scholarly journals Circularization of tidal debris around white dwarfs: implications for gas production and dust variability

2020 ◽  
Author(s):  
Uri Malamud ◽  
Evgeni Grishin ◽  
Marc Brouwers
Keyword(s):  
Mass Range ◽  
Gas Production ◽  
Small Subset ◽  
Tidal Disruption ◽  
Tidal Forces ◽  
Gaseous Component ◽  
Ram Pressure ◽  
Tidal Stream ◽  
Large Parameter Space ◽  
Gas Drag

Abstract White dwarf (WD) pollution is thought to arise from the tidal disruption of planetary bodies. The initial fragment stream is extremely eccentric, while observational evidence suggest that discs are circular or nearly so. Here we propose a novel mechanism to bridge this gap and show that the fragments can rapidly circularise through dust or gas drag when they interact with a pre-existing compact disc. We assume that the tidal stream mainly consists of small cohesive fragments in the size range 10-1000 m, capable of resisting the WD tidal forces, whereas the compact discs span a wide mass range. We provide an analytical model, accompanied by N-body simulations, and find a large parameter space in fragment sizes and orbital separation that leads to full circularization. Partial circularization is possible for compact discs that are several orders of magnitudes less massive. We show that dust-induced circularization inherently produces gas as tidal fragments collisionally vaporize the pre-existing dust along their path. We show that ongoing gas production has a higher probability to occur during the early stages of tidal disruption events, resulting from the fact that smaller fragments are the first to circularize. Intermittent gas production however becomes more likely as the tidal stream matures. This could explain why only a small subset of systems with dusty compact discs also have an observed gaseous component. Additionally, the interaction yields fragment erosion by collisional shattering, sputtering, sublimation and possibly ram-pressure. Material scattered by the collisions might form a thin dusty halo that evolves through PR drag, in compatibility with observed infrared variability.

scholarly journals Quantifying tidal stream disruption in a simulated Milky Way

2017 ◽  
Vol 470 (1) ◽  
pp. 522-538 ◽  
Author(s):  
Emily Sandford ◽  
Andreas H. W. Küpper ◽  
Kathryn V. Johnston ◽  
Jürg Diemand
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Galactic Halo ◽  
Mass Range ◽  
Galactic Centre ◽  
High Dimensions ◽  
Density Profiles ◽  
Upper Limits ◽  
Tidal Stream ◽  
Tidal Streams

Abstract Simulations of tidal streams show that close encounters with dark matter subhaloes induce density gaps and distortions in on-sky path along the streams. Accordingly, observing disrupted streams in the Galactic halo would substantiate the hypothesis that dark matter substructure exists there, while in contrast, observing collimated streams with smoothly varying density profiles would place strong upper limits on the number density and mass spectrum of subhaloes. Here, we examine several measures of stellar stream ‘disruption' and their power to distinguish between halo potentials with and without substructure and with different global shapes. We create and evolve a population of 1280 streams on a range of orbits in the Via Lactea II simulation of a Milky Way-like halo, replete with a full mass range of Λcold dark matter subhaloes, and compare it to two control stream populations evolved in smooth spherical and smooth triaxial potentials, respectively. We find that the number of gaps observed in a stellar stream is a poor indicator of the halo potential, but that (i) the thinness of the stream on-sky, (ii) the symmetry of the leading and trailing tails and (iii) the deviation of the tails from a low-order polynomial path on-sky (‘path regularity') distinguish between the three potentials more effectively. We furthermore find that globular cluster streams on low-eccentricity orbits far from the galactic centre (apocentric radius ∼30–80 kpc) are most powerful in distinguishing between the three potentials. If they exist, such streams will shortly be discoverable and mapped in high dimensions with near-future photometric and spectroscopic surveys.

scholarly journals Revised Estimation Method for Emissions from Automated Plunger Lift Liquid Unloadings

Environments ◽  
2020 ◽  
Vol 7 (4) ◽  
pp. 25
Author(s):  
Adam Pacsi ◽  
David W. Sullivan ◽  
David T. Allen
Keyword(s):  
Direct Measurement ◽  
Oil And Gas ◽  
Measurement Data ◽  
Estimation Method ◽  
The United States ◽  
Gas Production ◽  
Small Subset ◽  
Emission Estimate ◽  
National Measurement ◽  
The Individual

