adsabs/FOCAL huggingface dataset:
Type II supernovae (SNe II) are believed to originate from the core collapse of massive stars with initial masses larger than 8 M⊙ (Heger et al. 2003). They are characterized by prominent P-Cygni profiles of Balmer series in their spectra (Filippenko 1997). Photometrically, they are classified as SNe IIP if their light curves show extended plateau features (∼100 d), and SNe IIL if their light curves display post-peak linear declines (Barbon, Ciatti & Rosino 1979). Such a two-type classification is favoured by some statistical studies of SNe II (e.g. Faran et al. 2014a, b). However, Anderson et al. (2014) pointed out that if the sample is sufficiently large, one will find that SNe IIP and SNe IIL belong to a continuous distribution. Such a distribution is believed to be related to the mass of the hydrogen envelope maintained by the progenitor stars, as evidenced by the results that SNe having larger envelope masses produce light curves with shallower plateau slopes and longer plateau durations (Barbon et al. 1979; Swartz, Wheeler & Harkness 1991; Blinnikov & Bartunov 1993). In spite of the variety of envelope masses, the initial masses of the progenitor stars of SNe II are restricted to a certain range. Stellar evolution theory predicts an upper limit of 25 M⊙ for SN-II progenitors (Heger et al. 2003). Based on analyses of pre-explosion images (e.g. Smartt 2009), the progenitors of most SNe II are found to be red supergiants (RSGs), but their masses lie in a narrow range (i.e. ∼9–17 M⊙). This inconsistency is known as the ‘RSG problem’ and can be partially explained by the ‘failed SNe’ theory (Lovegrove & Woosley 2013). As SNe II can also be used to determine distances, thus they are intriguing to the cosmology community. The measurement methods include the Expanding Photosphere Method (EPM; Kirshner & Kwan 1974; Hamuy 2001) and the Standard Candle Method (SCM; Hamuy & Pinto 2002). The basic idea of EPM is to derive the intrinsic luminosity from the photospheric radius and the temperature, and then compare the intrinsic luminosity with the apparent value to obtain the distance, while the SCM is based on the correlation between the expansion velocity and the luminosity at a specific epoch.
Citation: Swartz, Wheeler & Harkness 1991
Citation function: Motivation
With regard to Ni isotopes in the metal phase of iron meteorites, multiple studies have analyzed samples belonging to the same iron groups (e.g., IIAB, IIIAB, IVA, IVB) using broadly similar techniques (i.e., wet chemical separation of Ni followed by mass spectrometry). The initial studies reported no nucleosynthetic anomalies (Cook et al. 2006; Quitté et al. 2006). As analytical precision improved, anomalies were reported in some subsequent studies (e.g., Bizzarro et al. 2007; Regelous et al. 2008; Steele et al. 2011) but not in others (e.g., Dauphas et al. 2008; Chen et al. 2009), and no clear picture has emerged. Moreover, the interpretation of Ni isotopic data is hampered by the omission of data for 64Ni, the least abundant Ni isotope, from multiple studies. For Fe isotopes, initial studies pointed to a high degree of homogenization among various meteorite classes (e.g., Dauphas et al. 2008; Tang & Dauphas 2012). However, more recent studies (Cook & Schönbächler 2017; Schiller et al. 2020) have revealed small non-mass-dependent variations in Fe isotopes. A related issue, also without consensus, concerns the magnitude of the initial abundance of the radionuclide 60Fe in the early solar system. A wide variety of sample types have been analyzed in an attempt to constrain the solar system initial 60Fe/56Fe ratio including CAIs (e.g., Quitté et al. 2007), chondrules (e.g., Tachibana et al. 2006; Telus et al. 2018), chondritic metal (Cook et al. 2006), and differentiated meteorites, such as angrites and eucrites (e.g., Tang & Dauphas 2012, 2015). These studies have broadly used one of two analytical approaches: wet chemical separation of Ni followed by mass spectrometry or in situ analyses using ion microprobe (aka SIMS). Among these studies, estimates of 60Fe/56Fe span more than a factor of 100 (e.g., Quitté et al. 2007; Tang & Dauphas 2012, 2015) from ≈2 × 10−6 to ≈1 × 10−8. Determining the initial 60Fe/56Fe ratio in the protoplanetary disk is important for studies of early solar system chronology. Furthermore, radioactive decay of 60Fe may have been an important heat source on early-formed bodies, but this depends on its abundance (Kohman & Robison 1980; Yoshino et al. 2003).
Citation: Schiller et al. 2020
Citation function: Compare/Contrast; Compare/Contrast
For over a decade, a tight correlation between metallicity and galaxy stellar mass (





