63,896 research outputs found
Deep far infrared ISOPHOT survey in "Selected Area 57", I. Observations and source counts
We present here the results of a deep survey in a 0.4 sq.deg. blank field in
Selected Area 57 conducted with the ISOPHOT instrument aboard ESAs Infrared
Space Observatory (ISO) at both 60 um and 90 um. The resulting sky maps have a
spatial resolution of 15 x 23 sq.arcsec. per pixel which is much higher than
the 90 x 90 sq.arcsec. pixels of the IRAS All Sky Survey. We describe the main
instrumental effects encountered in our data, outline our data reduction and
analysis scheme and present astrometry and photometry of the detected point
sources. With a formal signal to noise ratio of 6.75 we have source detection
limits of 90 mJy at 60 um and 50 mJy at 90 um. To these limits we find
cumulated number densities of 5+-3.5 per sq.deg. at 60 um and 14.8+-5.0 per
sq.deg.at 90 um. These number densities of sources are found to be lower than
previously reported results from ISO but the data do not allow us to
discriminate between no-evolution scenarios and various evolutionary models.Comment: 15 pages, 11 figures, accepted by Astronomy & Astrophysic
Optimisation of Mobile Communication Networks - OMCO NET
The mini conference “Optimisation of Mobile Communication Networks” focuses on advanced methods for search and optimisation applied to wireless communication networks. It is sponsored by Research & Enterprise Fund Southampton Solent University.
The conference strives to widen knowledge on advanced search methods capable of optimisation of wireless communications networks. The aim is to provide a forum for exchange of recent knowledge, new ideas and trends in this progressive and challenging area. The conference will popularise new successful approaches on resolving hard tasks such as minimisation of transmit power, cooperative and optimal routing
Automatically Discovering, Reporting and Reproducing Android Application Crashes
Mobile developers face unique challenges when detecting and reporting crashes
in apps due to their prevailing GUI event-driven nature and additional sources
of inputs (e.g., sensor readings). To support developers in these tasks, we
introduce a novel, automated approach called CRASHSCOPE. This tool explores a
given Android app using systematic input generation, according to several
strategies informed by static and dynamic analyses, with the intrinsic goal of
triggering crashes. When a crash is detected, CRASHSCOPE generates an augmented
crash report containing screenshots, detailed crash reproduction steps, the
captured exception stack trace, and a fully replayable script that
automatically reproduces the crash on a target device(s). We evaluated
CRASHSCOPE's effectiveness in discovering crashes as compared to five
state-of-the-art Android input generation tools on 61 applications. The results
demonstrate that CRASHSCOPE performs about as well as current tools for
detecting crashes and provides more detailed fault information. Additionally,
in a study analyzing eight real-world Android app crashes, we found that
CRASHSCOPE's reports are easily readable and allow for reliable reproduction of
crashes by presenting more explicit information than human written reports.Comment: 12 pages, in Proceedings of 9th IEEE International Conference on
Software Testing, Verification and Validation (ICST'16), Chicago, IL, April
10-15, 2016, pp. 33-4
Observational constraints on the progenitors of core-collapse supernovae : the case for missing high mass stars
Over the last 15 years, the supernova community has endeavoured to identify
progenitor stars of core-collapse supernovae in high resolution archival images
of their galaxies.This review compiles results (from 1999 - 2013) in a distance
limited sample and discusses the implications. The vast majority of the
detections of progenitor stars are of type II-P, II-L or IIb with one type Ib
progenitor system detected and many more upper limits for progenitors of Ibc
supernovae (14). The data for these 45 supernovae progenitors illustrate a
remarkable deficit of high luminosity stars above an apparent limit of Log L ~=
5.1 dex. For a typical Salpeter IMF, one would expect to have found 13 high
luminosity and high mass progenitors. There is, possibly, only one object in
this time and volume limited sample that is unambiguously high mass (the
progenitor of SN2009ip). The possible biases due to the influence of
circumstellar dust and sample selection methods are reviewed. It does not
appear likely that these can explain the missing high mass progenitor stars.
This review concludes that the observed populations of supernovae in the local
Universe are not, on the whole, produced by high mass (M > ~18Msun) stars.
Theoretical explosions of model stars also predict that black hole formation
and failed supernovae tend to occur above M > ~18Msun. The models also suggest
there are islands of explodability for stars in the 8-120Msun range. The
observational constraints are quite consistent with the bulk of stars above M >
~18Msun collapsing to form black holes with no visible supernovae. (Abridged).Comment: Invited review article for Publications of the Astronomical Society
of Australia, to be published in a special PASA collection on "SN1987A and
Supernovae in the Local Universe". This is the accepted version, after
referee review. Additional minor corrections to match proofs. (25 pages
The Phoenix Deep Survey: X-ray properties of faint radio sources
In this paper we use a 50ks XMM-Newton pointing overlapping with the Phoenix
Deep Survey, a homogeneous radio survey reaching muJy sensitivities, to explore
the X-ray properties and the evolution of star-forming galaxies. UV, optical
and NIR photometry is available and is used to estimate photometric redshifts
and spectral types for radio sources brighter than R=21.5mag (total of 82).
Sources with R<21.5mag and spiral galaxy SEDs (34) are grouped into two
redshift bins with a median of z=0.240 and 0.455 respectively. Stacking
analysis for both the 0.5-2 and 2-8keV bands is performed on these subsamples.
A high confidence level signal (>3.5sigma) is detected in the 0.5-2keV band
corresponding to a mean flux of ~3e-16cgs for both subsamples. This flux
translates to mean luminosities of ~5e40 and 1.5e41cgs for the z=0.240 and
0.455 subsamples respectively. Only a marginally significant signal (2.6sigma)
is detected in the 2-8keV band for the z=0.455 subsample. We argue that the
stacked signal above is dominated by star-formation. The mean L_X/L_B ratio and
the mean L_X of the two subsamples are found to be higher than optically
selected spirals and similar to starbursts. We also find that the mean L_X and
L_1.4 of the faint radio sources studied here are consistent with the L_X-L_1.4
correlation of local star-forming galaxies. Moreover, the X-ray emissivity of
sub-mJy sources to z~0.3 is found to be elevated compared to local HII
galaxies. The observed increase is consistent with L_X evolution of the form
(1+z)^3. Assuming that our sample is indeed dominated by starbursts this is
direct evidence for evolution of such systems at X-ray wavelengths. Using an
empirical L_X to SFR conversion we estimate a global SFR density at z~0.3 of
\~0.029M_o/yr/Mpc in agreement with previous studies.Comment: 12 pages, 6 figures, accepted for publication in MNRA
Intermediate Old Star Clusters in a Young Starburst: The case of NGC 5253
We investigate the star cluster population in the outer parts of the
starburst galaxy NGC 5253 using archive images taken with the Hubble Space
Telescope's Advanced Camera for Surveys. Based on the F415W, F555W, and F814W
photometry ages and masses are estimated for bona-fide star cluster candidates.
We find three potentially massive (\ge 10 \time 10^5 \Msun) star clusters at
ages of order of 1-2 Gyr, implying, if confirmed, a high global star formation
rate in NGC 5253 during that epoch. This result underlines earlier findings
that the current star burst is just one episode in an very active dwarf galaxy.Comment: accepted for publication in MNRAS - The definitive version is (will
be) available at www.blackwell-synergy.co
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