adsabs/FOCAL huggingface dataset:
Although a correlation does exist, it is offset from the one-to-one line that one would expect, overestimating the number of spiral arms by approximately three. This may be due to how mass is assigned to the bulge and disc. We use photometric decompositions of Simard et al. (2011) and Mendel et al. (2014) to assign mass to the bulge and the disc. Such a model fits a classical bulge with n= 4 and an exponential disc. This may cause a systematic for two reasons. First, the photometric decomposition of galaxies may introduce a bias due to image resolution effects. The second issue is the pseudo- versus classical bulge argument – the model we use assumes an inner classical spherical bulge; bulges instead may be pseudo-bulges, which may not have a spherical shape, and profile well-described by a spherical Hernquist profile (Carollo et al. 1997; Gadotti & dos Anjos 2001; Kormendy et al. 2006; Fisher & Drory 2008; Gadotti 2009). Studying bulges and discs in detail is beyond the scope of this paper. Another possibility is that the assumption that spiral arms are measured at 2Rd may not be valid – if spiral arms were instead measured closer to the inner regions of galaxies, then this offset is negated. Unfortunately, the binary nature of visual morphological classifications, where arms either are or are not recorded, prevents further investigation of this point. Finally, there may be some spiral arms which are impossible to observe with visual morphology in the way presented in this paper. Of particular note is the case where the model predicts very high spiral arm numbers. In this case, the spiral arms may instead be wakelets which are difficult to observe visually; our observed arm number measurements may therefore be systematically low for these galaxies. Investigating which caveat, or which combination of caveats is responsible requires higher resolution imaging of galaxies than those used in this paper. Any study of this nature would be severely restricted in terms of sample size and completeness compared to the results we present in this paper.
Citation: Gadotti & dos Anjos 2001
Citation function: Compare/Contrast
In the present era of “high precision” cosmology (see Riess et al. 2016), it is important to exploit the full potential of Cepheids as precise extragalactic distance indicators for determining the expansion rate of the universe and setting constraints on cosmology models. To achieve these goals, a deeper understanding and characterization of Cepheids is needed. Recent discoveries such as circumstellar environments (Nardetto et al. 2016), infrared excesses (Mérand et al. 2015), and ultraviolet emission line variability and possible more recent X-ray emissions (Engle et al. 2014) show that some important aspects of Cepheids may not be well understood. Cepheids have also been found to show additional complications that include cycle-to-cycle variations in their light and radial velocity curves (see Evans et al. 2015b; Anderson 2016; Anderson et al. 2016; Smolec & Śniegowska 2016; Derekas et al. 2017). These newly discovered properties and time-dependent phenomena of Cepheids, unless better understood and accounted for, could place impediments on achieving the challenging goal of determining the local Hubble constant (H0) with a precision of ∼1%, as suggested by Suyu et al. (2012). Great efforts are being undertaken to achieve this level of precision, and hopefully resolve the developing “Hubble Discrepancy” (see Riess et al. 2016), where theoretical values of the Hubble constant (H0) derived via the Lambda-cold dark matter (Λ-CDM) cosmology model (Λ = the cosmological constant), including cosmic microwave background data (e.g., Planck, WMAP (Wilkinson Microwave Anisotropy Probe)), show a small (albeit statistically significant) disagreement with the value of H0  will be derived via standard candles (e.g., Cepheids, SNe Ia (type Ia Supernovae)). As discussed by Suyu et al. (2012) and more recently by Riess et al. (2016), improved measurements of H0 provide critical independent constraints on dark energy and the validity of the present Λ-CDM model.
