scholarly journals Radiative AGN feedback on a moving mesh: the impact of the galactic disc and dust physics on outflow properties

2020 ◽  
Vol 494 (1) ◽  
pp. 1143-1164 ◽  
Author(s):  
David J Barnes ◽  
Rahul Kannan ◽  
Mark Vogelsberger ◽  
Federico Marinacci
Keyword(s):  
Galaxy Formation ◽  
Front Propagation ◽  
Opening Angle ◽  
Dust Grains ◽  
Physical Treatment ◽  
Disc Galaxy ◽  
Outflow Rate ◽  
Mass Outflow ◽  
Set Up ◽  
The Impact

ABSTRACT Feedback from accreting supermassive black holes (BHs), active galactic nuclei (AGNs), is now a cornerstone of galaxy formation models. In this work, we present radiation-hydrodynamic simulations of radiative AGN feedback using the novel arepo-rt code. A central BH emits radiation at a constant luminosity and drives an outflow via radiation pressure on dust grains. Utilizing an isolated Navarro–Frenk–White (NFW) halo we validate our set-up in the single- and multiscattering regimes, with the simulated shock front propagation in excellent agreement with the expected analytic result. For a spherically symmetric NFW halo, an examination of the simulated outflow properties with radiation collimation demonstrates a decreasing mass outflow rate and momentum flux, but increasing kinetic power and outflow velocity with decreasing opening angle. We then explore the impact of a central disc galaxy and the assumed dust model on the outflow properties. The contraction of the halo during the galaxy’s formation and modelling the production of dust grains result in a factor 100 increase in the halo’s optical depth. Radiation then couples momentum more efficiently to the gas, driving a stronger shock and producing a mass-loaded $\sim \!10^{3}\, \mathrm{M}_{\odot }\, \mathrm{yr}^{-1}$ outflow with a velocity of $\sim \!2000\, \mathrm{km}\, \mathrm{s}^{-1}$. However, the inclusion of dust destruction mechanisms, like thermal sputtering, leads to the rapid destruction of dust grains within the outflow, reducing its properties below the initial NFW halo. We conclude that radiative AGN feedback can drive outflows, but a thorough numerical and physical treatment is required to assess its true impact.

scholarly journals Multiwavelength campaign on Mrk 509

2019 ◽  
Vol 623 ◽  
pp. A82 ◽  
Author(s):  
G. A. Kriss ◽  
N. Arav ◽  
D. Edmonds ◽  
J. Ely ◽  
J. S. Kaastra ◽  
...  
Keyword(s):  
High Energy ◽  
Resolving Power ◽  
Host Galaxy ◽  
Active Nucleus ◽  
X Ray ◽  
Transmission Grating ◽  
Outflow Rate ◽  
Mass Outflow ◽  
Far Ultraviolet ◽  
The Impact

Aims. To elucidate the location, physical conditions, mass outflow rate, and kinetic luminosity of the outflow from the active nucleus of the Seyfert 1 galaxy Mrk 509, we used coordinated UV and X-ray spectral observations in 2012 to follow up our lengthier campaign conducted in 2009. Methods. We observed Mrk 509 with the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST) on 2012-09-03 and 2012-10-11 coordinated with X-ray observations using the High Energy Transmission Grating on the Chandra X-ray Observatory. Our far-ultraviolet spectra used grating G140L on COS to cover wavelengths from 920–2000 Å at a resolving power of ∼2000, and gratings G130M and G160M to cover 1160–1750 Å at a resolving power of ∼15, 000. Results. We detect variability in the blueshifted UV absorption lines on timescales spanning 3–12 years. The inferred densities in the absorbing gas are greater than log n cm−3 ∼ 3. For ionization parameters ranging over log U = −1.5 to −0.2, we constrain the distances of the absorbers to be closer than 220 pc to the active nucleus. Conclusions. The impact on the host galaxy appears to be confined to the nuclear region.

