scholarly journals Forbidden line diagnostics of photoevaporative disc winds

2020 ◽  
Vol 496 (3) ◽  
pp. 2932-2945 ◽  
Author(s):  
G Ballabio ◽  
R D Alexander ◽  
C J Clarke
Keyword(s):  
Sound Speed ◽  
Central Star ◽  
High Energy ◽  
Emission Lines ◽  
Limiting Factor ◽  
Line Profiles ◽  
Gas Temperature ◽  
Characteristic Emission ◽  
Extreme Uv ◽  
High Sound

ABSTRACT Photoevaporation driven by high-energy radiation from the central star plays an important role in the evolution of protoplanetary discs. Photoevaporative winds have been unambiguously detected through blue-shifted emission lines, but their detailed properties remain uncertain. Here we present a new empirical approach to make observational predictions of these thermal winds, seeking to fill the gap between theory and observations. We use a self-similar model of an isothermal wind to compute line profiles of several characteristic emission lines (in particular the [Ne ii] line at 12.81 μm, and optical forbidden lines such as [O i] 6300 Å and [S ii] 4068/4076 Å), studying how the lines are affected by parameters such as the gas temperature, disc inclinations, and density profile. Our model successfully reproduces blue-shifted lines with $v_{\rm peak} \lesssim 10$ km s−1, which decrease with increasing disc inclination. The line widths increase with increasing disc inclinations and range from $\Delta v\sim 15\text{ to }30$ km s−1. The predicted blue-shifts are mostly sensitive to the gas sound speed (and therefore the temperature). The observed [Ne ii] line profiles are consistent with a thermal wind and point towards a relatively high sound speed, as expected for extreme-UV photoevaporation. However, the observed [O i] line profiles require lower temperatures, as expected in X-ray photoevaporation, and show a wider scatter that is difficult to reconcile with a single wind model; it seems likely that these lines trace different components of a multiphase wind. We also note that the spectral resolution of current observations remains an important limiting factor in these studies, and that higher resolution spectra are required if emission lines are to further our understanding of protoplanetary disc winds.

scholarly journals Emission Lines in the Far-UV and Extreme-UV Region

1997 ◽  
Vol 159 ◽  
pp. 108-115
Author(s):  
W. Zheng
Keyword(s):  
Excitation Energy ◽  
Spectral Region ◽  
High Energy ◽  
Emission Lines ◽  
Collisional Excitation ◽  
Ionized Gas ◽  
Model Calculations ◽  
X Ray ◽  
Extreme Uv ◽  
The Continuum

AbstractRecent observations with HST and HUT have been made of the spectral region shortward of Lyα in AGN. Emission lines in this region, such as O VIλ1035 and Ne VIIIλ774, are mainly produced by collisional excitation. Their strengths and the lack of other significant emission lines of higher excitation energy indicate a temperature of ~ 6 × 104 K for the highly ionized gas in line-emitting clouds. Model calculations suggest that the strength of O VI and Ne vIII emission is correlated to the intensity of the high-energy photons above 100 eV. Therefore, these lines are useful diagnostics of the continuum shape in the soft X-ray range. The luminosity dependence of emission-line equivalent widths is more prominent for lines of higher ionization level, suggesting that the UV bump in AGN spectra may be weaker at higher luminosities.

Possibility to locate the position of the H2O snowline in protoplanetary disks through spectroscopic observations

2017 ◽  
Vol 13 (S332) ◽  
pp. 113-120
Author(s):  
Shota Notsu ◽  
Hideko Nomura ◽  
Catherine Walsh ◽  
Mitsuhiko Honda ◽  
Tomoya Hirota ◽  
...  
Keyword(s):  
Protoplanetary Disks ◽  
Central Star ◽  
Velocity Profiles ◽  
Emission Lines ◽  
High Dispersion ◽  
Line Profiles ◽  
Mid Infrared ◽  
Spectroscopic Observations ◽  
T Tauri ◽  
Hot Surface

