adsabs/FOCAL huggingface dataset:
It is not clear which mechanism is operating to accelerate electrons up to relativistic energies. It could be shock acceleration, stochastic acceleration or magnetic reconnection (see Zdziarski et al. 2014, for some discussions), or shock interaction in a magnetic reconnection site (Lazarian & Vishniac 1999; de Gouveia dal Pino & Lazarian 2005). The diffusive shock acceleration involving the first-order Fermi process is often regarded as the most effective scenario in jets. However, this process requires that electrons are pre-heated up to a value comparable to the energy of thermal ions. Fortunately, a quasi-Maxwellian electron distribution with strong coupling with protons has been found in PIC simulations of collisionless relativistic (Spitkovsky 2008; Sironi & Spitkovsky 2011) and non-relativistic (Riquelme & Spitkovsky 2011) shocks. For the current study, jets are relativistic or should be at least mildly relativistic. In fact, the low-energy tail of electrons with a thermal distribution has a relatively small contribution to the SEDs. On one hand, a sharp low-energy cutoff, 





, from which electrons can be energized, is assumed in Zdziarski et al. (2014) for the jets of black hole X-ray binaries in the low/hard state. On the other hand, a hard injection spectrum below 





, which could approximate the Maxwellian distribution, is used to model a sample of blazars (e.g., Ghisellini & Tavecchio 2009; Zhang et al. 2012). Similarly to the latter, the relativistic electrons injected in the dissipation region are considered as
4





where 





 is the break energy of relativistic electrons, and p and q are the energy spectral indices of the electrons below 





 and above 





, respectively. The normalization constant of the electrons, 





, is determined by
5





where 





 is the accretion power of the system via Roche lobe outflows of the companion star. Here, 





 is the mass accretion rate. The power of relativistic electrons, 





, accounts for a fraction of the jet power of 





. We further consider 





 to be 0.1 and 





 an adjustable parameter. 





 (assuming to be 1) and 





 are minimum and maximum energies of the relativistic electron, respectively.
Citation: Spitkovsky 2008
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In this work, we use APOGEE calibrated atmospheric parameters and chemical abundances from the Sloan Digital Sky Survey IV (SDSS-IV; Gunn et al. 2006; Blanton et al. 2017) Data Release 14 (DR14; Abolfathi et al. 2017). The APOGEE target selection is described in Zasowski et al. (2013) and data reduction is described in Nidever et al. (2015). The atmospheric parameters and chemical abundances are determined using the APOGEE Stellar Parameters and Chemical Abundances Pipeline (ASPCAP; García Pérez et al. 2016). ASPCAP uses the code ferre (Allende Prieto et al. 2006) in combination with grids of normalized stellar synthetic spectra (see Zamora et al. 2015), as created with extensive atomic and molecular linelists (Shetrone et al. 2015), to simultaneously determine Teff, log g, [M/H], [α/M], [C/M], [N/M], and microturbulance through χ2 minimization. During this process, ASPCAP fits for the overall abundance of metals [M/H] and the relative abundance of α-elements [α/M], using O, Mg, Si, S, Ca, and Ti; the relative abundances of non-α elements (except for C and N) are set to solar ratios when inferring [M/H]. The measurements of both [M/H] and [α/M] are dominated by different elements in different temperature regimes. The abundances of the individual elements are then determined by fitting specific spectral windows containing relevant absorption lines while varying the corresponding family of elements (Holtzman et al. 2015, in preparation). The DR14 abundances have been internally calibrated to remove Teff correlations in open clusters, similar to the corrections to DR12 described in Holtzman et al. (2015); see Holtzman (in preparation) for a description of the DR14 calibrations. The APOGEE team has found that the metallicity parameter [M/H] closely correlates with the [Fe/H] measurement (Holtzman et al. 2015, in preparation). In this paper, we will assume that the ASPCAP measurements of [M/H] and [α/M] can be taken as proxies from [Fe/H] and [α/Fe], and therefore compared to literature results and theoretical models for these ratios.
Citation: García Pérez et al. 2016
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In this context, MWC 758 (HD 36112) offers a unique environment to probe the existence of planetary companions and to explore the connection between disk structures and planet formation. MWC 758 is a young stellar object (3.5 ± 2 Myr, Meeus et al. 2012) at a distance of 151
$^{+9}_{-8}$




