Stellar populations in local star-forming galaxies

NASA Astrophysics Data System (ADS)

Perez-Gonzalez, P. G.

2003-11-01

The main goal of this thesis work is studying the main properties of the stellar populations embedded in a statistically complete sample of local active star-forming galaxies: the Universidad Complutense de Madrid (UCM) Survey of emission-line galaxies. This sample contains 191 local star-forming galaxies at an average redshift of 0.026. The survey was carried out using an objective-prism technique centered at the wavelength of the Halpha nebular emission-line (a common tracer of recent star formation). (continues)

VizieR Online Data Catalog: Diffuse ionized gas in the Antennae galaxy (Weilbacher+, 2018)

NASA Astrophysics Data System (ADS)

Weilbacher, P. M.; Monreal-Ibero, A.; Verhamme, A.; Sandin, C.; Steinmetz, M.; Kollatschny, W.; Krajnovic, D.; Kamann, S.; Roth, M. M.; Erroz-Ferrer, S.; Marino, R. A.; Maseda, M. V.; Wendt, M.; Bacon, R.; Dreizler, S.; Richard, J.; Wisotzki, L.

2017-11-01

We provide two-dimensional maps of two different ways to measure the diffuse ionized gas as traced by the Halpha emission line in the Antennae Galaxy, both for the central field and the field at the end of the southern tidal tail. We provide a velocity map derived from the Halpha emission line, binned to a S/N~30. Finally, we provide line measurements and derived properties for all HII regions discussed in the paper. (4 data files).

Spectroscopy of an unusual emission line M star

NASA Technical Reports Server (NTRS)

Schneider, Donald P.; Greenstein, Jesse L.; Schmidt, Maarten; Gunn, James E.

1991-01-01

Moderate-resolution spectroscopy of an unusual late-type faint emission-line star, PC 0025 + 0047, is reported. A very strong (greater than 250 A equivalent width) an H-alpha emission line was detected by the present automated line search algorithm. The spectrum was found to have two unresolved emission lines (H-alpha and H-beta) near zero velocity, superposed on the absorption spectrum of a very red M dwarf which has strong K I, and relatively weak bands of TiO. From the weakness of the subordinate lines of Na I (8192 A) and other spectral features, it is inferred that it is definitely a cooler, and probably fainter, analog of LHS 2924. The strength of the emission lines indicates that PC 0025 + 0447 is very young and may be a fading predecessor brown drawf at an estimated M(bol) approaching 14m at a distance of about 60 pc.

The stars with H-alpha missing

NASA Technical Reports Server (NTRS)

Downes, Ronald A.

1987-01-01

During the course of a survey for ultraviolet-excess objects, a group of objects were found that spectroscopically resemble the subdwarf B stars, except for variable strength H-alpha absorption. The H-alpha line can have the nominal strength predicted from the other Balmer lines, or it can be completely absent. Observations reveal significant changes in the H-alpha profile on both a night-to-night and month-to-month basis. IUE observations of three stars reveal few features in the ultraviolet region and, when combined with optical data, allow a rough determination of photospheric temperatures. A binary model is proposed for these systems, and the ramifications of the objects found here and in the Palomar-Green survey are discussed.

A spectroscopic search for colliding stellar winds in O-type close binary systems. III - 29 UW Canis Majoris

NASA Technical Reports Server (NTRS)

Wiggs, Michael S.; Gies, Douglas R.

1993-01-01

The orbital-phase variations in the optical emission lines and UV P Cygni lines of the massive O-type binary 29 UW Canis Majoris are investigated in a search for evidence of colliding winds. High SNR spectra of the H-alpha and He I 6678-A emission lines are presented, and radial velocity curves for several features associated with the photosphere of the more luminous primary star are given. The H-alpha features consists of a P Cygni component that shares the motion of the primary, and which probably originates at the base of its wind, and a broad, stationary emission component. It is proposed that the broad emission forms in a plane midway between the stars where the winds collide. A simple geometric model is used to show that this placement of the broad component can explain the lack of orbital velocity shifts, the near-constancy of the emission strength throughout the orbit, the large velocities associated with the H-alpha wings, and the constancy of the velocity range observed.

Detection of H-alpha emission in the hot white dwarf G191-B2B

NASA Astrophysics Data System (ADS)

Reid, Neill; Wegner, Gary

1988-12-01

High-resolution spectra of G191-B2B, the hottest known DA white dwarf were obtained which reveal emission in the core of the H-alpha line. The observations show little variation in the line profile over a period of four days, ruling out line-doubling in a close binary as an explanation. The observed emission cannot be due to a nearby red dwarf companion, while the absence of any spatially extended emission argues against either a planetary nebula remnant or local ionization of the interstellar medium. The determination of the systemic velocity, using the companion red dwarf G191-B2A, is 5 + or - 2 km/s and shows that both the H-alpha emission and the high-excitation species observed in the ultraviolet are redshifted by 19 + or - 3 km/s, suggesting a photospheric origin. The low redshift implies a mass of 0.45 solar mass for this hot white dwarf, although the uncertainties in the effective temperature and parallax permit masses in the range 0.29 to 0.60 solar mass.

COLLIMATION AND SCATTERING OF THE ACTIVE GALACTIC NUCLEUS EMISSION IN THE SOMBRERO GALAXY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menezes, R. B.; Steiner, J. E.; Ricci, T. V., E-mail: robertobm@astro.iag.usp.br

2013-03-10

We present an analysis of a data cube of the central region of M104, the Sombrero galaxy, obtained with the GMOS-IFU of the Gemini-South telescope, and report the discovery of collimation and scattering of the active galactic nucleus (AGN) emission in the circumnuclear region of this galaxy. Analysis with PCA Tomography and spectral synthesis revealed the existence of collimation and scattering of the AGN featureless continuum and also of a broad component of the H{alpha} emission line. The collimation and scattering of this broad H{alpha} component was also revealed by fitting the [N II] {lambda}{lambda}6548, 6583 and H{alpha} emission linesmore » as a sum of Gaussian functions. The spectral synthesis, together with a V-I image obtained with the Hubble Space Telescope, showed the existence of circumnuclear dust, which may cause the light scattering. We also identify a dusty feature that may be interpreted as a torus/disk structure. The existence of two opposite regions with featureless continuum (P.A. = -18 Degree-Sign {+-} 13 Degree-Sign and P.A. = 162 Degree-Sign {+-} 13 Degree-Sign ) along a direction perpendicular to the torus/disk (P.A. = 72 Degree-Sign {+-} 14 Degree-Sign ) suggests that this structure is approximately edge-on and collimates the AGN emission. The edge-on torus/disk also hides the broad-line region. The proposed scenario is compatible with the unified model and explains why only a weak broad component of the H{alpha} emission line is visible and also why many previous studies detected no broad H{alpha}. The technique used here proved to be an efficient method not only for detecting scattered light, but also for testing the unified model in low-luminosity AGNs.« less

A long-term study of H(alpha) line variations in FK Comae Berenices

NASA Technical Reports Server (NTRS)

Welty, Alan D.; Ramsey, Lawrence W.; Iyengar, Mrinal; Nations, Harold L.; Buzasi, Derek L.