), i.e., the mass–metallicity relation (MZR), has been quantitatively established, from the vast database of local galaxies observed by the Sloan Digital Sky Survey (SDSS; Tremonti et al. 2004; Zahid et al. 2012; Andrews & Martini 2013). This relation has been further extended to high redshifts, using deep near-infrared (IR) spectroscopy facilitated by large ground-based and space-based telescopes (Erb et al. 2006; Maiolino et al. 2008; Zahid et al. 2011; Henry et al. 2013; Steidel et al. 2014; Sanders et al. 2015; Guo et al. 2016). The measurements of the MZR as a function of redshift can cast useful constraints on various galaxy evolution models, since the slope of the MZR is sensitive to the properties of outflows, such as the mass loading factor and the outflow speed (see, e.g., Davé et al. 2012; Lu et al. 2015a). This slope can also be explained by variations of star-formation efficiency and gas mass fraction in galaxies with different stellar masses (see, e.g., Baldry et al. 2008; Zahid et al. 2014). The normalization of the MZR can shed light upon the stellar chemical yield across cosmic time (Finlator & Davé 2008). Mannucci et al. (2010) first suggested that there exists a so-called fundamental metallicity relation (FMR) in the 3D parameter space spanned by 





, star-formation rate (SFR), and metallicity, such that the MZR is merely a 2D projection of this more fundamental 3D manifold (see also Hunt et al. 2016). This 3D scaling relation shows a tight scatter (∼0.05 dex) in metallicity and is speculated to not evolve with z. In this context, the apparent redshift evolution of the MZR normalization originates primarily from sampling the FMR in terms of galaxies with different SFR. This concept of the FMR is in accord with the gas regulator model proposed by Lilly et al. (2013), even though mergers can also play a subtle role in shaping the form of the FMR by increasing the scatter (Michel-Dansac et al. 2008). However, at high redshifts, the validity of the FMR is still under investigation (see, e.g., Wuyts et al. 2014; Sanders et al. 2015).
Citation: Henry et al. 2013
Citation function: Background
Afterglows of gamma-ray bursts (GRBs) are generally believed to be produced by a relativistic jet interacting with the surrounding medium (e.g., Mészáros & Rees 1997; Sari et al. 1998; Kumar & Zhang 2015). Very early multi-wavelength afterglows are critical to reveal the properties of the radiating fireball and its environment as well as the central engine of GRBs. Using the prompt slewing and precise locating capacity of the X-ray telescope (XRT) on board the Swift mission, very early X-ray and optical afterglows were obtained with the XRT and ground-based optical telescopes. The early X-ray afterglows are usually dominated by erratic X-ray flares and the tail emission of prompt gamma-rays are due to the arrival time delay of photons in the high latitude of the radiating fireball (Liang et al. 2006; O’Brien et al. 2006; Zhang et al. 2006, 2007a). The flares and prompt tail emission are usually not seen in the early optical afterglow data (Li et al. 2012; Wang et al. 2013). About one-third of well-sampled optical afterglow light curves show a clear smooth bump (Li et al. 2012). It may be attributed to deceleration of the fireball by the ambient medium (see Rees & Mészáros 1992; Mészáros & Rees 1993 and Sari & Piran 1999 for the thin shell case; Kobayashi et al. 1999 and Kobayashi & Zhang 2007 for the thick shell case). This may give the most robust estimate for the initial Lorentz factor (





) of the fireball since the deceleration time weakly depends on other model parameters than 





 (e.g., Molinari et al. 2007; Melandri et al. 2010; Xin et al. 2015). With a sample of GRBs with a detected optical afterglow onset bump, Liang et al. (2010) derived their 





 and found a tight 





 relation (see also a 





 relation in Lu et al. 2012). Furthermore, by incorporating the peak energy of the 