Gauging the effect of feedback from QSOs on their host galaxies

2019 ◽  
Vol 15 (S359) ◽  
pp. 265-266
Author(s):  
Bruno Dall’Agnol de Oliveira ◽  
Thaisa Storchi-Bergmann
Keyword(s):  
Star Formation ◽  
Optical Emission ◽  
Analytical Models ◽  
Host Galaxies ◽  
Evolution Of Galaxies ◽  
Gas Kinematics ◽  
Outflow Rate ◽  
Mass Outflow ◽  
Star Formation In Galaxies ◽  
The Impact

AbstractOften associated with the regulation of star formation in galaxies, active galactic nuclei (AGN) play a fundamental role in the evolution of galaxies through their feedback effects. To investigate the impact of these effects, we analysed the optical emission-line properties of 8 type II AGNs with bolometric luminosities LBol > 1045 erg s−1, using integral field spectroscopy (IFS) observations with Gemini Multi-Object Spectrograph (GMOS). The gas kinematics was obtained by fitting Gaussian components to the profiles of the emission lines of the ionized gas. Using only the broadest component – that we associate with the gas in outflow – we calculated the mass outflow rate (Ṁout), finding values of up to 10 M⊙ yr−1. The outflow kinetic power (Ėout reaches maximum values between 1041 and 1043 erg s−1, which correspond to feedback efficiencies of ∼0.001−0.1 % of Lbol. These values are below that required to quench the star formation during the evolution of galaxies in simulations and analytical models. We also investigated the effect of uncertainties on the values of the physical quantities used in the calculations – such as the electron density – on the final values of Ṁout and Ėout.

scholarly journals Impact of the reduced speed of light approximation on the post-overlap neutral hydrogen fraction in numerical simulations of the epoch of reionization

2019 ◽  
Vol 626 ◽  
pp. A77 ◽  
Author(s):  
P. Ocvirk ◽  
D. Aubert ◽  
J. Chardin ◽  
N. Deparis ◽  
J. Lewis
Keyword(s):  
Galaxy Formation ◽  
Neutral Hydrogen ◽  
Photoionization Cross Section ◽  
Hydrogen Gas ◽  
Photon Density ◽  
Speed Of Light ◽  
Photon Propagation ◽  
Full Speed ◽  
Set Up ◽  
The Impact

Context. The reduced speed of light approximation is used in a variety of simulations of the epoch of reionization and galaxy formation. Its popularity stems from its ability to drastically reduce the computing cost of a simulation by allowing the use of larger and therefore fewer timesteps to reach a solution. This approximation is physically motivated by the fact that ionization fronts rarely propagate faster than some fraction of the speed of light. However, no global proof of the physical validity of this approach is available and possible artefacts resulting from this approximation therefore need to be identified and characterized to allow its proper use. Aims. In this paper we investigate the impact of the reduced speed of light approximation on the predicted properties of the intergalactic medium. Methods. To this end we used fully coupled radiation-hydrodynamics RAMSES-CUDATON simulations of the epoch of reionization. Results. We find that reducing the speed of light by a factor 5 (20, 100) leads to overestimating the post-reionization average volume-weighted neutral hydrogen fraction by a similar factor ∼5 (20, 100) with respect to full speed of light simulations. We show that the error is driven by the hydrogen – photon chemistry by considering the analytical solution for a strongly ionized hydrogen gas in photoionization equilibrium. In this regime, reducing the speed of light has the same effect as artificially reducing the photon density or the hydrogen photoionization cross section and leads to an underestimated ionizing intensity. We confirm this interpretation by running additional simulations using a reduced speed of light in the photon propagation module, but this time we keep the true speed of light in the chemistry module. With this set-up, the post-reionization neutral hydrogen fractions converge to the full speed of light value, which validates our explanation. Increasing spatial resolution beyond a cell size of 1 kpc physical, so as to better resolve Lyman-limit systems, does not significantly affect our conclusions.

