scholarly journals Dissecting the EUV Spectrum of Capella

1996 ◽  
Vol 152 ◽  
pp. 105-112 ◽  
Author(s):  
Nancy S. Brickhouse
Keyword(s):  
Extreme Ultraviolet ◽  
Emission Measure ◽  
Continuous Distribution ◽  
Line Emission ◽  
Local Maximum ◽  
Abundance Ratio ◽  
Emission Lines ◽  
Cool Star ◽  
The Individual ◽  
The Continuum

Extreme ultraviolet spectra of Capella, obtained at various orbital phases over the past two years by the EUVE satellite, show strong emission lines from a continuous distribution of temperatures (~ 105 − 107.3 K). In addition to the strong He II λ303.8, the spectra are dominated by emission lines of highly ionized iron. Strong lines of Fe IX, XV, XVI, and XVIII–XXIV are used to construct emission measure distributions for the individual pointings, which show several striking features, including a minimum near 106 K and a local maximum at 106.8 K. Furthermore, intensities of the highest temperature lines (Te > 107 K) show variations (factors of 2–3) at different orbital phases, while the lower temperature Fe lines show variations of about 30% or less. The low variability of most of the strong low temperature features motivates a detailed analysis of the summed spectrum. With ~ 280 ks of total exposure time, we have measured over 200 emission features with S/N ≥ 3.0 in the summed spectrum. We report here initial results from the analysis of this spectrum. We can now identify lines of Fe VIII and X–XIV, as well as a number of electron density and abundance diagnostic lines.We also report here the first direct measurement of the continuum flux around ~ 100 Å in a cool star atmosphere with EUVE. The continuum flux can be predicted from the emission measure model based on Fe line emission, and demonstrates that the Fe/H abundance ratio is close to the solar photospheric value.

scholarly journals Longslit spectroscopy of the peculiar Seyfert 2 galaxy HRG 10103

2010 ◽  
Vol 6 ◽  
pp. 11-16
Author(s):  
Paulo C.R. Poppe ◽  
Vera A.F. Martin ◽  
Max Faúndez-Abans ◽  
Mariângela De Oliveira-Abans ◽  
Iranderly F. De Fernandes
Keyword(s):  
Spectroscopic Data ◽  
Rotation Curve ◽  
Abundance Ratio ◽  
Emission Lines ◽  
Physical Parameters ◽  
Narrow Line ◽  
Optical Range ◽  
Peculiar Galaxy ◽  
The Galaxy ◽  
The Continuum

We present the rst optical longslit spectroscopy for the galaxy HRG 10103, an Sa(r) type peculiar galaxy seen face-on with an asymmetrical elliptical structure. The main goal of this work is to provide the spectral classication of the current object using the `traditional' diagnostic diagrams. However, we also present a diagnostic involving the known emission line ratio R23, usually used to estimate the O/H abundance ratio. The idea is to make a better distinction between the narrow-line AGNs and the H II galaxies. The spectra were obtained in two observatories (OPD-LNA/MCT and Gemini-South) and includes some of the most important emission lines for ionization diagnostic. Based on the observed spectra, HRG 10103 is a Seyfert 2 galaxy with typical line-ratios values in the optical range. We have estimated nuclear redshift of z = 0.039. The resulting reddening values as a function of distance from the nucleus are presented too. The errors in the  fluxes were mostly caused by uncertainties in the placement of the continuum level. The rotation curve is typical of spiral disks, rising shallowly and  attening at an observed amplitude of about 200 km s^(-1). Some other physical parameters have been derived whenever possible. The spectroscopic data reduction was carried out using the GEMINI.GMOS package as well as the standard IRAF procedures.

scholarly journals NIR Line Observations of Starburst Galaxies

1999 ◽  
Vol 186 ◽  
pp. 286-286
Author(s):  
H. Sugai ◽  
M.A. Malkan ◽  
M.J. Ward ◽  
R.I. Davies ◽  
I.S. McLean
Keyword(s):  
Line Emission ◽  
Starburst Galaxies ◽  
Emission Lines ◽  
Ionized Gas ◽  
The Galaxy ◽  
Component C ◽  
Band Spectra ◽  
Marginal Detection ◽  
The Continuum ◽  
K Band