1993-01-01

We present observations of H(alpha) V/R ratio variations in FK Comae Berencies obtained during several observing seasons from 1981 to 1992. The raw H(alpha) emission profile is always observed to be double peaked due to the stellar-absorption component. During the most years the V/R ratio varies regularly with the period of the photometric light curve. The V/R periodicity is most obvious when time spans no longer than several stellar rotations are considered. We propose that the bulk of the emission component of the H(alpha) line arises in corotating circumstellar material that may be similar to that of a quiescent solar prominence. The lifetime of these structures appears to be on the order of weeks. A weak contribution from a circumstellar disk is evident and chromospheric emission may also be present. The appearance or disappearance of circumstellar structures over periods longer than a few weeks, or the total absence of such structures, blurs the more regular variations in H(alpha) seen over short time scales. Other more stochastic activity, such as flares, also clearly occurs. Phase shifts of the V/R ratio from year to year rule out the hypothesis that mass tranfer in a close binary system is responsible for the V/R variations.

SPECTRAL OPTICAL MONITORING OF THE NARROW-LINE SEYFERT 1 GALAXY Ark 564

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shapovalova, A. I.; Burenkov, A. N.; Popovic, L. C.

2012-09-15

We present the results of a long-term (1999-2010) spectral optical monitoring campaign of the active galactic nucleus (AGN) Ark 564, which shows a strong Fe II line emission in the optical. This AGN is a narrow-line Seyfert 1 (NLS1) galaxy, a group of AGNs with specific spectral characteristics. We analyze the light curves of the permitted H{alpha}, H{beta}, optical Fe II line fluxes, and the continuum flux in order to search for a time lag between them. Additionally, in order to estimate the contribution of iron lines from different multiplets, we fit the H{beta} and Fe II lines with amore » sum of Gaussian components. We find that during the monitoring period the spectral variation (F{sub max}/F{sub min}) of Ark 564 is between 1.5 for H{alpha} and 1.8 for the Fe II lines. The correlation between the Fe II and H{beta} flux variations is of higher significance than that of H{alpha} and H{beta} (whose correlation is almost absent). The permitted-line profiles are Lorentzian-like and do not change shape during the monitoring period. We investigate, in detail, the optical Fe II emission and find different degrees of correlation between the Fe II emission arising from different spectral multiplets and the continuum flux. The relatively weak and different degrees of correlations between permitted lines and continuum fluxes indicate a rather complex source of ionization of the broad-line emission region.« less

Activity in X-ray-selected late-type stars

NASA Technical Reports Server (NTRS)

Takalo, Leo O.; Nousek, J. A.

1988-01-01

A spectroscopic study has been conducted of nine X-ray bright late-type stars selected from two Einstein X-ray surveys: the Columbia Astrophysical Laboratory Survey (five stars) and the CFA Medium Sensitivity Survey (MSS; four stars). Spectral classes were determined and radial and V sin(i) velocities were measured for the stars. Four of the Columbia Survey stars were found to be new RS CVn-type binaries. The fifth Columbia survey star was found to be an active G dwarf star without evidence for binarity. None of the four MSS stars were found to be either binaries or optically active stars. Activity in these stars was assessed by measuring the excess emission in H-alpha and the Ca II IRT (8498, 8542) lines in comparison with inactive stars of similar spectral types. A correlation was found between X-ray luminosity and V sin(i) and H-alpha line excess. The measured excess line emission in H-alpha was also correlated with V sin(i) but not with the IRT line excess.

Analysis of hydrogen H-alpha observations of the coma of Comet P/Halley

NASA Technical Reports Server (NTRS)

Smyth, William H.; Marconi, M. L.; Scherb, Frank; Roesler, Fred L.

1993-01-01

The Monte Carlo Particle Trajectory Model of Combi and Smyth (1988) is used here to analyze observations of the H-alpha coma of Comet Halley. The solar excitation mechanism for the H-alpha emissions line is described. The H2O production rates derived for the H-alpha brightness measurements are shown to be very consistent with the H2O production rates determined from other Comet Halley observations of the H, O, and OH comae. Revised H2O production rates determined from 6300 A brightness measurements are presented.

The Influence of Gas Composition in Dielectric Barrier Discharges on the Broadening of the Hydrogen H{alpha} Transition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Janus, H. W.

The distribution of hydrogen atoms responsible for emission of the Balmer H{alpha} line in the region of the dielectric barrier discharges in the helium and hydrogen as well as in the argon and hydrogen mixtures, in the direction perpendicular to the electrode surfaces, has bee determined by the optical emission spectroscopy accounting for the polarization of the emitted light. The procedure of fitting the measured line profiles accounting for the Stark effect has been used for determination of the distribution of the electric field in the discharge region.

BAT AGN Spectroscopic Survey - III. An Observed Link Between AGN Eddington Ratio and Narrow-Emission-Line Ratios

NASA Technical Reports Server (NTRS)

Oh, Kyuseok; Schawinski, Kevin; Koss, Michael; Trakhtenbrot, Benny; Lamperti, Isabella; Ricci, Claudio; Mushotzky, Richard; Veilleux, Sylvain; Berney, Simon; Crenshaw, D. Michael;

The peculiar type II supernova 1993J in M81: Transition to the nebular phase

NASA Technical Reports Server (NTRS)

Filippenko, Alexei V.; Matheson, Thomas; Barth, Aaron J.

1994-01-01

We present optical spectra of the bright, peculiar Type II supernova 1993J in M81 spanning the first 14 months of its existence, revealing its transition to the nebular phase. Unlike the case in normal Type II supernovae, during the first 2-10 months the H-alpha emission line gradually becomes less prominent relative to other features such as (O I) lambda lambda 6300, 6364 and (Ca II) lambda lambda 7291, 7324, as we had predicted based on early-time (tau less than or approximately equal to 2 months) spectra. The nebular spectrum resembles those of the Type Ib/Ic supernovae 1985F and 1987M, although weak H-alpha emission is easily visible even at late times in SN 1993J. At tau = 8 months a close similarity is found with the spectrum of SN 1987K, the only other Type II supernova known to have undergone such a metamorphosis. The emission lines are considerably broader than those of normal Type II supernovae at comparable phases, consistent with the progenitor having lost a majority of its hydrogen envelope prior to exploding. Consequently, there is now little doubt that Type Ib, and probably Type Ic, supernovae result from core collapse in stripped, massive stars; models of the chemical evolution of galaxies in which these subtypes are ascribed to exploding white dwarfs must be appropriately modified. Although all of the emission lines in spectra of SN 1993J fade roughly exponentially for a considerable time, the fading of H-alpha begins to slow down at tau approximately = 8 months, and in the interval tau = 10-14 months its flux is constant, or even slightly rising in the wings of the line. This behavior, together with the box-like shape and great breadth (full width at half maximum (FWHM) approximately = 17 000 km/s) of the line profile, suggests that the H-alpha emission is being produced by the high-velocity outer layer of hydrogen ejecta interacting with circumstellar gas released by the progenitor prior to its explosion. A similar phenomenon has previously been seen at later phases in several Type II supernovae, most notably SN 1980K. Bumps (FWHM approximately = 1000 km/s, amplitude approximately = 20%) in the H-alpha profile are probably indicative of Rayleigh-Taylor instabilities in the cool gas behind the reverse shock. A very narrow component (unresolved, FWHM less than or approximately equal to 200 km/s) of H-alpha at the symmetric velocity of SN 1993J may instead be produced by a superposed H II region, or perhaps by recombination in a large circumstellar shell or ring that was ionized during the first few hours after outburst. In the near future the spectrum of SN 1993J should become increasingly dominated by broad H-alpha emission.