151

−9

+8



4




 pc (Gaia Collaboration 2016) close to the edge of the Taurus star forming region (stellar properties are given in Table 1). Measurements of resolved CO emission around the star determined the stellar mass to be 2.0 ± 0.2 M⊙ and the disk to have an inclination of 21° ± 2° and a position angle of the semi-major axis of 65° ± 7° (Isella et al. 2010). The mass and age estimates were based on the previously adopted hipparcos distances of 200 pc (van den Ancker et al. 1998) and 279 pc (van Leeuwen 2007). Given the revised Gaia distance, the star could be older and lighter than previously thought. In this paper, we assume a stellar mass of 1.5 ±0.2 M⊙, reflecting the scaling of the dynamical mass estimate to the new Gaia distance. Based on its SED, MWC 758 has been classified as a pre-transition disk (Grady et al. 2013). Although a cavity of 55 astronomical units (au) in radius has been inferred from dust millimeter emission (Andrews et al. 2011), infrared polarized intensity observations have found no clear evidence for a cavity in scattered light (Grady et al. 2013; Benisty et al. 2015). Using Ks-band (2.15 μm) direct imaging andH-band (1.65 μm) polarimetric imaging with the High-Contrast Instrument with Adaptive Optics (HiCIAO) at the Subaru Telescope, Grady et al. (2013) detected two spiral arms and polarized light down to 0.′′ 1 (15 au) from the star. Recent VLT Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) observations in the Y band (1.04 μm) have confirmed the presence of scattered light at least down to 14 au (Benisty et al. 2015). The asymmetries observed by Isella et al. (2010) in the mm-dust distribution and in CO emission suggest that the disk may be gravitationally perturbed by a low-mass companion orbiting within a radius of 23 au (assuming a distance of 151 pc). The asymmetric cm-dust distribution was shown to follow the location of the mm-dust (Marino et al. 2015a), hinting towards the hypothesis of a dust trap, which could also be created by a companion in the gap through the Rossby wave instability (e.g., Pinilla et al. 2012b). Hydrodynamical simulations of the disk indicate that the observed spirals could instead be launched by a massive planet or brown dwarf at larger separations (~ 100 au based on the revised Gaia distance, Dong et al. 2015b). The presence of stellar companions down to a mass limit of 12 MJup at 0.′′ 25 and of planets outside 0.′′5 (5 MJup at 0.′′ 5, and 3 MJup at 1′′ , according to the BT-SETTL models; Allard et al. 2012) has been ruled out based on a combination of sparse aperture masking observations at L′ band and angular differential imaging at K′ and Ks bands (Grady et al. 2013).
Citation: Grady et al. 2013
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The core/cusp problem is a clear example of this controversy: on the one hand, cosmological dark matter only N-body simulations predict cuspy dark halo density profiles; on the other hand, the rotation curves of low surface brightness disc and gas-rich dwarf galaxies favour shallower or cored dark matter density distributions (de Blok 2010 and references therein). Also for dSphs, for which the determination of the dark matter density distribution is more difficult, there are indications that cored dark matter density profiles may be favoured with respect to cuspy profiles (Kleyna et al. 2003; Goerdt et al. 2006, Battaglia et al. 2008; Walker & Peñarrubia 2011; Salucci et al. 2012; Amorisco, Agnello & Evans 2013; Zhu et al. 2016), though this finding is still debated (Richardson & Fairbairn 2014; Strigari, Frenk & White 2017). It must be stressed, however, that cored dark haloes in dSphs do not necessarily imply a failure of ΛCDM: dark matter only cosmological simulations may not reliably predict the present-day dark matter distribution in dSphs because, by definition, they neglect the effects of baryons on the dark haloes. Even in a galaxy that is everywhere dark matter dominated today, baryons must have been locally dominant in the past to permit star formation. Therefore, the effect of baryon physics on the dark halo is expected to be important also in dSphs. For instance, Nipoti & Binney (2015) showed how, due to the fragmentation of a disc in cuspy dark halo, dynamical friction may cause the halo to flatten the original cusp into a core even before the formation of the first stars (see also El-Zant, Shlosman & Hoffman 2001; Mo & Mao 2004; Goerdt et al. 2010; Cole, Dehnen & Wilkinson 2011; Arca-Sedda & Capuzzo-Dolcetta 2017). Moreover, the results of hydrodynamical simulations suggest that, following star formation, supernova feedback can also help to flatten the central dark matter distribution, by expelling the gas (Navarro, Eke & Frenk 1996a; Read & Gilmore 2005) and thus inducing rapid fluctuations in the gravitational potential (Mashchenko, Couchman & Wadsley 2006, Pontzen & Governato 2012, Tollet et al. 2016).
Citation: Goerdt et al. 2006
