Widths Of Balmer Lines Research Articles

Spectral Properties of Quasars from Sloan Digital Sky Survey Data Release 14: The Catalog

Abstract We present measurements of the spectral properties for a total of 526,265 quasars, out of which 63% have a continuum signal-to-noise ratio > 3 pixel−1, selected from the fourteenth data release of the Sloan Digital Sky Survey (SDSS-DR14) quasar catalog. We performed a careful and homogeneous analysis of the SDSS spectra of these sources to estimate the continuum and line properties of several emission lines such as Hα, Hβ, Hγ, Mg ii, C iii], C iv, and Lyα. From the derived emission line parameters, we estimated single-epoch virial black hole masses (M BH) for the sample using Hβ, Mg ii, and C iv emission lines. The sample covers a wide range in bolometric luminosity ( erg s−1) between 44.4 and 47.3 and between 7.1 and 9.9 M ⊙. Using the ratio of L bol to the Eddington luminosity as a measure of the accretion rate, the logarithm of the accretion rate is found to be in the range between −2.06 and 0.43. We performed several correlation analyses between different emission line parameters and found them to match the correlation known earlier using smaller samples. We note that strong Fe ii sources with a large Balmer line width and highly accreting sources with large M BH are rare in our sample. We make an extended and complete catalog available online that contains various spectral properties of 526,265 quasars derived in this work along with other properties culled from the SDSS-DR14 quasar catalog.

Lyman continuum leakage versus quenching with the James Webb Space Telescope: the spectral signatures of quenched star formation activity in reionization-epoch galaxies

ABSTRACT In this paper, we study the effects of a recent drop in star formation rate (SFR) on the spectra of epoch of reionization (EoR) galaxies, and the resulting degeneracy with the spectral features produced by extreme Lyman continuum leakage. In order to study these effects in the wavelength range relevant for the upcoming James Webb Space Telescope (JWST), we utilize synthetic spectra of simulated EoR galaxies from cosmological simulations together with synthetic spectra of partially quenched mock galaxies. We find that rapid declines in the SFR of EoR galaxies could seriously affect the applicability of methods that utilize the equivalent width of Balmer lines and the ultraviolet spectral slope to assess the escape fraction of EoR galaxies. In order to determine if the aforementioned degeneracy can be avoided by using the overall shape of the spectrum, we generate mock NIRCam observations and utilize a classification algorithm to identify galaxies that have undergone quenching. We find that while there are problematic cases, JWST/NIRCam or NIRSpec should be able to reliably identify galaxies with redshifts z∼ 7 that have experienced a significant decrease in the SFR (by a factor of 10–100) in the past 50–100 Myr with a success rate ${\gtrsim } 85\,{per\,cent}$. We also find that uncertainties in the dust-reddening effects on EoR galaxies significantly affect the performance of the results of the classification algorithm. We argue that studies that aim to characterize the dust extinction law most representative in the EoR would be extremely useful.

Are there reliable methods to estimate the nuclear orientation of Seyfert galaxies?

Orientation, together with accretion and evolution, is one of the three main drivers in the Grand Unification of Active Galactic Nuclei (AGN). Being unresolved, determining the true inclination of those powerful sources is always difficult and indirect, yet it remains a vital clue to apprehend the numerous, panchromatic and complex spectroscopic features we detect. There are only a hundred inclinations derived so far; in this context, can we be sure that we measure the true orientation of AGN? To answer this question, four methods to estimate the nuclear inclination of AGN are investigated and compared to inclination-dependent observables (hydrogen column density, Balmer linewidth, optical polarization, and flux ratios within the IR and relative to X-rays). Among these orientation indicators, the method developed by Fisher, Crenshaw, Kraemer et al., mapping and modeling the radial velocities of the [O iii] emission region in AGN, is the most successful. The [O iii]-mapping technique shows highly statistically significant correlations at >95% confidence level for rejecting null hypothesis for all the test cases. Such results confirm that the Unified Model is correct at a scale ranging from kiloparsec to a fraction of a parsec. However, at a radial distance less than 0.01 pc from the central black hole, warps and misalignments may change this picture.