AbstractObservationally measuring the location of the H2O snowline is crucial for understanding the planetesimal and planet formation processes, and the origin of water on Earth. The velocity profiles of emission lines from protoplanetary disks are usually affected by Doppler shift due to Keplerian rotation and thermal broadening. Therefore, the velocity profiles are sensitive to the radial distribution of the line-emitting regions. In our work (Notsu et al. 2016, 2017), we found candidate water lines to locate the position of the H2O snowline through future high-dispersion spectroscopic observations. First, we calculated the chemical composition of the disks around a T Tauri star and a Herbig Ae star using chemical kinetics. We confirmed that the abundance of H2O gas is high not only in the hot midplane region inside the H2O snowline but also in the hot surface layer and the photodesorption region of the outer disk. The position of the H2O snowline in the Herbig Ae disk exists at a larger radius from the central star than that in the T Tauri disk. Second, we calculated the H2O line profiles and identified that H2O emission lines with small Einstein A coefficients (∼10−6 − 10−3 s−1) and relatively high upper state energies (∼ 1000K) are dominated by emission from the hot midplane region inside the H2O snowline, and therefore their profiles potentially contain information which can be used to locate the position of the H2O snowline. The wavelengths of the H2O lines which are the best candidates to locate the position of the H2O snowline range from mid-infrared to sub-millimeter, and the total line fluxes tend to increase with decreasing wavelengths. We investigated the possibility of future observations using the ALMA and mid-infrared high-dispersion spectrographs (e.g., SPICA/SMI-HRS). Since the fluxes of those identified lines from a Herbig Ae disk are stronger than those of a T Tauri disk, the possibility of a successful detection is expected to increase for a Herbig Ae disk.

scholarly journals Emission Line Profiles in the Planetary Nebulae IC 4593 and NGC 6153

1989 ◽  
Vol 131 ◽  
pp. 189-189
Author(s):  
D.P.K. Banerjee ◽  
B. G. Anandarao
Keyword(s):  
High Resolution ◽  
Emission Line ◽  
Planetary Nebulae ◽  
Central Star ◽  
Compact Objects ◽  
Emission Lines ◽  
Complex Structures ◽  
Line Profiles ◽  
Fabry Perot ◽  
Central Regions

The Planetary Nebulae IC 4593 and NGC 6153 are two rather compact objects not well studied. The nebula IC 4593 is about 12 arcsec in diameter and has a central star of Type 07 f; while the southern nebula NGC 6153 is about 22 arcsec in diameter and its central star is faint and of unknown spectral type. Using a high-resolution scanning Fabry-Pérot spectrometer we have made profile measurements of emission lines Hα λ6563 A, [O III] λ5007 A, and [N II] λ6584 A in the central regions of these two nebulae. We have found expansion velocities for IC 4593 of 40 km s−1 in [N II] and 16 km s−1 in [O III]. In the case of NGC 6153, we have obtained expansion velocities of 15 km s−1 in [N II] and 13 km s−1 in [O III] line. The profiles in Hα in both the nebulae dis not show a double peaked feature due to the larger thermal broadening. In the case of IC 4593, both [O III] and [N II] profiles showed complex structures. These results and their interpretation will be discussed.

scholarly journals Predicting the broad-lines polarization emitted by supermassive binary black holes

2019 ◽  
Vol 623 ◽  
pp. A56 ◽  
Author(s):  
D. Savić ◽  
F. Marin ◽  
L. Č. Popović
Keyword(s):  
Black Holes ◽  
Emission Lines ◽  
Polarization Angle ◽  
Broad Line ◽  
Line Profiles ◽  
Binary Black Holes ◽  
True Nature ◽  
Line Shapes ◽  
Highly Sensitive ◽  
Balmer Lines

Context. Some Type-1 active galactic nuclei (AGN) show extremely asymmetric Balmer lines with the broad peak redshifted or blueshifted by thousands of km s−1. These AGN may be good candidates for supermassive binary black holes (SMBBHs). The complex line shapes can be due to the complex kinematics of the two broad line regions (BLRs). Therefore other methods should be applied to confirm the SMBBHs. One of them is spectropolarimetry. Aims. We rely on numerical modeling of the polarimetry of binary black holes systems, since polarimetry is highly sensitive to geometry, in order to find the specific influence of supermassive binary black hole (SMBBH) geometry and dynamics on polarized parameters across the broad line profiles. We apply our method to SMBBHs in which both components are assumed to be AGN with distances at the subparsec scale. Methods. We used a Monte Carlo radiative transfer code that simulates the geometry, dynamics, and emission pattern of a binary system where two black holes are getting increasingly close. Each gravitational well is accompanied by its own BLR and the whole system is surrounded by an accretion flow from the distant torus. We examined the emission line deformation and predicted the associated polarization that could be observed. Results. We modeled scattering-induced broad line polarization for various BLR geometries with complex kinematics. We find that the presence of SMBBHs can produce complex polarization angle profiles φ and strongly affect the polarized and unpolarized line profiles. Depending on the phase of the SMBBH, the resulting double-peaked emission lines either show red or blue peak dominance, or both the peaks can have the same intensity. In some cases, the whole line profile appears as a single Gaussian line, hiding the true nature of the source. Conclusions. Our results suggest that future observation with the high resolution spectropolarimetry of optical broad emission lines could play an important role in detecting subparsec SMBBHs.