We have obtained images of the H2and Brγ emission lines in the galaxy interacting system NGC 3690 + IC 694. We have also obtained simultaneous H- and K-band spectra for three of its 2μm continuum peaks. The most detectable line emission is concentrated at the continuum peaks. Therefore, the emission lines as well as stellar absorption lines can be used as tracers of the activity in the nuclei themselves. From the strong Brγ and marginal detection of Br10 at the nucleus of IC 694, we derive a large extinction for the fully ionized gas in this nucleus. If we adopt this extinction also for the [Fe II]1.64μm emission, the extinction-corrected [Fe II]1.64μm/Brγ ratio will lie at the higher end of starburst galaxies, and is typical for AGNs or AGN/starburst composites. This might imply that many SNRs are involved in the starburst at this nucleus, unless it includes an AGN. All of our results for Component C, including very little CO absorption in the K band, a largeEW(Brγ), a small H2/Brγ ratio, the effective temperature (Teff≃ 40,000K) derived from HeI 1.70μm/Br10 and HeI 2.06μm/Brγ, are consistent with a very young starburst.

scholarly journals Discovery of Molecular-line Polarization in the Disk of TW Hya

2021 ◽  
Vol 922 (2) ◽  
pp. 139
Author(s):  
Richard Teague ◽  
Charles L. H. Hull ◽  
Stéphane Guilloteau ◽  
Edwin A. Bergin ◽  
Anne Dutrey ◽  
...  
Keyword(s):  
Linear Polarization ◽  
Line Emission ◽  
Emission Lines ◽  
Continuum Emission ◽  
Azimuthal Dependence ◽  
Molecular Line ◽  
Polarization Fraction ◽  
Co Emission ◽  
Higher Sensitivity ◽  
The Continuum

Abstract We report observations of polarized line and continuum emission from the disk of TW Hya using the Atacama Large Millimeter/submillimeter Array. We target three emission lines, 12CO (3–2), 13CO (3–2), and CS (7–6), to search for linear polarization due to the Goldreich–Kylafis effect, while simultaneously tracing the continuum polarization morphology at 332 GHz (900 μm), achieving a spatial resolution of 0.″5 (30 au). We detect linear polarization in the dust continuum emission; the polarization position angles show an azimuthal morphology, and the median polarization fraction is ∼0.2%, comparable to previous, lower frequency observations. Adopting a “shift-and-stack” technique to boost the sensitivity of the data, combined with a linear combination of the Q and U components to account for their azimuthal dependence, we detect weak linear polarization of 12CO and 13CO line emission at a ∼10σ and ∼5σ significance, respectively. The polarization was detected in the line wings, reaching a peak polarization fraction of ∼5% and ∼3% for the two molecules between disk radii of 0.″5 and 1″. The sign of the polarization was found to flip from the blueshifted side of the emission to the redshifted side, suggesting a complex, asymmetric polarization morphology. Polarization is not robustly detected for the CS emission; however, a tentative signal, comparable in morphology to that found for the 12CO and 13CO emission, is found at a ≲3σ significance. We are able to reconstruct a polarization morphology, consistent with the azimuthally averaged profiles, under the assumption that this is also azimuthally symmetric, which can be compared with future higher-sensitivity observations.

scholarly journals The Arcetri Spectral Code for Optically-Thin Plasmas

1996 ◽  
Vol 152 ◽  
pp. 543-552
Author(s):  
Brunella C. Monsignori Fossi ◽  
Massimo Landini
Keyword(s):  
Temperature Distribution ◽  
Emission Measure ◽  
Line Emission ◽  
Numerical Code ◽  
Distribution Model ◽  
Atomic Processes ◽  
Differential Emission Measure ◽  
Synthetic Spectra ◽  
Theoretical Predictions ◽  
The Continuum

