adsabs/FOCAL huggingface dataset:
The deconvolution of large galaxy survey images requires that the spatial variation of the point spread function (PSF) across the field of view is taken into account. The PSF field is usually estimated beforehand through parametric models and simulations as in Krist et al. (2011) or is directly estimated from the (noisy) observations of stars in the field of view (Bertin 2011; Kuijken et al. 2015; Zuntz et al. 2018; Mboula et al. 2016; Schmitz et al. 2020). Even when the PSF is known perfectly, this ill-posed deconvolution problem is challenging, in particular because of the size of the image that is to be processed. Starck et al. (2000) proposed an object-oriented deconvolution that consists of first detecting galaxies and then deconvolving each object independently, taking the PSF at the position of the center of the galaxy into account (but not the variation in the PSF field at the galaxy scale). Following this idea, Farrens et al. (2017) introduced a space-variant deconvolution approach for galaxy images that is based on two regularization strategies: using either a sparse prior in a transformed domain (Starck et al. 2015a), or trying to learn without supervision a low-dimensional subspace for galaxy representation using a low-rank prior on the recovered galaxy images. When a sufficient number of galaxies were processed jointly (more than 1000), the authors found that the low-rank approach provided significantly lower ellipticity errors than sparsity. This illustrates the importance of learning adequate representations for galaxies. To proceed in learning, supervised deep-learning techniques that use databases of galaxy images might be employed to learn complex mappings that might regularize our deconvolution problem. Deep convolutional architectures have also proved to be computationally efficient in processing large numbers of images when the model has been learned. They are therefore promising in the context of modern galaxy surveys.
Citation: Starck et al. (2000)
Citation function: Background
Major differences between our approach and a full re-calculation of the hydrodynamics were not expected since the changes in the 14N and 22Ne abundances at the different metallicities do not alter the energy release in the hydrodynamic simulations significantly. The situation is different for deflagrations where the buoyancy, and therefore the Rayleigh-Taylor instabilities, depend on Ye. In contrast to detonations, the propagation of a deflagration front is thus affected by the metallicity (e.g., Meakin et al. 2009). The assumption we made here is confirmed by the comparison of the models presented in Table 1. Model M2a is taken from Gronow et al. (2020). The model was calculated at zero metallicity and has a total mass of 1.05 M⊙ with a He shell of 0.07 M⊙ at He ignition. Model M10_05_1, on the other hand, has a similar mass configuration, though it was calculated at solar metallicity (Model M10_05 in Gronow et al. 2021). Model M2a_pp is the same model as Model M2a, but the postprocessing step was calculated with solar metallicity instead of zero metallicity. An inspection of the abundances of Models M2a_pp and M10_05_1 at t = 100 s after He detonation ignition shows that the results of the postprocessing step with varying metallicities are in reasonably good agreement with a full re-calculation of the hydrodynamic model. The maximum difference in the yields produced in the core detonation is only 10%, while the maximum difference is 50% in the He detonation (excluding 12C in both). However, differences in the yields produced in the He detonation can in part be attributed to the slightly different setups of Model M2a (and therefore Model M2a_pp) and Model M10_05_1 at the beginning of the relaxation simulation, with the differences in the total and shell masses being less than 1% (see Gronow et al. 2021 for an explanation of the difference). Generally, the contribution of the yields from the He detonation to the total nucleosynthetic yields are small compared to those of the core detonation. Our approach is thus sufficient to derive nucleosynthetic yields for GCE studies. It saves significant computational costs as additional 3D hydrodynamical simulations of the explosion do not need to be carried out. Nevertheless, there might be slight differences visible in the observables because they are sensitive to the products of the He shell detonation (Höflich et al. 1996; Nugent et al. 1997; Kromer et al. 2010).