Hydrogen emission in meteors as a potential marker for the exogenous delivery of organics and water

NASA Technical Reports Server (NTRS)

Jenniskens, Peter; Mandell, Avram M.

2004-01-01

We detected hydrogen Balmer-alpha (H(alpha)) emission in the spectra of bright meteors and investigated its potential use as a tracer for exogenous delivery of organic matter. We found that it is critical to observe the meteors with high enough spatial resolution to distinguish the 656.46 nm H(alpha) emission from the 657.46 nm intercombination line of neutral calcium, which was bright in the meteor afterglow. The H(alpha) line peak stayed in constant ratio to the atmospheric emissions of nitrogen during descent of the meteoroid. If all of the hydrogen originates in the Earth's atmosphere, the hydrogen atoms are expected to have been excited at T = 4400 K. In that case, we measured an H(2)O abundance in excess of 150 +/- 20 ppm at 80-90 km altitude (assuming local thermodynamic equilibrium in the air plasma). This compares with an expected <20 ppm from H(2)O in the gas phase. Alternatively, meteoric refractory organic matter (and water bound in meteoroid minerals) could have caused the observed H(alpha) emission, but only if the line is excited in a hot T approximately 10000 K plasma component that is unique to meteoric ablation vapor emissions such as Si(+). Assuming that the Si(+) lines of the Leonid spectrum would need the same hot excitation conditions, and a typical [H]/[C] = 1 in cometary refractory organics, we calculated an abundance ratio [C]/[Si] = 3.9 +/- 1.4 for the dust of comet 55P/Tempel-Tuttle. This range agreed with the value of [C]/[Si] = 4.4 measured for comet 1P/Halley dust. Unless there is 10 times more water vapor in the upper atmosphere than expected, we conclude that a significant fraction of the hydrogen atoms in the observed meteor plasma originated in the meteoroid.

Fabry-Perot Observations of [OI]6300, Hα, H-Beta, and NH2 Emissions from Comet Hyakutake C/1996B2

NASA Astrophysics Data System (ADS)

Scherb, F.; Roesler, F. L.; Tufte, S.; Haffner, M.

1996-05-01

During the period 16-23 March 1996, observations of Comet Hyakutake were carried out with the new WHAM facility at the University of Wisconsin Pine Bluff Observatory, near Madison. WHAM is a second-generation double-Fabry-Perot/CCD spectrometer that is more than ten times as efficient as our previous large-aperture Fabry-Perot instruments. Specifications of WHAM in the spectral mode are: a 1-degree field of view (FOV) on the sky, 10 km/sec velocity resolution, 200 km/sec range, and 20 sigma detection of a 1-Rayleigh H-alpha emission line in about 30 seconds. WHAM can also operate in a mode in which an image of an emission source over a 1-degree FOV can be obtained at a spectral resolution of about 10 km/sec. Spectra of cometary [OI]6300, H-alpha, H-beta, and NH2 emissions were obtained with the FOV centered on the comet head and also located 3/4 degree sunward of the comet head, repectively. This was the first time that cometary H-beta emission has been detected. Images of cometary [OI]6300 and NH2 emissions were obtained with the FOV centered on the comet head. The interpretation of these observations using coma gas dynamic and photochemical models yields values of the H2O production rate from both the [OI]6300 and H-alpha data. Comparison of the cometary H-alpha and H-beta intensities provides unique ground-based information on the EUV solar Lyman-beta and Lyman-gamma emission lines. These results will be presented.

Emission-line galaxies in the third list of the Case Low-Dispersion Northern Sky Survey

NASA Technical Reports Server (NTRS)

Weistrop, Donna; Downes, Ronald A.

1991-01-01

Observations of 47 galaxies in the third Case list are reported. Thirty-five of the galaxies in the sample were selected for the presence of emission lines on the objective prism plates. At the higher spectral dispersion of the data, significant line emission was found in 46 of the 47 galaxies. Twenty-six galaxies are found to be undergoing significant bursts of star formation. Ten additional galaxies may be starburst galaxies with low-excitation spectra. Two galaxies are probably type Seyfert 2. The most distant object, CG 200, at a redshift of 0.144, has a strong broad H-alpha emission line, and is probably a Seyfert 1. Seventeen of the galaxies have been detected by IRAS. Eight of the IRAS galaxies have H-II-region-type spectra and eight have low-ionization starburst spectra. The galaxies represent a mixture of types, ranging from intrinsically faint dwarf galaxies with Mb equalling -16 mag, to powerful galaxies with MB equalling -23 mag. Galaxies CG 234 and CG 235 are interacting, as are galaxies CG 269 and CG 270.

A spectroscopic search for colliding stellar winds in O-type close binary systems. IV - Iota Orionis

NASA Technical Reports Server (NTRS)

Gies, Douglas R.; Wiggs, Michael S.; Bagnuolo, William G., Jr.

1993-01-01

We present H-alpha and He I 6678 A line profiles for the eccentric orbit binary Iota Ori. We have applied a tomography algorithm which uses the established orbital velocity curves and intensity ratio to reconstruct the spectral line profiles for each star. The He I profiles appear as pure photospheric lines, and H-alpha shows variable emission in the line core throughout the orbit (which is typical of O giants) and in the blue wing near periastron passage. We show that the blue wing emission is consistent with an origin between the stars which probably results from a dramatic focusing of the primary's stellar wind at periastron. We also present IUE archival spectra of the UV wind lines N V 1240 A and C IV 1550 A.

Double-peaked broad line emission from the LINER nucleus of NGC 1097

NASA Technical Reports Server (NTRS)

Storchi-Bergmann, Thaisa; Baldwin, Jack A.; Wilson, Andrew S.

1993-01-01

We report the recent appearance of a very broad component in the H-alpha and H-beta emission lines of the weakly active nucleus of the Sersic-Pastoriza galaxy NGC 1097. The FWZI of the broad component is about 21,000 km/s, and its profile is double-peaked; the presence of a blue, featureless continuum in the nucleus is also suggested. The broad component was first observed in H-alpha in November 2, 1991, and confirmed 11 months later. The H-alpha profile and flux did not change in this time interval. Comparison with previously published spectral data indicates that the broad lines have only recently appeared. Together with the relatively high X-ray luminosity and the compact nuclear radio source, our results characterize the presence of a Seyfert 1 nucleus in a galaxy which had previously shown only LINER characteristics. Obscuring material along our line of sight to the nucleus appears to have recently cleared, permitting a direct view of the active nucleus. We discuss two possible structures for the broad line region, biconical outflow and an accretion disk, that could give rise to the observed profile.

