adsabs/WIESP2022-NER huggingface dataset:
Paper: 2017A&A...599A.132L (fulltext)
mode of HDO at 1475 cm is not clearly visible as a result of the signal-to-noise (S/N) level. The bending mode is at least four times weaker than the stretching mode, which is not detectable for the S/N achieved here ( Oba et al. 2014 ). This means that the produced OD radicals either form DO or abstract an H-atom from CH. The availability of D atoms on the surface results in the barrierless deuteration of a CH radical. Since the D atoms are abundant and diffuse quickly, other radical-radical reactions are prevented. The CHOD or CH yields lie below the sensitivity of our RAIRS technique, that is, reactions R7 and R8 are not relevant here. Note that the abstraction reaction between HO and CH has a barrier of K ( Aguilera-Iparraguirre et al. 2008 ), and we therefore exclude any CH radical production via this route. Furthermore, none of the control experiments (numbers 2–4) resulted in the detection of CHD. This means that the CHD detected in experiment 1 is not the cause of contamination (follows from experiment 2) nor the result of H-abstraction from CH by D atoms directly (follows from control experiments 3 and 4). In other words, in our experimental setup, the reaction between CH and the D atom does not proceed within our experimental sensitivity. Since the same setup is used for experiments 1, 3, and 4, essentially for identical conditions, we conclude that the reaction CH + OD is more efficient and the only one responsible for the formation of the observed CHD. This result can be rationalized by realizing that the reaction CH + H CH + H has a high barrier of 69407545 K ( Nyman et al. 2007 ; Corchado et al. 2009 ), making it highly unlikely to be competitive at the low temperatures considered here, even if it were to occur via tunneling. Indeed, the (bimolecular) rate constants calculated on several PES at 300 K are six orders of magnitude lower than the bimolecular rate constants calculated here for CH + OH (compare Corchado et al. 2009 ; Espinosa-García et al. 2009 ; and Li et al. 2013 with values mentioned in Appendix A ). The next question is whether or not the isotope-substituted reaction R5, CD + OH CD + HDO, leads to D-abstraction by OH radicals. In this case, the mass of the atom that is transferred is twice as high, the activation energy is also higher due to a ZPE effect, and if tunneling is important, the reaction rate should drop significantly. In Fig. 3 , and especially from the zoomed-in spectra in Fig. 4 , it is clear that no detectable amounts of CDH are produced during experiment 5. Since OH radicals are present, HO is formed and can be seen at its respective peak positions, around 3315, 2835, and 1385 cm ( Oba et al. 2014 ). Furthermore, the OH radicals that are produced are not being used for reactions with CD and therefore are available for other reactions, leading to the formation and detection of the HO bending mode at 1630 cm, while the stretching mode overlaps with that of HO. HO can also be formed via H + HO HO +
Paper: 2019ApJ...881..108J (fulltext)
), and it has a mass accretion rate of about 10 −9 M ⊙ yr −1 (Hartmann et al. 1998 ). The outer edge of the dust disk inferred from continuum emission is at ∼150 au (Piétu et al. 2007 ; Isella et al. 2012 ). The dust mass estimated from 1.3 mm continuum observation is about 5 × 10 −4 M ⊙ (Isella et al. 2012 ). Recent images of scattered light suggest a warped inner disk component inside the inner gap, providing clear picture details of the inner gap region of the LkCa 15 disk (Thalmann et al. 2015 , 2016 ; Oh et al. 2016 ). As a young star, LkCa 15 is a luminous source of X-ray and extreme ultraviolet (EUV) emission (Skinner Güdel 2013 ), indicating that the LkCa 15 disk could still be undergoing the active evolution phase of disk physics and chemistry. Consequently, the protoplanetary disk of LkCa 15 has been found to be especially chemically rich and has been detected in several molecular transitions (Thi et al. 2004 ; Piétu et al. 2007 ; Chapillon et al. 2008 ; Öberg et al. 2010 ; Punzi et al. 2015 ). Molecular line emission shows that the gas disk around LkCa 15 is the size of ∼900 au (Piétu et al. 2007 ; Isella et al. 2012 ). It is highly optically thick in the emission of 12 CO but is optically thin in 13 CO emission (Punzi et al. 2015 ; van der Marel et al. 2015 ). The discrepancy between the outer disk radii shown in the dust continuum and molecular line emissions (∼150 au versus 900 au) suggests that the mm-size dust is depleted in the outer part of the LkCa 15 disk, which is consistent with dust drifting and trapping models (Birnstiel et al. 2010 ; Pinilla et al. 2012 ). Being a protoplanetary disk that may have a young planet candidate, the LkCa 15 system serves as a unique laboratory to study the dust evolution models under planet–disk interaction (Zhu et al. 2011 ; Pinilla et al. 2012 ). The distribution of dust and gas in the LkCa 15 disk provides an important constraint on theoretic models. Here, we fit the gas and dust surface density profiles based on the high-resolution dust continuum image and CO 3–2 line maps obtained from the ALMA. We study how the goodness-of-fit changes along with different key parameters used in the disk density profile, which is related with different physics. Our disk model and the parameter grid is described in Section 3 . In Section 4 , we show the best-fit model with respect to the observed 12 CO image. We discuss the dependence of the parameters in Section 5 . 