Discovery of an activity cycle in the solar analog HD 45184

(Abridged) Most stellar activity cycles similar to that found in the Sun have been detected by using the chromospheric Ca II H&K lines as stellar activity proxies. However, it is unclear if such activity cycles could be identified using other optical lines. Aims. To detect activity cycles in solar-analog stars and determine if these can be identified through other optical lines, such as Fe II and Balmer lines. We study the solar-analog star HD 45184. Methods. We analyse the activity signatures of HD 45184 by using 291 HARPS spectra obtained between 2003 and 2014. In order to search for line-core fluxes variations, we focus on Ca II H&K and Balmer H$\alpha$, H$\beta$ lines, which are usually used as optical chromospheric activity indicators. We calculate the HARPS-S index from Ca II H&K lines and convert it to the Mount-Wilson scale. In addition, we also consider as activity indicators the equivalent widths of Balmer lines. Moreover, we analyse the possible variability of Fe II and other metallic lines in the optical spectra. Results. We report for the first time a long-term 5.14-yr activity cycle in the solar-analog star HD 45184. This makes HD 45184 one of most similar stars to the Sun with known activity cycle. Such variation is also evident in the first lines of the Balmer series, which not always show a correlation with activity in solar-type stars. Notably, unlike the solar case, we also found that the equivalent widths of the high photospheric Fe II lines (4924 \AA, 5018 {\AA} and 5169 \AA) are modulated ($\pm$ 2 m\AA) by the chromospheric cycle of the star. From short-term modulation of the S index we calculate a rotational period of 19.98 days, which agrees with its mean chromospheric activity level.

Broad Balmer line emission and cosmic ray acceleration efficiency in supernova remnant shocks

Balmer emission may be a powerful diagnostic tool to test the paradigm of cosmic ray (CR) acceleration in young supernova remnant (SNR) shocks. The width of the broad Balmer line is a direct indicator of the downstream plasma temperature. In case of efficient particle acceleration an appreciable fraction of the total kinetic energy of the plasma is channeled into CRs, therefore the downstream temperature decreases and so does the broad Balmer line width. This width also depends on the level of thermal equilibration between ions and neutral hydrogen atoms in the downstream. Since in general in young SNR shocks only a few charge exchange (CE) reactions occur before ionization, equilibration between ions and neutrals is not reached, and a kinetic description of the neutrals is required in order to properly compute Balmer emission. We provide a method for the calculation of Balmer emission using a self-consistent description of the shock structure in the presence of neutrals and CRs. We use a recently developed semi-analytical approach, where neutral particles, ionized plasma, accelerated particles and magnetic fields are all coupled together through the mass, momentum and energy flux conservation equations. The distribution of neutrals is obtained from the full Boltzmann equation in velocity space, coupled to Maxwellian ions through ionization and CE processes. The computation is also improved with respect to previous work thanks to a better approximation for the atomic interaction rates. We find that for shock speeds >2500km/s the distribution of broad neutrals never approaches a Maxwellian and its moments differ from those of the ionized component. These differences reflect into a smaller FWHM than predicted in previous calculations, where thermalization was assumed. The method presented here provides a realistic estimate of particle acceleration efficiency in Balmer dominated shocks.

Rest-frame optical properties of luminous, radio-selected broad absorption line quasars

We have obtained IRTF/SpeX spectra of eight moderate-redshift (z=0.7-2.4), radio-selected (log R*~0.4-1.9) broad absorption line (BAL) quasars. The spectra cover the rest-frame optical band. We compare the optical properties of these quasars to those of canonically radio-quiet (log R*<1) BAL quasars at similar redshifts and to low-redshift quasars from the Palomar-Green catalog. As with previous studies of BAL quasars, we find that [OIII] 5007 is weak, and optical FeII emission is strong, a rare combination in canonically radio-loud (log R*>1) quasars. With our measurements of the optical properties, particularly the Balmer emission line widths and the continuum luminosity, we have used empirical scaling relations to estimate black hole masses and Eddington ratios. These lie in the range (0.4-2.6)x10^9 M_sun and 0.1-0.9, respectively. Despite their comparatively extreme radio properties relative to most BAL quasars, their optical properties are quite consistent with those of radio-quiet BAL quasars and dissimilar to those of radio-loud non-BAL quasars. While BAL quasars generally appear to have low values of [OIII]/FeII, an extreme of "Eigenvector 1", the Balmer line widths and Eddington ratios do not appear to significantly differ from those of unabsorbed quasars at similar redshifts and luminosities.