Hydrogen production rate from comet Austin 1982g

NASA Technical Reports Server (NTRS)

Shih, P.; Scherb, F.; Roesler, F. L.

1984-01-01

Meaningful measurements with respect to the cometary Balmer-alpha (H-alpha) emission are difficult and require the use of special equipment. The first ground-based observations of H-alpha emission from a cometary hydrogen corona were conducted on comet Kohoutek 1973 XII with a large-aperture Fabry-Perot spectrometer installed at the McMath solar telescope at Kitt Peak National Observatory. The present investigation is concerned with the second ground-based observations of cometary H-alpha emission carried out during the apparition of comet Austin 1982g. A 150 mm dual-etalon Fabry-Perot spectrometer was employed in the experiment. Use was made of an observatory which is designed for the high spectral resolution study of faint extended sources such as interstellar and geocoronal emission lines. The investigation demonstrates that hydrogen production rates from comets as faint as about 7th magnitude can be routinely measured from the ground at minimal cost.

A multi-wavelength investigation of Seyfert 1.8 and 1.9 galaxies

NASA Astrophysics Data System (ADS)

Trippe, Margaret L.

We focus on determining the underlying physical cause of a Seyfert galaxy's appearance as type a 1.8 or 1.9. Are these "intermediate" Seyfert types typical Seyfert 1 nuclei reddened by central dusty tori or by nuclear dust lanes/spirals in the narrow-line region? Or, are they similar to NGC 2992, objects that have intrinsically weak continua and weak broad emission lines? Our study compares measurements of the reddenings of the narrow and broad-line regions with each other and with the X-ray column derived from XMM Newton 0.5--10 keV spectra to determine the presence and location of dust in the line of sight for a sample of 35 Seyfert 1.8s and 1.9s. From this, we find that Seyfert 1.9s are an almost equal mix of low-flux objects with unreddened broad line regions, and objects with broad line regions reddened by an internal dust source, either the torus or dust structures on the same size scale as the narrow line region. The 1.9s that recieved this designation due to a low continuum flux state showed variable type classifications. All three of the Seyfert 1.8s in our study are probably in low continuum states. Many objects have been misclassified as Seyfert 1.8/1.9s in the past, probably due to improper [N II]/Halpha deconvolution leading to a false detection of weak broad Halpha. INDEX WORDS: Active galaxies, Seyfert galaxies, Optical spectroscopy, X-ray spectroscopy, Astronomical dust

Ongoing Search for Metal Line Emission in Intermediate and High Velocity Clouds with WHAM

NASA Astrophysics Data System (ADS)

Barger, K. A.; Haffner, L. M.; Madsen, G. J.; Hill, A. S.; Wakker, B. P.

2010-01-01

We present new observations of the ionized gas in Complexes A, K, and L obtained with the Wisconsin H-Alpha Mapper (WHAM). To date, there have been only a limited number of studies of the ionized components of intermediate and high velocity clouds. Investigating their emission provides a rare probe of the physical conditions of the clouds and the halo they are embedded within. These types of measurements will help guide discussion of the origin and evolution of these neutral halo structures. Here we follow up on the H-alpha maps we have presented elsewhere with deeper observations in H-alpha, [S II], [N II], and [O I]. Distance constraints from absorption studies place this gas in the mid to lower Galactic halo. Complex A has been constrained to a distance of 8-10 kpc (Wakker et al. 2008); Complex K has an upper limit of 6.8 kpc; and Complex L at a distance of 8-15 kpc (Wakker 2000). Some halo gas structures have clear metal line emission (e.g., Smith Cloud; Hill et al. 2009 and this meeting); however, the lack of [S II] emission toward Complex C combined with absorption-line observations demonstrates that it has very low metallically (Wakker, et al. 1999). Such discoveries reveal ongoing gas replenishment of the evolving Milky Way. Here, we find a similar lack of emission toward the high-velocity Complex A. In particular, the cores of its cloud components designated III and IV show no evidence for metal line emission in our new observations, which places new constraints on the metallically of this complex. These observations were taken with WHAM at Kitt Peak, and we thank the excellent, decade-long support from its staff. WHAM operations are supported through NSF award AST-0607512.

Discovery and observation of BY Draconis variables

NASA Astrophysics Data System (ADS)

Bopp, B. W.; Noah, P. V.; Klimke, A.; Africano, J.

1981-10-01

The discovery of BY Draconis variables was efficiently accomplished by a spectroscopic survey of dK-M stars for weak H-alpha emissions, using 1-2 A resolution. The four BY Dra variables discovered are all spectroscopic binaries with P values lower than about 10 d, in light of which, it is noted that the onset of high surface activity and appearance of H-alpha emission occur sharply at v(equator) of approximately 5 km/sec. At v(equator) of about 3 km/sec, dK-M stars have low levels of surface activity. It is found that while there is a range of Ca II emission strength, and only the strongest emitters of this line are BY Dra and/or flare stars, the H-alpha feature changes abruptly to an emission feature signaling the onset of flaring and/or the BY Dra syndrome. An increase of the rotation rate above v(equator) 5 km/sec does not appear to increase the level of surface activity.

A magnetic study of spotted UV Ceti flare stars and related late-type dwarfs

NASA Astrophysics Data System (ADS)

Vogt, S. S.

1980-09-01

A multichannel photoelectric Zeeman analyzer has been used to investigate the magnetic nature of the spotted UV Ceti flare stars. Magnetic observations were obtained on a sample of 19 program objects, of which 5 were currently spotted dKe-dMe stars, 7 were normal dK-dM stars, 7 were UV Ceti flare stars, and 1 was a possible post-T Tauri star. Contrary to most previously published observations and theoretical expectations, no magnetic fields were detected on any of these objects from either the absorption lines or the H-alpha emission line down to an observational uncertainty level of 100-160 gauss (standard deviation).

FAR-ULTRAVIOLET OBSERVATION OF THE AQUILA RIFT WITH FIMS/SPEAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, S.-J.; Min, K.-W.; Seon, K.-I.

2012-07-20

We present the results of far ultraviolet (FUV) observations of the broad region around the Aquila Rift including the Galactic plane. As compared with various wavelength data sets, dust scattering is found to be the major origin of the diffuse FUV continuum in this region. The FUV intensity clearly correlates with the dust extinction level for E(B - V) < 0.2, while this correlation disappears for E(B - V) > 0.2 due to heavy dust extinction combined with the effect of nonuniform interstellar radiation fields. The FUV intensity also correlates well with H{alpha} intensity, implying that at least some fractionmore » of the observed H{alpha} emission could be the dust-scattered light of H{alpha} photons originating elsewhere in the Galaxy. Most of the Aquila Rift region is seen devoid of diffuse FUV continuum due to heavy extinction while strong emission is observed in the surrounding regions. Molecular hydrogen fluorescent emission lines are clearly seen in the spectrum of 'Aquila-Serpens', while 'Aquila-East' does not show any apparent line features. CO emission intensity is also found to be higher in the 'Aquila-Serpens' region than in the 'Aquila-East' region. In this regard, we note that regions of star formation have been found in 'Aquila-Serpens' but not in 'Aquila-East'.« less

Optical and UV spectroscopy of the peculiar RS CVn system, RT Lacertae

NASA Technical Reports Server (NTRS)

Huenemoerder, D. P.; Barden, S. C.