2. Observation The LkCa 15 was observed on 2014 August 17 and 29 with ALMA Band 7 (345 GHz, 880 μ m) in ALMA program 2012.1.00870.S (PI Pérez, L. M.). The 12 CO, 13 CO, and C 18 O 3–2 line maps and 0.87 mm dust continuum image were taken with two different tunings. The 12 CO 3–2 data were obtained with a spectral window centered on 345.796 GHz with 1885 channels of 122.06 kHz (0.106 km s −1 ) channel width. The angular resolution of the 12 CO image is 036 × 023 (50 au × 32 au). The 13 CO 3–2 data were centered on 330.588 GHz, with 1967
Paper: 2018ApJ...863...96Y (fulltext)
Si iv . Solid contours represent and 1.04. The dotted contour represents T b = 6500 K. An animation of the observations is available. The animation runs from 14:19 to 14:54 UT on 2017 April 29. (An animation of this figure is available.) Panel (b) shows the distribution of the relative brightness in the ALMA 100 GHz data defined aswhereis a temporally averaged brightness over the entire observed period (Δ t ≈ 1 hr). The ALMA 100 GHz relative brightness and its corresponding animation (panel b) show a dynamic thorn-like structure coming from the saw-tooth patterns on the limb. Because these structures show dynamic motion with elongation and shortening, hereafter we call them ALMA jets. Their length reaches at least 8′′, suggesting jet-like activity in the ALMA microwave range. Unfortunately owing to the insufficient signal-to-noise ratio in the data beyond the limb particularly in the area more than 10′′ beyond the limb (see Section 4 ), we can not recognize the maximum height of the elongated jets. The speed of the elongation is 30–40 km s −1 . The width of each jet is less than the spatial resolution of the observation, i.e., less than ≈2′′. The IRIS /SJI Mg ii images (panel d) clearly show the appearance of spicules on the limb. Some of the spicular jets reach more than 20′′ beyond the Mg ii limb. It is noteworthy that the spicular jets show clustered structures, i.e., multiple needle-like features display a collective up-and-down motion. Each needle-like structure has a width less than 1′′ and each cluster has a few to several needle-like structures. In comparison with the ALMA data (contours in panel d), the ALMA jets are in good agreement with the IRIS jet clusters. The IRIS Mg ii limb (panel d) is ≈5′′ below the ALMA limb. Again, this confirms the distribution of cool chromospheric plasmas between the IRIS Mg ii and ALMA limbs (For an IRIS limb analysis, see Alissandrakis et al. 2018 ). In the IRIS /SJI Si data (panel f), one can observe the activities on the solar surface inside the limb. Some of them correspond to the footpoints of the Mg ii spicules. The AIA 304 Å data (panel e) has a low signal-to-noise ratio and is difficult to extract information on jet activities. In one of the tall jets in IRIS Mg ii , an ALMA blob ejection was found. From Figure 2 , one can find the trajectory of the blob co-located with the Mg ii jet. The brightness enhancement in the ALMA images is by 135 K beyond the background (Figure 3 ). The blob shows a systematic proper motion at a speed of 40 km s −1 (panel c), which is similar to the IRIS jet speed (panel e). There are no significant features in the IRIS Si or the AIA data sets co-located with this blob event. However, by the careful inspection of the IRIS Si data, we found short (≈a few arcseconds) elongated structures at the base of this event. They show shifting from east to west changing its inclination angle. Figure 2. ALMA blob-ejection event associated with a tall IRIS Mg ii jet. (a) Brightness
Paper: 2018A&A...615A..93W (fulltext)