SDSS J154751.94+025550 with double-peaked broad H β but single-peaked broad H α: a candidate for central binary black hole system?

2021 ◽  
Vol 507 (4) ◽  
pp. 5205-5213
Author(s):  
XueGuang Zhang
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
Broad Line ◽  
Line Profiles ◽  
Physical Conditions ◽  
Binary Black Hole ◽  
Sinusoidal Function

ABSTRACT In this manuscript, an interesting blue active galactic nuclei (AGNs) SDSS J154751.94+025550 (=SDSS J1547) is reported with very different line profiles of broad Balmer emission lines: double-peaked broad H β but single-peaked broad H α. SDSS J1547 is the first AGN with detailed discussions on very different line profiles of the broad Balmer emission lines, besides the simply mentioned different broad lines in the candidate for a binary black hole (BBH) system in SDSS J0159+0105. The very different line profiles of the broad Balmer emission lines can be well explained by different physical conditions to two central BLRs in a central BBH system in SDSS J1547. Furthermore, the long-term light curve from CSS can be well described by a sinusoidal function with a periodicity about 2159 d, providing further evidence to support the expected central BBH system in SDSS J1547. Therefore, it is interesting to treat different line profiles of broad Balmer emission lines as intrinsic indicators of central BBH systems in broad line AGN. Under assumptions of BBH systems, 0.125 per cent of broad-line AGN can be expected to have very different line profiles of broad Balmer emission lines. Future study on more broad line AGN with very different line profiles of broad Balmer emission lines could provide further clues on the different line profiles of broad Balmer emission lines as indicator of BBH systems.

scholarly journals Spectrophotometry of Supernovae

1974 ◽  
Vol 3 ◽  
pp. 533-544
Author(s):  
R. P. Kirshner
Keyword(s):  
Emission Lines ◽  
Absorption Lines ◽  
Spectral Energy ◽  
Line Profiles ◽  
Energy Distributions ◽  
Maximum Light ◽  
Balmer Lines ◽  
B Lines ◽  
Infrared Triplet ◽  
The Continuum

AbstractAbsolute spectral energy distributions for supernovae of both types I and II have been obtained. These observations demonstrate three facets of supernova spectra. First, both SN I’s and SN II’s have a continuum that varies slowly and uniformly with time, and which carries the bulk of the radiated flux at early epochs. Second, some lines in both SN I’s and SN II’s have P Cygni profiles: broad emissions flanked on their violet edges by broad absorptions. Third, some lines are common to SN I’s and SN II’s and persist throughout the evolution of the spectrum. The continuum temperatures for both SN I’s and SN II’s are about 10000 K at the earliest times of observation and drop in one month’s time to about 6000 K for SN II’s and about 7000 K for SN I’s. After several months, the continuum may cease to carry the bulk of the flux, which might be in emission lines, but continues to exist, as shown by the presence of absorption lines. The P Cygni line profiles indicate expansion velocities of 15000 km s-1 in SN II’s and 20000 km s-11 in the SN I 1972e in NGC 5253. Line identifications for SN II’s include Hα, Hβ, H and K of Ca II, the Ca II infrared triplet at λ8600, the Na I D-lines, the Mg I b-lines at λ5174, and perhaps Fe II. The [O I] lines λλ6300, 6363 and [Ca II] lines λλ7291, 7323 appear after eight months. For SN I’s, the lines identified are H and K of Ca II, the infrared Ca II lines, the Na I D-lines, and the Mg I b-lines. There is some evidence that Balmer lines are present two weeks after maximum. The strong and puzzling λ4600 features drifts with time from λ4600 near maximum light to λ4750 after 400 days.

scholarly journals Twenty years of observations of PM 1-188: Its chemical abundances and extraordinary kinematics