1985-01-01

Spectra in the H-alpha and H-beta regions of the peculiar double-lined RS CVn binary, RT Lacertae, were obtained in the fall of 1984. Limited International Ultraviolet Explorer (IUE) long wavelength low and high resolution spectra were obtained concurrently. The ground based spectra have shown an asymmetry with orbital phase in the H-alpha profile. The H-beta profiles were consistent with the same effect. One hemisphere showed excess emission and the other excess absorption, with a broad Gaussian emission component superposed upon the excess H-alpha line. An improved radial velocity curve, giving a better determined mass ratio and geometry was derived. This combined with the radii implied by the rotational broadening of the spectra, showed one component to be 80 to 90% filling the equilibrium Roche surface. The two-faced nature is, therfore, very likely due to mass transfer from the contact component impacting upon its companion. Low resolution ultraviolet data showed that the supposed cooler component is bluer than its companion. High resolution ultraviolet data taken during secondary eclipse showed Mg II emission strength which decreased more slowly than the area visible. The phase behavior of the low resolution data support the former situation, indicating traditional chromospheric activity.

Optical and UV spectroscopy of the peculiar RS CVn system, RT Lacertae

NASA Astrophysics Data System (ADS)

Huenemoerder, D. P.; Barden, S. C.

1985-11-01

Spectra in the H-alpha and H-beta regions of the peculiar double-lined RS CVn binary, RT Lacertae, were obtained in the fall of 1984. Limited International Ultraviolet Explorer (IUE) long wavelength low and high resolution spectra were obtained concurrently. The ground based spectra have shown an asymmetry with orbital phase in the H-alpha profile. The H-beta profiles were consistent with the same effect. One hemisphere showed excess emission and the other excess absorption, with a broad Gaussian emission component superposed upon the excess H-alpha line. An improved radial velocity curve, giving a better determined mass ratio and geometry was derived. This combined with the radii implied by the rotational broadening of the spectra, showed one component to be 80 to 90% filling the equilibrium Roche surface. The two-faced nature is, therfore, very likely due to mass transfer from the contact component impacting upon its companion. Low resolution ultraviolet data showed that the supposed cooler component is bluer than its companion. High resolution ultraviolet data taken during secondary eclipse showed Mg II emission strength which decreased more slowly than the area visible. The phase behavior of the low resolution data support the former situation, indicating traditional chromospheric activity.

Color gradients in cooling flow cluster central galaxies and the ionization of cluster emission line systems

NASA Technical Reports Server (NTRS)

Romanishin, W.

1988-01-01

Preliminary results are given for a program to measure color gradients in the central galaxies in clusters with a variety of cooling flow rates. The objectives are to search for extended blue continuum regions indicative of star formation, to study the spatial distribution of star formation, and to make a quantitative measure of the amount of light from young stars, which can lead to a measure of the star formation rate (for an assumed initial mass function). Four clusters with large masses and large cluster H-alpha emission fluxes are found to have an excess of blue light concentrated to the centers of the cluster central galaxy. Assumption of a disk IMF leads to the conclusion that the starlight might play a major role in ionizing the emission line gas in these clusters.

X-radiation /E greater than 10 keV/, H-alpha and microwave emission during the impulsive phase of solar flares.

NASA Technical Reports Server (NTRS)

Vorpahl, J. A.

1972-01-01

A study has been made of the variation in hard (E greater than 10 keV) X-radiation, H-alpha and microwave emission during the impulsive phase of solar flares. Analysis shows that the rise-time in the 20-30-keV X-ray spike depends on the electron hardness. The impulsive phase is also marked by an abrupt, very intense increase in H-alpha emission in one or more knots of the flare. Properties of these H-alpha kernels include: (1) a luminosity several times greater than the surrounding flare, (2) an intensity rise starting about 20-30 sec before, peaking about 20-25 sec after, and lasting about twice as long as the hard spike, (3) a location lower in the chromosphere than the remaining flare, (4) essentially no expansion prior to the hard spike, and (5) a position within 6000 km of the boundary separating polarities, usually forming on both sides of the neutral line near both feet of the same tube of force. Correspondingly, impulsive microwave events are characterized by: (1) great similarity in burst structure with 20-32 keV X-rays but only above 5000 MHz, (2) typical low frequency burst cutoff between 1400-3800 MHz, and (3) maximum emission above 7500 MHz.

Observational studies of the symbiotic stars. III High-dispersion IUE and H-alpha observations of EG Andromedae

NASA Technical Reports Server (NTRS)

Oliversen, N. A.; Anderson, C. M.; Slovak, M. H.; Stencel, R. E.

1985-01-01

High-dispersion IUE and optical spectra are presented for the symbiotic star EG Andromedae (HD 4174). Remarkable emission-line strength and profile variations are confirmed for the S IV, O IV, C IV, and He II ultraviolet lines as well as H-alpha. Accurate cross-correlation absorption-line velocities determined from Ti I, Ca I, and Fe I features convincingly demonstrate that EG And is a single-lined spectroscopic binary. The velocity curve suggests that the photometric ephemeris reported by Smith in 1980 should be revised by a redefinition of zero phase by about 0.08 of a period. The primary of the system may be similar to the central star of a planetary nebula embedded in a dense nebula with a mild stellar wind. The behavior of the emission lines is interpreted to indicate that the primary and its surrounding nebula suffer a partial eclipse by the cool giant secondary.

Two views of the Andromeda Galaxy H-alpha and far infrared

NASA Technical Reports Server (NTRS)

Devereux, Nicholas A.; Price, Rob; Wells, Lisa A.; Duric, Neb

1994-01-01

A complete H-alpha image of the Andromeda Galaxy (M31) is presented allowing the first direct measurement of the total H-alpha luminosity which is (7.3 +/- 2.4) x 10(exp 6) solar luminosity. The H-alpha emission is associated with three morphologically distinct components; a large scale star-forming ring, approximately 1.65 deg in diameter, contributing 66% of the total H-alpha emission, a bright nucleus contributing 6% of the total H-alpha emission with the remaining 28% contributed by a previously unidentified component of extended and filamentary H-alpha emission interior to the star forming ring. The correspondence between the H-alpha image and the Infrared Astronomy Satellite (IRAS) far-infrared high resolution image is striking when both are convolved to a common resolution of 105 arcsec. The close correspondence between the far-infrared and H-alpha images suggests a common origin for the two emissions. The star-forming ring contributes 70% of the far-infrared luminosity of M31. Evidence that the ring emission is energized by high mass stars includes the fact that peaks in the far-infrared emission coincide identically with H II regions in the H-alpha image. In addition, the far-infrared to H-alpha luminosity ratio within the star-forming ring is similar to what one would expect for H II regions powered by stars of spectral types ranging between O9 and B0. The origin of the filamentary H-alpha and far-infrared luminosity interior to the star-forming ring is less clear, but it is almost certainly not produced by high mass stars.