, and references therein) also been explained as a possible delayed effect (not perfectly stable thermohaline circulation) of the deglaciation in the carbon cycle (e.g., Muscheler et al. 2004 ). However, as we show here, this explanation is unlikely for two reasons. More details of the long-term relation between the series are shown in Fig. 9 , where we plot the pairwise wavelet coherence between the modulation potential (shown in Fig. 12 ) from the three long series. Panel a shows that the EDML series is coherent with the 14 C series at all timescales shorter than ≈2000 yr and again (but insignificantly) longer than 4000 yr, while no coherence exists between 2000 and 4000 yr. The GRIP-based series (panel b) is well coherent with the 14 C one on timescales longer than 100–200 yr, and the coherence disappears at timescales longer than 2000–3000 yr. The two 10 Be are hardly coherent with each other on timescales longer than 1000 yr (panel c), with a small insignificant isle of coherence beyond the cone of influence. It is noteworthy that each of the 10 Be series exhibits a higher coherence with the 14 C one than with each other. A similar conclusion was made by Usoskin et al. (2009) using different 10 Be data series. A reason for this discrepancy is yet to be discovered. Since the reason for this discrepancy is unknown, we did not correct for it. In the following we apply fixed coefficients for 10 Be series, thus keeping the long-term variability as it exists in the original data. It is interesting that while the coherence between EDML- and 14 C-based reconstructions has been improved compared to the coherence between the raw data series ( Fig. 4 ), the coherence is degraded for the GRIP series (panels b) in timescales longer than 2000 yr. This suggests that beryllium may be better mixed for Greenland than was derived through the applied beryllium transport parametrization based on Heikkilä et al. (2009) . The reconstruction based on the 14 C series has no residual correlation with VADM ( R 2 0.01). A new full-size model of the atmospheric transport and deposition of 10 Be in polar regions, particularly in Greenland, is needed to resolve the issue. 4.4 Reconstructions from individual series Two beryllium series, GRIP and EDML, were used here for a preliminary assessment of this method for their overlap. The mean modulation potential for the period 6800 BC–700 AD based on radiocarbon is ⟨ φ 14C ⟩ = 0.468 GV. First, we scaled each 10 Be series individually with a free scaling factor κ 0 and reconstructed the series of φ . The values of κ 0 were defined such that the mean value ⟨ φ 10Be ⟩ is equal to that for 14 C for the same period. The scaling factor we found for the GRIP data is close to unity, κ 0 = 1.1. This implies that 14 C and 10 Be data are fully consistent in the framework of the model, and that our modeling of the cosmogenic isotope production and transport or deposition is appropriate. The best-fit scaling factor for EDML is κ 0 = 0.8,
Paper: 2018MNRAS.474.1482P (fulltext)
may have a significant impact on dynamical processes that remain poorly known, such as star formation in molecular clouds, dissolution of open clusters in galactic tidal fields, tidal heating of thin discs, etc. Crucially, our results open up the possibility to test the existence of planet-sized microhaloes via experiments that are sensitive to tidal force fluctuations induced by dark matter substructures, e.g. by measuring the heating rate of weakly bound gravitational systems in different regions of the stellar halo, as well as in the dwarf spheroidal galaxies of the Milky Way (see also Peñarrubia et al. 2010 ). This type of experiments may also constrain a wide range of cosmological theories where dark matter is made of ‘warm’ particles or ULAs (see Section 4.2 ). The mathematical technique explored in this paper provides a computationally efficient tool to model the gravitational perturbations induced by an arbitrarily large number of CDM microhaloes. In follow-up contributions, we plan to run numerical experiments that follow the trajectories of tracer particles in smooth galactic potentials that incorporate the force and tidal distributions derived in Sections 2 and 3 as external stochastic fields. Such codes may provide a useful tool to model observational data (e.g. the separation function of wide binaries, see Section 4.3 ) at a low computational cost. Finally, it is worth stressing that our statistical method can also be used to describe stochastic fluctuations in the force and tidal fields generated by baryonic substructures covering a wide range of mass and sizes, such as GMCs, MACHOs, black holes, stellar clusters, individual stars, planetoids, etc., which may have several applications in areas other than cosmology. APPENDIX A: THE LOCAL APPROXIMATION In Sections 2 and 3 , we derive the distributions and , respectively, under the assumption that the number density of substructures remains constant across the entire system, and that corresponds to the value measured at the galactocentric location of the tracer particle, . Although the local approximation greatly simplifies analytical derivations 1 of the Fourier transform , in general it fails on scales r ≳ d , where d = |∇ n / n | −1 is the distance associated with the spatial variation of the number density profile ( 61 ) The fact that γ 1 in cosmological simulation of structure formation implies that the scalelength d decreases towards the centre of the potential, suggesting that the local approximation may not be valid at small galactocentric radii. The second scale of relevance corresponds to the average separation between substructures, D ( R ). In Section 2 , we found that the large-force fluctuations generated by non-overlapping subhalo populations are dominated by the nearest substructure, which is typically located at a distance D ( R ) ≈ [2π n ( R )] − 1/3 . Hence, the local approximation is justified for d ≫ D , that is when the number density profile varies on
