adsabs/FOCAL huggingface dataset:
The right panel of Fig. 7 shows the relation between ΣSFR and R52. For each object, we computed ΣSFR = SFR/(2πR2), where R is a representative value of the galaxy radius. The latter is rather arbitrary and it depends on the chosen tracer, the depth, resolution, and wavelength of the observations. Here we adopted the ALMA sizes from circular Gaussian fitting for our sample, assuming R = FWHM/2. As mentioned in Sect. 3.2, this estimate combines all the available lines and continuum measurements, resulting in a size representative of the dust and gas content of each galaxy (Puglisi et al. 2019). We further recomputed the ΣSFR for the BzK galaxies in D15, using the Gaussian best-fit results of the rest-frame UV observations to be consistent with our estimates. For the SPT-SMGs, we used the sizes of Spilker et al. (2016), while we employed the 1.4 GHz radio measurements in Liu et al. (2015b) for the local spirals. For reference, we also show the mean values for the BzK galaxies, the local spirals, and ULIRGs as in D15. The best-fit model to the observed points returns a 60% flatter slope than in D15 (Table 3), but the trends are qualitatively similar. We restate that the choice of the tracer, the resolution, and depth of the observations play a major role in setting the exact values of the slope and intercept in our simple linear model, which should be thus taken with a grain of salt. This is particularly true for spatially resolved local objects, where we attempted to replicate the global, galaxy-scale measurements that can be obtained for distant objects. The observed data points in Fig. 7 qualitatively agree with the simulations by Narayanan & Krumholz (2014) and Bournaud et al. (2015), and they support the validity of ΣSFR as a good proxy for the gas conditions in galaxies. The total SFR is a worse predictor of the gas excitation conditions (Lu et al. 2014; Kamenetzky et al. 2016), since it does not correlate with the density and temperature probability distribution functions in clouds (Narayanan & Krumholz 2014). Interestingly, this seems to be partially confirmed by the linear regression analysis we applied here (Table 3): when modeling R52 as a function of LIR (∝SFR, Fig. 5) and ΣSFR, we do find similar slopes, but also a larger correlation coefficient ρ for ΣSFR than for LIR. However, LIR alone does correlate with the CO line luminosity ratio.
Citation: Spilker et al. (2016)
Citation function: Uses
It is much harder to localize and track the formation of current sheets in realistic black hole accretion flows in a larger domain and for a longer period because of the effects of the more complicated global dynamics governed by the central object, and due to the turbulence induced by the MRI. Both the evolution of accretion flows and the formation of current sheets therein strongly depend on the magnetic field geometry. We model an accretion disk around a rotating black hole, varying the initial conditions to study current sheet formation in different scenarios of magnetic field geometry. In the magnetically arrested disk (MAD; Igumenshchev et al. 2003; Narayan et al. 2003) scenario, the MRI and subsequent turbulence in the inner accretion disk are suppressed due to large-scale magnetic flux (see, e.g., White et al. 2019). In axisymmetric simulations as considered here, the arrested inflow is regularly broken by frequent bursts of accretion, allowing for a macroscopic equatorial current sheet to form and break in a periodic fashion. In a full 3D setup, magnetically buoyant structures are interchanged with less-magnetized dense fluid (Igumenshchev 2008; White et al. 2019), resulting in a magnetic Rayleigh–Taylor instability (Kruskal & Schwarzschild 1954) potentially sourcing interchange-type magnetic reconnection. In the Standard And Normal Evolution (SANE; Narayan et al. 2012; Sadowski et al. 2013) state, a fully turbulent accretion disk can develop due to a smaller magnetic flux (see, e.g., Porth et al. 2019), and current sheets can ubiquitously form and interact with the turbulent flow. Polarized synchrotron radiation observed by the Event Horizon Telescope (Event Horizon Telescope Collaboration et al. 2019a) can probe the field-line structure at event-horizon scales and put tighter constraints on the magnetization and address whether the accretion is in a SANE or a MAD state (Event Horizon Telescope Collaboration et al. 2019b).