A variety of liquid unloading techniques are used to clear accumulated liquids from the wellbore to increase production rates for oil and gas wells. Data from national measurement studies indicate that a small subset of wells with plunger lift assist, that vent with high frequency and short event duration, contribute a significant fraction of methane emissions from liquid unloading activities in the United States. Compared to direct measurement of emissions at 24 wells in a field campaign, the most commonly used engineering emission estimate for this source category, which is based on the volume of gas in the wellbore, does not accurately predict emissions at the individual well (R2 = 0.06). An alternative emission estimate is proposed that relies on the duration of the venting activity and the gas production rate of the well, which has promising statistical performance characteristics when compared to direct measurement data. This work recommends well parameters that should be collected from future field measurement campaigns that are focused on this emission source.

scholarly journals GMRT observations of the group Holmberg 124: Evolution by tidal forces and ram pressure?

2005 ◽  
Vol 435 (2) ◽  
pp. 483-496 ◽  
Author(s):  
N. G. Kantharia ◽  
S. Ananthakrishnan ◽  
R. Nityananda ◽  
A. Hota
Keyword(s):  
Tidal Forces ◽  
Ram Pressure

scholarly journals Environmental Mechanisms Shaping the Nature of Dwarf Spheroidal Galaxies: The View of Computer Simulations

2010 ◽  
Vol 2010 ◽  
pp. 1-21 ◽  
Author(s):  
Lucio Mayer
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Dwarf Galaxy ◽  
Feedback Mechanism ◽  
Gas Stripping ◽  
Morphological Transformation ◽  
Dwarf Spheroidal Galaxies ◽  
Tidal Forces ◽  
Ram Pressure ◽  
Low Metallicity

We review numerical works carried out over the last decade on the role of environmental mechanisms in shaping nature of the faintest galaxies known, dwarf spheroidals (dSphs). The combination of tidally induced morphological transformation, termed tidal stirring, with mass loss due to tidal and ram-pressure stripping aided by heating due to the cosmic ionizing background can turn late-type dwarfs resembling present-day dIrrs into classic dSphs. The time of infall into the primary halo is shown to be a key parameter. Dwarfs accreting at when the cosmic ultraviolet ionizing flux was much higher than today, and was thus able to keep the gas in the dwarfs warm and diffuse, were rapidly stripped of their baryons via ram pressure and tidal forces, producing very dark-matter-dominated objects with truncated star-formation histories, such as the Draco dSph. The low star-formation efficiency expected in such low-metallicity objects prior to their infall was crucial for keeping their disks gas dominated until stripping took over.Therefore gas stripping along with inefficient star-formation provides a new feedback mechanism, alternative to photoevaporation or supernovae feedback, playing a crucial role in dwarf galaxy formation and evolution. We also discuss how the ultra-faint dSphs belong to a different population of lower-mass dwarf satellites that were mostly shaped by reionization rather than by environmental mechanisms (“reionization fossils”). Finally, we scrutinize the various caveats in the current understanding of environmental effects as well as other recent ideas on the origin of Local Group dSphs.

scholarly journals Observational Progress in Identifying and Characterizing Tidal Disruption Flares

2016 ◽  
Vol 12 (S324) ◽  
pp. 93-98
Author(s):  
S. Bradley Cenko
Keyword(s):  
Black Hole ◽  
Optical Spectra ◽  
Starburst Galaxies ◽  
Electromagnetic Spectrum ◽  
Speed Of Light ◽  
Tidal Disruption ◽  
Massive Black Hole ◽  
X Ray ◽  
Tidal Forces

AbstractI present an overview of observational efforts across the electromagnetic spectrum to identify and study tidal disruption flares (TDFs), when a star wanders too close to a super-massive black hole and is torn apart by tidal forces. In particular I will focus on four unexpected surprises that challenge the most basic analytic picture of these events: 1) large inferred radii for the optical/UV-emitting material; 2) the ubiquity of outflows, detected at radio, X-ray, and UV wavelengths, ranging from speeds of 100 km/s to near the speed of light; 3) the peculiar atomic abundances observed in the UV and optical spectra of these objects; and, 4) the preference for these events to occur in post-starburst galaxies.

