1,891 research outputs found
Reddening, Absorption, and Decline Rate Corrections for a Complete Sample of Type Ia Supernovae leading to a Fully Corrected Hubble Diagram to v<30,000kms-1
Photometric BVI and redshift data corrected for streaming motions are
compiled for 111 "Branch normal", 4 1991T-like, 7 1991bg-like, and 2 unusual
SNe Ia. Color excesses E(B-V)host of normal SNe Ia, due to the absorption of
the host galaxy, are derived by three independent methods leading to the
intrinsic colors at maximum of (B-V)00=-0.024, and (V-I)00=-0.265 if normalized
to a common decline rate of Dm_15=1.1. The strong correlation between redshift
absolute magnitudes (based on Ho=60), corrected only for the extrinsic Galactic
absorption, and the derived E(B-V)host leads to well determined, yet abnormal
absorption-to-reddening ratios of R_BVI=3.65, 2.65, and 1.35. Comparison with
the canonical Galactic values of 4.1, 3.1, 1.8 forces the conclusion that the
law of interstellar absorption in the path length to the SN in the host galaxy
is different from the local Galactic law. Improved correlations of the fully
corrected absolute magnitudes with host galaxy type, decline rate, and
intrinsic color are derived. The four peculiar 1991T-type SNe are significantly
overluminous as compared to Branch-normal SNe Ia. The overluminosity of the
seven 1999aa-like SNe is less pronounced. The seven 1991bg-types in the sample
constitute a separate class of SNeIa, averaging in B two magnitudes fainter
than the normal Ia. New Hubble diagrams in BVI are derived out to ~30,000kms-1
using the fully corrected magnitudes and velocities, corrected for streaming
motions. Nine solutions for the intercept magnitudes in these diagrams show
extreme stability at the 0.04 level using various subsamples of the data. The
same precepts for fully correcting SN magnitudes we shall use for the
luminosity recalibration of SNe Ia in the forthcoming final review of our HST
Cepheid-SN experiment for the Hubble constant.Comment: 49 pages, 15 figures, 8 tables, accepted for publication in the
Astrophysical Journa
Luminosity distributions of Type Ia Supernovae
We have assembled a dataset of 165 low redshift, 0.06, publicly available type Ia supernovae (SNe Ia). We produce maximum light magnitude ( and ) distributions of SNe Ia to explore the diversity of parameter space that they can fill. Before correction for host galaxy extinction we find that the mean and of SNe Ia are mag and mag respectively. Host galaxy extinction is corrected using a new method based on the SN spectrum. After correction, the mean values of and of SNe Ia are and mag respectively. After correction for host galaxy extinction, `normal' SNeIa (mag) fill a larger parameter space in the Width-Luminosity Relation (WLR) than previously suggested, and there is evidence for luminous SNe Ia with large . We find a bimodal distribution in , with a pronounced lack of transitional events at =1.6 mag. We confirm that faster, low-luminosity SNe tend to come from passive galaxies. Dividing the sample by host galaxy type, SNe Ia from star-forming (S-F) galaxies have a mean mag, while SNe Ia from passive galaxies have a mean mag. Even excluding fast declining SNe, `normal' ( mag) SNe Ia from S-F and passive galaxies are distinct. In the -band, there is a difference of 0.40.13 mag between the median () values of the `normal' SN Ia population from passive and S-F galaxies. This is consistent with (10)% of `normal' SNe Ia from S-F galaxies coming from an old stellar population
Associated Absorption Lines in the Radio-Loud Quasar 3C 351: Far-Ultraviolet Echelle Spectroscopy from the Hubble Space Telescope
As one of the most luminous radio-loud quasars showing intrinsic ultraviolet
(UV) and X-ray absorption, 3C 351 provides a laboratory for studying the
kinematics and physical conditions of such ionized absorbers. We present an
analysis of the intrinsic absorption lines in the high-resolution ( 7
km/s) far-UV spectrum which was obtained from observations with the Space
Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope
(HST). The spectrum spans wavelengths from 1150 \AA to 1710 \AA, and shows
strong emission lines from O VI and Ly. Associated absorption lines are
present on the blue wings of the high-ionization emission doublets O VI
1032,1038 and N V 1238,1242, as well as the
Lyman lines through Ly. These intrinsic absorption features are
resolved into several distinct kinematic components, covering rest-frame
velocities from -40 to -2800 km/s, with respect to the systemic redshift of
. For the majority of these absorption line regions, strong
evidence of partial covering of both the background continuum source and the
BELR is found, which supports the intrinsic absorption origin and rules out the
possibility that the absorption arises in some associated cluster of galaxies.