Citation: White et al. 2019
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In hydrodynamic and magnetohydrodynamic systems, different fluctuations interact with each other nonlinearly, generating turbulence (Matthaeus et al. 2015). One of the most important characteristics of turbulence is the existence of intermittency among various scales. Spatial intermittency manifests as coherent structures with large gradient at small scales. In ordinary fluids, coherent structures include a tangle of vortex filaments where vorticity is highly concentrated (Frisch 1995). In the turbulent plasma environments, examples of intermittent structures include current sheets, discontinuities, shock waves, and Alfvénic vortices (Veltri & Mangeney 1999; Sundkvist et al. 2007; Lion et al. 2016; Wang et al. 2019). The intermittency will influence the measured statistical properties of the fluctuating quantities. For example, the growth of flatness with decreasing scales indicates the existence of intermittency. Plenty of simulation works (Servidio et al. 2011; Karimabadi et al. 2013; Tenbarge & Howes 2013; Wan et al. 2015, 2016; Zhang et al. 2015) have indicated that dissipation, acceleration, and thermalization of turbulent plasmas mainly take place near intermittent structures on kinetic scale, while the actual physical mechanisms behind dissipation remain unclear. There are a variety of diagnostic approaches to measure intermittency. (1) Probability density functions (PDFs) of scale-dependent field increments develop heavy tails because of intermittency, and the tail is more enhanced with increasing intermittency (Marsch & Tu 1994). (2) The scale dependency of the normalized fourth-order moment, known as flatness, 





, where δv = v(t + τ)−v(t), is an alternative representation. This quantity increases as the intermittency becomes more significant along with decreasing scales. (3) The p-th order structure function, 





, will be larger than that for Gaussian PDF without intermittency and the scaling exponent, ζ(p), has a nonlinear form when intermittency presents. Based on such diagnostic approaches, the properties of intermittency in plasmas have been widely investigated in the solar atmosphere, magnetosheath, solar wind, termination shock, etc. (Burlaga 1991a, 1991b; Marsch & Liu 1993; Horbury et al. 1995; Macek et al. 2011, 2017; Chasapis et al. 2018). These observational analyses have revealed that intermittency is widely existing in the heliosphere and immensely influencing plasma dynamics.
Citation: Tenbarge & Howes 2013
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ASASSN-14li was discovered by the All Sky Automated Search for Supernova (ASASSN; Shappee et al. 2014) on ut 2014–11–22.63 (MJD 56983.6) as a 16.5 magnitude source in the V band (Jose et al. 2014; Holoien et al. 2016; Brown et al. 2017a). The position of the source was found to be consistent with the centre of the post-starburst galaxy PGC 043234, with a measured projected separation of 0.04 arcsec. This galaxy is at redshift z = 0.0206 with a luminosity distance of 90.3 Mpc (for cosmological parameters H0 = 73 kms−1 Mpc−1, Ωmatter = 0.27, and ΩΛ = 0.73). It was established through archival X-ray observations of PGC 043234 from the ROSAT All-Sky Survey (Voges et al. 1999) that the galaxy does not contain an efficiently accreting AGN, with the count rate implying a luminosity orders of magnitude below standard active nuclei (e.g. Miller et al. 2015). A small number (currently six) of confirmed TDEs, including ASASSN-14li, have also been detected at radio wavelengths and the population may form a bi-modal distribution, consisting of more common non-relativistic ‘thermal’ events and rarer relativistic jets. Three events (Swift J1644+57; Burrows et al. 2011; Zauderer et al. 2011, Swift J2058+05; Cenko et al. 2012, Swift J1112.2; Brown et al. 2017b) have isotropic ∼5 GHz luminosities of between 1040 and 1042 erg s−1 whereas the rest (IGR J12580+0134; Irwin et al. 2015, XMMSL1 J0740-85; Alexander et al. 2017, ASASSN-14li; van Velzen et al. 2016; Alexander et al. 2016) have luminosities in the range 1037 to 1039 erg s−1 at similar frequencies. The higher power events are believed to result from observing down the axis of a relativistic jet, resulting in the energy of photons being significantly boosted. Even accounting for boosting, these relativistic events have a higher total energy output than their thermal counterparts. The origin of the radio emission from the thermal events is currently uncertain, with transient jets (van Velzen et al. 2016), non-relativistic winds (Alexander et al. 2016), and shocks driven by unbound material (Krolik et al. 2016) all feasible scenarios. ASASSN-14li is by far the best studied of the ‘thermal’ TDE category, having been observed extensively at Optical, UV, X-ray (where ASASSN-14li is unusually loud for an optically selected TDE), and radio wavelengths. The high cadence X-ray and radio observations in particular allow for the X-ray/radio coupling to be probed.