 spectrum in the burst frame (





) into the 





 relation, a tighter 





 relation is found (Liang et al. 2015). This relation places strong constraints on the composition of GRB fireballs.
Citation: O’Brien et al. 2006
Citation function: Background
Unlike the CMB, the 21 cm signal is highly non-Gaussian, because patchy, bubble-like structures of ionized hydrogen (H ii) regions are produced surrounding the ionizing sources. Thus, there is potentially a wealth of information in the 21 cm signal that is not contained in the 21 cm power spectrum, a two-point statistics of 21 cm brightness temperature fluctuations that is traditionally well studied in the literature. It is therefore essential to develop new methods that maximally exploit the full information in the 3D 21 cm images obtained by the SKA. Toward this goal, conventionally, new summary statistics that can only be measured with imaging have been proposed. These include the three-point correlation function (Hoffmann et al. 2019; Jennings et al. 2020), bispectrum (Yoshiura et al. 2015; Shimabukuro et al. 2016, 2017; Majumdar et al. 2018, 2020; Hutter et al. 2020; Saxena et al. 2020; Kamran et al. 2021), one-point statistics (Harker et al. 2009; Shimabukuro et al. 2015; Gorce et al. 2021), topological quantities such as the Minkowski functionals (Gleser et al. 2006; Chen et al. 2019; Kapahtia et al. 2021) and Betti numbers (Giri & Mellema 2021), the cross correlation between the 21 cm line and other probes, such as the CO line (Gong et al. 2011; Lidz et al. 2011), the C ii line (Gong et al. 2012; Beane & Lidz 2018), the kinetic Sunyaev–Zel’dovich (kSZ) effect (Ma et al. 2018; La Plante et al. 2020), and novel techniques such as the antisymmetric cross correlation between the 21 cm line and CO line (Zhou et al. 2021). Since those summary statistics are fully determined by the parameters in the reionization models (hereafter “reionization parameters”), in principle, Monte Carlo Markov Chain (MCMC) methods can be employed to constrain the reionization parameters from measurements of those statistics with futuristic 21 cm experiments (see, e.g., Watkinson et al. 2022), just as the MCMC analysis with the 21 cm power spectrum (Greig & Mesinger 2015, 2017, 2018).
Citation: Jennings et al. 2020
Citation function: Background
Citation: Saxena et al. 2020
Citation function: Background; Background
Globular clusters are of particular dynamical interest because of the phenomena of core collapse and binary burning. Stellar interactions in dense globular clusters tend to drive the central core towards a collapse to a state of extremely small radius and high density. Primordial binary populations may delay the onset of this core collapse by serving as dynamical energy sources, but eventually become depleted by various destruction mechanisms (e.g. Verbunt & Freire 2014), allowing core collapse to proceed (e.g. Fregeau et al. 2003, and references therein). Several studies suggest that black hole binaries, rather than main-sequence (MS) binaries, are critical for delaying core collapse (e.g. Breen & Heggie 2013; Wang et al. 2016; Kremer et al. 2019). In addition, an intermediate-mass black hole (IMBH) in a cluster core will act as a strong central energy source able to delay, or even prevent, core collapse (e.g. Baumgardt, Makino & Ebisuzaki 2004; Gill et al. 2008; Lützgendorf, Baumgardt & Kruijssen 2013). In any case, after an initial collapse, the cluster core will undergo gravothermal oscillations of expansion and contraction, as first demonstrated by Sugimoto & Bettwieser (1983), during which the core radius remains quite small. About 20–25 globular clusters, including NGC 6397 and NGC 6752, have very compact (rc ≲ 10 arcsec), high-density cores that appear to be post-collapse. The post-collapse oscillations of these cores should produce episodic bursts of strongly enhanced dynamical binary formation and ejection during the densest phases, as noted by Lugger et al. (2007). Their reasoning is based on the scaling of the encounter rate Γ, which is given by the integral of ρ2/v over the cluster volume, where ρ is spatial mass density and v is the velocity dispersion (Verbunt & Hut 1987; Bahramian et al. 2013). The encounter rate can be approximated by the simplified expression $\Gamma \propto \rho _0^2 r_c^3/v_0$ (Pooley et al. 2003), where ρ0 is central density, rc is the core radius, and v0 is the central velocity dispersion. This results in $\Gamma \propto r_c^{-1.4}$ for a simple homologous model for core collapse, in which $\rho _0 \propto r_c^{-2.2}$ and $v_0 \propto r_c^{-0.05}$ (Cohn 1980).
Citation: Baumgardt, Makino & Ebisuzaki 2004
Citation function: Background
