adsabs/FOCAL huggingface dataset:
While both Suprime-Cam/NB359 and HST/F336W trace LyC for sources at z > 3.06, NB359 has a narrower filter bandpass, and it preferentially captures ionizing photons closer to the Lyman limit (see Fig. 1). Because IGM attenuation varies as a function of wavelength, expected transmissions of photons through the IGM (here we denote the ratio of flux density with and without IGM attenuation as ‘IGM transmission’) are different for different filters. In Fig. 2 we show the median and 68 percentile IGM transmission values of NB359 andF336W for a source at a redshift range of 3.1 ≤ z ≤ 3.8. These IGM transmissions are estimated from Monte Carlo simulations (Inoue & Iwata 2008) which generate 10 000 sightlines for redshifts consistent with the H i cloud distribution defined analytically by Inoue et al. (2014). For each sightline we calculate IGM transmission through NB359 or F336W for an object with a flat SED in fν (i.e. fν = constant) and obtain median and 68 percentile values from the 10 000 instances. These calculations are repeated from z = 3.1 to 3.8 with a redshift step of 0.1. The median values of IGM transmission for NB359 are higher than those for F336W, especially at the lower redshift range. This is because NB359  traces a rest-frame wavelength range close to the Lyman limit where IGM transmission is higher than that for photons with shorter wavelengths. If the same limiting magnitude is achieved, NB359 is more sensitive for detecting LyC photons from z > 3 galaxies than F336W. Median values of IGM transmission for both NB359 and F336W rapidly decrease as the source redshift increases, which indicates that the detection of LyC photons becomes increasingly difficult due to increasing IGM opacity. However, higher-side 68 percentile IGM transmission values at z = 3.5 are 0.33 for NB359 and 0.20 for F336W, respectively. The fluctuation of IGM transmission among different sightlines is large, and there are still a reasonable number of sightlines with significant IGM transparency for LyC in the redshift range studied in this paper.
Citation: Inoue & Iwata 2008
Citation function: Uses; Uses
As well as being directly excited from the ground state, Balmer lines (intensity, line profile, polarization and so on) are affected by the conversion of Lyman lines to Balmer lines. For example, the absorption of Ly β by a hydrogen atom results in radiative excitation from 1s to 3p, and the excited atom can emit H α by the spontaneous transition from 3p to 2s. Simultaneously, the conversion yields the 2s-state hydrogen atom, which creates the two-photon continuum by the spontaneous transition from 2s to 1s. Thus, the Ly β to H α conversion impacts the total intensity, line profile, and net polarization of H α. Moreover, an adequate density of 2s-sate atoms can further scatter H α photons. Although such fundamental physics is well known, it has not been well studied in SNR shocks. In fact, it is usually assumed that the Ly β photons are at the limits of either completely optically thick or optically thin at SNR shocks, i.e. they are completely converted to H α photons or not at all (e.g. Heng & McCray 2007; van Adelsberg et al. 2008; Morlino et al. 2012, 2013b; Shimoda et al. 2018). Contrary to this, Ghavamian et al. (2001) studied the conversion of Ly β and Ly γ to H α and H β by Monte Carlo simulations and claimed that intermediate conversion occurs. However, they and previous studies did not consider the population of 2s-state hydrogen atoms. In this paper, we provide a formulation of the radiative line transfer with the rate equation of atomic population and study the nature of Balmer line emissions from SNR shocks. In this paper we do not consider the polarization, deferring that instead to a later work. Note that as a first step, our model makes several simplifications in the treatment of the SNR shock, handling the hydrogen atoms as fluids and supposing no particles leaking back upstream (e.g. cosmic rays). Our calculation of radiative transfer is based on so-called the ray-tracing method and uses updated atomic data from the literature (e.g. Heng & Sunyaev 2008; Tseliakhovich, Hirata & Heng 2012). Moreover, we consider only hydrogen line emissions and ignore bremsstrahlung radiation, thermal emissions from the SNR ejecta, and external radiation sources. Thus, our model possibly predicts somewhat smaller population of 2s-state hydrogen atoms than would be the case in a realistic SNR shock.