Citation: Gronow et al. 2021
Citation function: Similarities; Differences; Similarities
According to the Dst index reconstructed by Love, Hayakawa & Cliver (2019), the interval of the telegraphic glitches taking place between ∼13:35 ut and ∼17:20 ut corresponds to the storm main phase (Dst ∼ −320 nT to ∼ −570 nT). This interval also corresponds to that of the low-latitude aurorae witnessed at many points at ±40° MLAT. A large-amplitude of the GIC is induced by magnetospheric and/or ionospheric current system. One possible cause of the telegraphic disturbance is the storm-time ring current that developed between ∼11:40 ut and ∼17:40 ut. Kappenman (2004) has shown that the magnitude of GICs flowing in the Japanese power grid increases with the magnitude of the Dst index. Another possible cause is the substorm–current wedge system that consists of field-aligned current and the tail current (McPherron, Russell & Aubry 1973). Downward field-aligned current is connected to the dawnside ionosphere, and upward field-aligned current is connected to the duskside ionosphere. The pair of field-aligned currents causes magnetic disturbances at mid- and low- latitudes (Pytte, Mcpherron & Kokubun 1976). The magnetic disturbance recorded at Tokyo (Fig. 5) shows a decrease in the H-component and a positive excursion of the D-component during the interval of ∼22–23 LT (∼13–14 ut). It is probable that Tokyo would be located at southwest of the upward field-aligned current during this interval. The D-component variation shows a few negative excursions during ∼25:40–30:00 LT (∼16:40–21:00 ut). Although the disturbance of the H-component is unavailable during this interval, it can be speculated that Tokyo was located at southeast of the downward field-aligned current. In addition to the development of the ring current, the formation of the substorm current wedge may also cause the telegraphic disruption. By considering the above discussion, at mid-latitude, we suggest that there are two regions where GICs can be caused by field-aligned currents. One is southwest of the upward field-aligned current, and the other is southeast of the downward field-aligned current. In these regions, the H-component of the magnetic field is expected to decrease significantly because of the combination of the effects of the ring current and the current wedge. Tokyo was probably situated in such hazardous regions during the 25 September 1909 storm.
Citation: McPherron, Russell & Aubry 1973
Citation function: Uses; Uses
The dynamical interaction with a companion is proposed to be the driving force behind most features seen in transition discs including the formations of dust traps. For our RC-TDs, van der Marel et al. (2015a, 2016a, 2018) showed gas cavities inside dust cavities for SR21, HD135344B, DoAr44, J1604, Sz111, J16083070. van der Plas et al. (2019) utilized SPH and radiative transfer codes to show some disc features seen in HD100453 can be attributed to an undetected, low mass close companion within the disc’s cavity. The study of HD100453 is further refined by Gonzalez et al. (2020) and Nealon et al. (2020), who show that while the outer disc morphology can be caused by a companion star on an inclined orbit exterior to the disc, the inner cavity can be explained by a $\rm \lesssim 5$ MJ planet, less massive than previously suggested (van der Plas et al. 2019), at 15–20 au. Using similar 1D radial brightness profiles for the majority of our sources (HD135344B, RY Lup, J1608, Sz111, SR24S, and DoAr44), Pinilla et al. (2017, 2018) suggest that the clearing of the inner cavity could be attributed to the dynamical interaction with an embedded planet. For HD169142, Fedele et al. (2017) uses a thermo-chemical code to model the gas and dust distribution. Their results suggest that dynamical interaction between the disc and two giant embedded planets results in the depletion of the inner disc and creates two pressure bumps that aid in the trapping of dust at each observable ring position. It still remains unclear for the majority of transition discs if a companion is indeed responsible for the formation of the cavity, whether this companion is an embedded planet or a binary star. What is notable about our sample is that for the RC-TDs the 8.8 mm and sub-mm grains share a similar cavity size ($\rm R_{peak}$ value). This is also seen in SR24S and HD142527 (included in Fig. 4). Pinilla et al. (2019) present a planet-disc model for SR24S that predicts both mm and sub-mm grains will share a similar radial peak in the dust density. Price et al. (2018) extensively modelled HD142527 with 3D hydrodynamical simulations considering several possible orbits for the M-dwarf binary companion presented in Lacour et al. (2016). They conclude that all the observable disc features can be attributed to the tidal truncation of the disc from the binary companion. Given that our RC-TDs and HD142527 follow the one-to-one correlation shown in Fig. 4, we suggest similar physical mechanisms affecting the grain evolution for these discs may have occurred.