Optical and UV spectroscopy of the peculiar RS CVn system RT Lacertae

NASA Technical Reports Server (NTRS)

Huenemoerder, D. P.; Barden, S. C.

1986-01-01

H-alpha and H-beta spectra of the peculiar double-lined RS CVn binary RT Lacertae have been obtained using the IUE, together with a ground-based coude-feed telescope at KPNO. The ground-based spectra show an asymmetry related to the orbital phase in the H-alpha profile. H-beta profiles showed excess emission in one hemisphere and excess absorption in the other, with a broad Gaussian emission component superposed on the excess H-alpha line. A radial velocity curve was derived to estimate the mass ratio and geometry of the system. It is shown that the component of RT Lac fills 80-90 percent of the equilibrium Roche surface. Low-resolution ultraviolet data show that the supposed cooler component is bluer than its companion, suggesting evidence of a scattering shell or a cloud produced by the splash of a gas stream. The phase behavior of the low resolution ultraviolet data support the conclusion that RT Lac is a mass transfer system and that mass transfer is the primary cause of its activity.

Constraining the Accretion Mode in LINER 1.9s

NASA Astrophysics Data System (ADS)

Sabra, Bassem; Der Sahaguian, Elias; Badr, Elie

2016-01-01

The accretion mode and the dominant power source in low-ionization nuclear emission-line regions (LINERs), a class of active galactic nuclei (AGN), are still elusive. We focus on a sample of 22 LINER 1.9s (Ho et al. 1997), a subclass of LINERs that show broad Halpha lines, a signature of blackhole-powered accretion, to test the hypothesis that the ionizing continuum emitted by a radiatively inefficient accretion flow (RIAF) could lead to the LINER ultraviolet (UV) emission-line ratios. Optical line-ratio diagrams are a weak diagnostic tool in distinguishing between possible power sources (Sabra et al. 2003). We search the Mikulski Archive for Space Telescopes (MAST) for UV spectra of the objects in the above sample and also perform photoionization simulations using CLOUDY (Ferland et al. 2013). Unfortunately, only one object (NGC 1052; Gabel et al. 2000) of the 22 LINER 1.9s has UV spectra that cover many emission lines; the rest of the objects either do not have any UV spectra, the spectral coverage is in-adequate, or the spectra have very low signal-to-noise ratios. Our photoionization simulations set up two identical grids of clouds with a range of densities and ionization parameters. We illuminate one grid with radiation emitted by a thin accretion disk (AD) and we illuminate the other grid with radiation from a RIAF. We overplot the UV emission-line ratio predictions for AD and RIAF illumination, together with the available line ratios for NGC 1052. Initial results show that UV lines could be used as diagnostics for the accretion mode in AGN. More UV spectral coverage of LINER 1.9s is needed in order to more fully utilize the diagnostic powers of UV emission line ratios.

Mass loss from hot, luminous stars

NASA Astrophysics Data System (ADS)

Burnley, Adam Warwick

A general enquiry into the physics of mass loss from hot, luminous stars is presented. Ha spectroscopy of 64 Galactic early-type stars has been obtained using the telescopes of the Isaac Newton Group (ING) and the Anglo-Australian Observatory (AAO). The sample was selected to include objects with published radio and/or mm fluxes. The Halpha observations are quantitatively modelled using a modified version of the FORSOL code developed by Puls et al. (1996). FORSOL has been coupled with the PIKAIA subroutine (Charbonneau and Knapp, 1996) to create PHALTEE (Program for Halpha Line Transfer with Eugenic Estimation), in order to search a specified parameter space for the 'best' (quasi- least-squares) model fit to the data, using a genetic algorithm. This renders Ha modelling both more objective and automated. Where possible, both mass-loss rates and velocity field beta-exponents are determined for the sample. New mm-wave observations of nineteen Galactic early-type stars, including a subset of the Halpha sample, have been obtained using the Sub-millimetre Common User Bolometer Array (SCUBA). Where possible, mean fluxes are calculated, and these data used with the results of a literature survey of mm and cm fluxes to determine mass-loss rates for a larger sample, of 53 Galactic early-type stars. The incidence of nonthermal emission is examined, with 23% of the sample exhibiting strong evidence for nonthermal flux. The occurrence of binarity and excess X-ray emission amongst the nonthermal emitters is also investigated. For the subset of 36 stars common to both the Halpha and mm/radio samples, the results permit a comparison of mass-loss rates derived using diagnostics that probe the wind conditions at different radial depths. A mean value of log (Mradio/MHalpha) = 0.02 +/- 0.05 is obtained for the thermal radio emitters. The wind-momentum-luminosity relationship (WLR) for the sample is also investigated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devereux, Nick, E-mail: devereux@erau.edu

Dual epoch spectroscopy of the lenticular galaxy, NGC 4203, obtained with the Hubble Space Telescope has revealed that the double-peaked component of the broad H{alpha} emission line is time variable, increasing by a factor of 2.2 in brightness between 1999 and 2010. Modeling the gas distribution responsible for the double-peaked profiles indicates that a ring is a more appropriate description than a disk and most likely represents the contrail of a red supergiant star that is being tidally disrupted at a distance of {approx}1500 AU from the central black hole. There is also a bright core of broad H{alpha} linemore » emission that is not time variable and identified with a large-scale inflow from an outer radius of {approx}1 pc. If the gas number density is {>=}10{sup 6} cm{sup -3}, as suggested by the absence of similarly broad [O I] and [O III] emission lines, then the steady state inflow rate is {approx} 2 Multiplication-Sign 10{sup -2} M{sub Sun} yr{sup -1}, which exceeds the inflow requirement to explain the X-ray luminosity in terms of radiatively inefficient accretion by a factor of {approx}6. The central active galactic nucleus (AGN) is unable to sustain ionization of the broad-line region; the discrepancy is particularly acute in 2010 when the broad H{alpha} emission line is dominated by the contrail of the infalling supergiant star. However, ram pressure shock ionization produced by the interaction of the infalling supergiant with the ambient interstellar medium may help alleviate the ionizing deficit by generating a mechanical source of ionization supplementing the photoionization provided by the AGN.« less

Momentum balance in four solar flares

NASA Technical Reports Server (NTRS)

Canfield, Richard C.; Metcalf, Thomas R.; Zarro, Dominic M.; Lemen, James R.

1990-01-01

Solar Maximum Mission soft X-ray spectra and National Solar Observatory (Sacramento Peak) H-alpha spectra were combined in a study of high-speed flows during the impulsive phase of four solar flares. In all events, a blue asymmetry (indicative of upflows) was observed in the coronal Ca XIX line during the soft X-ray rise phase. In all events a red asymmetry (indicative of downflows) was observed simultaneously in chromospheric H-alpha. These oppositely directed flows were concurrent with impulsive hard X-ray emission. Combining the velocity data with estimates of the density based on emission measurements and volume estimates, it is shown that for the impulsive phase as a whole the total momentum of upflowing soft X-ray plasma equaled that of the downflowing H-alpha plasma, to within an order of magnitude, in all four events. Only the chromospheric evaporation model predicts equal total momentum in the upflowing soft X-ray-emitting and downflowing H-alphba-emitting materials.