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Many near-equal mass MBH mergers in the LISA band may occur in gaseous environments, given that the galactic mergers that lead to the eventual formation of an MBH binary often carry a fresh supply of gas into the post-merger galactic nucleus (see Mayer 2013 for a review). Likewise, ‘gas-embedded’ E/IMRIs may frequently occur in the accretion discs expected in active galactic nuclei (AGNs) in which an MBH is surrounded by a thin, dense accretion disc. Compact objects in the nucleus can eventually align their orbits with the disc, provided a sufficient number of disc-crossing intersections (e.g. Syer, Clarke & Rees 1991; Artymowicz et al. 1993; Artymowicz, Lin & Wampler 1993; Rauch 1995; Just et al. 2012; McKernan et al. 2012; Kennedy et al. 2016; Panamarev et al. 2018; Fabj et al. 2020; MacLeod & Lin 2020), or such events may arise from in-situ star formation in the disc that leaves compact remnants (Goodman & Tan 2004; Levin 2007). Embedded stars and BHs can subsequently accrete, migrate, and merge with each other (Bellovary et al. 2016; Secunda et al. 2019, 2020; Tagawa, Haiman & Kocsis 2020a), before eventually merging with the central MBH. While the event rate for E/IMRIs has previously been estimated in dry nuclei (e.g. Barausse, Cardoso & Pani 2015), the rate may be considerably higher when including formation pathways in accretion discs. The recent discovery of stellar-mass BH mergers by the ground based interferometer LIGO has stimulated work on such mergers that may be occurring in AGN discs, showing that they might contribute to LIGO events (McKernan et al. 2014; Bartos et al. 2017; Stone, Metzger & Haiman 2017; McKernan et al. 2018; Gröbner et al. 2020). Subsequent work has suggested that some of the LIGO events, based on their high chirp masses, may indeed have formed via this channel – large masses are expected both because of the preferential capture of heavier BHs by the disc (Yang et al. 2019b) and because repeated mergers are common and lead to hierarchical build-up (Yang et al. 2019a). The high effective spin provides additional support for this channel (Gayathri et al. 2020) as well as events with more unequal mass ratios (e.g. GW190412; see Tagawa et al. 2020b) which have been predicted to occur naturally via dynamical interactions in a dense, gaseous environment (McKernan et al. 2020; Secunda et al. 2020; Tagawa et al. 2020a). These results suggest that BH mergers indeed occur in gas discs, and that they could constitute the building blocks of IMBHs (McKernan et al. 2012; Tagawa et al. 2020a). Recent semi-analytical estimates of in-situ star formation suggest that the accretion of embedded compact objects may also contribute substantially to the growth of MBHs (Dittmann & Miller 2020).
Citation: Just et al. 2012
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The evolution of our Universe from the Cosmic Dawn (CD) and Epoch of Reionization (EoR) is not very well understood. The H i 21-cm line promises to be an excellent probe into these epochs (Furlanetto, Oh & Pierpaoli 2006a; Morales & Wyithe 2010; Pritchard & Loeb 2012). The global 21-cm experiments aim to measure the sky-averaged signature of this redshifted line, by using ground-based radio telescopes. Examples of such experiments are the Shaped Antenna measurement of the background RAdio Spectrum (SARAS; Patra et al. 2013; Singh et al. 2017), the Large-Aperture Experiment to Detect the Dark Ages (LEDA; Greenhill & Bernardi 2012), SCI-HI (Voytek et al. 2014), the Broadband Instrument for Global HydrOgen ReioNisation Signal (BIGHORNS; Sokolowski et al. 2015), and the Cosmic Twilight Polarimeter (CTP; Nhan et al. 2019). The Experiment to Detect the Global EoR Signature (EDGES; Bowman et al. 2018) has reported a possible detection of the sky-averaged H i 21-cm global signal from the CD. However, this signal has an absorption trough of about 0.5 K, which is twice the amplitude predicted by the standard model of cosmology. If confirmed, this measured signal would give us a completely new insight into the physics of the evolution of the Universe. Following this detection, several models explaining this exceedingly deep absorption trough has been explored. Barkana (2018), Fraser et al. (2018), Pospelov et al. (2018), and Slatyer & Wu (2018) had explained this with models with excess cooling from non-standard physics, including dark matter particles scattering off baryons. Fialkov, Barkana & Cohen (2018), Fraser et al. (2018), Pospelov et al. (2018), Ewall-Wice et al. (2018), and Feng & Holder (2018) have explored various possible 21-cm signals, varying the properties of the dark matter particles, in addition to varying the astrophysical parameters. Ewall-Wice et al. (2018), Feng & Holder (2018), and Fialkov & Barkana (2019) have explored models that produce an excess radio background, in addition to the cosmic radio background to explain the large amplitude of the absorption feature in the EDGES detection. This radio excess could be, for example, due to supernovae (Jana, Nath & Biermann 2019; Mirocha & Furlanetto 2019) or primordial black holes (Ewall-Wice et al. 2018).