2021 ◽  
Author(s):  
Miriam Peña ◽  
Liliana Hernández-Martínez ◽  
Francisco Ruiz-Escobedo
Keyword(s):  
Chemical Composition ◽  
Planetary Nebula ◽  
Central Star ◽  
Emission Lines ◽  
Type I ◽  
Chemical Abundances ◽  
Line Intensities ◽  
Physical Conditions ◽  
The Past ◽  
Spectrophotometric Data

Abstract The analysis of 20 years of spectrophotometric data of the double shell planetary nebula PM 1-188 is presented, aiming to determine the time evolution of the emission lines and the physical conditions of the nebula, as a consequence of the systematic fading of its [WC 10] central star whose brightness has declined by about 10 mag in the past 40 years. Our main results include that the [O iii], [O ii], [N ii] line intensities are increasing with time in the inner nebula as a consequence of an increase in electron temperature from 11 000 K in 2005 to more than 14 000 K in 2018, due to shocks. The intensity of the same lines are decreasing in the outer nebula, due to a decrease in temperature, from 13 000 K to 7000 K, in the same period. The chemical composition of the inner and outer shells was derived and they are similar. Both nebulae present subsolar O, S and Ar abundances, while they are He, N and Ne rich. For the outer nebula the values are 12+log He/H = 11.13 ± 0.05, 12+log O/H = 8.04 ± 0.04, 12+log N/H = 7.87 ± 0.06, 12+log S/H = 7.18 ± 0.10 and 12+log Ar = 5.33 ± 0.16. The O, S and Ar abundances are several times lower than the average values found in disc non-Type I PNe, and are reminiscent of some halo PNe. From high resolution spectra, an outflow in the N-S direction was found in the inner zone. Position-velocity diagrams show that the outflow expands at velocities in the −150 to 100 km s−1 range, and both shells have expansion velocities of about 40 km s−1.

scholarly journals Beating absorption in solid-state high harmonics

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Hanzhe Liu ◽  
Giulio Vampa ◽  
Jingyuan Linda Zhang ◽  
Yu Shi ◽  
Siddharth Buddhiraju ◽  
...  
Keyword(s):  
Vacuum Ultraviolet ◽  
Crystalline Silicon ◽  
High Harmonic ◽  
Ultra Violet ◽  
Fold Increase ◽  
High Energy ◽  
High Order ◽  
Limiting Factor ◽  
X Ray ◽  
On Chip

Abstract Since the new millennium coherent extreme ultra-violet and soft x-ray radiation has revolutionized the understanding of dynamical physical, chemical and biological systems at the electron’s natural timescale. Unfortunately, coherent laser-based upconversion of infrared photons to vacuum-ultraviolet and soft x-ray high-order harmonics in gaseous, liquid and solid targets is notoriously inefficient. In dense nonlinear media, the limiting factor is strong re-absorption of the generated high-energy photons. Here we overcome this limitation by generating high-order harmonics from a periodic array of thin one-dimensional crystalline silicon ridge waveguides. Adding vacuum gaps between the ridges avoids the high absorption loss of the bulk and results in a ~ 100-fold increase of the extraction depth. As the grating period is varied, each high harmonic shows a different and marked modulation, indicating their waveguiding in the vacuum slots with reduced absorption. Looking ahead, our results enable bright on-chip coherent short-wavelength sources and may extend the usable spectral range of traditional nonlinear crystals to their absorption windows. Potential applications include on-chip chemically-sensitive spectro-nanoscopy.

scholarly journals Atomic Physics of the 12-μm and Related Lines

1994 ◽  
Vol 154 ◽  
pp. 297-307
Author(s):  
Edward S. Chang
Keyword(s):  
Atomic Physics ◽  
Stark Effect ◽  
Disk Center ◽  
Emission Peak ◽  
Emission Lines ◽  
Line Profiles ◽  
Great Progress ◽  
Quadratic Stark Effect ◽  
Rydberg Transitions ◽  
Made In

The 12 μm emission lines were unexpectedly detected about a decade ago. Great progress has been made in understanding the atomic physics underlying these high-l Rydberg transitions in Mg I and other atoms. In a magnetic field, their Landé g factor is shown to be unity. At disk center, the shift of the absorption trough relative to the emission peak is demonstrated to be due to the quadratic Stark Effect, permitting measurement of the photospheric electric field strengths. Other related lines of Mg I require accurate atomic fine structure data to interpret properly their complex line profiles. Related lines are found in the ATMOS spectra for C I, Na I, Al I, Si I, Ca I, and Fe I, in addition to H I.

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