Citation: Burrows et al. 2011
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Citation: Zauderer et al. 2011
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The only way to access the transitions which trace warmer molecular gas is to get above the atmosphere as did the Herschel Space Observatory The Herschel SPIRE Fourier Transform Spectrometer (FTS) was simultaneously sensitive to the J = 4−3 (EJ = 4 = 55 K) up to the J = 13−12 (EJ = 13 = 503 K) line of CO for local galaxies. With this access to higher energy CO transitions, Herschel gave us the tools to more finely discern the lower and higher excitation components of the multiphase molecular ISM. To more finely measure the excitation of the molecular ISM is to better understand energy exchange between the star formation and the ISM. Many studies of individual galaxies (Panuzzo et al. 2010; Rangwala et al. 2011; Hailey-Dunsheath et al. 2012; Kamenetzky et al. 2012; Spinoglio et al. 2012; Meijerink et al. 2013; Pellegrini et al. 2013; Rigopoulou et al. 2013; Israel et al. 2014; Papadopoulos et al. 2014; Rosenberg et al. 2014; Schirm et al. 2014; Glenn et al. 2015; Wu et al. 2015) and surveys (Papadopoulos et al. 2010, 2012a,b; Pereira-Santaella et al. 2013, 2014; Greve et al. 2014; Kamenetzky et al. 2014, 2016; Lu et al. 2014; Daddi et al. 2015; Israel, Rosenberg & van der Werf 2015; Liu et al. 2015; Mashian et al. 2015) have shown that the higher J lines of CO arise from warmer, denser gas than the cold gas responsible for the emission of for example CO J = 1−0. Though this warm gas is only a small fraction (∼10 per cent) of the total molecular mass, it is responsible for ∼90 per cent of the CO luminosity (Kamenetzky et al. 2014). This high CO luminosity cannot be explained by excitation from the ultraviolet (UV) light from young O and B stars in photon-dominated regions (PDRs); mechanical heating is often required. Theorists have attempted to use hydrodynamical galaxy simulations to produce galaxy-integrated spectral line energy distributions (SLEDs) of CO emission (Narayanan et al. 2008; Olsen et al. 2016), but we still lack a comprehensive picture of the mechanisms responsible for this emission. Furthermore, even higher J lines of CO than addressed here (above J = 13−12) have been detected, for example with Herschel PACS, indicating a third, even higher temperature component of molecular gas (NGC1068, Hailey-Dunsheath et al. 2012). The CO SLEDs from J = 14−13 through J = 30−29 show a large range in SLED shape, even among similar galaxies (Mashian et al. 2015).
Citation: Glenn et al. 2015
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The origin of the radio emission in radio-loud active galactic nuclei (RL AGN) is clear, luminous relativistic jets of magnetized plasma, which can extend far out, on the host galaxy scale and beyond. Conversely, radio-quiet (RQ) AGN are associated with radio emission which is typically 103 times weaker (as defined by Kellermann et al. 1989), in smaller structures (kpc-pc scale; e.g. Blundell et al. 1996; Nagar et al. 1999; Ulvestad et al. 2005a; Gallimore et al. 2006) with sub-relativistic velocities (e.g. Middelberg et al. 2004; Ulvestad, Antonucci & Barvainis 2005b) compared to RL AGN. The reduced sizes and low brightness of the radio emission of RQ AGN create a major challenge for detailed studies, in sharp contrast with the thoroughly studied RL AGN. The fewer radio studies of RQ AGN (e.g. Barvainis & Antonucci 1989; Kellermann et al. 1994; Barvainis, Lonsdale & Antonucci 1996; Kukula et al. 1998; Ulvestad et al. 2005a; Leipski et al. 2006; Doi et al. 2011; Padovani et al. 2011; Zakamska et al. 2016; Jarvis et al. 2019, 2021; Fawcett et al. 2020; Nyland et al. 2020; Smith et al. 2020b; Baldi et al. 2021a) generally lead to mixed results. This encourages to keep investigating it, as it indicates that the origin of the radio emission in RQ AGN is still an open question. If a number of different processes are indeed involved, then the radio band can be used to probe a range of physical processes, rather than being heavily dominated by a single process, as occurs in RL AGN (see Blandford, Meier & Readhead 2019 Panessa et al. 2019 for reviews). From large scale to small scale: (i) host galaxy star formation (SF) could account for the observed FIR-to-radio emission observed in active and non-active galaxies (Condon et al. 2013; Zakamska et al. 2016); (ii) an AGN-driven wind is expected to shock the interstellar gas, leading to particle acceleration and radio synchrotron emission, which may reach the observed flux level (Jiang et al. 2010); (iii) the intense radiation of the AGN photoionizes large volumes of ambient gas, as supported by the strength of the narrow and broad line emission observed in type-1 AGN, leading to thermal free–free emission in the radio band (Baskin & Laor 2021); (iv) a scaled-down jet, physically similar to the one in RL AGN, but much fainter, less energetic and slower (Barvainis et al. 1996; Gallimore et al. 2006; Talbot, Sijacki & Bourne 2021); (v) a tight radio/X-ray luminosity relation for AGN (∼10−5; Laor & Behar 2008) similar to coronally active stars (Güdel & Benz 1993; Güdel et al. 2002) suggests that coronal emission from magnetic activity above the accretion disc (Field & Rogers 1993; Gallimore, Baum & O’Dea 1997) may produce the observed radio emission.