Citation: Derekas et al. 2017
Citation function: Motivation
The ability to retrieve the polarized quantities of a radio source is entirely dependent on the ability to find radio sources within noisy images. It is of importance to planned future surveys to investigate suitable strategies for source-finding in linear polarization with interferometers such as LOFAR, which are very well suited for deep radio surveys (e.g. Hardcastle et al. 2016; Clarke et al. 2017), but are particularly technically challenging due to operation at low radio frequencies (Varenius et al. 2015), with potentially sub-arcsecond angular resolution (Moldón et al. 2015), at high sensitivity (Shimwell et al. 2016), and with the ability to make precise Faraday rotation measurements (Sotomayor-Beltran et al. 2013). Nevertheless, finding linearly polarized sources faces many hurdles: (i) at sub-arcminute resolution, the peak in linearly polarized intensity can be offset from the peak in total intensity (see e.g. fig. 1 in O'Sullivan et al. 2015), (ii) the statistics in polarized intensity, $P=\sqrt{Q^2+U^2}$, are Rician, rather than Gaussian, while all publicly available source-finders are geared towards Gaussian noise statistics, (iii) the full sensitivity is not provided in any single channel of Q, U, or P, and RM Synthesis is therefore required to retrieve the full point-source sensitivity from the data, (iv) sources detected in Q and U can have both positive and negative brightness, and these values oscillate and mix across the observing bandwidth due to Faraday rotation, and (v) in some cases, Q and U images can be more sensitive than I images, which in principle could lead to sources that can be found in P but not in I. Source-finding in circular polarization, Stokes V, is beyond the scope of this paper in which we focus on linear polarization, but also faces similar challenges due to the full sensitivity not being provided in a single channel and the process of Faraday conversion across the observing band. Moreover, the linear feeds used for observations at low radio frequencies with instruments such as LOFAR are more suitable for measuring circular rather than linear polarization, which further increases the difficulty of detecting faint linearly polarized sources.
Citation: Sotomayor-Beltran et al. 2013
Citation function: Background; Background
With photometry in hand for the majority of our galaxy spectroscopy sample, we can also investigate velocity segregation effects as a function of galaxy luminosity. We use cluster galaxy brightness measurements in units relative to m*, a standard quantity that can be easily incorporated into both observational data and simulated clusters (Cole et al. 2001; Cohen 2002; Rudnick et al. 2006, 2009). Specifically, we use m* values computed from Bruzual & Charlot (2003) models in the same fashion as described in previous SPT publications (High et al. 2010; Song et al. 2012; Bleem et al. 2015). Figure 7 shows the distribution of cluster member galaxies with brightness measurements as described in Section 2.4 plotted relative to the characteristic magnitude, m*, for the full cluster member sample as well as the subsamples of cluster members of different spectral types. We use these data, in combination with the normalized peculiar velocities of each cluster member in the ensemble to plot the expectation value for the absolute peculiar velocity of cluster members as a function of brightness for all galaxies together, as well as for each of the passive, post-starburst, and star-forming galaxy subsets (Figure 8). It is clear that the brightest galaxies—independent of spectral type—universally prefer smaller absolute peculiar velocities, and that when we treat all galaxies together we see a strong drop in the absolute peculiar velocities of galaxies brighter than 





, while galaxies fainter than this tend to remain approximately flat in absolute peculiar velocity as a function of brightness. There is no statistically significant evidence in our data for an evolution in the presence or of velocity luminosity segregation with redshift. Specifically, if we split our sample into two redshift bins at z = 0.45—which optimally balances the number of bright galaxies in the high and low bins—we see the strong drop in peculiar velocity for bright galaxies in each of the high and low-redshift bins.
Citation: High et al. 2010
Citation function: Similarities
About a quarter of the known exoplanets orbit at short distances (≲0.1 au) from their star (from the Exoplanet Encyclopaedia in December 2016; Schneider et al. 2011). Heating by the stellar energy can lead to the expansion of their upper atmospheric layers and their eventual escape. As a result of this expansion, the upper atmosphere produces a deeper absorption than the planetary disk alone when observed in the UV, in particular in the stellar Lyman-α (Ly-α) line of neutral hydrogen (e.g., Vidal-Madjar et al. 2003; Lecavelier des Etangs et al. 2012). Super-Earths and smaller planets display a large diversity in nature and composition (e.g., Seager et al. 2007; Rogers & Seager 2010; Fortney et al. 2013), which can only be investigated through observations of their atmospheres. The reduced scale height of the lower atmospheric layers makes them difficult to probe in the visible and the infrared. In contrast, very deep UV transit signatures can be produced by the upper atmospheres of small planets. The warm Neptune GJ436b, which is the lowest mass planet found evaporating to date (Ehrenreich et al. 2015), shows transit absorption depths up to 60% in the Ly-α line. The formation of such an extended exosphere is due in great part to the low mass of GJ436b and the gentle irradiation from its M-dwarf host (Bourrier et al. 2015, 2016b). Few attempts have been made to detect atmospheric escape from Earth-size planets, and Ly-α transit observations of the super-Earth 55 Cnc e (Ehrenreich et al. 2012) and HD 97658 b (Bourrier et al. 2016a) showed no evidence of hydrogen exospheres. In the case of 55 Cnc e, this non-detection hinted at the presence of a high-weight atmosphere – or the absence of an atmosphere – recently supported by the study of its brightness map in the IR (Demory et al. 2016). Understanding the conditions that can lead to the evaporation of Earth-size planets will be necessary to determine the stability of their atmospheres and their possible habitability. For example, large amounts of hydrogen in the upper atmosphere of a close-in terrestrial planet could indicate the presence of a steam envelope being photodissociated, and replenished by evaporating water oceans (Jura 2004; Léger et al. 2004).