Dynamics of flares on late type dMe stars

We investigate the spectral signatures of stellar flares in the wavelength range 3600 Å to 4500 Å and in broad band photometry. We study the phenomenology of the spectral signatures and we found that flares are best described by two main phases; an impulsive phase and a gradual phase, for which the physical properties are different. Important spectral differences between flares lead us to distinguish four main classes: (i) solar-like chromospheric or two-ribbon flares, (ii) white-light flares, (iii) combined white-light flares with distinct impulsive and gradual phases, and (iv) non solar-like flares (usually occuring on RS CVn type stars). We show how this classification corresponds to substantial differences in the physical properties of the flare components. We compiled all available spectroscopic data for stellar flares. We found several new empirical correlations between the time lags in the spectral lines (rise and decay times). We found for instance that during the gradual phase, the rise time in the H line is well correlated to the rise time in the Ca ii K line, and that the Ca ii K line is 1.63 times slower to rise than the H line. Similar correlations were found between the rise and decay times in these lines. These correlations are evidence that there is a dominant mechanism commanding the temporal flux evolutions during the gradual phase of flares. This mechanism applies on time scales ranging from one minute to more than a hundred minutes. We found correlations between the time lags and the maximum fluxes in the Johnson U-band and the spectral lines. These correlations show that the larger the flare the longer it takes to evolve. We show that the maximum flux in the Johnson U-band correlates well, but not linearly with the maximum flux in the H line during the impulsive phase, and over five orders of magnitude. We argue how this correlation can provide constraints on the currently available models. The spectral line maximum fluxes during the gradual phase also correlate with the Johnson U-band flux, which demonstrates that somehow the impulsive and gradual phases are physically linked. The correlation between the H and Caii K line fluxes during the gradual phase and the lack of dependence of the flux ratio of those lines on flare magnitude reveal that larger flares are not “hotter” than smaller flares during the gradual phase. We examine the behaviour of the spectral line widths: While the Ca ii K line width shows essentially no detectable variation, the Balmer line widths show a complex dependency on the white light intensity. We distinguish three energy domains where the Balmer line widths exhibit a different behaviour: (i) for small flares, the widths remain rather constant as a function of white light intensity, which suggests that in this energy range the U-band is not a good diagnostic of the total energy release and that dense “kernels” do not dominate the Balmer emission, (ii) for medium size flares, the widths rapidly increase with the U-band flux up to about 15 Å, which indicates that emission in the Balmer lines is then dominated by kernel emission, and (iii) for large flares the widths decrease with increasing U-band flux, which suggests that the Balmer line emission is then increasingly dominated by a radiative pumping process between the white light and the Balmer lines. Finally, we remark that the Balmer line fluxes are well correlated to the white light flux during the impulsive phase of flares, and not only at flare maximum. We obtain a power law correlation between the Balmer line and U-band fluxes that is evidence for either a common source (“kernels”) or strongly related flare components.

Measuring stellar oscillations using equivalent widths of absorption lines

Kjeldsen et al. have developed a new technique for measuring stellar oscillations, and claimed a detection in the G subgiant ηBoo. The technique involves monitoring temperature fluctuations in a star via their effect on the equivalent width of Balmer lines. In this paper we use synthetic stellar spectra to investigate the temperature dependence of the Balmer lines, Ca II, Fe I, the Mg b feature and the G band. We present a list of target stars likely to show solar-like oscillations, and estimate their expected amplitudes. We also show that centre-to-limb variations in Balmer-line profiles allow one to detect oscillation modes with ℓ ≤4, which accounts for the detection by Kjeldsen et al. of modes with degree ℓ = 3 in integrated sunlight.

Simultaneous uvbyβ photometry and Hα spectroscopy of Be stars in open clusters

The usual methods of spectral clasification, equivalent widths of Balmer lines or photometric calibrations are not suitable for the determination of the astrophysical parameters of the underlying star in Be-type objects. The spectrum is distorted by the circumstellar envelope lines, while the contribution of the envelope continuum radiation contaminates the photometric indices.

