adsabs/FOCAL huggingface dataset:
Since the age determination using asteroseismology relies on the mass-age relation that red giants follow, this means that the method is biased by any event that changes the stellar mass, such as mass accretion from a companion or stellar mergers (blue stragglers or stars rejuvenated by accretion, e.g. Boffin et al. 2015) or mass loss. One way to look for mass accretion events from a companion is to look for radial velocity, photometric variations, or chemical signs of accretion (e.g. high carbon and s-process enhancements; Beers & Christlieb 2005; Abate et al. 2015). The effect of mass loss can be minimised by looking at stars in the low-RGB phase, in which the effect of mass loss is smaller compared to red clump stars (Anders et al. 2017). The first study to determine masses for a sample of metal-poor halo giants with both seismic information (from Kepler; Borucki et al. 2010) and chemistry from high-resolution APOGEE (Majewski et al. 2017) spectra, was by Epstein et al. (2014). The authors used scaling relations at face value and reported masses larger (M >  1 M⊙) than what would be expected for a typical old population. Similar results were obtained by Casey et al. (2018), also using scaling relations for three metal-poor stars. These findings led to the need for further tests of the use of asteroseismology in the low metallicity regime. Miglio et al. (2016) analysed a group of red giants in the globular cluster M4 ([Fe/H] = −1.10 dex and [α/Fe] = 0.4 dex) with seismic data from K2 mission (Howell et al. 2014). These authors found low seismic masses compatible with the old age of the cluster, hence suggesting that seismic masses and radii estimates would be reliable in the metal-poor regime provided that a correction to the Δν scaling relation is taken into account for red giant branch (hereafter RGB) stars. The correction presented in Miglio et al. (2016) is a correction that is theoretically motivated based on the computation of radial mode frequencies of stellar modes.
Citation: Epstein et al. (2014)
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Single-burst stellar population (SSP) models mimic uniform stellar populations of fixed age and metallicity, and are an important tool to study unresolved stellar clusters and galaxies. They are created by populating theoretical stellar evolutionary tracks with stars of a stellar library, according to a prescription given by a chosen initial mass function (IMF). Thus, the quality of the resulting SSP models depends significantly on the completeness of the used input stellar library in terms of evolutionary phases represented by the atmospheric parameters temperature, Teff, surface gravity, log (g), and metallicity. A sufficiently large spectral coverage is equally crucial when constructing reasonable SSP models. Theoretical stellar libraries like, e.g. BaSeL (Kurucz 1992; Lejeune et al. 1997, 1998; Westera et al. 2002), or PHOENIX (Allard et al. 2012; Husser et al. 2013) are generally available for both a large range in wavelength and in stellar parameters, whereas empirical libraries are found to be more incomplete in both respects. However, the advantage of the latter ones is that they are not hampered by the still large uncertainties in the calculation of model atmospheres. Examples of empirical stellar libraries in the optical wavelenth range encompass the Pickles library (Pickles 1998), ELODIE (Prugniel & Soubiran 2001), STELIB (Le Borgne et al. 2003), Indo-US (Valdes et al. 2004), MILES (Sánchez-Blázquez et al. 2006), and CaT (Cenarro et al. 2001, 2007). In the near-infrared (NIR) and mid-infrared (MIR)1, only very few empirical libraries have been observed so far (e.g. Lançon & Wood 2000; Cushing et al. 2005; Rayner et al. 2009). The NASA Infrared Telescope Facility (IRTF) spectral library, described in the latter two papers, is to date the only empirical stellar library in the NIR and MIR which offers a sufficiently complete coverage of the stellar atmospheric parameter space to construct SSP models. In the future, the X-Shooter stellar library, which contains around 700 stars, and which covers the whole optical (see Chen et al. 2014) and NIR wavelength range until 2.5 μm, will clearly improve the current situation in the NIR.