Citation: van der Plas et al. 2019
Citation function: Differences; Differences
Ideally, however, one would want to go beyond the description of cosmic global history, and trace galaxy evolution on a galaxy-by-galaxy basis to understand the physical processes driving it. In this respect, great progress has been made by surveys at different redshifts that have established the existence of a strong dependence of galaxy histories on galaxy stellar mass. On average, more massive galaxies have formed their stars and completed their star formation activity at higher z than less massive galaxies (the so-called downsizing effect, Cowie et al. 1996; Gavazzi et al. 2006; De Lucia et al. 2007; Sánchez-Blázquez et al. 2009). The existence of relations between SFR and galaxy stellar mass (SFR–Mass) and specific star formation rate and mass (sSFR = SFR/Mass) have been established from z = 0 out to z > 2 (Brinchmann et al. 2004; Daddi et al. 2007; Noeske et al. 2007; Salim et al. 2007; Rodighiero et al. 2011; Whitaker et al. 2012; Sobral et al. 2014; Speagle et al. 2014), and many other galaxy properties have been found to be correlated with galaxy mass. Furthermore, a number of works have pointed out that galaxy properties are even more strongly correlated with a combination of galaxy mass and galaxy ‘size’, arguing for velocity dispersion (Bernardi et al. 2003; Franx et al. 2008; Smith, Lucey & Hudson 2009; Wake, van Dokkum & Franx 2012) or galaxy surface mass density (Brinchmann et al. 2004; Kauffmann et al. 2006) as principal drivers. The exact origin of these trends is still unknown, but evidence has accumulated for a dependence of galaxy stellar population ages on galaxy sizes at fixed mass (van der Wel et al. 2009; Cappellari et al. 2012; Poggianti et al. 2013), suggesting that also galaxy structure, and not just stellar mass, is relevant. In a recent paper, Omand, Balogh & Poggianti (2014) argue that the observed correlation of the quenched fraction with M/R1.5 is related to the dominance of the bulge component with respect to the disc, suggesting it might ultimately be linked with galaxy morphology (see also Driver et al. 2013). Even the sSFR–Mass relation might be due to the increase of the bulge mass fractions with galaxy stellar mass, as the ratio of SFR and stellar mass of the galaxy disc is virtually independent of total stellar mass (Abramson et al. 2014).
Citation: Brinchmann et al. 2004
Citation function: Background; Background; Background
Ultra-fast outflows (UFOs) of highly ionised gas observed at sub-parsec scales (Reeves et al. 2003; Tombesi et al. 2012) have been proposed as the likely origin of galaxy-wide outflows, interpreted as the result of the impact of UFOs on the ISM (King & Pounds 2015, and references therein). Furthermore, both models and observations of kiloparsec-scale outflows seem to indicate a UFO-ISM interaction in an energy-conserving regime, whereby the swept-up gas expands adiabatically. So far, the co-existence of a massive molecular outflow with a nuclear UFO has been confirmed in a handful of AGNs with LBol  ∼  1044 − 1046 erg s−1 (Tombesi et al. 2015; Feruglio et al. 2015; Longinotti et al. 2015) and in APM 08279+5255 (Feruglio et al. 2017), which is a gravitationally lensed QSO at z  ∼  4 with an estimated intrinsic LBol of a few times 1047 erg s−1 (Saturni et al. 2018). In all these sources the momentum boost (i.e. the momentum flux of the wind normalised to the AGN radiative momentum output, LBol/c) of the UFO is ∼1, while the momentum rate of the molecular outflow is usually ≫1, in qualitative agreement with the theoretical predictions for an energy-conserving expansion (Faucher-Giguère & Quataert 2012; Costa et al. 2014). However, these results are still limited to a very small sample and suffer from large observational uncertainties, mostly due to the relatively low signal-to-noise ratio of the UFO- or outflow-related features confirmed in spectra, or to the limited spatial resolution of sub-millimetre observations. Recent studies increasing the statistics of sources with detection of molecular outflows have widened the range of measured energetics (e.g. García-Burillo et al. 2014; Veilleux et al. 2017; Feruglio et al. 2017; Brusa et al. 2018; Barcos-Muñoz et al. 2018; Fluetsch et al. 2019). These outflows are consistent with driving mechanisms alternative to the energy-conserving expansion, such as direct radiation pressure onto the host-galaxy ISM (e.g. Ishibashi & Fabian 2014; Ishibashi et al. 2018; Costa et al. 2018).