The relationship between the far-UV absorbers and X-ray `warm' absorbers are
studied with the assistance of photoionization models. Most of the UV
associated absorption components have low values of the ionization parameter
and total hydrogen column densities, which is inconsistent with previous claims
that the UV and X-ray absorption arises in the same material. Analysis of these
components supports a picture with a wide range of ionization parameters,
temperatures, and column densities in AGN outflows.Comment: 27 pages with 5 figures, accepted by Ap
Measuring primality in numerical semigroups with embedding dimension three
Electronic version of an article published as Journal of Algebra and Its Applications, 15, 1, 2016, 1650007. DOI:10.1142/S0219498816500079 © World Scientific Publishing Company https://www.worldscientific.com/doi/abs/10.1142/S0219498816500079In this paper, we find the Ï-value of the generators of any numerical semigroup with embedding dimension three. This allows us to determine all possible orderings of the Ï-values of the generators. In addition, we relate the Ï-value of the numerical semigroup to its catenary degree.The first and third authors received National Science Foundation support under DMS-1262897. The second author is supported by the projects MTM2010-15595, FQM-343, FQM-5849, NSF-1061366 and FEDER funds
The Role of a Hot Gas Environment on the Evolution of Galaxies
Most spiral galaxies are found in galaxy groups with low velocity
dispersions; most E/S0 galaxies are found in galaxy groups with relatively high
velocity dispersions. The mass of the hot gas we can observe in the E/S0 groups
via their thermal X-ray emission is, on average, as much as the baryonic mass
of the galaxies in these groups. By comparison, galaxy clusters have as much or
more hot gas than stellar mass. Hot gas in S-rich groups, however, is of low
enough temperature for its X-ray emission to suffer heavy absorption due to
Galactic HI and related observational effects, and hence is hard to detect. We
postulate that such lower temperature hot gas does exist in low velocity
dispersion, S-rich groups, and explore the consequences of this assumption. For
a wide range of metallicity and density, hot gas in S-rich groups can cool in
far less than a Hubble time. If such gas exists and can cool, especially when
interacting with HI in existing galaxies, then it can help link together a
number of disparate observations, both Galactic and extragalactic, that are
otherwise difficult to understand.Comment: 16 pages with one figure. ApJ Letters, in pres
Evaluation of Load Transfer in the Cellulosic-Fiber/Polymer Interphase Using a Micro-Raman Tensile Test
The objectives of this research were (1) to use a Raman micro-spectroscopic technique to determine the tensile stress distributions of a cellulosic-fiber/polymer droplet interphase, and (2) to examine if the stress profile could be used to evaluate load transfer in fiber/polymer adhesion. Cellulosic fibers were treated with various silanes (amino, phenylamino, phenyl, and octadecyl functionalities) and a styrene-maleic anhydride copolymer to create different interphases upon bonding with polystyrene. A single fiber, bonded with a micro-droplet of polystyrene in the mid-span region of its gage length, was strained in tension. Raman spectra were collected at five-micrometer intervals along the embedded region of the fiber. The stress-dependent peak of cellulose (895 cm-1) was analyzed for frequency shift so that the local tensile stress in the interface region could be determined. Results showed that the local tensile stresses of the strained fiber were lower in the embedded region compared to the exposed region, suggesting a transfer of load from the fiber to the matrix polymer. A deeper and sharper decline of the stress profile was observed when the fiber/droplet interaction was enhanced. Further analyses, involving conversion of tensile stress profiles to shear stress distributions in the interphase, confirmed that the micro-Raman/tensile test can be employed to evaluate fiber/matrix interfacial bonding in composites. This success signifies the possibility of evaluating adhesion between cellulosic fibers and brittle polymers, which is difficult to study using common micromechanical tests. Use of the micro-Raman technique can improve our understanding of wood/polymer adhesion
Multi-phase High-Velocity Clouds toward HE 0226-4110 and PG 0953+414
We study the physical conditions, elemental abundances, and kinematics of the
high-velocity clouds (HVCs) along the sight lines toward active galaxies
HE0226-4110 and PG0953+414 using Hubble Space Telescope Imaging Spectrograph
and Far Ultraviolet Spectroscopic Explorer data. Our observations reveal
multiple components of HVC absorption in lines of HI, CII, CIII, CIV, OVI,