Citation: Husser et al. 2013
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Citation: Kurucz 1992
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As a general remark, whether the locally calibrated metallicity diagnostics are applicable to high-redshift galaxies is still a matter of great debate. Diagnostics that are expected to be little affected by the ionization conditions of the gas (see e.g. Dopita et al. 2016) have been suggested to be valuable for high-redshift galaxies, where strong variations in ionization parameter and excitation conditions compared to local galaxies have been invoked to explain the observed evolution in the emission-line ratios (as seen, for example, from the offset of high-z sources in the classical BPT diagrams with respect to the local sequence (Kewley et al. 2013; Nakajima et al. 2013; Steidel et al. 2014; Kashino et al. 2017; Strom et al. 2017). However, since such diagnostics usually involve the [N ii]/[O ii] or the [N ii]/[S ii] line ratios, they are strongly dependent on the assumed relation between the N/O ratio as a function of the oxygen abundance O/H, which is affected by a large scatter and whose evolution with cosmic time and/or dependence on galaxy mass is also indicated as a possible origin of the observed evolution of the emission-line properties in high-zgalaxies (Masters et al. 2014, 2016; Shapley et al. 2015). Therefore, strong-line indicators based only on alpha elements (like, e.g. oxygen) have also been suggested as appropriate to high redshift studies, since galaxies at z ∼ 1.5–2.5 seem to show no appreciable offset from local trends in oxygen-based diagnostic diagrams (e.g. R23 versus O32, Shapley et al. 2015). However, the location on the abovementioned diagram could even be sensitive to a variation in the hardening of the radiation field at a fixed metallicity rather than a variation in abundances (Steidel et al. 2016; Strom et al. 2017). In any case, at redshifts ∼1.5 (where the majority of KLEVER galaxies considered in this work lie), the lack of the [O ii] doublet in the NIR bands observable from KMOS prevents us from using purely oxygen diagnostics, thus forcing us to exploit the nitrogen-based ones. When the survey will be complete, we will investigate the spatially resolved behaviour of z ∼ 2 galaxies on the R23 versus O32 diagram in a more statistically robust manner. Recently, Patrício et al. (2018) have shown that oxygen-based diagnostics z ∼ 2 provide metallicities comparable to those inferred from the electron temperature method; unfortunately, just a handful of robust auroral line detections have been reported so far in high-z sources (e.g. Jones, Martin & Cooper 2015b; Sanders et al. 2016; see also Patrício et al. 2018, and references therein), due to the intrinsic observational challenges in detecting the faint auroral lines with current instrumentation. Only the advent of new facilities like JWST or the MOONS spectrograph on the VLT will ultimately allow us to tackle this issue in the next few years, allowing us to properly calibrate the metallicity diagnostics against fully Te-based abundance determination at high redshifts and providing the key to overcome all these potential discrepancies.
Citation: Masters et al. 2014
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In an effort to understand the character of RG encounters with ICM shocks and the observable consequences, we have initiated an MHD simulation study of such interactions. The simulations include passive, but energy-dependent transport of CRe, so that resulting radio synchrotron properties can be modeled appropriately. Nolting et al. (2019a, 2019b) explored interactions between ICM-strength shocks and lobed RGs. Here, we extend that work to include such shock interactions with so-called “narrow-angle tail” (NAT) RGs. NATs, which are especially common in clusters, (e.g., Blanton et al. 2001; Garon et al. 2019) result from sustained relative motion between an RG and its ambient ICM; that is, the RG effectively evolves in a wind that deflects the RG jets and their discharge downwind. The NATs can extend multiple hundreds of kpc from their AGN sources, and, so long as the AGN jets remain “powered on,” simulations suggest that NAT tails remain dynamic and highly inhomogeneous (O’Neill et al. 2019). Their considerable lengths and elongated morphologies make them interesting candidates to supply CRe at ICM shocks to form radio relics. We refer readers to O’Neill et al. (2019) and references therein for details of NAT formation dynamics. We do provide in Section 2 an outline of salient features of the simulated NAT presented in O’Neill et al. (2019) that are especially relevant to the present work. Our focus in this paper is on the interactions of shocks with such a previously formed NAT. Specifically, we use new three-dimensional (3D) MHD simulations to see what happens when plane shocks moving transverse to the NAT major axis collide with the NAT. That geometry is both relatively simple, and, on the face of it, perhaps the best able to form a radio relic in such a manner. Our study includes cases with shock Mach numbers, 





, in order to span the range of shock strengths most often mentioned in this context. As in the aforementioned studies, we carry out synthetic, frequency-dependent radio synchrotron observations of our simulated objects in order to better understand the relationships between their dynamical and observable properties.