The Arcetri-95 spectral code for optically thin plasmas computes the continuum and line emission of the ions of the most abundant elements. It includes the most updated atomic models and the main atomic processes for ions from Fe IX to Fe XXIII and for ions of the Belike, C-like, and N-like isoelectronic sequences. The power emitted per unit emission measure is produced as a function of temperature and density.Comparison with observations requires the knowledge of the differential emission measure (DEM) as a function of temperature. A numerical code evaluates the best DEM distribution that satisfies observations and theoretical predictions. The spectral code together with the DEM code allows to compute synthetic spectra for any specified temperature distribution model of the plasma.

scholarly journals Fabry-Perot Observations of Cen A

1987 ◽  
Vol 127 ◽  
pp. 419-420
Author(s):  
J.J.E. Hayes ◽  
R.A. Schommer ◽  
T.B. Williams
Keyword(s):  
Velocity Dispersion ◽  
Line Emission ◽  
Emission Lines ◽  
Peculiar Galaxy ◽  
Fabry Perot ◽  
Construct Maps ◽  
The Continuum

We present Fabry–Perot spectrophotometry of the well-known peculiar galaxy Cen A (NGC 5128). The observations were carried out using the Rutgers Fabry–Perot system and a CCD as a detector. We scanned the Hα and [NII] (λ6583) emission lines. From these data we were able to construct maps of the continuum, line emission, velocity and velocity dispersion. The velocity maps in both Hα and [NII] have smooth gradients and twists in the line of nodes. The deprojected emission maps strongly resemble emission maps of face-on spirals. We speculate that Cen A is a merger between an elliptical and a spiral.

scholarly journals Microlensing Induced Spectral Variability In Q2237+0305

1996 ◽  
Vol 173 ◽  
pp. 241-246
Author(s):  
Geraint F. Lewis ◽  
Mike J. Irwin ◽  
Paul C. Hewett
Keyword(s):  
Emission Line ◽  
Line Emission ◽  
Emission Lines ◽  
Broad Line ◽  
Spectral Variability ◽  
Broad Emission ◽  
Quasar Spectra ◽  
Line Region ◽  
Broad Emission Line ◽  
The Continuum

The degree of microlensing induced amplification is dependent upon the size of a source. As quasar spectra consist of the sum of emission from different regions this scale dependent amplification can produce spectral differences between the images of a macrolensed quasar. This paper presents the first direct spectroscopic evidence for this effect, providing a limit on the scale of the continuum and the broad line emission regions at the center of a source quasar (2237+0305). Lack of centroid and profile differences in the emission lines indicate that substructure in the broad emission line region is > 0.05 parsecs.

scholarly journals Effects of Eccentric Orbit of BF Cygni on IUE and Optical Spectra

1988 ◽  
Vol 103 ◽  
pp. 299-300
Author(s):  
J. Mikolajewska ◽  
M. Mikolajewski
Keyword(s):  
Emission Measure ◽  
Line Emission ◽  
Optical Spectra ◽  
Emission Lines ◽  
Recent Analysis ◽  
Emission Region ◽  
Galactic Rotation ◽  
Resonance Emission ◽  
High Ionization ◽  
Cosmic Abundance

A recent analysis of all available photometric data has resulted in a new ephemeris for BF Cyg: MIN=JD 2415058 + 756.8E. Simultaneously, optical spectra collected in 1979–1986 showed periodic changes of all emission lines (Mikolajewska 1987; Mikolajewska & lijima 1987). It is interesting that the forbidden lines of [OIII] varied in antiphase to the permitted emission lines and optical brightness.IUE spectra taken in 1979–1981 showed a strong hot continuum and high ionization resonance emission lines of NV, SilV CIV, intercombination lines of NIV], NIII], SiIII], CIII] and OIII] as well as Hell emission. The observed λ2200Å interstellar absorption band suggests E(B-V)≃0.3. Taking into account the interstellar reddening distribution in the vicinity of BF Cyg (Lucke 1978; Mikolajewska & Mikolajewski 1980), the observed extinction implies a distance d≲1.5kpc. This distance is in good agreement with the observed low value of the systemic radial velocity (∼15 km/s, Fig.1) of BF Cyg and the standard galactic rotation law. The standard extinction curve with E(B-V)=0.3 (Seaton 1979) was used for reddening correction of the spectra. The UV continuum of BF Cyg can be interpreted as a combination of a hot subdwarf (Teff≃60000K, L≃2500L⊙ for d=1.5kpc) and hydrogen bf+ff emission (Te≃10000K). The emission measure of the nebular (bf+ff) continuum varied from ∼4×1059cm−3 at maximum to ∼1059cm−3 at minimum. Assuming cosmic abundance of Si/C the observed SiIII]/CIII] line ratio implies ne≃2×l010cm−3 at the photometric maximum and ne≃3×109cm−3 at the minimum. We assume that these values are representative of the region where the bulk of the HI Balmer and intercombination line emission is produced. The ratio of NV(1240)/NIV(1720) gives Te(NV)≃11500K close to the value derived for the Balmer emission region from the UV continuum fit.