Paper: 2020A&A...644A..65B (fulltext)
steps; we therefore estimate the above convergence to be sufficient. Convergence is however not fully reached in the line wings within the allocated computing time. Development of efficient acceleration methods would be desirable for future work. Fig. 2. Convergence of the linear polarization rate Q / I , for the D 2 line ( left ) and for the D 1 line ( right ) at line center ( upper row ) and in the line far wing ( lower row ). Fig. 3. Convergence of the emerging linear polarization Q / I : evolution of the step increment Δ( Q / I ) as a function of the step number N . The aim is to show that the step increment decreases more rapidly than the inverse of the step number 1/ N (as for a Riemann series). In this respect, their ratio is the upper plot and the logarithm of their ratio is the lower plot, which also includes linear fits and their equations. The two terms of the Q / I ratio, namely the Stokes parameters Q and I , each nevertheless converge much less quickly, in such a way that they are not at all converged within the 166 iteration steps. However, the behavior of the ratio Q / I appears to be different, because some simplifications certainly occur when forming the ratio. 4. Concluding discussion Although the calculation seems reasonably converged in the line wings, the agreement between the observed and computed profiles remains only qualitative. As described below, we investigated the different possible causes of this difference. We questioned the accuracy of collision rate calculations, in particular those with hydrogen neutral atoms that determine the coherent scattering weight in PRD, and therefore in the far wings. We artificially varied these rates, but the Na I D 2 wing profile was not improved with respect to observations. We questioned the model electron density, whose determination is very indirect from observations, and in light of the recent investigation by Bommier (2020) , who suggests that the electron density at the solar surface would be much higher than in present models, and similar to the neutral hydrogen atom density. We artificially varied the model electron density, but again the Na I D 2 wing profile was not improved with respect to observations. We questioned the accuracy of our model of Rayleigh scattering on neutral hydrogen atoms, which is responsible for the continuum below spectral lines, which is of more relative importance in their wings. Our model is taken from the MALIP code for computing the Stokes parameter profiles of magnetoactive Fraunhofer lines by Landi Degl’Innocenti (1976) , and we did not try to modify it. We questioned the very rough HOLMUL approximation ( Holweger Mueller 1974 ) we applied to our atmosphere model. This approximation consists in not considering atmosphere higher than the temperature minimum. The temperature reversal there may be responsible for a central bump in the line profile, following a well-known result for a two-level atom in LTE. As our model considers only the
Paper: 2020MNRAS.492.3728B (fulltext)
agreement with the numbers published by Hassan et al. ( 2017 ) (∼50 sources in 5 h and in 10 000 deg 2 ), while it is intermediate (but broadly consistent, considering the large uncertainties) between the expectations discussed by Padovani Giommi ( 2015 ) (100–160 BL Lacs expected) and the values estimated by De Franco et al. ( 2017 ) (24 detections). The predictions by Hassan et al. ( 2017 ) are extrapolated by the Fermi -LAT (3FHL) catalogue and, therefore, they consider only the blazars currently detected by Fermi -LAT. In our work, we are considering also Fermi -LAT undetected objects but, as discussed above, the expected detections in 5 h exposure times (3 objects) are all present in current Fermi -LAT catalogue (FL8Y). This means that current predictions for a (shallow) CTA extragalactic survey based on Fermi -LAT catalogue should be reliable while, for deeper pointing, the current Fermi -LAT catalogues could miss up to 50 per cent of objects. In the very close future e-ROSITA (extended ROentgen Survey with an Imaging Telescope Array, Merloni et al. 2012 ) will survey the entire sky, reaching in the soft X-ray band (0.5–2 keV) a flux 100 