Citation: Garon et al. 2019
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The galaxy merging process can cause enhanced accretion onto the central SMBHs and thus initiate activity. One or both of the dual SMBHs may be active or re-activated. Simulations (e.g., Van Wassenhove et al. 2012) suggest that simultaneous activity is mostly expected at the late phases of mergers, at or below 10 kpc scale separations. Additionally, the recent work of Fu et al. (2015b) indicates that mergers trigger and tend to synchronize activity at separations of a few kiloparsecs. Therefore dual AGNs are expected to be observed, but they are not easily resolvable with current observing facilities. The number of convincing dual AGN systems, mostly detected by X-ray and radio observations (e.g., Beswick et al. 2001; Junkkarinen et al. 2001; Komossa et al. 2003; Hudson et al. 2006; Bianchi et al. 2008; Fu et al. 2011b; Koss et al. 2011, 2012; Mazzarella et al. 2012; Liu et al. 2013; Comerford et al. 2015; Müller-Sánchez et al. 2015), are relatively few compared to the theoretically predicted abundance (see also, Komossa & Zensus 2016). While very long baseline interferometric (VLBI) radio observations currently provide the highest spatial resolutions, making them a promising tool for the detection of dual AGNs6

6
In fact, thanks to its superior resolution, the first binary AGN was discovered using VLBI technique (Rodriguez et al. 2006).
, only about 10% of AGNs are radio-loud, therefore dual radio-emitting active nuclei would be quite rare. Moreover, when trying to confirm the existence of dual AGNs in candidate sources, non-detection in the radio bands does not immediately falsify the dual AGN hypothesis, because radio-quiet nuclei may also be present. Burke-Spolaor (2011) searched the archival VLBI observations of 3114 radio-emitting AGNs for sources containing compact double sources. Only one source (B3 0402+379) was found with a double nucleus with separation of about 7 pc, which was already known from the observations of Rodriguez et al. (2006).
Citation: Mazzarella et al. 2012
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As a first approximation, we consider that most part of the accretion luminosity is emitted in the soft X-ray spectrum (10 eV–10 keV), thus, soft X-ray luminosity is simply estimated by using the mass accretion parameter, $\dot{m}$(1)$$\begin{eqnarray*}
L_{\rm AC}= \frac{GM\dot{m}}{R},
\end{eqnarray*}$$where M and R are the mass and radius of the object, respectively, which can be either a white dwarf, neutron star, or black hole. Mass–radius relation is employed to estimate radius in case of white dwarfs and neutron stars (see e.g. Barstow 1991, 1993; Lopes & Menezes 2012; Berti 2013; Carvalho, Marinho & Malheiro 2018; de Santi & Santarelli 2019; Carvalho et al. 2020), and Schwarzschild radius is taken for black holes. We reinforce that the model above is only a way to estimate the X-ray flux produced by compact objects due to accretion. The accretion rate, $\dot{m}$, is the parameter which defines the luminosity for a given system. However, in this work, we will not study any particular object, instead we will take fiducial values for mass and radius of the compact object along with standard values for snow line distances to estimate the time-scales ices need to reach chemical equilibrium. So, the model does not define if the compact object is isolated or in a binary system. We assume that accretion rate, $\dot{m}$, is constant on time, which means that the systems we are studying are well behaved, not presenting any sudden infall of matter, bursts, substantial outflows, or strong winds. The main aim, as stated, is to obtain an estimate of the time-scales for ices to reach chemical equilibrium. The assumption of constant accretion rate is feasible in most cases because the time-scale for ices close to compact systems to reach chemical equilibrium is smaller than the time-scale for changes on mass, as one can notice from power-law parametrizations (Chen et al. 2019), where we see that $\dot{m}$ scales with Myr or Gyr, while the time-scales for chemical equilibrium are at most 0.1 Myr for distances smaller than 100 LY, as we are going to show.