scholarly journals Taking snapshots of the jet-ISM interplay with ALMA

2020 ◽  
Vol 15 (S359) ◽  
pp. 243-248
Author(s):  
Raffaella Morganti ◽  
Tom Oosterloo ◽  
Clive N. Tadhunter
Keyword(s):  
Large Scale ◽  
Radio Galaxies ◽  
Plasma Jets ◽  
Molecular Gas ◽  
Radio Jets ◽  
Evolutionary Phase ◽  
Outflow Rate ◽  
Mass Outflow ◽  
Low Mass ◽  
The Impact

AbstractWe present an update of our ongoing project to characterise the impact of radio jets on the interstellar medium (ISM). This is done by tracing the distribution, kinematics and excitation of the molecular gas at high spatial resolution using ALMA. The radio active galactic nuclei (AGN) studied are in the interesting phase of having a recently born radio jet. In this stage, the plasma jets can have the largest impact on the ISM, as also predicted by state-of-the-art simulations. The two targets we present have quite different ages, allowing us to get snapshots of the effects of radio jets as they grow and evolve. Interestingly, both also host powerful quasar emission, making them ideal for studying the full impact of AGN. The largest mass outflow rate of molecular gas is found in a radio galaxy () hosting a newly born radio jet still in the early phase of emerging from an obscuring cocoon of gas and dust. Although the molecular mass outflow rate is high (few hundred), the outflow is limited to the inner few hundred pc region. In a second object (), the jet is larger (a few kpc) and is in a more advanced evolutionary phase. In this object, the distribution of the molecular gas is reminiscent of what is seen, on larger scales, in cool-core clusters hosting radio galaxies. Interestingly, gas deviating from quiescent kinematics (possibly indicating an outflow) is not very prominent, limited only to the very inner region, and has a low mass outflow rate. Instead, on kpc scales, the radio lobes appear associated with depressions in the distribution of the molecular gas. This suggests that the lobes have broken out from the dense nuclear region. However, the AGN does not appear to be able, at present, to stop the star formation observed in this galaxy. These results support the idea that the effects of the radio source start in the very first phases by producing outflows which, however, tend to be limited to the kpc region. After that, the effects turn into producing large-scale bubbles which could, in the long term, prevent the surrounding gas from cooling. Thus, our results provide a way to characterise the effect of radio jets in different phases of their evolution and in different environments, bridging the studies done for radio galaxies in clusters.

MOTIF DAN DAMPAK PERNIKAHAN DINI DI INDARUNG NGALAU BATU GADANG

2018 ◽  
Vol 1 (1) ◽  
pp. 1
Author(s):  
Murisal Murisal
Keyword(s):  
Young Men ◽  
Early Marriage ◽  
Marriage Law ◽  
Men And Women ◽  
Home Life ◽  
Family Household ◽  
Set Up ◽  
The Impact ◽  
Husband And Wife

Motif and Impact of Early Marriage in Indarung Ngalau Batu Gadang.Penelitian is motivated by teenagers who married early on. Today, young men and women have a tendency to be less prepared to enter the home life, they are only ready to marry (ready here can be interpreted, maturity in terms of financial, understand what the meaning of marriage according to marriage law) is the bond of inner birth between a man and a woman as husband and wife for the purpose of forming a happy and eternal family (household) based on the Supreme Godhead while they are not ready to set up a home, whereas to build a household requires preparation both physically and spiritually . The purpose of this study to determine the motives underlying adolescents to make early marriage and the impact caused in the household as a result of the marriage.

Dissent and Education

2018 ◽  
Author(s):  
Mark Burden
Keyword(s):  
Eighteenth Century ◽  
Seventeenth Century ◽  
Educational Activity ◽  
Educational Institutions ◽  
Higher Educational Institutions ◽  
Legal Restrictions ◽  
Higher Educational ◽  
Set Up ◽  
The Impact ◽  
Dissenting Academies

Much eighteenth-century Dissenting educational activity was built on an older tradition of Puritan endeavour. In the middle of the seventeenth century, the godly had seen education as an important tool in spreading their ideas but, in the aftermath of the Restoration, had found themselves increasingly excluded from universities and schools. Consequently, Dissenters began to develop their own higher educational institutions (in the shape of Dissenting academies) and also began to set up their own schools. While the enforcement of some of the legal restrictions that made it difficult for Dissenting institutions diminished across the eighteenth century, the restrictions did not disappear entirely. While there has been considerable focus on Dissenting academies and their contribution to debates about doctrinal orthodoxy, the impact of Dissenting schools was also considerable.