Citation: Morlino et al. 2012
Citation function: Compare/Contrast
The energy dependent pulse arrival time can usually be observed in AMXPs. Soft lags are most often seen in AMXPs, where the pulse arrival times of the pulsations from softer energy bands lag compared to the ones from the harder energy bands. This phenomenon was first discovered by Cui et al. (1998) during the 1998 outburst of the SAX J1808.4–3658. The soft lag tendency can clearly be detected from 2 keV extended up to 10 keV (hereafter, the break point) for about 200 μs (∼0.08 cycles) but saturated for harder X-ray bands. Similar energy dependent pulse arrival time behavior can also be found in XTE J1751–305 (Gierliński & Poutanen 2005), XTE J1814–338 (Watts & Strohmayer 2006), HETE J1900.1–2455 (Galloway et al. 2007), and XTE J1807–294 (Chou et al. 2008) with different break point energies. However, the energy dependent pulse arrival time acts differently in IGR J00291+5934. Falanga et al. (2005) found that the soft lags can extend to the break point energy at ∼6 keV but the tendency reverses instead of saturation for the pulse of energy bands harder than the break point (hereafter hard lags) during its 2005 outburst. Similar behaviors are also observed during its 2015 outburst (Sanna et al. 2017) with a different break point energy at ∼8 keV. Such hard lags are also marginally detected in IGR J17511–3057 (Falanga et al. 2011) and IGR J17498–2921 (Falanga et al. 2012). On the other hand, the energy dependent pulse arrival times for two AMXPs are rather peculiar. The pulse arrival times seem independent of energy bands below ∼17 keV for SAX J1748.9–2021 (Patruno et al. 2009a) and only hard lags are detected in IGR J18245–2452 (De Falco et al. 2017). The newly discovered AMXP IGR J17379-3747 also shows unusual energy dependent pulse arrival times. Regular soft lags can be observed between 0.5 and 6 keV with no break point being detected; however, the phase difference between the softest and hardest bands can be as high as ∼0.3 cycles (or ∼110°; Bult et al. 2019).
Citation: Chou et al. 2008
Citation function: Background; Background; Background
Solar prominences or filaments are cool, dense plasmas embedded in the million-Kelvin corona (Mackay et al. 2010). The plasmas originate from the direct injection of chromospheric materials into a pre-existing filament channel, levitation of chromospheric mass into the corona, or condensation of hot plasmas from the chromospheric evaporation due to the thermal instability (Xia et al. 2011, 2012; Keppens & Xia 2014; Zhou et al. 2014). Prominences are generally believed to be supported by the magnetic tension force of the dips in sheared arcades (Guo et al. 2010b; Terradas et al. 2015) or twisted magnetic flux ropes (MFRs; Cheng et al. 2012, 2014a; Su & van Ballegooijen 2012; Sun et al. 2012a; Zhang et al. 2012a; Xia et al. 2014a, 2014b). They can keep stable for several weeks or even months, but may get unstable after being disturbed. Large-amplitude and long-term filament oscillations before eruption have been observed by spaceborne telescopes (Chen et al. 2008; Li & Zhang 2012; Zhang et al. 2012b; Bi et al. 2014; Shen et al. 2014) and reproduced by numerical simulations (Zhang et al. 2013), which makes filament oscillation another precursor for coronal mass ejections (CMEs; Chen 2011) and the accompanying flares. When the twist of a flux rope supporting a filament exceeds the threshold value (2.5π–3.5π), it will also become unstable and erupt due to the ideal kink instability (KI; Hood & Priest 1981; Kliem et al. 2004; Török et al. 2004, 2010; Fan 2005; Srivastava et al. 2010; Aschwanden 2011; Kumar et al. 2012). However, whether the eruption of the kink-unstable flux rope is failed or ejective depends on how fast the overlying magnetic field declines with height (Török & Kliem 2005; Liu 2008; Kumar et al. 2010). When the decay rate of the background field exceeds a critical value, the flux rope loses equilibrium and erupts via the so-called torus instability (TI; Kliem & Török 2006; Amari et al. 2014; Jiang et al. 2014). On the other hand, if the confinement from the background field is strong enough, the filament will decelerate to reach the maximum height before falling back to the solar surface, which means the eruption has failed (Ji et al. 2003; Liu et al. 2009; Guo et al. 2010a; Kumar et al. 2011; Joshi et al. 2013, 2014; Song et al. 2014).