Citation: Carvalho et al. 2020
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Once we have the completeness corrections, we can estimate the relative luminosity function of SNe Ia, which we show in Fig. 3. In the left panel we show the observed distribution of absolute magnitudes. The black histogram shows the full sample, and the red histogram shows the volume-limited sample; the dot--dashed blue histogram shows the distribution of the volume-limited LOSS sample (Li et al. 2011b). The volume-limited samples have a higher fraction of low-luminosity SNe Ia than the full magnitude-limited sample. We convert the ASAS-SN distributions into estimates of the true luminosity function using the V/Vmax method (Schmidt 1968; Huchra & Sargent 1973; Felten 1976). For each SN, we compute the maximum volume (Vmax) in which the SN could be recovered by a survey with a limiting magnitude mV = 16.8. This is an empirical limiting magnitude; this value produces a median value of V/Vmax close to 0.5, which is to be expected if sources uniformly populate the survey volume. We compute the relative luminosity function for each bin in absolute magnitude centred on M as 
(2)
\begin{eqnarray*}
\Phi (M) = \sum _{i=1}^{N} \frac{1}{V_{M,i}} \times w_i \times (1+z_i), 
\end{eqnarray*}
where the sum is over all the SNe within the bin. The weights $w$i correct for the incompleteness given the apparent peak magnitude of each SN, and the factor of (1 + $z$) accounts for time dilation. The results are shown in the right panel of Fig. 3. The black circles show the relative luminosity function computed from the full sample, the red squares show the results for the volume-limited sample, and the blue crosses show the control-time weighted counts from Li et al. (2011b). The luminosity functions are normalized to the bin at MV = −19. In this paper we are not aiming for an absolute rate calibration. The shape of the relative luminosity function is consistent with the volume-limited luminosity function presented in Li et al. (2011b). We fit a Schechter (1976) function 
(3)
\begin{eqnarray*}
\phi (L) \propto \left(\frac{L}{L_*}\right)^{\alpha } \exp \left(-\frac{L}{L_*}\right) 
\end{eqnarray*}
to the relative luminosity function of both the full and volume-limited samples, where α is the faint-end slope, and L* (alternatively M* in magnitude space) determines the ‘knee’ of luminosity function. Our fits are shown in Fig. 3 as dashed lines. We find (α, M*) corresponding to (1.3 ± 0.4, −18.1 ± 0.1) and (2.1 ± 0.3, −17.8 ± 0.1) for the full sample and the volume-limited sample, respectively.
Citation: Huchra & Sargent 1973
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The downsizing scenario is evident in several cases of galaxy evolution (Fontanot et al. 2009). In the case of ETGs at z ~ 0, one of the first pieces of observational evidence can be referred to the studies of Dressler et al. (1987), Faber et al. (1992) and Worthey et al. (1992), who found more massive elliptical galaxies to be more enriched in α-elements than less massive ones. These works suggested selective mass-losses, different initial mass functions (IMF) and/or different star-formation timescales as possible explanations for the high level of [α/Fe]. Subsequent studies found the same trend of [α/Fe] with mass (Carollo et al. e.g 1993; Davies et al. 1993; Bender et al. 1993; Thomas et al. 2005; 2010; McDermid et al. 2015), leading to the dominant interpretation that in more massive ETGs, the duration of star formation was substantially shorter than in less massive ones, with timescales short enough (e.g. 0.5 Gyr) to avoid the dilution of the α element abundance (produced by Type II supernovae) by the onset of Fe production by Type Ia supernovae. This is considered to be one of the main pieces of evidence for the shortening of star formation. The age of the ETG stellar populations at z ~ 0 also show evidence of downsizing, with more massive objects being older than less massive ones. These results have been derived both in clusters (Thomas et al. 2005, 2010; Nelan et al. 2005) and in the field (Heavens et al. 2004; Jimenez et al. 2007; Panter et al. 2007; see also Renzini 2006). Most of these studies are based on fitting individual spectral features with the Lick/IDS index approach (Burstein et al. 1984; Worthey et al. 1994) which allows us to mitigate the problem of the age-metallicity degeneracy (Graves & Schiavon 2008; Thomas et al. 2005, 2010; Johansson et al. 2012a; Worthey et al. 2013). However, more recently, other approaches based on the full-spectrum fitting have been developed (e.g. STARLIGHT, Cid Fernandes et al. 2005; VESPA, Tojeiro et al. 2009, 2013, and FIREFLY, Wilkinson et al. 2015), and applied to samples of ETGs at z ~ 0  (Jimenez et al. 2007; Conroy et al. 2014; McDermid et al. 2015). The results based on Lick indices are in general quite consistent with those of full spectral fitting within 10−30% (e.g. Conroy et al. 2014) and support the downsizing evolutionary pattern.