Citation: Nhan et al. 2019
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Calculating the magnetic helicity in the corona by finite volume methods is more complicated than estimating the magnetic helicity flux through the photosphere by optical flow methods, and the significant point of the finite volume methods is how to obtain coronal magnetic fields. Cargill (2009) pointed out the difficulties in the traditional approach of using the Zeeman effect to measure coronal magnetic fields. Some researchers have attempted to explain the observations of coronal oscillations by using magnetohydrodynamic (MHD) wave models, and the magnetic field strength of coronal magnetic fields can be inferred in this process (Nakariakov et al. 1999; Tomczyk et al. 2007). Another approach involves using sophisticated numerical computations to reconstruct realistic 3D nonlinear force-free coronal magnetic field models, which need observed photospheric vector magnetograms as boundary conditions (Wiegelmann & Sakurai 2012, 2021). These coronal models include the MHD models, the magnetohydrostatics (MHS) models, the nonlinear force-free field (NLFFF) models, and the potential-field source-surface models. The force-free approach is a static model that neglects time-dependent phenomena and plasma flows, and the gradient of the plasma pressure and the gravity force in the MHS equation are also neglected as these terms are at least four orders of magnitude smaller than the magnetic pressure in the corona, so that the Lorentz force is vanishing and the electric currents are parallel/antiparallel to the magnetic field lines (Wiegelmann et al. 2017). However, whichever numerical computation method is chosen to approximate the 3D coronal magnetic field, they all have limitations. DeRosa et al. (2015) compared the influence of spatial resolution on the NLFFF model, and they found that the output of the NLFFF model depends on the spatial resolution of the input photospheric magnetograms (bottom boundary), with the values of free energy generally tending to be higher with increasing resolution, while the values of the relative magnetic helicity vary significantly with different resolutions. They also found that the results from the more highly resolved data were more self-consistent.
Citation: Wiegelmann & Sakurai; 2021
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The exciting star of the H ii region has not been clearly identified so far. According to Ortiz et al. (2007), Obj1a (B0 v) and Obj2 (O9 v) are the best candidates for ionization sources of the RCW 41 region. At 5.8 μm, the region shows a cavity at its center, surrounded by PAH emission in the PhotoDissociation Region (PDR). The Hα emission is strongest in the center of the nebula (see Fig. 1), implying that the ionizing source might be embedded within the nebula. This phenomenon has been observed in many bubbles associated with H ii regions (e.g., Deharveng et al. 2010). Thus, we believe that the exciting star must be inside the 5.8 μm cavity that surrounds the Hα emission, which excludes the Obj1a source as a potential candidate. Also Obj1a is at the extreme edge of the Hα emission, which makes it unlikely to be the ionizing candidate. To identify the probable ionizing candidates of the individual H ii regions, we then used a JHKs catalog of the region inside the cavity and searched for ionizing sources in a circular area of radius ~1.15 pc (i.e., the radius of the 5.8 μm cavity) from the center of the bubble. Using the extinction laws of Rieke & Lebofsky (1985), the observed (J − H) color and MJ-spectral type calibration table of Bessel & Brett (1988), and a distance of 1.3 kpc, we selected luminous sources that have spectral types earlier than B3 MS star. We followed the same prescription as described in Samal et al. (2010) of rejecting the most likely giants and foreground sources based on (J × [J − H]) and ([J − H] × [H − Ks]) diagrams. After these eliminations, we are left with only one massive O-type star located close to the northwestern border of 5.8 μm cavity. This source is associated with a group of stars in its close vicinity, possibly part of an exciting cluster. The source corresponds to the “Obj2” identified by Santos et al. (2012), whose spectroscopic spectral type agrees with the photometric spectral derived form our observations. From the above discussion, we conclude that the Obj2 source is the most likely ionizing star of the RCW 41 H ii region.
Citation: Deharveng et al. 2010
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Complex organic molecules (or COMs) are the building blocks of life. COMs are believed to first form on the icy mantle of dust grains (e.g., Garrod et al. 2008; Jiménez-Serra et al. 2016). Subsequently, COMs are released to the gas phase during the warm and hot phase, where icy grain mantles can be heated to high temperatures 