Mass loss in the 96 day binary UU Cancri

NASA Technical Reports Server (NTRS)

Eaton, Joel A.; Hall, Douglas S.; Honeycutt, R. K.

1991-01-01

A series of 16 high-dispersion spectra at H-alpha have been obtained for the tidally distorted K giant-containing long-period binary UU Cnc, in order to both study the K giant's Doppler profiles and search for the effects of accretion onto the second component. While Doppler profiles of the system for a semidetached configuration fit the observations very well, those for existing overcontact light-curve solutions all yield poorer fits. Although the H-alpha line is always stronger than those of the common giants, its equivalent width is consistent with a K4 II classification reflective of the star's 50 solar radius size. Emission wings in H-alpha are possible evidence for an accretion disk.

Broad Halpha Wing Formation in the Planetary Nebula IC 4997.

PubMed

Lee; Hyung

2000-02-10

The young and compact planetary nebula IC 4997 is known to exhibit very broad wings with a width exceeding 5000 km s-1 around Halpha. We propose that the broad wings are formed through Rayleigh-Raman scattering that involves atomic hydrogen, by which Lybeta photons with a velocity width of a few 102 km s-1 are converted to optical photons and fill the Halpha broad wing region. The conversion efficiency reaches 0.6 near the line center, where the scattering optical depth is much larger than 1, and rapidly decreases in the far wings. Assuming that close to the central star there exists an unresolved inner compact core of high density, nH approximately 109-1010 cm-3, we use the photoionization code "CLOUDY" to show that sufficient Lybeta photons for scattering are produced. Using a top-hat-incident profile for the Lybeta flux and a scattering region with a H i column density NHi=2x1020 cm-2 and a substantial covering factor, we perform a profile-fitting analysis in order to obtain a satisfactory fit to the observed flux. We briefly discuss the astrophysical implications of the Rayleigh-Raman processes in planetary nebulae and other emission objects.

VIRUS-P Integral Field Spectroscopy of NGC 3310

NASA Astrophysics Data System (ADS)

Powell, Kathryn E.; Dufour, R. J.; Kwitter, K. B.; Robertson, P.

2012-05-01

We present the results of spectrophotometric mapping of the SAB(r)bc galaxy NGC 3310 using the VIRUS-P integral field spectrograph on the 2.7m Harlan Smith Telescope at McDonald Observatory (Hill et al. 2008 Proc. SPIE, 7014, 701470). VIRUS-P has an IFU consisting of 246 fibers arranged in an array covering a 2.82 arcmin square FOV with each fiber covering a 4.16 arcsec diameter region. The fibers have a 1/3 filling factor so the observations were dithered with alternating object-sky integrations. The FOV essentially covered the entire visible disk of NGC 3310, enabling a spatial study of the H II regions and stellar properties. Two grating tilts were used, resulting in spectra covering 3400-5600 A and 4600-6800 A with 5 A resolution. The spectra were combined, sky subtracted, and calibrated using the photometric standard star HZ44. We produced an integrated spectrum of the galaxy, which we compare with that from a study of NGC 628 with a similar instrument by Sanchez et al. (2011 MNRAS, 410, 313). We also present an analysis of radial variations in diagnostic emission line ratios of the H II regions such as [O III]5007/Hbeta (excitation), [N II]6583/Halpha, [S II]6717/6730 (electron density), and Halpha/Hbeta (reddening) among others. Since VIRUS-P obtained spectra of the stellar population adjacent to the H II regions, we can partially subtract the underlying stellar continua Balmer line absorption to improve the true Halpha/Hbeta ratio in the nebulae that is useful for mapping the radial variation in reddening and dust content. We also analyzed the radial variation in various emission lines in the H II regions to assess abundance gradients. This research is supported in part by a Rice University undergraduate research grant to K. Powell. We also express gratitude to McDonald Observatory, University of Texas at Austin, for a generous allotment of observing time.

Spectral observations of Be stars in the visible range. I - Phi Per, Psi Per, 11 Cam, and Phi And

NASA Astrophysics Data System (ADS)

Krugov, V. D.

1986-02-01

Phi Per was found to display considerable variations of emission in H-alpha and H-beta. The H-alpha and H-beta emission profiles of Psi Per appeared to vary with a period of several years. A complete disappearance of H-alpha emission was observed for 11 Cam. Finally, the H-alpha emission for Phi And did not display intensity variations during the entire period of observations in 1983.

A surprise at the bottom of the main sequence: Rapid rotation and NO H-alpha emission

NASA Technical Reports Server (NTRS)

Basri, Gibor; Marcy, Geoffrey W.

1995-01-01

We report Kech Observatory high-resolution echelle spectra from 640-850 nm for eight stars near the faint end of the main sequence. These spectra are the highest resolution spectra of such late-type stars, and clearly resolve the TiO, VO, and atomic lines. The sample includes the field brown-dwarf candidate, BRI 0021-0214 (M9.5+). Very unexpectedly, it shows the most rapid rotation in the entire samples, v sin i approximately 40 km/s, which is 20x faster than typical field nonemission M stars. Equally surprising is that BRI 0021 exhibits no emission or absorptionat H-alpha. We argue that this absence is not simply due to its cool photosphere, but that stellar activity declines in a fundamental way at the end of the main sequence. As it is the first very late M dwarf observed at high spectral resolution, BRI 0021 may be signaling a qualitative change in the angular momentum loss rate among the lowest mass stars. Conventionally, its rapid rotation would have marked BRI 0021 as very young, consistent with the selection effect which arises if the latest-type dwarfs are really brown dwarfs on cooling curves. In any case, it is unprecedented to find no sign of stellar activity in such a rapidly rotating convective star. We also discuss the possible conflict between this observation and the extremely strong H-alpha seen in another very cool star, PC 0025+0447. Extrapolation of M-L relations for BRI 0021 yields M approximately 0.065 solar mass, and the other sample objects have expected masses near the H-burning limit. These include two Pleiades brown-dwarf candidates, four field M6 dwarfs and one late-type T Tauri star. The two Pleiades M6 dwarfs have v sin i of 26 and 37 km/s, H-alpha in emission, and radial velocities consistent with Pleiades M6 dwarfs have v sin i of 26 and 37 km/s, H-alpha in emission, and radial velocities consistent with Pleiades membership. Similarly, the late-type T Tauri star has v sin i approximately 30 km/s and H alpha emission indicate of its youth. Two of the four late-type field dMe star also exhibit rotation above 5 km/s, consistent with expectations. BRI 0021 has no measurable absoprtion due to lithium, indicating that it is likely to be more massive than 0.065 solar mass.

