960 research outputs found
Detecting z > 2 Type IIn Supernovae
Type IIn supernovae (SNe IIn) dominate the brightest supernova events in
observed FUV flux (~1200-2000A). We show that multi-band, multi-epoch optical
surveys complete to m_r = 27 can detect the FUV emission of ~25 z > 2 SNe IIn
deg^-2 yr^-1 rest-frame (~10 SNe IIn deg^-2 yr^-1 observed-frame) to 4 sigma
using a technique monitoring color-selected galaxies. Moreover, the strength
and evolution of the bright emission lines observed in low redshift SNe IIn
imply that the Ly-a emission features in ~70% of z > 2 SNe IIn are above
8m-class telescope spectroscopic thresholds for ~2 yr rest-frame. As a result,
existing facilities have the capability to both photometrically detect and
spectroscopically confirm z > 2 SNe IIn and pave the way for efficient searches
by future 8m-class survey and 30m-class telescopes. The method presented here
uses the sensitivities and wide-field capabilities of current optical
instruments and exploits (1) the efficiency of z > 2 galaxy color-selection
techniques, (2) the intrinsic brightness distribution ( = -19.0 +/-0.9)
and blue profile of SNe IIn continua, (3) the presence of extremely bright,
long-lived emission features, and (4) the potential to detect blueshifted SNe
Ly-a emission shortward of host galaxy Ly-a features.Comment: 26 pages (pre-print), 6 figures, accepted Ap
Pregnancy-Related Lumbopelvic Pain: Listening to Australian Women
Objective. To investigate the prevalence and nature of lumbo-pelvic pain (LPP), that is experienced by women in the lumbar and/or sacro-iliac area and/or symphysis pubis during pregnancy. Design. Cross-sectional, descriptive study. Setting. An Australian public hospital antenatal clinic. Sample population: Women in their third trimester of pregnancy. Method. Women were recruited to the study as they presented for their antenatal appointment. A survey collected demographic data and was used to self report LPP. A pain diagram differentiated low back, pelvic girdle or combined pain. Closed and open ended questions explored the experiences of the women. Main Outcome Measures. The Visual Analogue Scale and the Oswestry Disability Index (Version 2.1a). Results. There was a high prevalence of self reported LPP during the pregnancy (71%). An association was found between the reporting of LPP, multiparity, and a previous history of LPP. The mean intensity score for usual pain was 6/10 and four out of five women reported disability associated with the condition. Most women (71%) had reported their symptoms to their maternity carer however only a small proportion of these women received intervention. Conclusion. LPP is a potentially significant health issue during pregnancy
Adaptive Optics Discovery of Supernova 2004ip in the Nuclear Regions of the Luminous Infrared Galaxy IRAS 18293-3413
We report a supernova discovery in Ks-band images from the NAOS CONICA
adaptive optics (AO) system on the ESO Very Large Telescope (VLT). The images
were obtained as part of a near-infrared search for highly-obscured supernovae
in the nuclear regions of luminous and ultraluminous infrared galaxies. SN
2004ip is located within a circumnuclear starburst at 1.4 arcsec (or 500 pc)
projected distance from the K-band nucleus of the luminous infrared galaxy IRAS
18293-3413. The supernova luminosity and light curve are consistent with a
core-collapse event suffering from a host galaxy extinction of up to about 40
magnitudes in V-band which is as expected for a circumnuclear starburst
environment. This is the first supernova to be discovered making use of AO
correction and demonstrates the potential of the current 8-meter class
telescopes equipped with AO in discovering supernovae from the innermost
nuclear regions of luminous and ultraluminous infrared galaxies.Comment: 4 pages, 3 figures, ApJ Letters (accepted
Helium and Iron in X-ray galaxy clusters
I discuss the role of the sedimentation of helium in galaxy cluster cores on
the observed X-ray properties and present a history of the metal accumulation
in the ICM, with new calculations with respect to my previous work following
the recent evidence of a bi-modal distribution of the delay time in Supernovae
Type Ia.Comment: 6 pages. To appear in the Proceedings of "Heating vs. Cooling in
Galaxies and Clusters of Galaxies", August 2006, Garching (Germany
High Redshift Supernova Rates
We use a sample of 42 supernovae detected with the Advanced Camera for
Surveys on-board the Hubble Space Telescope as part of the Great Observatories
Origins Deep Survey to measure the rate of core collapse supernovae to z~0.7
and type Ia supernovae to z~1.6. This significantly increases the redshift
range where supernova rates have been estimated from observations.