Citation: Ehrenreich et al. 2015
Citation function: Background; Background
Galaxy formation theory has developed dramatically over the last three decades. Λ cold dark matter (ΛCDM) has been established as the standard model for cosmological structure formation, and its parameters have been increasingly tightly constrained by observations. In parallel, simulations of galaxy formation within this standard model have grown in complexity in order to treat more accurately the many baryonic processes that impact the evolution of the galaxy population. Semi-analytic modelling is a particular simulation method which is optimized to connect the observed properties of the galaxy population – abundances, scaling relations, clustering and their evolution with redshift – to the astrophysical processes that drive the formation and evolution of individual galaxies (e.g. White 1989; Cole 1991; Lacey & Silk 1991; White & Frenk 1991; Kauffmann, White & Guiderdoni 1993; Cole et al. 1994; Kauffmann et al. 1999; Somerville & Primack 1999; Springel et al. 2001, 2005; Hatton et al. 2003; Kang et al. 2005; Lu et al. 2011; Benson 2012). Simple phenomenological descriptions of the relevant processes are needed, each typically involving uncertain efficiency and scaling parameters. These must be determined by comparison with observation or with more detailed simulations. As the range and quality of observational data have increased, so has the number of processes that must be included to model them adequately, and hence the number of adjustable parameters. In recent years, robust statistical methods have been introduced in order to sample the resulting high-dimensional parameter spaces and to determine the regions that are consistent with specific observational data sets. This development began with the work of Kampakoglou, Trotta & Silk (2008) and Henriques et al. (2009) and has since been extended to a wide range of models and sampling methods (Benson & Bower 2010; Bower et al. 2010; Henriques & Thomas 2010; Lu et al. 2011, 2012; Henriques et al. 2013; Mutch, Poole & Croton 2013; Benson 2014; Ruiz et al. 2015).
Citation: Springel et al.; 2005
Citation function: Background
For the study of each of the individual reactions we have characterized the stationary points on their respective potential energy surfaces by means of density functional theory (DFT) calculations. We have employed the mPWB1K exchange and correlation functional of Zhao & Truhlar (2004) in combination with the def2-TZVP basis set (Weigend & Ahlrichs 2005). The main advantage of this functional for this investigation is that it was designed for the easy determination of activation energies. Minima and transition states (TSs) were optimized using the DL-FIND (Kästner et al. 2009) program of the ChemShell suite (Sherwood et al. 2003; Metz et al. 2014). A search of TS was done by means of potential energy surface scans and posterior optimization in cases where a kinetic barrier was predicted. Assessment of the nature of the stationary points was performed by computing the molecular Hessian of each. Additionally, we have addressed the validity of the DFT method by computing single-point calculations on the relevant DFT geometries at the CCSD(T)-F12/cc-PVTZ-F12 level of theory using Molpro 2015 (Werner et al. 2012, 2015). We have found excellent agreement between DFT and coupled cluster methods for the reaction barriers, with deviations of less than 1 kcal mol−1 in all cases. Furthermore, we have carried out intrinsic reaction coordinate (IRC) calculations to ensure a proper connection between our calculated TSs and their associated minima. For reactions with a barrier, we have computed both classical bimolecular reaction rate coefficients as well as tunneling-corrected ones. The inclusion of quantum tunneling in our calculations has been performed using semi-classical instanton theory (Rommel & Kästner 2011; Rommel et al. 2011), following a sequential cooling scheme for temperatures below the crossover temperature, and reduced instanton theory for temperatures above (McConnell & Kästner 2017). Crossover temperatures are defined—with 