Is There a Fifth-Force? Using Galaxy Mergers to Constrain Dark-Matter Self-Interactions

2017 ◽  
Author(s):  
Maggie McLean
Keyword(s):  
Dark Matter ◽  
Numerical Simulations ◽  
Fundamental Problem ◽  
Interacting Galaxies ◽  
Galaxy Mergers ◽  
Tidal Disruption ◽  
Fifth Force ◽  
Tidal Forces ◽  
Visible Matter ◽  
The Universe

Over ninety percent of the matter in the universe is believed to be “dark matter,” a mysterious form of matter the nature of which is still unknown. Since it cannot be detected directly, dark matter can only be inferred from its effect on visible matter. This leaves a significant gap in our knowledge. Without the ability to measure the influence of dark matter on other dark matter, we could miss a possible fifth fundamental force which mediates dark matter self-interactions. We propose a means of constraining the existence of a “fifth-force” by observing galaxies that are in the process of merging. Using numerical simulations, we examine the effect of including a hypothetical fifth-force on the tidal disruption of visible matter during galaxy mergers. We find distinct differences in the formation and appearance of tidal features produced during these interactions, providing an observable constraint on the strength of any “fifth-force.” The sheer volume of interacting galaxies that can be observed makes tidal forces a valuable tool in studying a fundamental problem that would otherwise pose a great challenge for physicists.

scholarly journals Tidal Disruption of Magnetars as the Sources of Fast Radio Burst

2020 ◽  
Author(s):  
Kushaal Kumar Pothula
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Strong Magnetic Field ◽  
Accretion Disk ◽  
High Energy ◽  
Tidal Disruption ◽  
High Energy Cosmic Rays ◽  
Tidal Forces ◽  
Fast Radio Burst ◽  
The Magnetic Field

Abstract Fast Radio Bursts (FRBs) are mysterious millisecond duration radio transients, and some FRBs repeat. FRBs are highly polarized, indicating that the source is within a strong magnetic field. I hypothesize their origin as Tidal Disruption Events (TDEs) of magnetars by black holes. The TDE releases energy stored in the magnetic field of the magnetar, producing an FRB. Occasionally the magnetar is disrupted into multiple debris chunks, and as individual chunks get consumed, multiple FRBs are produced, forming a repeating FRB. Another process of formation of repeating FRBs is starquakes on magnetars because of tidal forces from black holes. Due to the strong magnetic field of the accretion disk, the FRB is produced in jets. Sometimes the magnetar debris surrounding the magnetic field gets accelerated, producing Ultra-high energy cosmic rays, whose source remains unknown. The FRB signal produced gets polarized by the magnetosphere of the accretion disk and intergalactic magnetic fields.

scholarly journals The distinct stellar metallicity populations of simulated Local Group dwarfs

2019 ◽  
Vol 488 (2) ◽  
pp. 2312-2331 ◽  
Author(s):  
Anna Genina ◽  
Carlos S Frenk ◽  
Alejandro Benítez-Llambay ◽  
Shaun Cole ◽  
Julio F Navarro ◽  
...  
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Mass Range ◽  
Spatial Segregation ◽  
Ram Pressure ◽  
History Of ◽  
Hydrodynamical Simulations ◽  
Two Populations ◽  
Poor Population

ABSTRACT A number of Local Group dwarf galaxies are known to have two spatially segregated stellar metallicity populations, a centrally concentrated metal-rich population, and a more extended metal-poor population. In this work we discuss mechanisms that lead to the formation of two spatially segregated metallicity populations. Using a set of high-resolution hydrodynamical simulations of Local Group-like environments, we select a sample of satellite and field galaxies, spanning the stellar mass range 106–109 M⊙, that exhibit bimodality in their metallicity distributions. Among those, we identify a subsample with a strong spatial segregation in the two populations. We find three distinct mechanisms for their formation. In field dwarfs and in a small fraction of satellites, a merger causes the metal-poor stars to migrate to larger radii and encourages the available gas to sink to the centre of the dwarf. Most of the gas is subsequently blown out of the halo through star formation feedback, but the remaining gas is consumed in the formation of a metal-rich population. In the exclusive case of satellites that have retained some of their gas at infall, it is the compression of this gas by ram pressure near pericentre that triggers the formation of metal-rich stars, whilst simultaneously preventing star formation at larger radii through stripping. Additionally, in a small number of field and satellite dwarfs, interactions with gaseous filaments and other galaxies can result in the formation of a metal-rich population. Regardless of the formation mechanism, a history of mergers typically enhances the spatial segregation.