Magnetic fields are actively searched for at the surface of all kinds of stars throughout the Hertzsprung-Russell diagram (HRD), as they probably impact stellar evolution from birth to death in various ways (see e.g., Donati & Landstreet 2009 for a general review; and Wade et al. 2016; Alecian et al. 2013; Vidotto et al. 2014; Folsom et al. 2016 for recent spectropolarimetric surveys on massive, intermediate-mass, and low-mass stars). Recently, magnetic fields have been unambiguously detected via Zeeman signatures in a large sample of single G-K giants observed with the spectropolatimeters TBL/Narval and CFHT/ESPaDOnS (Konstantinova-Antova et al. 2013; Aurière et al. 2015; Borisova et al. 2016; Tsvetkova et al. 2017). Interestingly, the cool intermediate-mass evolved stars with surface magnetic fields are found to cluster in certain regions of the HRD that correspond to precise moments of their evolution where convective envelopes make up a significant fraction of the stellar mass. These observations are of particular importance for stellar-evolution modeling, since magnetic fields may play a crucial role in the angular momentum evolution of different types of stars. For instance, it is well established that magnetic fields affect the rotation rate of solar-type stars through the torque applied to stellar surfaces by magnetically coupled stellar winds (e.g., Schatzman 1962; Matt et al. 2015; Réville et al. 2015; Amard et al. 2016). However, the efficiency and the impact of magnetic braking for evolved stars are not well studied yet. In addition, because of the angular momentum they transport (e.g., Spruit 1999; Mathis & Zahn 2005), magnetic fields may play an important role in explaining the properties of core and surface rotation in giants as seen by asteroseismology (e.g., Beck et al. 2012; Mosser et al. 2012b,a; Deheuvels et al. 2012, 2014; Cantiello et al. 2014; Di Mauro et al. 2016), as well as the rotation rate of white dwarf remnants (Suijs et al. 2008). By comparing the observed rotational and magnetic properties of stars at different evolutionary phases with the predictions of rotating stellar models, one may thus obtain strong constraints on the input physics of the stellar models. Conversely, it is important to know whether the possible presence and the global properties of the magnetic field of a given star can be anticipated from its position in the Hertzsprung-Russell diagram (see Gregory et al. 2012 for the case of pre-main sequence stars).
Citation: Konstantinova-Antova et al. 2013
Citation function: Background
The search for observational evidence of dark matter substructure in galaxies is on-going, as traditional methods for in-directly detecting dark matter sub-haloes (e.g. modelling tidal streams and gravitational lensing) have yet to agree on either the Milky Way’s or an external galaxies’ current substructure composition. Gravitational lensing allows for constraints to be placed on the dark matter substructure content of external galaxies, as orbiting sub-haloes will result in anomalies in strong gravitational lenses (Mao & Schneider 1998; Dalal & Kochanek 2002; Vegetti et al. 2012). The disruption of stellar streams by dark matter sub-haloes in the Milky Way has also been well studied (e.g. Johnston, Spergel & Haydn 2002; Ibata et al. 2002; Carlberg 2009; Erkal et al. 2016; Sanders, Bovy & Erkal 2016; Bovy, Erkal & Sanders 2017; Carlberg 2017), with gaps in stellar streams believed to be a tell-tale sign that a stream has recently encountered a sub-halo. Hence the presence of gaps in a tidal stream, or lack thereof, can be used to constrain the dark-matter substructure properties of the Milky Way (Yoon, Johnston & Hogg 2011; Carlberg 2012; Erkal & Belokurov 2015a,b; Bovy 2016; Carlberg 2016; Banik et al. 2018; Bonaca et al. 2019). However gaps in tidal streams, as well as overdensities and asymmetry, can also be produced as stars are tidally stripped from a star cluster along its orbit (Küpper et al. 2010), disc shocking (Odenkirchen et al. 2003), spiral arms (Dehnen et al. 2004), a tri-axial halo (Küpper et al. 2015), the Galactic bar (Pearson, Price-Whelan & Johnston 2017), interactions with giant molecular clouds (Amorisco et al. 2016), the stream’s progenitor cluster (Webb & Bovy 2018), and complex dynamical histories (i.e a time-dependent tidal field due to galaxy growth via mergers or accretion) (Carlberg 2018). Banik & Bovy (2018) recently studied these effects in detail for the Pal 5 stream and found that the bar and molecular clouds can each individually explain the observed structure of the Pal 5 stream. Hence new methods are required in order to help search for dark matter substructure in the Milky Way and constrain its properties.
Citation: Mao & Schneider 1998
Citation function: Motivation