scholarly journals On Kaufmann's theory of the impact of the pianoforte hammer

1920 ◽  
Vol 97 (682) ◽  
pp. 99-110 ◽  
Keyword(s):  
Initial Conditions ◽  
Practical Importance ◽  
Prima Facie ◽  
Point Of View ◽  
Infinite Length ◽  
Modes Of Vibration ◽  
Rigorous Treatment ◽  
The Subject ◽  
Set Up ◽  
The Impact

The theory of the vibrations of the pianoforte string put forward by Kaufmann in a well-known paper has figured prominently in recent discussions on the acoustics of this instrument. It proceeds on lines radically different from those adopted by Helmholtz in his classical treatment of the subject. While recognising that the elasticity of the pianoforte hammer is not a negligible factor, Kaufmann set out to simplify the mathematical analysis by ignoring its effect altogether, and treating the hammer as a particle possessing only inertia without spring. The motion of the string following the impact of the hammer is found from the initial conditions and from the functional solutions of the equation of wave-propagation on the string. On this basis he gave a rigorous treatment of two cases: (1) a particle impinging on a stretched string of infinite length, and (2) a particle impinging on the centre of a finite string, neither of which cases is of much interest from an acoustical point of view. The case of practical importance treated by him is that in which a particle impinges on the string near one end. For this case, he gave only an approximate theory from which the duration of contact, the motion of the point struck, and the form of the vibration-curves for various points of the string could be found. There can be no doubt of the importance of Kaufmann’s work, and it naturally becomes necessary to extend and revise his theory in various directions. In several respects, the theory awaits fuller development, especially as regards the harmonic analysis of the modes of vibration set up by impact, and the detailed discussion of the influence of the elasticity of the hammer and of varying velocities of impact. Apart from these points, the question arises whether the approximate method used by Kaufmann is sufficiently accurate for practical purposes, and whether it may be regarded as applicable when, as in the pianoforte, the point struck is distant one-eighth or one-ninth of the length of the string from one end. Kaufmann’s treatment is practically based on the assumption that the part of the string between the end and the point struck remains straight as long as the hammer and string remain in contact. Primâ facie , it is clear that this assumption would introduce error when the part of the string under reference is an appreciable fraction of the whole. For the effect of the impact would obviously be to excite the vibrations of this portion of the string, which continue so long as the hammer is in contact, and would also influence the mode of vibration of the string as a whole when the hammer loses contact. A mathematical theory which is not subject to this error, and which is applicable for any position of the striking point, thus seems called for.

scholarly journals Impact of Air Infiltration on IAQ and Ventilation Efficiency in Higher Educational Classrooms in Spain

2021 ◽  
Vol 13 (12) ◽  
pp. 6875
Author(s):  
Irene Poza-Casado ◽  
Raquel Gil-Valverde ◽  
Alberto Meiss ◽  
Miguel Ángel Padilla-Marcos
Keyword(s):  
Natural Ventilation ◽  
Well Being ◽  
Cold Season ◽  
Climate Conditions ◽  
Air Infiltration ◽  
Ventilation Efficiency ◽  
Educational Buildings ◽  
Set Up ◽  
Total Volatile Organic Compounds ◽  
The Impact

Indoor air quality (IAQ) in educational buildings is a key element of the students’ well-being and academic performance. Window-opening behavior and air infiltration, generally used as the sole ventilation sources in existing educational buildings, often lead to unhealthy levels of indoor pollutants and energy waste. This paper evaluates the conditions of natural ventilation in classrooms in order to study how climate conditions affect energy waste. For that purpose, the impact of the air infiltration both on the IAQ and on the efficiency of the ventilation was evaluated in two university classrooms with natural ventilation in the Continental area of Spain. The research methodology was based on site sensors to analyze IAQ parameters such as CO2, Total Volatile Organic Compounds (TVOC), Particulate Matter (PM), and other climate parameters for a week during the cold season. Airtightness was then assessed within the classrooms and the close built environment by means of pressurization tests, and infiltration rates were estimated. The obtained results were used to set up a Computational Fluid Dynamics (CFD) model to evaluate the age of the local air and the ventilation efficiency value. The results revealed that ventilation cannot rely only on air infiltration, and, therefore, specific controlled ventilation strategies should be implemented to improve IAQ and to avoid excessive energy loss.