 being the frequency of the vibrational imaginary mode in the TS, and kB the Boltzmann constant—as
6
Citation: Sherwood et al. 2003
Citation function: Uses; Uses
The stochastic gravitational-wave background (SGWB)—the primary goal of the search of the PTA collaborations—is expected to be dominant in the nanohertz band, which might originate from supermassive black hole binaries (SMBHBs; Rajagopal & Romani 1995; Sesana 2013), comic strings (Damour & Vilenkin 2005; Blanco-Pillado et al. 2018), the first phase transition (Caprini et al. 2010), and scalar-induced GWs (Yuan et al. 2019). Over the last few decades, the PTA collaborations have not found GW signals, but the increasingly sensitive data sets offer increasingly stringent constraints on the SGWB (van Haasteren et al. 2011; Shannon et al. 2013; Lentati et al. 2015; Shannon et al. 2015; Arzoumanian et al. 2016, 2018; Chen et al. 2020). Recently, the NANOGrav collaboration reported that there is strong evidence in favor of a stochastic common-spectrum process, which is modeled by a power-law spectrum among the pulsars, over the independent red noise processes of each pulsar, in their 12.5 yr data set (Arzoumanian et al. 2020). However, given the lack of statistically significant evidence for quadrupolar spatial correlations, it is inconclusive to claim the detection of an SGWB consistent with general relativity. Note that the tensor transverse (TT) modes giving rise to quadrupolar spatial correlations constitute only two of the six GW polarization modes that are allowed in a general metric theory of gravity, which also includes one scalar transverse (ST) mode, two vectorial longitudinal (VL) modes, and one scalar longitudinal (SL) mode. Later on, Chen et al. (2021) searched for nontensorial SGWBs in the NANOGrav 12.5 yr data set, and found strong Bayesian evidence that the common-spectrum reported by the NANOGrav collaboration had ST spatial correlations. More recently, the PPTA collaboration has also found a common-spectrum process in their second data release (DR2), with PPTA DR2 showing no significant evidence for, or against, TT spatial correlations (Goncharov et al. 2021a).
Citation: Lentati et al. 2015
Citation function: Background
Fast radio bursts (FRBs) are cosmological radio transients with millisecond durations. Since the first FRB (FRB 010724, the Lorimer burst) was discovered in 2007 (Lorimer et al. 2007), hundreds of FRB sources have been detected, dozens of which are repeaters (e.g., the CHIME/FRB Collaboration et al. 2021). Recently, a Galactic FRB, FRB 200428, was detected to be associated with SGR J1935+2154 (Bochenek et al. 2020; CHIME/FRB Collaboration et al. 2020; Mereghetti et al. 2020; Li et al. 2021a; Ridnaia et al. 2021; Tavani et al. 2021), which suggests that at least some FRBs originate from magnetars born from the core collapse of massive stars (e.g., Popov & Postnov 2013; Katz 2016; Murase et al. 2016; Beloborodov 2017; Kumar et al. 2017; Yang & Zhang 2018, 2021; Metzger et al. 2019; Lu et al. 2020; Margalit et al. 2020; Wadiasingh et al. 2020; Wang et al. 2022; Zhang 2022). However, FRB 20200120E was found to be in a globular cluster of a nearby galaxy, M81 (Bhardwaj et al. 2021; Kirsten et al. 2022). This is in tension with the scenario that invokes active magnetars with ages ≲10 kyr formed in core-collapse supernovae (Kremer et al. 2021; Lu et al. 2022) and suggests that FRBs might originate from magnetars formed in compact binary mergers (Margalit et al. 2019; Wang et al. 2020; Zhong et al. 2020; Zhao et al. 2021). Therefore, the physical origin of FRBs is still not well constrained from the data (e.g., Cordes & Chatterjee 2019; Petroff et al. 2019; Zhang 2020; Xiao et al. 2021). The growing FRB detections start to shed light on the diversity among the phenomena. The repeaters presented in the first CHIME FRB catalog have relatively larger widths and narrower bandwidths compared with one-off FRBs (Pleunis et al. 2021). The behaviors of fluence with respect to peak flux exhibit statistically significant differences between bursts with long and short durations (Li et al. 2021c). Multiple origins for the FRB population seem increasingly likely.