scholarly journals A Search for Tidal Stellar Debris from the Magellanic Clouds: Survey Results from the First Two Years

1999 ◽  
Vol 190 ◽  
pp. 508-510 ◽  
Author(s):  
S. R. Majewski ◽  
J. C. Ostheimer ◽  
W. E. Kunkel ◽  
K. V. Johnston ◽  
R. J. Patterson ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Galactic Halo ◽  
Large Magellanic Cloud ◽  
Main Sequence Stars ◽  
Tidal Disruption ◽  
Negative Results ◽  
Ram Pressure ◽  
Survey Results ◽  
Magellanic Stream

An important discriminant between leading models for the origin of the Magellanic Stream is the presence of a stellar counterpart to the HI gas stream: ram pressure stripping of gas by a putative hot Galactic halo would act only on Magellanic gas while gravitational tidal stripping would act on both gas and stars. Several previous attempts to find tidal stellar debris have failed to find carbon stars, A stars, or other main sequence stars in the Magellanic Stream (Mathewson et al. 1979; Recillas-Cruz 1982; Brück & Hawkins 1983; Guhathakurta & Lin 1999). However, there has long been a suggestion (Kunkel 1979; Lynden-Bell 1982) of a possible Magellanic association of satellite galaxies and globular clusters that have similar orbits and may derive from the break up of a greater Magellanic galaxy (Lynden-Bell & Lynden-Bell 1995; Majewski et al. 1997). Recent models (Moore & Davis 1994; Johnston 1998) of the tidal disruption of Large Magellanic Cloud (LMC)-like systems indicate a wide dispersal of debris, much wider than the rather confined HI stream, so that the contrast of tidal debris against the Galactic fore/background would be low. If true, this could explain some of the previous negative results for tidal debris searches.

scholarly journals Tidal disruption events from massive black hole binaries: predictions for ongoing and future surveys

2019 ◽  
Vol 488 (3) ◽  
pp. 4042-4060 ◽  
Author(s):  
Stephen Thorp ◽  
Eli Chadwick ◽  
Alberto Sesana
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Low Frequency ◽  
Mass Range ◽  
Tidal Disruption ◽  
Massive Black Hole ◽  
Massive Black Holes ◽  
X Ray ◽  
Black Hole Binaries ◽  
Survey Instruments

ABSTRACT We compute the expected cosmic rates of tidal disruption events (TDEs) induced by individual massive black holes (MBHs) and by MBH binaries (MBHBs) – with a specific focus on the latter class – to explore the potential of TDEs to probe the cosmic population of sub-pc MBHBs. Rates are computed by combining MBH and MBHB population models derived from large cosmological simulations with estimates of the induced TDE rates for each class of objects. We construct empirical TDE spectra that fit a large number of observations in the optical, UV, and X-ray and consider their observability by current and future survey instruments. Consistent with results in the literature, and depending on the detailed assumption of the model, we find that LSST and Gaia in optical and eROSITA in X-ray will observe a total of 3000–6000, 80–180, and 600–900 TDEs per year, respectively. Depending on the survey, 1 to several per cent of these are prompted by MBHBs. In particular, both LSST and eROSITA are expected to see 150–450 MBHB-induced TDEs in their respective mission lifetimes, including 5–100 repeated flares. The latter provide an observational sample of binary candidates with relatively low contamination and have the potential of unveiling the sub-pc population of MBHBs in the mass range $10^5\lt M\lt 10^7\, \mathrm{M}_\odot$, thus informing future low-frequency gravitational wave observatories.

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