Citation: Terradas et al. 2015
Citation function: Background
The dynamics of stars can be related to the gravitational potential that they inhabit via the collisionless Boltzmann equation. For systems in a steady state with certain symmetry properties (typically spherical or axisymmetric) it is possible to find solutions to the phase-space distribution of a stellar tracer population, either through distribution function modelling or via the moments of the Boltzmann equation (Kapteyn 1922; Oort 1932; Bahcall 1984a,b; Kuijken & Gilmore 1989; Crézé et al. 1998; Holmberg & Flynn 2000; Bienayme et al. 2006; Binney & Tremaine 2008; Garbari et al. 2012; Bovy & Rix 2013; Salomon et al. 2020; Guo et al. 2020; Widmark et al. 2021a). Given the relatively quiet conditions necessary to form disk galaxies, the assumption of equilibrium for near-equilibrium systems has been widely and favourably applied to the Milky Way and other galaxies (McMillan 2011; Binney & McMillan 2011). Our place in the Milky Way makes it ideal to accurately measure its gravitational potential and mass distribution, since it is the only system where we have access to full six-dimensional phase space information, from its inner regions all the way to its outermost edge (e.g. Deason et al. 2021). A precise and robust measurement of the gravitational potential is crucial for our general understanding of the Milky Way (Dehnen & Binney 1998; Klypin et al. 2002; Widrow et al. 2008; Weber & de Boer 2010; McMillan 2011, 2017; Kafle et al. 2014; Cole & Binney 2017), and also for probing its distribution of dark matter (Read 2014; Nitschai et al. 2020; Cautun et al. 2020; Li et al. 2020; de Salas & Widmark 2021). The local dark matter density is of fundamental importance for direct and indirect dark matter detection experiments (Jungman et al. 1996; Klasen et al. 2015). In a broader sense, dark matter’s gravitational signatures, studied via stellar dynamics and gravitational lensing, is one of the most competitive avenues for constraining its thus far elusive particle nature (Bertone & Tait 2018; Ferreira 2021). The Gaia satellite has been instrumental to this field, pushing the size of the astrometric sample from a few hundred thousand stars (Perryman et al. 1997) to roughly two billion (Gaia Collaboration 2018a).
Citation: Widmark et al. 2021a
Citation function: Background
In addition to the galaxy mergers, the ram pressure may also induce AGN activity together to star formation in cluster galaxies (e.g., Poggianti et al. 2017; Marshall et al. 2018; Ramos-Martínez et al. 2018). The ram pressure, acting on galaxies in a galaxy cluster moving through the intra-cluster medium (ICM), can strip (ram pressure stripping) gas out of the galaxy where the gas is gravitationally bound to the galaxy less strongly than the force from the ICM medium wind due to the ram pressure. A typical effect of the ram pressure stripping is the formation of long tails of stripped gas behind galaxies. A good example of this effect is the Virgo cluster, the closest rich galaxy cluster, considered a ram pressure stripping laboratory since a number of clearly ram pressure stripped galaxies have been observed (e.g., Kenney et al. 2004; Crowl et al. 2005; Chung et al. 2007). Another example of long tails of stripped gas is the Norma cluster (Abell 3627), containing a very extended multi-phase gas stripped tail of a late-type galaxy (ESO137-001 Sun et al. 2007, 2010). In the literature, there is an open debate on the role of the ram pressure stripping on the AGN activity. Observations suggest that ram-pressure stripping tends to produce a decreasing of the radiative-mode AGN activity in the centres of clusters with respect to low density regions (e.g., Ellison et al. 2011; Ehlert et al. 2014; Khabiboulline et al. 2014). This happens because the ram pressure has depleted the gas supply of the central galaxies. However, models and hydrodynamical simulations show that a moderate ram pressure is also able to compress the gas in the galaxy and trigger star formation (e.g., Fujita & Nagashima 1999; Kronberger et al. 2008; Kapferer et al. 2009; Tonnesen & Bryan 2009; Bekki 2014). This effect, produced by a low level of ram pressure, is observationally supported (e.g., Lee et al. 2017). Moderate ram pressure can also produce the removal of angular momentum from the disk gas (Tonnesen & Bryan 2009), producing gravitational instability in the galactic disk (Schulz & Struck 2001) and consequentially the gas fueling towards the central AGN.
