194 research outputs found
Optical Photometry of the Type Ia SN 1999ee and the Type Ib/c SN 1999ex in IC 5179
We present UBVRIz lightcurves of the Type Ia SN 1999ee and the Type Ib/c SN
1999ex, both located in the galaxy IC 5179. SN 1999ee has an extremely well
sampled lightcurve spanning from 10 days before Bmax through 53 days after
peak. Near maximum we find systematic differences ~0.05 mag in photometry
measured with two different telescopes, even though the photometry is reduced
to the same local standards around the supernova using the specific color terms
for each instrumental system. We use models for our bandpasses and
spectrophotometry of SN 1999ee to derive magnitude corrections (S-corrections)
and remedy this problem. This exercise demonstrates the need of accurately
characterizing the instrumental system before great photometric accuracies of
Type Ia supernovae can be claimed. It also shows that this effect can have
important astrophysical consequences since a small systematic shift of 0.02 mag
in the B-V color can introduce a 0.08 mag error in the extinction corrected
peak B magnitudes of a supernova and thus lead to biased cosmological
parameters. The data for the Type Ib/c SN 1999ex present us with the first ever
observed shock breakout of a supernova of this class. These observations show
that shock breakout occurred 18 days before Bmax and support the idea that Type
Ib/c supernovae are due to core collapse of massive stars rather than
thermonuclear disruption of white dwarfs.Comment: 55 pages, 15 figures, accepted by the Astronomical Journa
The observable supernova rate in galaxyâgalaxy lensing systems with the TESS satellite
The Transiting Exoplanet Survey Satellite (TESS) is the latest observational effort to find exoplanets and map bright transient optical phenomena. Supernovae (SNe) are particularly interesting as cosmological standard candles for cosmological distance measures. The limiting magnitude of TESS strongly constrains SN detection to the very nearby Universe (m ⌠19, z \u3c 0.05). We explore the possibility that more distant SNe that are gravitationally lensed and magnified by a foreground galaxy can be detected by TESS, an opportunity to measure the time delay between light paths and constrain the Hubble constant independently. We estimate the rate of occurrence of such systems, assuming reasonable distributions of magnification, host dust attenuation, and redshift. There are approximately 16 Type Ia SNe (SNIa) and 43 core-collapse SNe (SNcc) expected to be observable with TESS each year, which translates to 18 and 43 per cent chance of detection per year, respectively. Monitoring the largest collections of known strong galaxyâgalaxy lenses from Petrillo et al., this translates into 0.6 and 1.3 per cent chances of an SNIa and an SNcc per year. The TESS all-sky detection rates are lower than those of the Zwicky Transient Facility and Vera Rubin Observatory. However, on the ecliptic poles, TESS performs almost as well as its all-sky search, thanks to its continuous coverage: 2 and 4 per cent chance of an observed SN (Ia or cc) each year. These rates argue for timely processing of full-frame TESS imaging to facilitate follow-up and should motivate further searches for low-redshift lensing system
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
Did Galaxy Assembly and Supermassive Black-Hole Growth go hand-in-hand?
In this paper, we address whether the growth of supermassive black-holes has
kept pace with the process of galaxy assembly. For this purpose, we first
searched the Hubble Ultra Deep Field (HUDF) for "tadpole galaxies", which have
a knot at one end and an extended tail. They appear dynamically unrelaxed --
presumably early-stage mergers -- and make up ~6% of the field galaxy
population. Their redshift distribution follows that of field galaxies,
indicating that -- if tadpole galaxies are indeed dynamically young -- the
process of galaxy assembly generally kept up with the reservoir of field
galaxies as a function of epoch. Next, we present a search for HUDF objects
with point-source components that are optically variable (at the >~3.0 sigma
level) on timescales of weeks--months. Among 4644 objects to i_AB=28.0 mag (10
sigma), 45 have variable point-like components, which are likely weak AGN.
About 1% of all field objects show variability for 0.1 < z < 4.5, and their
redshift distribution is similar to that of field galaxies. Hence supermassive
black-hole growth in weak AGN likely also kept up with the process of galaxy
assembly. However, the faint AGN sample has almost no overlap with the tadpole
sample, which was predicted by recent hydrodynamical numerical simulations.
This suggests that tadpole galaxies are early-stage mergers, which likely
preceded the ``turn-on'' of the AGN component and the onset of visible
point-source variability by >~1 Gyr.Comment: 9 pages, Latex2e requires 'elsart' and 'elsart3' (included), 10
postscript figures. To appear in the Proceedings of the Leiden Workshop on
"QSO Host Galaxies: Evolution and Environment", eds. P.D. Barthel & D.B.
Sanders (New Astron. Rev., 2006
Clues to AGN Growth from Optically Variable Objects in the Hubble Ultra Deep Field
We present a photometric search for objects with point-source components that
are optically variable on timescales of weeks--months in the Hubble Ultra Deep
Field (HUDF) to i'(AB)=28.0 mag. The data are split into four sub-stacks of
approximately equal exposure times. Objects exhibiting the signature of optical
variability are selected by studying the photometric error distribution between
the four different epochs, and selecting 622 candidates as 3.0 sigma outliers
from the original catalog of 4644 objects. Of these, 45 are visually confirmed
as free of contamination from close neighbors or various types of image
defects. Four lie within the positional error boxes of Chandra X-ray sources,
and two of these are spectroscopically confirmed AGN. The photometric redshift
distribution of the selected variable sample is compared to that of field
galaxies, and we find that a constant fraction of ~1% of all field objects show
variability over the range of 0.1<z<4.5. Combined with other recent HUDF
results, as well as those of recent state-of-the-art numerical simulations, we
discuss a potential link between the hierarchical merging of galaxies and the
growth of AGN.Comment: 9 pages, 6 figures, accepted for publication in Astrophysical
Journal, minor changes to reference
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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