Pulsation Variables in the AF stars of the Case Low-Dispersion Survey

AbstractThe AF stars are those of spectral types A and F that have been discovered on objective-prism plates taken with the Burrell Schmidt in the Case Low-Dispersion Northern Sky Survey (Pesch and Sanduleak, 1983). In SA 57, this survey is complete to V = 16.5. In this field and also in the Lick Astrograph RR Lyrae survey field RR 7 (in the anticenter) the AF stars comprise (a) blue horizontal branch stars and RR Lyrae stars of the halo and (b) stars which have the higher surface gravities of main sequence stars. The two groups can be separated primarily by their differing Balmer jumps and Balmer line-widths. The latter group (which may well include blue stragglers of both Pop I and Pop II) extends some 10 kpc above the galactic plane and shows a wide range of metallicity. Photoelectric photometry of this AF star sample has allowed the detection field RR Lyrae stars of lower-amplitudes than could have been found by conventional blinking techniques; this has led to a significant increase in the number of RR Lyrae stars that are known in SA 57 and RR 7. The cooler main sequence and/or blue straggler AF stars lie in the zone of pulsational instability and one higher-amplitude δ-Scuti star was detected in field RR 7. It is suggested that these AF stars provide a good sample for studying the incidence of pulsation in the population of older stars that extends beyond the thin disk.

IUE spectra of HD 269665 (Sk -68 deg 110), a hot subdwarf in the direction of the Large Magellanic Cloud

view Abstract Citations (1) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS IUE Spectra of HD 269665 (Sk -68 110), a Hot Subdwarf in the Direction of the Large Magellanic Cloud Hill, Robert S. ; Smith, Andrew M. Abstract Comparison of high- and low-resolution IUE spectra of HD 269665 (Sanduleak -68 deg 110) show that the star is a subdwarf with a temperature in the range 30,000-50,000 K. The visual spectrum shows Balmer lines and weak He II 4686 A lines. Balmer-line width and a fit of the UV-visual flux distribution using the Blackwell-Shallis (1977) algorithm yields an effective temperature between 30,000 and 38,000 K and log g = 5-6. A table is presented of photospheric UV spectral lines in HD 269665. The radial velocity of the star is found to be 5.8 + or - 0.5 km/s. Publication: The Astronomical Journal Pub Date: March 1989 DOI: 10.1086/115034 Bibcode: 1989AJ.....97..881H Keywords: Hot Stars; Iue; Magellanic Clouds; Stellar Spectra; Subdwarf Stars; Balmer Series; Emission Spectra; H Gamma Line; Radial Velocity; Spectral Line Width; Astrophysics; STARS: INDIVIDUAL; STARS: EARLY-TYPE full text sources ADS | data products SIMBAD (3) MAST (1)

The Nature of Balmer Line Variability in Chemically Peculiar Stars

Photoelectric measurements of the β-index were made for six Ap-stars (56 Ari, 41 Tau, φ Dra, HD 188041, HD 215441, HD 221568) and one He-rich star (HD 184927). For all these stars the minimum of β occurs at a phase of maximum light at a wavelength longward of the null-wavelength region. Such coincidence can be explained by the blanketing mechanism proposed by Kodaira (1973) for the explanation of the Hγ line variations in HD 221568. According to Kurucz (1979), for stars hotter than 9000K an increase of metal abundance in the atmosphere causes an increase of the visible flux and an simultanous decrease of equivalent widths of Balmer lines. The same changes of the visible flux and equivalent widths of Balmer lines can be obtained using a model atmosphere with a suitable higher temperature. Using the Kurucz (1979) model atmospheres, temperature differences were calculated, which are necessary to obtain the observed decrease of the (β-index and the increase of the flux in a given photometric band.