Citation: Feruglio et al. 2017
Citation function: Background; Background; Background
This additional heating effect would raise the temperature of the inflowing gases to a level where they cannot drive star formation effectively and begin to evaporate. We may use the virial theorem to estimate the time-scale over which filamentary inflows may halted in this manner: the virial temperature is the temperature above which gravitational collapse of gas is halted and, presumably, any heating to temperatures above this level would lead to evaporation. If assuming inflows persist over filaments of lengths of up to 50 kpc (Dekel et al. 2009; Stewart et al. 2013; Goerdt & Ceverino 2015; Dayal & Ferrara 2018) and that they are the sole driver of the star-formation activity arising at a rate of $\mathcal {R}_{\rm SF} \approx 16~\text{M}_{\odot }~\text{yr}^{-1}$ with a 30 per cent mass conversion efficiency (Meier, Turner & Beck 2002; Turner et al. 2015; Behroozi & Silk 2015; Sun & Furlanetto 2016) with an inflow velocity of 400 km s−1 (from the velocity offset of the Lyman-α line in MACS1149-JD1 – see Hashimoto et al. 2018), the steady-state mass of these inflows would be around 6.7 × 107 M⊙. If the typical diameter of these flows is similar to the galaxy which they feed, i.e. 1 kpc, this would give a virial temperature of Tvir ≈ 5000 K (Binney & Tremaine 2008). If adopting a number density of 10 cm−3 for the filamentary inflows (i.e. comparable to the mean density of the ISM in the host galaxy), the estimated CR heating rate of 10−25erg cm−3 s−1 would suggest it would take of order only a few Myrs for the virial temperature of the inflows to be exceeded. At this point, the supply of gas to the galaxy would be strangulated, halting star-formation within a dynamical time-scale τdyn (being the time required for the system to respond to the strangulation and internal heating). Since the strangulation and ISM quenching time-scales are comparatively short, the magnetic saturation and dynamical time-scales alone specify the time-scale over which star-formation would be quenched.
Citation: Stewart et al. 2013
Citation function: Uses; Uses
To confirm the importance of VO, water and an inversion layer (Evans et al. 2018; Mikal-Evans et al. 2019, 2020) obtained repeated HST observations of the transmission spectrum and the secondary eclipse using the STIS and WFC 3 instruments. The optical transmission spectrum displays rich variation, with multiple features consistent with VO absorption that Evans et al. (2018) could reproduce by assuming an isothermal T-P profile at 1500 K and a metallicity equivalent to 10× to 30× solar. Absorption bands of TiO appeared to be muted in the transmission spectrum, which was explained by Evans et al. (2018) as evidence of condensation of Ti-bearing species, which commences at higher temperatures than condensation of V-bearing species, producing for example, calcium titanates (Lodders 2002) while VO remains in the gas phase. Mikal-Evans et al. (2019) observed the day side emission spectrum with the G102 grism of WFC3 (0.8–1.1 μm), augmenting their earlier observations with the G141 grism. The G102 spectrum does not show the VO bands expected to be present there, and this led Mikal-Evans et al. (2019) to question the interpretation that the 1.2 μm feature is caused by VO emission. The secondary eclipse was observed at 2 μm (Kovács & Kovács 2019) and at optical wavelengths with the TESS instrument. These were analysed together with the preceding Hubble, Spitzer, and ground-based observations to yield tighter constraints on the atmospheric structure, composition and overall system parameters (Bourrier et al. 2020a; Daylan et al. 2019). These studies found that the hottest point on the day side exceeds a temperature of 3000 K, that the atmosphere is inverted on the day side, and a metallicity that is consistent with solar (Bourrier et al. 2020a) or slightly elevated (Daylan et al. 2019). Although the chemical retrievals follow different strategies (equilibriumversus free-chemistry), both indicate that a depletion of TiO relative to VO is needed to explain the observed emission spectrum, supporting the earlier findings by Mikal-Evans et al. (2019). Recently, Mikal-Evans et al. (2020) obtained new secondary-eclipse observations using the G141 grism of WFC3. Although confirming the presence of emission by H2O, a joint analysis with their previous WFC3 observations did not reproduce the emission feature at 1.2 μm, prompting the authors to entirely discard their previous interpretation of emission caused by VO.