The rate of core collapse supernovae can be used as an independent probe of
the cosmic star formation rate. Based on the observations of 17 core collapse
supernovae, we measure an increase in the core collapse supernova rate by a
factor of 1.6 in the range 0.3<z<0.7, and an overall increase by a factor of 7
to z~0.7 in comparison to the local core collapse supernova rate. The increase
in the rate in this redshift range in consistent with recent measurements of
the star formation rate derived from UV-luminosity densities and IR datasets.
Based on 25 type Ia supernovae, we find a SN Ia rate that is a factor 3-5
higher at z~1 compared to earlier estimates at lower redshifts (z<0.5),
implying that the type Ia supernova rate traces a higher star formation rate at
redshifts z>1 compared to low redshift. At higher redshift (z>1), we find a
suggested decrease in the type Ia rate with redshift. This evolution of the Ia
rate with redshift is consistent with a type Ia progenitor model where there is
a substantial delay between the formation of the progenitor star and the
explosion of the supernova. Assuming that the type Ia progenitor stars have
initial main sequence masses 3-8 M_Sun, we find that 5-7% of the available
progenitors explode as type Ia supernovae.Comment: 16 pages, 3 figures, accepted for publication in the Astrophysical
Journa
Near-IR Search for Lensed Supernovae Behind Galaxy Clusters - II. First Detection and Future Prospects
Powerful gravitational telescopes in the form of massive galaxy clusters can
be used to enhance the light collecting power over a limited field of view by
about an order of magnitude in flux. This effect is exploited here to increase
the depth of a survey for lensed supernovae at near-IR wavelengths. A pilot SN
search program conducted with the ISAAC camera at VLT is presented. Lensed
galaxies behind the massive clusters A1689, A1835 and AC114 were observed for a
total of 20 hours split into 2, 3 and 4 epochs respectively, separated by
approximately one month to a limiting magnitude J<24 (Vega). Image subtractions
including another 20 hours worth of archival ISAAC/VLT data were used to search
for transients with lightcurve properties consistent with redshifted
supernovae, both in the new and reference data. The feasibility of finding
lensed supernovae in our survey was investigated using synthetic lightcurves of
supernovae and several models of the volumetric Type Ia and core-collapse
supernova rates as a function of redshift. We also estimate the number of
supernova discoveries expected from the inferred star formation rate in the
observed galaxies. The methods consistently predict a Poisson mean value for
the expected number of SNe in the survey between N_SN=0.8 and 1.6 for all
supernova types, evenly distributed between core collapse and Type Ia SN. One
transient object was found behind A1689, 0.5" from a galaxy with photometric
redshift z_gal=0.6 +- 0.15. The lightcurve and colors of the transient are
consistent with being a reddened Type IIP SN at z_SN=0.59. The lensing model
predicts 1.4 magnitudes of magnification at the location of the transient,
without which this object would not have been detected in the near-IR ground
based search described in this paper (unlensed magnitude J~25). (abridged)Comment: Accepted by AA, matches journal versio
On the Relation Between Peak Luminosity and Parent Population of Type Ia Supernovae: A New Tool for Probing the Ages of Distant Galaxies
We study the properties of Type Ia Supernovae (SNe Ia) as functions of the
radial distance from their host galaxy centers. Using a sample of 62 SNe Ia
with reliable luminosity, reddening, and decline rate determinations, we find
no significant radial gradients of SNe Ia peak absolute magnitudes or decline
rates in elliptical+S0 galaxies, suggesting that the diversity of SN properties
is not related to the metallicity of their progenitors. We do find that the
range in brightness and light curve width of supernovae in spiral galaxies
extends to brighter, broader values. These results are interpreted as support
for an age, but not metallicity, related origin of the diversity in SNe Ia. If
confirmed with a larger and more accurate sample of data, the age-luminosity
relation would offer a new and powerful tool to probe the ages and age
gradients of stellar populations in galaxies at redshift as high as .