Citation: Yang & Zhang 2018
Citation function: Motivation
The simplest approach to handling the problem of completeness is to be extremely conservative, and discard all data in regions of parameter space where the observations are not complete or nearly so. However, this invariably requires one to discard much of the available data. A somewhat more sophisticated approach is forward modelling: rather than deriving the mass and age distribution of the population from estimates of mass age for individual clusters, one could instead consider a proposed distribution of masses and ages, predict the resulting photometry distribution including the effects of incompleteness, and adjust parameters of the mass and age distribution until they match the observations. Approaches of this type are widely used in astronomy, for example to infer star formation histories or stellar mass distributions from observed colour–magnitude diagrams (CMDs; e.g. Dolphin 2002; Harris & Zaritsky 2009; Weisz et al. 2013; Conroy & van Dokkum 2016; see Cerviño 2013 for a review). However, methods of this type have not previously been applied to deriving the properties of populations of star clusters, at least in part due a unique challenge not present in other applications. In existing applications such as CMD fitting, the forward model is deterministic, i.e. for a given stellar mass, age, and other properties, there is a single predicted colour and magnitude. This is not the case for star clusters with masses ≲ 3000 M⊙, because such clusters are too small to fully sample the stellar initial mass function (IMF, e.g. Cerviño & Luridiana 2004, 2006; da Silva, Fumagalli & Krumholz 2012). As a result, two clusters of the same total mass and age can produce wildly different luminosities and colours. This means that the forward model is not deterministic, but instead depends on an additional random variable that couples non-linearly with the deterministic variables like cluster mass and age. This situation presents computational challenges that are not addressed by existing methods.
Citation: Weisz et al. 2013
Citation function: Background
B335 is an isolated Bok globule with an embedded Class 0 protostar at a distance of 100 pc (Keene et al. 1980, 1983; Stutz et al. 2008; Olofsson & Olofsson 2009). The size of the dense core in B335 observed at millimeter wavelengths is ∼0.1 pc (Saito et al. 1999; Motte & André 2001; Shirley et al. 2002), and the core is slowly rotating (Saito et al. 1999; Yen et al. 2011; Kurono et al. 2013). Infalling and rotational motions on scales from 100 to 3000 au have been observed in molecular lines with single-dish telescopes and interferometers (Zhou et al. 1993; Choi et al. 1995; Zhou 1995; Saito et al. 1999; Evans et al. 2005, 2015; Yen et al. 2010, 2011, 2015b; Kurono et al. 2013). Nevertheless, no sign of Keplerian rotation was observed with the Atacama Large Millimeter/submillimeter Array (ALMA) at an angular resolution of 03 (30 au; Yen et al. 2015b), and the envelope rotation on a scale of 100–1000 au in B335 is an order of magnitude slower than in other Class 0 and I protostars surrounded by a Keplerian disk with a size of tens of au (Yen et al. 2015a). The presence of a small disk less than 10 au and the slow envelope rotation hints at the effects of the magnetic field on the gas kinematics in B335. In addition, ALMA observations in the C18O and H13CO+ lines show no detectable difference in the infalling velocities of neutral and ionized gas on a 100 au scale with a constraint on the upper limit of the ambipolar drift velocity of 0.3 km s−1, suggesting that the magnetic field likely remains well coupled with the matter in the inner envelope in B335 (Yen et al. 2018). The magnetic field structures on a 1000 au scale in B335 also show signs of being dragged toward the center and becoming pinched, as inferred from the ALMA polarimetric observations (Maury et al. 2018). Therefore, B335 is an excellent target to investigate the interplay between the magnetic field and gas motions and the effects of the magnetic field on the dynamics in collapsing dense cores.
Citation: Zhou et al. 1993
Citation function: Background