280 research outputs found
Evaluation of cosmic ray rejection algorithms on single-shot exposures
To maximise data output from single-shot astronomical images, the rejection
of cosmic rays is important. We present the results of a benchmark trial
comparing various cosmic ray rejection algorithms. The procedures assess
relative performances and characteristics of the processes in cosmic ray
detection, rates of false detections of true objects and the quality of image
cleaning and reconstruction. The cosmic ray rejection algorithms developed by
Rhoads (2000), van Dokkum (2001), Pych (2004) and the IRAF task xzap by
Dickinson are tested using both simulated and real data. It is found that
detection efficiency is independent of the density of cosmic rays in an image,
being more strongly affected by the density of real objects in the field. As
expected, spurious detections and alterations to real data in the cleaning
process are also significantly increased by high object densities. We find the
Rhoads' linear filtering method to produce the best performance in detection of
cosmic ray events, however, the popular van Dokkum algorithm exhibits the
highest overall performance in terms of detection and cleaning.Comment: 12 pages, 4 figures, accepted for publication in PAS
Feedback in the cores of clusters Abell 3581, 2A 0335+096, and Sersic 159-03
The cores of massive galaxy clusters, where hot gas is cooling rapidly,
appear to undergo cycles of self-regulating energy feedback, in which AGN
outbursts in the central galaxies episodically provide sufficient heating to
offset much of the gas cooling. We use deep integral-field spectroscopy to
study the optical line emission from the extended nebulae of three nearby
brightest cluster galaxies and investigate how they are related to the
processes of heating and cooling in the cluster cores. Two of these systems,
Abell 3581 and Sersic 159-03, appear to be experiencing phases of feedback that
are dominated by the activity and output of a central AGN. Abell 3581, shows
evidence for significant interaction between the radio outflows and the optical
nebula, in addition to accretion flows into the nucleus of the galaxy. X-ray
and radio data show that Sersic 159-03 is dominated by the feedback of energy
from the central AGN, but the kinematics of the optical nebula are consistent
with infall or outflow of material along its bright filaments. The third
system, 2A 0335+096, is dominated by mass accretion and cooling, and so we
suggest that it is in an accumulation phase of the feedback cycle. The outer
nebula forms a disk-like structure, ~14 kpc in radius, that rotates about the
central galaxy with a velocity amplitude of ~200 km/s. Overall, our data are
consistent with ongoing AGN-driven feedback cycles occurring in these systems.Comment: Preprint: 37 pages with 11 figures and 4 tables, accepted for
publication in Ap
Hydrogen Two-Photon Continuum Emission from the Horseshoe Filament in NGC 1275
Far ultraviolet emission has been detected from a knot of Halpha emission in
the Horseshoe filament, far out in the NGC 1275 nebula. The flux detected
relative to the brightness of the Halpha line in the same spatial region is
very close to that expected from Hydrogen two-photon continuum emission in the
particle heating model of Ferland et al. (2009) if reddening internal to the
filaments is taken into account. We find no need to invoke other sources of far
ultraviolet emission such as hot stars or emission lines from CIV in
intermediate temperature gas to explain these data.Comment: 9 pages, 8 figures. Accepted for publication in MNRA
Galaxy-Wide Shocks in Late-Merger Stage Luminous Infrared Galaxies
We present an integral field spectroscopic study of two nearby Luminous
Infrared Galaxies (LIRGs) that exhibit evidence of widespread shock excitation
induced by ongoing merger activity, IC 1623 and NGC 3256. We show the
importance of carefully separating excitation due to shocks vs. excitation by
HII regions and the usefulness of IFU data in interpreting the complex
processes in LIRGs. Our analysis focuses primarily on the emission line gas
which is extensive in both systems and is a result of the abundant ongoing star
formation as well as widespread LINER-like excitation from shocks. We use
emission-line ratio maps, line kinematics, line-ratio diagnostics and new
models as methods for distinguishing and analyzing shocked gas in these
systems. We discuss how our results inform the merger sequence associated with
local U/LIRGs and the impact that widespread shock excitation has on the
interpretation of emission-line spectra and derived quantities of both local
and high-redshift galaxies.Comment: 14 pages, 11 figures, Accepted to Ap
Optical IFU Observations of the Brightest Cluster Galaxy NGC 4696: The Case for a Minor Merger and Shock-excited Filaments
We present deep optical integral-field spectroscopic observations of the
nearby (z ~ 0.01) brightest cluster galaxy NGC 4696 in the core of the
Centaurus Cluster, made with the Wide Field Spectrograph (WiFeS) on the ANU
2.3m telescope at Siding Spring Observatory. We investigate the morphology,
kinematics, and excitation of the emission-line filaments and discuss these in
the context of a model of a minor merger. We suggest that the emission-line
filaments in this object have their origin in the accretion of a gas-rich
galaxy and that they are excited by v ~100-200 km/s shocks driven into the cool
filament gas by the ram pressure of the transonic passage of the merging system
through the hot halo gas of NGC 4696.Comment: 19 pages, 15 figures, accepted for publication in The Astrophysical
Journa
Menstrual cycle phase does not predict political conservatism
Recent authors have reported a relationship between women's fertility status, as indexed by menstrual cycle phase, and conservatism in moral, social and political values. We conducted a survey to test for the existence of a relationship between menstrual cycle day and conservatism. 2213 women reporting regular menstrual cycles provided data about their political views. Of these women, 2208 provided information about their cycle date, 1260 provided additional evidence of reliability in self-reported cycle date, and of these, 750 also indicated an absence of hormonal disruptors such as recent hormonal contraception use, breastfeeding or pregnancy. Cycle day was used to estimate day-specific fertility rate (probability of conception); political conservatism was measured via direct self-report and via responses to the "Moral Foundations” questionnaire. We also recorded relationship status, which has been reported to interact with menstrual cycle phase in determining political preferences. We found no evidence of a relationship between estimated cyclical fertility changes and conservatism, and no evidence of an interaction between relationship status and cyclical fertility in determining political attitudes. Our findings were robust to multiple inclusion/exclusion criteria and to different methods of estimating fertility and measuring conservatism. In summary, the relationship between cycle-linked reproductive parameters and conservatism may be weaker or less reliable than previously thought