scholarly journals MODELING THE SS 433 JET BENDS

2008 ◽  
Vol 17 (10) ◽  
pp. 1925-1930 ◽  
Author(s):  
H. L. MARSHALL ◽  
CLAUDE R. CANIZARES ◽  
NORBERT S. SCHULZ ◽  
SEBASTIAN HEINZ ◽  
TODD C. HILLWIG ◽  
...  
Keyword(s):  
Emission Measure ◽  
Line Emission ◽  
Optical Emission ◽  
Local Environment ◽  
Emission Lines ◽  
X Ray ◽  
Ss 433 ◽  
Jet Cooling ◽  
Doppler Shifts ◽  
Optical Line

We fit Chandra HETGS data obtained for the unusual X-ray binary SS 433. While line strengths and continuum levels hardly change, the jet Doppler shifts show aperiodic variations that probably result from shocks in interactions with the local environment. The X-ray and optical emission line regions are found to be related but not coincident as the optical line emission persists for days while the X-ray emission lines fade in less than 5000 s. The X-ray spectrum of the blueshifted jet shows over two dozen emission lines from plasma at a variety of temperatures. The emission measure distribution derived from the spectrum can be used to test jet cooling models.

scholarly journals The Evolution of QSO Spectra: Evidence for Microlensing?

1996 ◽  
Vol 173 ◽  
pp. 289-290
Author(s):  
Paul J. Francis ◽  
Anuradha Koratkar
Keyword(s):  
Equivalent Width ◽  
High Redshift ◽  
Line Emission ◽  
Compact Objects ◽  
Emission Lines ◽  
Continuum Emission ◽  
The Continuum

We find that the spectra of QSOs evolve: high redshift QSOs (z > 1.5) have lower equivalent width emission lines than low redshift QSOs (z < 0.5) with the same luminosities and radio properties.We propose that microlensing by compact objects may account for the apparent evolution. If Ω ∼ 0.05 in compact objects, the continuum emission from many high redshift QSOs will be amplified, but not the line emission, leading to the observed decrease in the apparent equivalent widths.

scholarly journals Implications of Nonlinear Line Response in Variable Seyfert Nuclei

1994 ◽  
Vol 159 ◽  
pp. 459-459
Author(s):  
Joseph C. Shields ◽  
Gary J. Ferland ◽  
Bradley M. Peterson
Keyword(s):  
Nonlinear Response ◽  
Direct Evidence ◽  
Emission Measure ◽  
Emission Lines ◽  
Broad Line ◽  
Incident Flux ◽  
Ionization Structure ◽  
Line Region ◽  
Nonlinear Line ◽  
The Continuum

Variable Seyfert nuclei exhibit correlations between emission-line and continuum luminosity consistent with photoionization, although the emission lines (including recombination features such as Lyα) tend to respond nonlinearly to changes in the continuum. A nonlinear response will result if some of the broad-line region (BLR) clouds become fully ionized in hydrogen, such that their emission measure does not then vary in proportion to the incident continuum flux. For thin clouds, emission in transitions from heavy elements may grow or decline with increasing incident flux, reflecting changes in the ionization structure of the cloud. Direct evidence for a fully ionized component within the BLR is provided by correlation analysis of ultraviolet line response in NGC 5548 (Sparke, 1993).

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