Citation: Kenney et al. 2004
Citation function: Background
Molecular line ratio diagrams for NGC 4710, NGC 5866 and a variety of other galaxies. Our data for NGC 4710 and NGC 5866 are shown as filled circles and squares, respectively, while our data for the nuclear discs and inner rings are shown in blue and red, respectively (black for the intermediate region). Upper and lower limits are represented by arrows. Other lenticular galaxies are indicated by magenta filled stars (Krips et al. 2010; Crocker et al. 2012), starburst nuclei by dark green filled stars, Seyferts by brown filled stars, spiral arm GMCs by black circles with an X (see Baan et al. 2008; table 3 in Krips et al. 2010 and references therein), NGC 6946 (starburst) GMCs by black circles with a cross (Topal et al. 2014), and M31 GMCs by turquoise circles with an X (Brouillet et al. 2005). The data for NGC 1266 (a lenticular galaxy with a molecular outflow) are shown by magenta squares with a filled star (Alatalo et al. 2011). The green shaded region in panel a indicates the typical range of 12CO(1–0)/HCN(1–0) ratios in starbursts with LFIR > 1011 L⊙ (see table B2 in Baan et al. 2008). The range of R11 ratios in the nuclear disc and inner ring of NGC 5866 (this work) are indicated by respectively the blue and red horizontal lines in panel b, while the typical range in spirals with LFIR  1011 L⊙ (Paglione et al. 2001) is indicated by the pale grey shaded region. In panels a and b, Crocker et al.'s (2012) single-dish observations of NGC 4710 and NGC 5866 are shown as an open black circle and an open black square, respectively (see table 4 of Crocker et al. 2012). The HCN(1–0)/HCO+ ratios for M31 GMCs (Brouillet et al. 2005) are indicated by the turquoise shaded region in panels c and d. The green shaded region in panel d indicates the typical range of 13CO(1–0)/HCO+(1–0) ratios in the disc of M82 (starburst; Tan et al. 2011). The 12CO(1–0)/HCN(1–0) ratios in spirals (Gao & Solomon 2004a) are indicated by the dark grey shaded region in panels a, e and f, respectively. The black solid lines in a number of panels show the 1 : 1 relation and are there to guide the eye. Similarly, the black dashed lines show a ratio of 1 in panels c, d and f.
Citation: Brouillet et al. 2005
Citation function: Uses; Uses
Large numbers of works have extensively studied the binary-disk system in the Newtonian regime with analytic methods (Paczynski 1977; Papaloizou & Pringle 1977; Kocsis, Haiman & Loeb 2012a, b) and hydrodynamical simulations (Lin & Papaloizou 1979; Artymowicz & Lubow 1994; MacFadyen & Milosavljević 2008; Mayama et al. 2010; de Val-Borro et al. 2011; Shi et al. 2012; D’Orazio et al. 2013; Farris et al. 2014; Ju, Stone & Zhu 2016; Muñoz & Lai 2016; Nelson A. & Marzari 2016; Miranda, Muñoz & Lai 2017; Tang, MacFadyen & Haiman 2017; Tang, Haiman & MacFadyen 2018; Muñoz, Miranda & Lai 2019). Simulations within the Newtonian regime during the inspiral of the binary black hole have also been investigated (Baruteau, Ramirez-Ruiz & Masset 2012; Farris et al. 2015; Cerioli, Lodato & Price 2016; Tang et al. 2018). Two-dimensional simulations by Noble et al. (2012) and three-dimensional ones by Zilhão et al. (2015) conducted the fully relativistic magnetohydrodynamic evolution of a circumbinary disk surrounding two non-spinning black holes with equal mass using the near zone metric. Later on, the fully relativistic magnetohydrodynamic simulations of SMBBH–disk interaction with both the near zone metric and the inner zone metric have been performed (Bowen et al. 2017, 2018, 2019; d’Ascoli et al. 2018) and these simulations are limited to several binary orbits. In particular, Bowen et al. (2017) showed that the gravitational potential of the binary black hole in the post-Newtonian (PN) regime is shallower than that in the Newtonian regime, and that such shallow potential in the PN regime has significant effects on the dynamics of the mini-disk around each SMBH. Simulations of SMBBH–disk interaction with full numerical relativity are so computationally expensive that the evolution of disk around SMBBH is constrained within the stage near merger (Farris et al. 2012; Giacomazzo 2012). In this work, we present hydrodynamical simulations of accretion of equal mass SMBBH by using PN hydrodynamics in which the near zone metric of SMBBH is used.