T


d


∼
100
–
300

K


 (e.g., Blake et al. 1987; Brown et al. 1988; Bisschop et al. 2007). COMs are increasingly observed in the environs of young stellar objects, including hot cores/corinos around high-mass/low-mass protostars and protoplanetary disks (see Herbst & van Dishoeck 2009 and van Dishoeck 2014 for recent reviews). In particular, many surveys that search for COMs toward the nearest massive star-forming regions, the Orion Becklin–Neugebauer/Kleinmann–Low object (BN/KL), have been conducted with single-dish telescopes from the ground, e.g., IRAM-30 m (Tercero et al. 2010, 2011; Cernicharo et al. 2016), in space, e.g., Herschel (Bergin et al. 2010; Crockett et al. 2014), and with interferometers, e.g., IRAM Plateau de Bure (Favre et al. 2011; Peng et al. 2012; Brouillet et al. 2013), and ALMA (Tercero et al. 2015, 2018; Favre et al. 2017; Pagani et al. 2017, 2019; Peng et al. 2017, 2019). The single-dish telescopes are unable to spatially/spectrally separate the contribution of the different sources in Orion BN/KL because of their low resolution (i.e., lines are overlapped). All constraints from those data, therefore, are manifested as uncertainties. Conversely, the extremely high spatial resolution of interferometers naturally can separate the components, which reveals the complexity of the chemical and physical structure in Orion BN/KL. Observations show the existence of large COMs with very strong binding energies, such as acetic acid (CH3COOH), ethyl formate (C2H5OCHO), propyl cyanide (C3H7CN), methyl acetate (CH3COOCH3), methoxymethanol (CH3OCH2OH), ethylene glycol (OHCH2CH2OH), etc. The sublimation temperature of these large COMs is higher than that of water, i.e., 






T


sub


≳
152


 K (see Section 2.1). However, the dust temperature estimated in Orion BN/KL is far from Tsub. This casts doubt on the popular sublimation mechanism and suggests nonthermal mechanisms that can desorb COMs within these environments.
Citation: Herbst & van Dishoeck 2009
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