Citation: Mikal-Evans et al. (2019)
Citation function: Background
Citation: Mikal-Evans et al. (2019)
Citation function: Compare/Contrast; Compare/Contrast
MAXI J1820 is a BHT that was observed for the first time in the optical band by the All-Sky Automated Search for SuperNovae ASSAS-SN (Shappee et al. 2014) on 2018 March 3 (Tucker et al. 2018), and one week later by MAXI in X-rays (Kawamuro et al. 2018). Detailed studies of the optical counterpart revealed that the system hosts a stellar-mass black hole (∼8.5 M⊙) accreting from a ∼0.4 M⊙ companion star (Torres et al. 2019, 2020). Since its discovery, the source has undergone a long (approximately one year) and bright outburst, becoming at its peak the second brightest object in the X-ray sky. Due to its brightness, the system was the object of an impressive multi-wavelength observing campaign (see, e.g., Shidatsu et al. 2018; Paice et al. 2019; Hoang et al. 2019; Trushkin et al. 2018; Bright et al. 2020; Tetarenko et al. 2021) and of a large number of studies. The most recent and precise measure of the distance, determined via radio parallax, is 3.0 ± 0.3 kpc (Atri et al. 2020). Furthermore, the system shows X-ray dips (Kajava et al. 2019) but not eclipses, suggesting an inclination between 60° and 80°. Other evidence of the high inclination of the system are provided by optical spectroscopy (Torres et al. 2019) and by the estimate of the inclination of the jet axis (Atri et al. 2020; Wood et al. 2021), which is about 63°. The orbital period of the system has also been estimated to be around 0.68 days (Patterson et al. 2018; Torres et al. 2020). In X-rays, the outburst was studied in detail in HS (see, e.g., Bharali et al. 2019; Buisson et al. 2019; Zdziarski et al. 2021), SS (see, e.g., Fabian et al. 2020) and in its final phase (see, e.g., Xu et al. 2020). The truncation of the disk during the HS is one of the most controversial aspects of the system. On the one hand, a number of spectral-timing works have pointed out that the disk reaches the ISCO already in HS, while a contracting lamppost corona is responsible for the hard X-ray emission (Kara et al. 2019; Buisson et al. 2019; You et al. 2021; Wang et al. 2021). On the other hand, a truncated disk scenario has also been proposed on the basis of further spectral-timing analyses, even on the same sets of data (Zdziarski et al. 2021; De Marco et al. 2021; Axelsson & Veledina 2021).
Citation: Paice et al. 2019
Citation function: Motivation; Motivation
In the modelling, it is assumed that the low-energy peak (from radio to optical–UV) is due to synchrotron emission from ultrarelativistic electrons in the jet with an energy distribution as given by equation (2). Instead, the HE peak is due to the IC scattering of internal (SSC; Ghisellini et al. 1985; Maraschi et al. 1992; Bloom & Marscher 1996) or external photons (EIC; Sikora et al. 1994; Błażejowski et al. 2000; Ghisellini & Tavecchio 2009). The IC scattering of external photons is considered, since the SEDs of FSRQS are better explained by EIC, as shown by the previous studies (e.g. Abeysekara et al. 2015; Ahnen et al. 2015; Hayashida et al. 2015b; Gasparyan et al. 2018; MAGIC Collaboration 2018), and the CD is evident in the SEDs of the considered sources (Fig. 6). Localization of the emission region in the jet is an open question and along the jet, depending on the distance from the central black hole, different photon fields can be dominant for the IC scattering (Sikora et al. 2009). In this paper, we assume that the emitting region is outside the broad-line region (BLR) where the dominant photon field is the IR emission from the dusty torus. Sikora et al. (2002) showed that in MeV blazar SEDs the shift of the peak of the HE component to lower energies is most likely due to the Comptonization of IR photons from the dusty torus. The IR radiation from the dusty torus is assumed to have a blackbody spectrum with a luminosity of LIR = 0.6 Ldisc (see Ahnen et al. 2015) where Ldisc is the accretion disc luminosity, which fills a volume that for simplicity is approximated as a spherical shell with a radius of RIR = 2.5 × 1018 (Ld/1045)1/2 cm (Nenkova et al. 2008) with the energy density of $u_{\rm IR}=0.6\:L_{\rm d}/4 \pi R_{\rm IR}^2\:\delta ^2$ in the co-moving frame of the jet. In Ghisellini et al. (2011) and Marcotulli et al. (2017), the HE component in the SED of distant blazars was modelled by IC scattering of BLR reflected photons, adopting a smooth broken power-law shape of the emitting electrons. We refer the reader to these papers for details on the modelling when BLR reflected photons are considered.
Citation: Ahnen et al. 2015
Citation function: Uses; Uses
Citation: Ahnen et al. 2015
Citation function: Uses