Citation: Muñoz, Miranda & Lai 2019
Citation function: Background; Background
Similar results of the on-disk condensations are obtained to those of the on-disk quiescent coronal rain in AR closed loops in Hα (see Section 3.2). If we considered the AIA 304 Å observations alone, the on-disk condensation, and hence coronal rain events we report here would resemble those occurring in magnetically closed field lines (Antolin & Rouppe van der Voort 2012; Antolin et al. 2012; Ahn et al. 2014), which are generally interpreted as a manifestation of the heating-condensation cycles due to thermal nonequilibrium (Schrijver 2001; Müller et al. 2003, 2004; Antolin 2020). However, combining the observations of SDO and STEREO A and B at different viewing angles, we find that the on-disk coronal rain in this study corresponds to the downflows of condensations facilitated by reconnection between open and closed structures. Similarly, if we analyze only the on-disk observations as recorded by the AIA as shown in Figure 7, it appears that the structures gradually brighten first in the 171 Å channel and then in the 131 Å channel. Such sequential appearance of coronal structures in the AIA channels sensitive to emission from progressively cooler plasma could be interpreted as a case of loop cooling after nanoflare heating (e.g., Viall & Klimchuk 2012; Li et al. 2015), for instance. In contrast, by employing observations from multiple vantage points, we show that the on-disk structure brightening in the AIA images is actually due to cooling and condensation of plasma facilitated by reconnection in the high corona that is not necessarily regulated by any heating mechanism. To search for the origination of structures harboring on-disk flow, e.g., coronal rain, in the transition region or chromospheric lines, observations from different viewing angles are thus quite important. If there is no observation from other viewing angles, evolution of the associated structures, that may be difficult to observe on the disk, in multiwavelength images during the cooling and condensation process needs to be examined because the condensation facilitated by reconnection cools down from ∼0.9 MK, the characteristic temperature of the 171 Å channel, rather than from the higher temperatures.
Citation: Schrijver 2001
Citation function: Compare/Contrast; Compare/Contrast; Compare/Contrast
There are several natural scenarios for the initial flare-caused impulsive perturbation of an active region to develop into a quasi-periodic response, which includes the effects of resonance in closed coronal plasma structures (acting as resonators), dispersion of a wave-guide, and non-linearity/self-organization (McLaughlin et al. 2018; Zimovets et al. 2021). The observed doubling of the QPP and shorter lifetime of shorter-period QPP modes strongly indicate in favour of resonant dynamics of magnetohydrodynamic waves in a coronal loop, for which the oscillation period is prescribed by the local plasma conditions (i.e. the Alfvén and sound speeds) and the loop length (Nakariakov et al. 2021; Wang et al. 2021). More specifically, fast- and slow-mode magnetoacoustic waves in coronal plasma structures are well-known to be subject to a frequency-dependent damping by e.g. resonant absorption and thermal conduction (e.g. Ofman & Aschwanden 2002; Ruderman & Roberts 2002; De Moortel & Hood 2003). Likewise, excitation of even and/or uneven parallel harmonics of fast- and slow-mode standing waves in a plasma loop is known to be highly sensitive to the location of the initial perturbation along the loop. For example, Tsiklauri et al. (2004) and Selwa, Murawski & Solanki (2005) theoretically demonstrated that the second parallel harmonic of a slow standing wave can be effectively excited if the impulsive energy release occurs near the apex of the loop. Observations of higher harmonics of fast-mode oscillations in coronal loops were also shown to be subject to the excitation mechanism and location of the initial displacement of the loop (e.g. De Moortel & Brady 2007; Srivastava et al. 2008; Yuan & Van Doorsselaere 2016; Pascoe et al. 2017; Duckenfield et al. 2019). Thus, taking cs = 600 km s−1 for the sound speed in a hot flaring loop, the Alfvén speed cA = 1200 km s−1 (e.g. Mathioudakis et al. 2006), and treating the observed QPP periods as characteristic acoustic or Alfvén transit times along the loop, we can estimate the corresponding loop lengths as 80–160 Mm for the 2018 flare and 50–100 Mm for the 2019 flare, i.e. 0.2–0.7 R⋆. These estimations agree with a typical length of solar coronal loops, and, are approximately an order of magnitude larger than those derived by Mathioudakis et al. (2006). However, the above authors ruled out these small loop lengths suggesting instead that they may be due to a fast-MHD wave, with the modulation of the emission being due to the magnetic field. The present observation in the doubling of the QPP in both YZ CMi flares presents rare and compelling evidence for the presence of compact plasma loops in a stellar corona.
Citation: Ruderman & Roberts 2002
Citation function: Uses