Telephone-based consultation in an acute eye clinic service: A patient satisfaction survey

2021 ◽  
pp. 112067212110307
Author(s):  
Julia Sieberer ◽  
Patrick Hughes ◽  
Indy Sian
Keyword(s):  
Healthcare Professionals ◽  
Medical Specialties ◽  
New Approach ◽  
High Satisfaction ◽  
Negative Comments ◽  
Patient Responses ◽  
Set Up ◽  
Strongly Agree ◽  
The Impact ◽  
Park Hospital

Objectives: The coronavirus pandemic has forced healthcare staff across all medical specialties to adapt new and different ways of working. A new approach has been set up in the Acute Referral Clinic (ARC) at Musgrove Park Hospital and a survey has been conducted to measure the impact of the new method on patient and healthcare professionals’ satisfaction with the new service. Methods: A telephone-based consultation was introduced in ARC at Musgrove Park Hospital in March 2020 and patients were instructed to fill out a questionnaire containing eight items using a Likert Scale 1 (‘very poor/disagree’) to 4 (‘very good/strongly agree’) plus two boxes for open positive and negative comments respectively. Likewise a questionnaire was designed in order to assess the healthcare professionals’ satisfaction using the new approach. Data collection took place over a two month period between the end of March 2020 and end of May 2020. The data underwent quality control and was analysed using descriptive statistics. Results: Patient responses illustrated high satisfaction scores with an overall rating of very good (89.4%). The healthcare professionals’ rating of the service was good (28.6% – ‘very good/strongly agree’, 57.1% – ‘good/agree’). The safety rating of the new approach was overall rated ‘very good’ with 90.4% and 71.4% of patients and healthcare professionals respectively. Conclusions: The telephone consultations introduced in the wake of COVID-19 are well accepted by both patients and doctors. There are some limitations of the approach, foremost being consultation time and clinic space but these do not outweigh the general benefit of this format amidst a pandemic setting.

scholarly journals The impact of translation modality on user experience: an eye-tracking study of the Microsoft Word user interface

2021 ◽  
Author(s):  
Ana Guerberof Arenas ◽  
Joss Moorkens ◽  
Sharon O’Brien
Keyword(s):  
User Interface ◽  
Eye Tracking ◽  
Cognitive Load ◽  
Task Completion ◽  
Eye Tracker ◽  
Software Products ◽  
Microsoft Word ◽  
Set Up ◽  
The Impact ◽  
The Given

AbstractThis paper presents results of the effect of different translation modalities on users when working with the Microsoft Word user interface. An experimental study was set up with 84 Japanese, German, Spanish, and English native speakers working with Microsoft Word in three modalities: the published translated version, a machine translated (MT) version (with unedited MT strings incorporated into the MS Word interface) and the published English version. An eye-tracker measured the cognitive load and usability according to the ISO/TR 16982 guidelines: i.e., effectiveness, efficiency, and satisfaction followed by retrospective think-aloud protocol. The results show that the users’ effectiveness (number of tasks completed) does not significantly differ due to the translation modality. However, their efficiency (time for task completion) and self-reported satisfaction are significantly higher when working with the released product as opposed to the unedited MT version, especially when participants are less experienced. The eye-tracking results show that users experience a higher cognitive load when working with MT and with the human-translated versions as opposed to the English original. The results suggest that language and translation modality play a significant role in the usability of software products whether users complete the given tasks or not and even if they are unaware that MT was used to translate the interface.

Sign in / Sign up

Export Citation Format

Share Document