NAC transcription factor ORE1 and senescence-induced BIFUNCTIONAL NUCLEASE1 (BFN1) constitute a regulatory cascade in Arabidopsis
Senescence is a highly regulated process that involves the action of a large number of transcription factors. The NAC transcription factor ORE1 (ANAC092) has recently been shown to play a critical role in positively controlling senescence in Arabidopsis thaliana, however, no direct target gene through which it exerts its molecular function has been identified previously. Here, we report that BIFUNCTIONAL NUCLEASE1 (BFN1), a well-known senescence-enhanced gene, is directly regulated by ORE1. We detected elevated expression of BFN1 already 2 hours after induction of ORE1 in estradiol-inducible ORE1 overexpression lines and 6 hours after transfection of Arabidopsis mesophyll cell protoplasts with a 35S:ORE1 construct. ORE1 and BFN1 expression patterns largely overlap, as shown by promoter - reporter gene (GUS) fusions, while BFN1 expression in senescent leaves and the abscission zones of maturing flower organs was virtually absent in ore1 mutant background. In vitro binding site assays revealed a bipartite ORE1 binding site, similar to the one of ORS1, a paralog of ORE1. A bipartite ORE1 binding site was identified in the BFN1 promoter; mutating the cis element within the context of the full-length BFN1 promoter drastically reduced ORE1-mediated transactivation capacity in transiently transfected Arabidopsis mesophyll cell protoplasts. Furthermore, chromatin-immunoprecipitation (ChIP) demonstrates in vivo binding of ORE1 to the BFN1 promoter. We also demonstrate binding of ORE1 in vivo to the promoters of two other senescence-associated genes, i.e. SAG29/SWEET15 and SINA1, supporting the central role of ORE1 during senescence
Exploring Older Adult Susceptibility to Fraudulent Computer Pop-Up Interruptions
© 2019, Springer International Publishing AG, part of Springer Nature. The proliferation of Internet connectivity and accessibility has been accompanied by an increase in cyber-threats, including fraudulent communications. Fake computer updates, which attempt to persuade people to download malicious software by mimicking trusted brands and/or instilling urgency, are one way in which fraudsters try to infiltrate systems. A recent study of young university students (M 18.52-years) found that when such pop-ups interrupt a demanding cognitive task, participants spent little time viewing them and were more likely to miss suspicious cues and accept these updates compared to when they were viewed without the pressure to resume a suspended task [1]. The aim of the current experiment was to test an older adult sample (N = 29, all >60 years) using the same paradigm. We predicted that they would be more susceptible to malevolent pop-ups [2]; trusting them more than younger adults (e.g., [3]), and would attempt to resume the interrupted task faster to limit forgetting of encoded items. Phase 1 involved serial recall memory trials interrupted by genuine, mimicked, and low authority pop-ups. During phase 2, participants rated messages with unlimited time and gave reasons for their decisions. It was found that more than 70% of mimicked and low authority pop-ups were accepted in Phase 1 vs ~80% genuine pop-ups (and these were all approximately 10% higher than [1]). This was likely due to a greater tendency to ignore or miss suspicious content when performing under pressure, despite spending longer with messages and reporting high awareness of scam techniques than younger adults. Older adult participants were more suspicious during Phase 2 performing comparably to the younger adults in [1]. Factors that may impact older adult decisions relating to fraudulent computer communications are discussed, as well as theoretical and practical implications
The Mice at play in the CALIFA survey: A case study of a gas-rich major merger between first passage and coalescence
We present optical integral field spectroscopy (IFS) observations of the
Mice, a major merger between two massive (>10^11Msol) gas-rich spirals NGC4676A
and B, observed between first passage and final coalescence. The spectra
provide stellar and gas kinematics, ionised gas properties and stellar
population diagnostics, over the full optical extent of both galaxies. The Mice
provide a perfect case study highlighting the importance of IFS data for
improving our understanding of local galaxies. The impact of first passage on
the kinematics of the stars and gas has been significant, with strong bars
likely induced in both galaxies. The barred spiral NGC4676B exhibits a strong
twist in both its stellar and ionised gas disk. On the other hand, the impact
of the merger on the stellar populations has been minimal thus far: star
formation induced by the recent close passage has not contributed significantly
to the global star formation rate or stellar mass of the galaxies. Both
galaxies show bicones of high ionisation gas extending along their minor axes.
In NGC4676A the high gas velocity dispersion and Seyfert-like line ratios at
large scaleheight indicate a powerful outflow. Fast shocks extend to ~6.6kpc
above the disk plane. The measured ram pressure and mass outflow rate
(~8-20Msol/yr) are similar to superwinds from local ULIRGs, although NGC4676A
has only a moderate infrared luminosity of 3x10^10Lsol. Energy beyond that
provided by the mechanical energy of the starburst appears to be required to
drive the outflow. We compare the observations to mock kinematic and stellar
population maps from a merger simulation. The models show little enhancement in
star formation during and following first passage, in agreement with the
observations. We highlight areas where IFS data could help further constrain
the models.Comment: 23 pages, 13 figures, accepted to A&A. A version with a complete set
of high resolution figures is available here:
http://www-star.st-and.ac.uk/~vw8/resources/mice_v8_astroph.pd
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