SiII, SiIII, and SiIV in both directions. We investigate whether
photoionization by the extragalactic background radiation or by escaping Milky
Way radiation can explain the observed ionization pattern. We find that
photoionization is a good explanation for the CII, CIII, SiII, and SiIII
features, but not for the OVI or CIV associated with the HVCs, suggesting that
two principal phases exist: a warm (T~10^4K), photoionized phase and a hotter
(T=1-3x10^5K), collisionally-ionized phase. The warm HVCs toward HE0226-4110
have high levels of ionization (97-99%), and metallicities ([Z/H] between -0.9
and -0.4) close to those in the Magellanic Stream, which lies eleven degrees
away on the sky at similar velocities. These HVCs have thermal pressures that
would place them close to equilibrium in a fully ionized 10^6 K Galactic corona
with n_H=4-9x10^{-5}cm^{-3} at 50 kpc. A mini-survey of the hot, collisionally
ionized HVC components seen here and in five other sight lines finds that in
11/12 cases, the high ions have kinematics and ionic ratios that are consistent
with an origin in conductive interfaces. However, the broad absorption wing on
the OVI profile toward PG0953+414 is not completely explained by the interface
scenario, and may be tracing the outflow of hot gas into the Milky Way halo as
part of a Galactic fountain or wind.Comment: 27 pages, 12 figures (9 in color), accepted for publication in Ap
Cepheid Calibration of the Peak Brightness of SNe Ia -- IX. SN 1989B in NGC 3627
(Abridged) Repeated imaging observations have been made of NGC 3627 with the
HST in 1997/98, over an interval of 58 days. Images were obtained on 12 epochs
in the F555W band and on five epochs in the F814W band. The galaxy hosted the
prototypical, `Branch normal', type Ia supernova SN 1989B. A total of 83
variables have been found, of which 68 are definite Cepheid variables with
periods ranging from 75 days to 3.85 days. The de-reddened distance modulus is
determined to be (m-M)_0= 30.22+/-0.12 (internal uncertainty) using a subset of
the Cepheid data whose reddening and error parameters are secure.
The photometric data of Wells et al. (1994), combined with the Cepheid data
for NGC 3627 give M_B(max)= -19.36+/-0.18 and M_V(max)= -19.34+/-0.16 for SN
1989B. Combined with the previous six calibrations in this program, plus two
additional calibrations determined by others gives the mean absolute magnitudes
at maximum of = -19.48+/-0.07 and = -19.48 +/-0.07 for `Branch
normal' SNe Ia at this interim stage in the calibration program.
The second parameter correlations of M(max) of blue SNe Ia with decay rate,
color at maximum, and Hubble type are re-investigated. The dependence of
on decay rate is non-linear, showing a minimum for decay rates between
1.0< Delta m_15 <1.6. Magnitudes corrected for decay rate show no dependence on
Hubble type, but a dependence on color remains. Correcting both the fiducial
sample of 34 SNe Ia with decay-rate data and the current 8 calibrating SNe Ia
for the correlation with decay rate as well as color gives H_0= 60+/-2
(internal) km/s/Mpc, in both B and V. The same value to within 4% is obtained
if only the SNe Ia in spirals (without second parameter corrections) are
considered.Comment: 32 pages (with 7 tables and 14 figures) LaTeX, uses emulateapj.sty; a
full-resolution version with complete figs. 4 and 5 is available at
http://www.astro.unibas.ch/cosmology/papers.html ; accepted for publication
in Ap
Dynamic response tests of inertial and optical wind-tunnel model attitude measurement devices
Results are presented for an experimental study of the response of inertial and optical wind-tunnel model attitude measurement systems in a wind-off simulated dynamic environment. This study is part of an ongoing activity at the NASA Langley Research Center to develop high accuracy, advanced model attitude measurement systems that can be used in a dynamic wind-tunnel environment. This activity was prompted by the inertial model attitude sensor response observed during high levels of model vibration which results in a model attitude measurement bias error. Significant bias errors in model attitude measurement were found for the measurement using the inertial device during wind-off dynamic testing of a model system. The amount of bias present during wind-tunnel tests will depend on the amplitudes of the model dynamic response and the modal characteristics of the model system. Correction models are presented that predict the vibration-induced bias errors to a high degree of accuracy for the vibration modes characterized in the simulated dynamic environment. The optical system results were uncorrupted by model vibration in the laboratory setup
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