Citation: Kukula et al. 199
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The FOCAS and NIRSPEC spectra of PSO J006+39 were obtained at two different epochs separated by 1 yr and 9 months (by slightly less than 3 months in the quasar rest frame). Previously, we found that the PS1 y-band light curve of PSO J006+39 shows brightness variations with a peak-to-peak amplitude of ∼0.7 mag over ∼4 yr (Koptelova et al. 2017), which might be due to the flux variations of both continuum and Lyα line of PSO J006+39. To infer the brightness state of PSO J006+39 at the epochs of its FOCAS and NIRSPEC observations, we first calculated the spectral slope of the quasar continuum from the NIRSPEC spectrum with a wider wavelength coverage than that of the FOCAS spectrum. Using wavelength intervals of 11100–11300, 11400–11600, 13085–13400, and 14700–15200 Å we measured a spectral slope of αλ = −1.35 ± 0.26, where the quoted uncertainty is the statistical error of the fit. The fitted power law is shown in Figure 2 with a solid line. The estimated continuum slope is consistent but somewhat flatter than the typical slope of luminous quasars (Zheng & Malkan 1993; Vanden Berk et al. 2001; Selsing et al. 2016). We then fitted the FOCAS data using the power law with a fixed spectral slope of αλ = −1.35 and spectral windows of 9700–9850 and 10050–10100 Å. The spectral windows adopted for the analysis of the FOCAS and NIRSPEC spectra were taken to be similar to the rest-frame wavelength intervals commonly used to fit the continua of quasars (Vanden Berk et al. 2001; Decarli et al. 2010; Lusso et al. 2015) and less affected by the contribution from emission lines on the red side of the Big Blue Bump (BBB; e.g., Malkan 1983). The estimated continuum flux of PSO J006+39 at the epoch of its FOCAS observations is shown in Figure 2 with a dashed line. By comparing the continuum flux at the epochs of the FOCAS and NIRSPEC observations, we find that the brightness state of PSO J006+39 was different at these two epochs. PSO J006+39 was brighter by about 0.8 mag during the FOCAS observations than during the NIRSPEC observations. Thus, the continuum flux of PSO J006+39 might be different at different epochs depending on the brightness state of the quasar. Figure 2 also shows the fluxes of PSO J006+39 in the FOCAS Y, and NIRSPEC N2, N4, and N6 bands at the epochs of the FOCAS and NIRSPEC observations (see also Table 1).
Citation: Vanden Berk et al. 2001
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Citation: Vanden Berk et al. 2001
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Much of the recent work on this topic has focused on gathering observational evidence for hierarchical growth through the identification of stellar streams and tidal interactions, which are thought to be the hallmark of low-mass galaxies having been accreted by more massive galaxies. The Sagittarius dwarf galaxy (Ibata et al. 1994) and the stellar streams associated with it (Belokurov et al. 2006) are some of the most well-studied examples of this type of hierarchical accretion in the Milky Way. Recent data from the Gaia mission (Gaia Collaboration et al. 2016) and other large-scale surveys, as well as analyses that combine kinematic data with information about chemical abundances and/or specific stellar populations, have led to discoveries of additional substructures in the Galaxy and brought renewed attention to this topic (e.g., Belokurov et al. 2018; Deason et al. 2018; Helmi et al. 2018; Myeong et al. 2018). The Andromeda galaxy (M31) has been studied in detail as well. Structures formed from spatial overdensities of the red giant branch (RGB) population, e.g., the Giant Stellar Stream, have been found in the outer halo of M31 by using resolved RGB star maps (Ibata et al. 2001; Ferguson et al. 2002). Using the surface density of resolved RGB stars, it is possible to infer the surface brightness distribution of the underlying light; structures revealed by this technique, such as faint streams and clumps of RGB stars, suggest a rich history of accretion events and tidal interactions for M31. Deep observations of galaxies outside the Local Group have also revealed streams, shells, and satellites using resolved RGB stars and unresolved low surface brightness (LSB) features (e.g., Janowiecki et al. 2010; Crnojevic et al. 2016; Mihos et al. 2017). However, in galaxies well beyond the Local Group, RGB stars are unresolved and a different tracer of hierarchical assembly processes and tidal interactions is required. Globular clusters (GCs) have a number of properties that make them well suited for this task.