Spectroscopy of the nebulosity around eight high-luminosity QSOs

view Abstract Citations (131) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopy of the nebulosity around eight high-luminosity QSOs. Boroson, T. A. ; Oke, J. B. Abstract Spectra between 5000 and 9500 A have been obtained for the nebulosities around eight QSOs. These QSOs are all radio sources and were chosen for their high optical luminosities. The spectra of the nebulosities show either blue continua and strong emission lines, or red continua with weak or no emission lines. It is suggested that all the continua arise from stars, although only one object, 3C 48, shows definite stellar absorption lines. Those objects showing strong emission lines require several times 100 million solar masses of gas within the underlying galaxy. The separation into the two groups correlates with many other properties of the QSOs, including radio morphology and spectral index, Fe II emission, and Balmer line width. Publication: The Astrophysical Journal Pub Date: June 1984 DOI: 10.1086/162126 Bibcode: 1984ApJ...281..535B Keywords: Astronomical Spectroscopy; Interstellar Matter; Luminous Intensity; Optical Emission Spectroscopy; Quasars; Balmer Series; Emission Spectra; Interstellar Gas; Line Spectra; Spectral Energy Distribution; Visible Spectrum; Astrophysics full text sources ADS | data products SIMBAD (8) NED (8)

The shell spectrum of CH Cygni in 1981

The shell spectrum of CH Cyg observed in 1981 has been analyzed by the curve of growth method and using the equivalent widths of Balmer lines. The following parameters for the region of the shell where the absorption spectrum is formed have been obtained: excitation temperatureTex=9000 K, microturbulent velocityv t =16 km s−1, electron densityne=6.3×1012, number of active hydrogen atoms in the second excited stateN0.2=5.8×1015, and the effective height of the absorption spectrum formation regionH=105 km.

Disk structure and nuclear activity in Seyfert 1 galaxies

view Abstract Citations (31) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Disk structure and nuclear activity in Seyfert 1 galaxies Su, H. J. ; Simkin, S. M. Abstract The relationships between Balmer line width, inclination to the line of sight, and morphological class for 38 Seyfert 1 galaxies have been investigated. Only one set of parameters shows a strong correlation: the width of the Balmer lines in Seyfert 1 galaxies is related to the morphological class (i.e., disk structure) of these objects. This relationship seems to show continuity between spiral Seyfert galaxies and extended, broad-line radio galaxies ('N' radio galaxies), which suggests that some Seyfert galaxies may evolve into extended radio sources. The random relationship between the width of the Balmer lines and inclination to the line of sight of Seyfert galaxies suggests that the broadening mechanism for these lines is spherically symmetric. Publication: The Astrophysical Journal Pub Date: May 1980 DOI: 10.1086/183244 Bibcode: 1980ApJ...238L...1S Keywords: Balmer Series; Disk Galaxies; Galactic Structure; Radio Galaxies; Seyfert Galaxies; Spectral Line Width; Classifications; Interstellar Extinction; Luminosity; Morphology; Nuclear Reactions; Spiral Galaxies; X Ray Spectra; Astrophysics full text sources ADS | data products NED (38)

Spectra of Variable White Dwarfs

Spectra of seven ZZ Ceti DA variables have been obtained with the multichannel spectrophotometer, several also with 7 Å resolution with the SIT digital spectrophotometer, one with the IUE. The colors fit hydrogen model atmospheres well; the combined IUE and MCSP energy distribution of G29-38 show no peculiarity from 10,000 to 2000 Å. Hydrogen model atmospheres yield &lt;log T&gt; = 4.073±0.008; the dispersion is σ = ±0.02, quite near the total observational and model-fitting error. Using an estimate of the intrinsic 2σ as a half-width the instability strip for hydrogen degenerates lies at 11,800±600 K (for log g = 8). This applies, of course, only to the northern ZZ Ceti stars observed. Another measure of how normal these variables appear is the equivalent width of Balmer lines, which are normal for that T, and are at the line-strength maximum (estimated for log g = 8.2). Possibly the mean Hα is slightly strong; since the Balmer jump is also at maximum strength, a slightly anomalous low boundary temperature might be present. This is also suggested by marginally more positive U-B color for their G-R (or larger log g). I have counts from MCSP data giving the frequency of 162 DA effective temperatures. The ZZ Ceti stars represent 7 of 27 stars in the bin ±0.05 wide in log T centered on 4.05. They are a substantial fraction, but not necessarily all, stars at that temperature. An attempt to observe Ha emission with the Boksenberg IPCS at the Palomar coudé failed for lack of photons.