times fainter than the ROSAT All Sky SURVEY (RASS) data and with an on-axis spatial resolution of ∼15 arcsec. A cross-match of the point sources detected by e-ROSITA with radio catalogues as the NVSS or the Sydney University Molonglo Sky Survey (SUMSS) will provide virtually all the expected ∼800 HBL that could be detected by CTA. 8 SUMMARY AND CONCLUSIONS We have presented a well-defined and representative sample of HBL selected from the REX survey that was obtained by cross-matching radio (NVSS) and X-ray data ( ROSAT -PSPC pointed data). In particular, we selected all the REX with an X-ray-to-radio flux ratio typical of an HBL and falling in a well-defined area of sky covering about 560 deg 2 . We then completed the spectroscopic follow-up of all these sources and we focused on the 46 sources showing no emission lines in the optical spectrum. We called these source Te-REX, standing for TeV-emitting REX candidates, since HBL are the most promising sources to be detected at TeV energies. Out of these 46 sources, 25 have a clear non-thermal nucleus detected in the optical spectrum as a significant reduction of the Ca ii break (40 per cent). In the remaining 21 Te-REX sources, instead, we measured a Ca ii break value above 40 per cent, i.e. the non-thermal nucleus is swamped by the stellar light. We called these 21 sources PEGs (for ‘PEGs’). We expect that most PEGs should be faint HBL nuclei dominated by the host galaxy light. We then evaluated the intensity of the VHE emission of all the 46 Te-REX. To this end, we compare the predicted SEDs with the sensitivity curves of current and future Cherenkov telescopes. Considering deep, pointed observations of 50 h, we found 14 Te-REX (2.5 objects per 100 deg 2 , corresponding to ∼800 objects on the entire extragalactic sky above ∣ b ∣ ≥ 10°) that could be
Paper: 2016A&A...596A..91H (fulltext)
of the largest angular scale being exceeded can be seen around zero velocity. It is important to be prudent when dealing with such data, as the potential for misinterpretation is significant. For instance, erroneously assuming a spherically symmetrical outflow for a source which is intrinsically EDE-like, or has both a radial outflow and an EDE-like component, may result in serious deviations on the estimations of the physical properties of the system. This has been shown by e.g. Homan et al. (2015) . The authors outline and quantify the uncertainties related to a misinterpretation of embedded spiral shapes in stellar winds. Their conclusions on the uncertainties, related to falsely interpreting the emission from a narrow spiral (which is effectively a kind of equatorial density enhancement) as originating from a simple spherically outflowing stellar wind, are also applicable here. 6.2. ALMA Using CASA we have simulated ALMA observations of the Keplerian disk model with a bipolar outflow. Since the considered radiative transfer model has no substructure, there is no reason to explore the effect of angular resolution. Its effect will only be of importance if the aim is to properly resolve the inner EDE, the edges of the EDE or the EDE-wind boundary. We have opted to show the effect of exceeding the chosen configuration’s largest angular scale (LAS), determined by the shortest baseline of the interferometer, on the emission distribution in the PV diagrams of the Keplerian disk model with a bipolar outflow. Table 5 The ALMA observation simulation specifications. A synthetic observation is shown in Fig. 23 , for which the main simobserve parameters are presented in Table 5 . To obtain the results in Fig. 23 we have simulated an observation with the most compact of the extended configurations, C36-1. This configuration has an angular resolution of 1.5 and a largest angular scale of 11. To properly show the effect of a decent observation, we have rescaled the pixel size to artificially place the object at the minimal distance for no EDE flux to be lost. Morphologically, the intrinsic emission and the emission in Fig. 23 are very similar, as expected. The sheer number of antennae available for cycle3 ensures even for modest integration times a decent filling of the UV-plane. The high inclination models show that even though the signature of the EDE is barely unaltered, the bipolar wind emission has exceeded the LAS of the antenna configuration around zero velocity. Some of the flux of the wind is thus lost. Because our models are confined to a numerical region, and bipolar outflows are not expected to exhibit such abrupt edges, this effect is expected to be more pronounced in real physical objects. Fig. 25 Synthetic ALMA observation simulation of the Keplerian disk model (with a bipolar outflow) with the C36-1 antenna configuration (, ), for which the original model has been rescaled to a size 18 times greater than it was in Fig. 23 . The effect