Citation: Helmi et al. 2018
Citation function: Motivation; Motivation
Here, for simplicity, computational convenience, and continuity with past works (Kopparapu et al. 2017; Haqq-Misra et al. 2018), we have assumed a slab ocean with zero ocean heat transport. Ocean heat transport may have a significant effect on climate and also the location of clouds (Way et al. 2018). Dynamic ocean heat transport on completely ocean-covered worlds (i.e., no continents) leads to warmer global mean temperatures and a reduction in day–night temperature differences on synchronously rotating planets (Hu & Yang 2014; Del Genio et al. 2019). Yang et al. (2019) argue that ocean heat transport is critical for the treatment of cold, partially ice-covered planets around M dwarf stars; however, it does not have a meaningful effect on the climate and thermal emission phase curves for warm terrestrial planets (Ts ∼ 300 K) residing close to the inner edge of the habitable zone. The presence of continents also presents a significant uncertainty in the net effect of ocean heat transport on climate, as continents can reroute or eliminate day-to-night ocean heat transport entirely, resulting in climate states that are similar to those found in simulations with zero ocean heat transport (Del Genio et al. 2019; Yang et al. 2019). In this work, we have argued that clouds are likely more important in modulating phase curves for habitable planets, compared to surface energy transports. Still, ocean heat transport patterns, combined with variations in continental configurations and topographic prominences, could have significant complex feedback on the surface temperature, sea ice and snow cover, and cloud distributions, respectively, all of which affect thermal and reflected light phase curves. In future works, our group plans to couple our GCM with a dynamic ocean model to study the interactions between oceans, continents, topography, and observable features. However, the long equilibration times for a coupled dynamic atmosphere-ocean model still present a significant computational hinderance for conducting 3D simulations across wider parameter spaces, as we have done here.
Citation: Hu & Yang 2014
Citation function: Motivation; Future Work
One possibility could be that the disk, since viewed at such high inclination, might create a “shadow” zone where part of the reflection incoming between Rin, 1 and Rin, 2 is obscured (see Fig. 10, panel a). As highlighted by the Figure, a jump in the scale height of the disk, located sufficiently far away from its inner edge, could in principle generate such self-shielding effect. A disk flared in the outer region was also put forward by Zdziarski et al. (2021) and Axelsson & Veledina (2021) in order to explain the presence of the outer reflection component and the variability associated to the iron line. However, it is not obvious whether a sudden puffing up of the disk could happen or not in a classical Shakura-Sunyaev disk, like the SAD. A jump could arise from a transition in the mechanism contributing mainly to the opacity in the disk. In the outer regions of a Shakura-Sunyaev disk, the opacity is expected to be mainly due to free-free absorption, while Thomson scattering dominates the opacity in the inner regions of the disk (see Eqs. (2.16) and (2.19) of Shakura & Sunyaev 1973). The geometrical thickness of the disk scales with the radius R following a (slightly) different relation; it is proportional to R−21/20 in the inner Thomson scattering-dominated, regions and to R−9/8 in the outer regions. At the boundary between these two zones (i.e., at a radius Rjump) a jump is expected. We calculated Rjump according to our results for Ṁin and assuming the same value for α in both equations. We found Rjump between 3 × 104 RG and 7 × 104 RG in all the epochs considered. In our fits the location of the outer reflector Rin, 2 was kept frozen to 300 RG. When the parameter is thawed, it is completely unconstrained, as shown in Fig. 11. Notwithstanding the uncertainty on Rin, 2, a boundary at beyond 104 RG is likely located too far away to produce an extra reflection component. However, a crucial role might be played by irradiation from the inner regions of the disk to the outer regions, an ingredient neglected in Shakura-Sunyaev disks. Beyond some boundary radius, we expect that the upper layers of the disk should be heated up by the impinging photons coming from the inner regions, leading to evaporation and to a larger effective scale height.
Citation: Shakura & Sunyaev 1973
Citation function: Uses; Uses