The absence of significant radial gradients in the peak and colors of SNe Ia supports the redding correction method of Phillips et
al (1999). We find no radial gradient in residuals from the SN Ia
luminosity-width relation, suggesting that the relation is not affected by
properties of the progenitor populations and supporting the reliability of
cosmological results based upon the use of SNe Ia as distance indicators.Comment: 19 pages, incl. 3 tables & 3 figures; to appear in Nov 2000 issue of
Ap
Determination of Primordial Metallicity and Mixing in the Type IIP Supernova 1993W
We present the results of a large grid of synthetic spectra and compare them
to early spectroscopic observations of SN 1993W. This supernova was discovered
close to its explosion date and at a recession velocity of 5400 km/s is located
in the Hubble flow. We focus here on two early spectra that were obtained
approximately 5 and 9 days after explosion. We parameterize the outer supernova
envelope as a power-law density profile in homologous expansion. In order to
extract information on the value of the parameters a large number of models was
required. We show that very early spectra combined with detailed models can
provide constraints on the value of the power law index, the ratio of hydrogen
to helium in the surface of the progenitor, the progenitor metallicity and the
amount of radioactive nickel mixed into the outer envelope of the supernova.
The spectral fits reproduce the observed spectra exceedingly well. The spectral
results combined with the early photometry predict that the explosion date was
4.7 \pm 0.7 days before the first spectrum was obtained. The ability to obtain
the metallicity from early spectra make SN IIP attractive probes of chemical
evolution in the universe and by showing that we have the ability to pin down
the parameters of the progenitor and mixing during the supernova explosion, it
is likely to make SN IIP useful cosmological distance indicators which are at
the same time complementary to SNe Ia.Comment: 30 pages, 4 Tables, 16 Figures (some color), submitted to Ap
Dust in the Host Galaxies of Supernovae
We present Spitzer/MIPS 24 micron observations of 50 supernova host galaxies
at 0.1<z<1.7 in the Great Observatories Origins Deep Survey (GOODS) fields. We
also discuss the detection of SN host galaxies in SCUBA/850 micron observations
of GOODS-N and Spitzer/Infrared Spectrograph (IRS) 16 micron observations of
GOODS-S. About 60% of the host galaxies of both Type Ia and core-collapse
supernovae are detected at 24 microns, a detection rate which is a factor of
1.5 higher than the field galaxy population. Among the 24 micron detected
hosts, 80% have far-infrared luminosities that are comparable to or greater
than the optical luminosity indicating the presence of substantial amounts of
dust in the hosts. The median bolometric luminosity of the Type Ia SN hosts is
\~10^10.5 L_sun, very similar to that of core-collapse SN hosts. Using the high
resolution Hubble/ACS data, we have studied the variation of rest-frame
optical/ultraviolet colors within the 24 micron detected galaxies at z<1 to
understand the origin of the dust emission. The 24 micron detected galaxies
have average colors which are redder by ~0.1 mag than the 24 micron undetected
hosts while the latter show greater scatter in internal colors. This suggests
that a smooth distribution of dust is responsible for the observed mid- and
far-infrared emission. 70% of supernovae that have been detected in the GOODS
fields are located within the half-light radius of the hosts where dust
obscuration effects are significant. Although the dust emission that we detect
cannot be translated into a line of sight A_V, we suggest that the factor of
2-3 larger scatter in the peak B-V colors that is seen in the high-z Type Ia
supernova sample relative to the low-z supernovae might be partially due to the
dust that we detect in the hosts.Comment: 22 pages, 4 figures, 4 tables; ApJ 635, Dec 20, 2005 issu
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