Citation: Davies et al. 1993
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In stars, there are two components to describe the tidal interaction, equilibrium tides and dynamical tides. Equilibrium tides correspond to a large-scale hydrostatic adjustment of a body and the resulting flow due to the gravitational field of a given companion (Zahn 1966; Remus et al. 2012). It is usually employed in the framework of the constant time lag model (see Mignard 1979; Hut 1981; Eggleton et al. 1998; Bolmont et al. 2011, 2012), which allows a fast computation of the orbital evolution of the planet and works for all eccentricities (Hut 1981; Leconte et al. 2010). In this model, the dissipation of the kinetic energy of the equilibrium tide inside the star is often taken to be constant throughout the system evolution and calibrated on observations (Hansen 2010, 2012). While considering such a constant equilibrium tide dissipation is a sensible assumption, several studies have shown that this quantity might vary during the different phases of stellar evolution. For example, Zahn & Bouchet (1989) showed that the dissipation of the equilibrium tide by the turbulent friction in the convective envelope of late-type stars is strongest during their PMS. Using this theoretical framework, Villaver & Livio (2009, see also Verbunt & Phinney 1995 recalled that the variation of the semi-major axis of a planet induced by such friction can be expressed as a function of the ratio of the mass of the convective envelope to the total mass of the star, the ratio between the radius of the star and the orbital semi-major axis (to the power 8), and finally of a power of the ratio between the tidal period and the convective turnover timescale. This allows the loss of efficiency of tidal friction to be modelled for rapid tides (e.g. Zahn 1966; Goldreich & Keeley 1977). Because of the variations of these quantities during post-MS phases (e.g. Charbonnel et al. 2017), this could lead to a more efficient dissipation than during the MS. Finally, Mathis et al. (2016) demonstrated that the action of rotation on convection deeply modifies the turbulent friction it applies on the equilibrium tide. In the regime of fast rotation, which corresponds to the end of PMS and early MS phase, the friction is several orders of magnitude lower than in a model ignoring rotation. This may lead to a loss of efficiency of the dissipation of the equilibrium tide. This shows that care should be taken when assuming a calibrated constant dissipation of the equilibrium tide during the evolution of stars.
Citation: Hansen 2010
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Using these quasar survey data, Clowes et al. (2013), Nadathur (2013), Einasto et al. (2014), and Park et al. (2015) found very large quasar groups and discussed the cosmological implications of the existence and properties of these extreme objects. Nadathur (2013), Einasto et al. (2014), and Park et al. (2015) pointed out that the cosmological interpretation by Clowes et al. (2013) of large quasar groups, which questions the validity of the cosmological assumption of homogeneity and isotropy, is misleading. They stressed the importance of a statistically precise analysis in order to draw conclusions on cosmological implications from the observation of one or a few extreme objects. Park et al. (2015) also emphasized that statistical comparison with cosmological simulations must be employed as well. The quasar survey data are also used for studies to constrain cosmological parameters (Han & Park 2015; Risaliti & Lusso 2015). Besides the studies directly related to cosmology, there are more studies exploring the clustering properties of quasars. Einasto et al. (2014) made a catalog of quasar groups with different linking lengths and examined their properties. They found that the characteristics of quasar groups such as number density, size, and richness, identified with linking lengths varying from 20 to 40 h−1 Mpc, are well correlated with those of galaxy superclusters. Therefore such quasar groups can be markers of galaxy superclusters. As a classical way to study clustering properties, correlation functions have been measured for quasars (AGNs in general) by many different groups (Shen et al. 2007b, 2009, 2013; Ross et al. 2009; Krumpe et al. 2010, 2012, 2015; Miyaji et al. 2011; Cappelluti et al. 2012; Richardson et al. 2012; Allevato et al. 2014; Eftekharzadeh et al. 2015). They have measured two-point cross-correlation functions (2PCCFs) between quasars and galaxies, and have found the typical mass of quasar-hosting dark matter halos (DMHs) and the dependence of the mass on quasar luminosity.
Citation: Risaliti & Lusso 2015
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