This dynamical limit on planetesimal sizes could suggest that these may exist in the belt a factor of 103 larger than the ${\sim }1\,$km sized lower limit predicted by collisional replenishment. However, if the assumed α = 3.5 Dohnanyi (1969) size distribution continued up to planetesimals of this size, then the disc mass would be $M_{\rm {disc}}{\sim }220\, M_{\oplus }$, a factor of ∼3 higher than the prediction of Schüppler et al. (2016) and over an order of magnitude larger than the lower limit derived from the collisional lifetime and age of the system. This would not violate our earlier calculation since these ≫1 km planetesimals could be abundant in the disc without having collided within the age of the system. Whilst this higher total disc mass is still consistent with the dust mass measurements of protoplanetary discs (for example, see Andrews & Williams 2005; Ansdell et al. 2016; Cieza et al. 2019), high debris disc masses, i.e. those in the range of $100\!-\!1000\, M_{\oplus }$, become problematic since these would require a very high efficiency of primordial dust being incorporated into these larger planetesimals (an example of the so-called ‘disc mass problem’, see Krivov et al. 2018; Krivov & Wyatt 2021). Nevertheless, it might still be possible to explain the observed level of stirring by embedded bodies while retaining a lower disc mass (i.e. if the largest bodies are less frequent than the α = 3.5 size distribution would predict). If instead the size distribution had a slope of α = 3.7, then even with these 1200 km bodies, the total disc mass estimate would be reduced from ${\sim }220\, M_\oplus$ to ${\sim }6\, M_\oplus$, since the total number of these would be greatly reduced. On the other hand, the size distribution could be truncated, being much steeper for planetesimals larger than a few kilometres, and shallower in other regions. We estimate the effect that this can have on the derived disc mass using equation (9) of Krivov & Wyatt (2021), and find that the total mass can be reduced by an order of magnitude from ${\sim }220\, M_\oplus$ to ${\sim }17\, M_\oplus$, if based on a triple power law size distribution, with qmed = 4, qbig = 3 and q = 3.5. Alternatively the measured vertical scale height could be due to other dynamical interactions (e.g. stirring by a planet internal or external to the belt, or a recent stellar fly-by) or even be a remnant of the primordial disc (e.g. if this disc was born stirred, Booth & Clarke 2016). In summary, whilst q1 Eri at an age of ${\sim }1.4\, \rm {Gyr}$ is an outlier in terms of its brightness, it need not be an outlier in terms of its disc mass unless many much larger planetesimals are present.
Citation: Krivov et al. 2018
Citation function: Compare/Contrast; Compare/Contrast
The nonaxisymmetric potential of a bar induces large-scale streaming motions in stars and gas into the central part of the galaxy (e.g., Athanassoula 1992a, 1992b; Sellwood & Wilkinson 1993). Being dissipative, the gas loses angular momentum and energy and flows inward toward the galactic center (Knapen etÂ al. 1995; Regan etÂ al. 1999; Sheth etÂ al. 2000, 2002), accumulating in the central â¼1Â kpc of galaxies (e.g., Sakamoto etÂ al. 1999; Sheth etÂ al. 2005). The accumulation of gas in the central parts leads to high levels of circumnuclear star formation activity (SÃ©rsic & Pastoriza 1965; Hawarden etÂ al. 1986; Devereux 1987; Martin 1995; Ho etÂ al. 1997; Sheth etÂ al. 2000, 2005; Gadotti & dos Anjos 2001; Ellison etÂ al. 2011; Coelho & Gadotti 2011; Wang etÂ al. 2012); this circumnuclear star formation is often in the shape of nuclear rings (Knapen etÂ al. 2002; ComerÃ³n etÂ al. 2010; Kim etÂ al. 2012; Seo & Kim 2013) and nuclear star clusters (BÃ¶ker etÂ al. 2002, 2004, 2011). Such star formation activities may help to create disky pseudobulges (Kormendy & Kennicutt 2004; Sheth etÂ al. 2005; Athanassoula 2005; Debattista etÂ al. 2006). Bars are the primary mechanism for transporting gas from a few kiloparsec scale to the central kiloparsec. However, there have been mixed answers to the question of whether the presence of a bar and active galactic nucleus (AGN) activity are connected. Some studies find weak statistical links among AGN activity and the presence of bars (e.g., Arsenault 1989; Knapen etÂ al. 2000; Laine etÂ al. 2002; Laurikainen etÂ al. 2004a; Coelho & Gadotti 2011), whereas others find little or no link (e.g., Moles etÂ al. 1995; McLeod & Rieke 1995; Mulchaey & Regan 1997; Ho etÂ al. 1997; Hunt & Malkan 1999; Martini etÂ al. 2003; Lee etÂ al. 2012; Cisternas etÂ al. 2013). While bar torques drive gas inside the bar corotation inward, they push the gas between the corotation and outer Lindblad resonance (OLR) outward (Combes 2008; Kubryk etÂ al. 2013).
Citation: Coelho & Gadotti 2011
Citation function: Background