X-ray galaxies

The currently identified classes of compact extragalactic X-ray sources comprise type 1 Seyfert galaxies, galaxies with active nuclei and relatively sharp emission lines, BL Lac objects and quasars. The known members of these categories are listed. In this paper, the properties of the first two classes are reviewed and discussed, with particular emphasis on their radio and optical properties and the relation between the various nuclear components. Electromagnetic spectra from radio to X-rays are presented for those galaxies detected in more than two wavebands. Optical observations of type 1 Seyferts indicate a wide range of scales for the emitting material. The continuum source and the broad wings on the Balmer lines probably originate in a region less than about 0.1 pc in extent, while the forbidden line region may occupy several hundred parsecs. From the point of view of their radio properties, galaxies with Seyfert or Seyfert-like spectra may be divided into four general categories, namely: (1) powerful (more than 10 25 W Hz -1 sr -1 at 1.4 GHz), very extended, double radio sources with steep spectra; (2) powerful (more than 10 24 W Hz -1 sr -1 at 1.4 GHz) compact radio sources with flat or inverted spectra, the radio emission originating from a small region in the nucleus; (3) weaker (10 20 -10 23 W Hz -1 sr -1 at 1.4 GHz) emission from the nucleus, usually with a steep non-thermal radio spectrum and occasionally an extended ( ca . 50 kpc) radio halo; and (4) no detected radio emission. The distinction between (3) and (4) is probably only a matter of observational selection and almost all Seyferts fall into these last two categories. When spatially resolved, the radio emitting region of category (3) galaxies usually has an approximately similar scale to the forbidden line region. The radio power is correlated with Seyfert type and forbidden line power, which may be interpreted in terms of a pressure balance between the filaments of thermal gas radiating the forbidden lines and the relativistic gas emitting the non-thermal radio radiation. The radio power is, however, uncorrelated with the thermal pressure, suggesting that the differences in radio and forbidden line power from galaxy to galaxy are dominated by variations in overall size or filling factor. Recent discussions of the infrared radiation have proposed a non thermal origin in type 1 Seyferts but a thermal mechanism in type 2 Seyferts. The infrared and radio powers seem to be correlated in both types. The X-rays originate in a region not more than 10 -2 pc in extent, and possibly much smaller. Type 1 Seyferts are intrinsically more powerful X-ray sources than type 2 Seyferts. The X-ray power appears to be correlated with the optical and infrared continuum luminosities and possibly with the Balmer line width. Studies of highly ionized species in the optical emission line spectrum are described with a view to their possible relation to the X-rays. Both [Fe x] λ 6374 Å and [Fe xi] λ 7892 Å are blue-shifted with respect to lines of lower ionization species by an amount ranging up to 300km s -1 . At least in NGC 3783, the line width is correlated with the ionization potential necessary to create the species in the sense that the higher the ionization, the greater the line width. This result fits into the scheme of a systematic decrease in density ( N e &gt; 10 8 -10 3 cm -3 ) and decrease in velocity dispersion(&lt; v &gt; = 10 4 -3 x 10 2 km s -1 ) with increasing distance from the central object ( r ≾ 0.1-5 x 10 2 pc). It is proposed that the highly ionized species occur in a region of intermediate velocity spread (&lt;v&gt; ≈ 1.5 x 10 3 km s -1 ) and distance ( r ≈ 2 pc). X-ray emitting galaxies with active nuclei but relatively sharp emission lines have X-ray luminosities in the range 10 41 -10 43 ergs -1 (1 erg s -1 = 10 -7 W), weaker than type 1 Seyferts (10 43 -10 45 ergs -1 ) but stronger than relatively normal galaxies ( ca .10 39 ergs -1 ). Lines from species of both high and low ionization are found in the optical spectra, implying ionization by a non-thermal continuum or by hot stars. These galaxies have very strong infrared excesses and are often detected as radio sources. They contain appreciable quantities of dust and, presumably, neutral gas and are either a member of an interacting pair or lie in a small group. Possibly the gas has been accreted from the neighbour(s), triggering the X-ray activity.

Balmer Line Widths in Hydrogen Arcs

The paper describes measurements of the widths of the Balmer lines Hα, Hβ and Hγ in D.C. hydrogen arcs (1-2 atmospheres pressure), for currents up to 10 amp. The results are used to deduce ion concentrations, and their bearing on the physical properties of the discharges is discussed.