galaxies theme seeks to determine how galaxies and the dark matter, gas, stars,
metals, morphological structures, and active nuclei within them evolved from
the epoch of reionization to the present day. The Birth of Stars and
Protoplanetary Systems theme seeks to unravel the birth and early evolution of
stars, from infall on to dust-enshrouded protostars to the genesis of planetary
systems. The Planetary Systems and the Origins of Life theme seeks to determine
the physical and chemical properties of planetary systems including our own,
and investigate the potential for the origins of life in those systems. To
enable these observations, JWST consists of a telescope, an instrument package,
a spacecraft and a sunshield. The telescope consists of 18 beryllium segments,
some of which are deployed. The segments will be brought into optical alignment
on-orbit through a process of periodic wavefront sensing and control. The JWST
operations plan is based on that used for previous space observatories, and the
majority of JWST observing time will be allocated to the international
astronomical community through annual peer-reviewed proposal opportunities.Comment: 96 pages, including 48 figures and 15 tables, accepted by Space
Science Review
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
Recommended from our members
Social Movements and International Relations: A Relational Framework
Social movements are increasingly recognized as significant features of contemporary world politics, yet to date their treatment in international relations theory has tended to obfuscate the considerable diversity of these social formations, and the variegated interactions they may establish with state actors and different structures of world order. Highlighting the difficulties conventional liberal and critical approaches have in transcending conceptions of movements as moral entities, the article draws from two under-exploited literatures in the study of social movements in international relations, the English School and Social Systems Theory, to specify a wider range of analytical interactions between different categories of social movements and of world political structures. Moreover, by casting social movement phenomena as communications, the article opens international relations to consideration of the increasingly diverse trajectories and second-order effects produced by social movements as they interact with states, intergovernmental institutions, and transnational actors
Viewpoints from Computing to the Epistemology of Experiments
Although experiments have been a core element of the scientific method since the 1600s, experiments per se only caught philosophers' interest in the 1980s. Since the 1980s dozens of philosophical analyses of experiments have been presented, based mostly on physics and biology. A number of philosophers of science have called for bottom-up, "naturalistic" investigations of experiments in various disciplines, especially fields other than physics. This paper presents an epistemological analysis of experiments in computing fields in terms of epistemological characteristics, research milieux, and epistemological features of results. Our analysis of experiments, based on how the term is operationalized in computer science papers, opens new critical viewpoints to the role of experiments in computing, as well as complementary viewpoints to the concept of experiment in the philosophy of science