ASCA Observations of "Type 2" LINERs Evidence for a Stellar Source of Ionization

NASA Technical Reports Server (NTRS)

Terashima, Yuichi; Ho, Luis C.; Ptak, Andrew F.; Mushotzky, Richard F.; Serlemitsos, Peter J.; Yaqoob, Tahir; Kunieda, Hideyo

1999-01-01

We present ASCA observations of LINERs without broad H.alpha emission in their optical spectra. The sample of "type 2" LINERs consists of NGC 404, 4111, 4192, 4457, and 4569. We have detected X-ray emission from all the objects except for NGC 404; among the detected objects are two so-called transition objects (NGC 4192 and NGC 4569), which have been postulated to be composite nuclei having both an H II region and a LINER component. The images of NGC 4111 and NGC 4569 in the soft (0.5-2 keV) and hard (2-7 keV) X-ray bands are extended on scales of several kpc. The X-ray spectra of NGC 4111, NGC 4457 and NGC 4569 are well fitted by a two-component model that consists of soft thermal emission with kT approximately 0.65 keV and a hard component represented by a power law (photon index approximately 2) or by thermal bremsstrahlung emission (kT approximately several keV). The extended hard X-rays probably come from discrete sources, while the soft emission most likely originates from hot gas produced by active star formation in the host galaxy. We have found no clear evidence for the presence of active galactic nuclei (AGNs) in the sample. Using black hole masses estimated from host galaxy bulge luminosities, we obtain an upper limit on the implied Eddington ratios less than 5 x 10(exp -5). If an AGN component is the primary ionization source of the optical emission lines, then it must be heavily obscured with a column density significantly larger than 10(exp 23)/sq cm, since the observed X-ray luminosity is insufficient to drive the luminosities of the optical emission lines. Alternatively, the optical emission could be ionized by a population of exceptionally hot stars. This interpretation is consistent with the small [O I] lambda6300/H.alpha ratios observed in these sources, the ultraviolet spectral characteristics in the cases where such information exists, and the X-ray results reported here. We also analyze the X-ray properties of NGC 4117, a low-luminosity Seyfert 2 galaxy serendipitously observed in the field of NGC 4111.

The Pleiades Using Astronomical Spectroscopic Technique within the Range of H-{alpha} Region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zambri Zainuddin, Mohd; Muhyidin, Meer Ashwinkumar; Ahmad, Nazhatulshima

2011-03-30

The Pleiades is an open star cluster located in the constellation of Taurus, which mainly consists of hot and luminous B-type stars. Observations were conducted over five-day period in December 2009 at Langkawi National Observatory, Malaysia by using 20-inch telescope diameter of Ritchey-Chretien reflector telescope, together with SBIG Self Guided Spectrograph and SBIG ST-7 CCD camera. The spectra of seven main members of the cluster, namely Alcyone; Atlas; Celaeno; Electra; Maia; Merope and Taygeta; and of Alcyone B; a smaller component of Alcyone quadruple system, were obtained in the optical range of approximately 6300 A to 7100 A. This rangemore » was picked due to the vicinity of Balmer H-{alpha} spectral line at 6562.852 A. Alcyone, Electra and Merope were found to have H-{alpha} emissions possibly caused by the presence of equatorial circumstellar disks or envelopes made up of ejected matter. Electra and Merope in particular exhibited peculiar asymmetric double emission peaks, which could be evidence of one-armed density wave in each of their circumstellar disks. Atlas, Celaeno, Merope, Taygeta and Alcyone B showed strong H-{alpha} absorptions with broadening characteristic of high rotational velocities. As deduced from the spectra, the stars were found to have atmospheres with similar chemical content, with spectral lines characteristics of singly ionized silicon, singly ionized iron and singly ionized oxygen. The measured radial velocities of all eight stars also suggest that the cluster could someday disperse.« less

Ultraviolet imaging telescope and optical emission-line observations of H II regions in M81

NASA Technical Reports Server (NTRS)

Hill, Jesse K.; Cheng, K.-P.; Bohlin, Ralph C.; Cornett, Robert H.; Hintzen, P. M. N.; O'Connell, Robert W.; Roberts, Morton S.; Smith, Andrew M.; Smith, Eric P.; Stecher, Theodore P.

1995-01-01

Images of the type Sab spiral galaxy M81 were obtained in far-UV and near-UV bands by the Ultraviolet Imaging Telescope (UIT) during the Astro-1 Spacelab mission of 1990 December. Magnitudes in the two UV bands are determined for 52 H II regions from the catalog of Petit, Sivan, & Karachentsev (1988). Fluxes of the H-alpha and H-beta emission lines are determined from CCD images. Extinctions for the brightest H II regions are determined from observed Balmer decrements. Fainter H II regions are assigned the average of published radio-H-alpha extinctions for several bright H II regions. The radiative transfer models of Witt, Thronson, & Capuano (1992) are shown to predict a relationship between Balmer Decrement and H-alpha extinction consistent with observed line and radio fluxes for the brightest 7 H II regions and are used to estimate the UV extinction. Ratios of Lyman continuum with ratios predicted by model spectra computed for initial mass function (IMF) slope equal to -1.0 and stellar masses ranging from 5 to 120 solar mass. Ages and masses are estimated by comparing the H-alpha and far-UV fluxes and their ratio with the models. The total of the estimated stellar masses for the 52 H II regions is 1.4 x 10(exp 5) solar mass. The star-formation rate inferred for M81 from the observed UV and H-alpha fluxes is low for a spiral galaxy at approximately 0.13 solar mass/yr, but consistent with the low star-formation rates obtained by Kennicutt (1983) and Caldwell et al. (1991) for early-type spirals.

Predicting the Redshift 2 H-Alpha Luminosity Function Using [OIII] Emission Line Galaxies

NASA Technical Reports Server (NTRS)

Mehta, Vihang; Scarlata, Claudia; Colbert, James W.; Dai, Y. S.; Dressler, Alan; Henry, Alaina; Malkan, Matt; Rafelski, Marc; Siana, Brian; Teplitz, Harry I.;

H-alpha images of the Cygnus Loop - A new look at shock-wave dynamics in an old supernova remnant

NASA Technical Reports Server (NTRS)

Fesen, Robert A.; Kwitter, Karen B.; Downes, Ronald A.

1992-01-01

Attention is given to deep H-alpha images of portions of the east, west, and southwest limbs of the Cygnus Loop which illustrate several aspects of shock dynamics in a multiphase interstellar medium. An H-alpha image of the isolated eastern shocked cloud reveals cloud deformation and gas stripping along the cloud's edges, shock front diffraction and reflection around the rear of the cloud, and interior remnant emission due to upstream shock reflection. A faint Balmer-dominated filament is identified 30 arcmin further west of the remnant's bright line of western radiative filaments. This detection indicates a far more westerly intercloud shock front position than previously realized, and resolves the nature of the weak X-ray, optical, and nonthermal radio emission observed west of NGC 6960. Strongly curved Balmer-dominated filaments along the remnant's west and southwest edge may indicate shock diffraction caused by shock wave passage in between clouds.

Observing Supernova 1987A with the Refurbished Hubble Space Telescope

NASA Technical Reports Server (NTRS)

France, Kevin; McCray, Richard; Heng, Kevin; Kirshner, Robert P.; Challis, Peter; Bouchet, Patrice; Crotts, Arlin; Dwek, Eli; Fransson, Claes; Garnavich, Peter M.;

Observations of a Windy Star

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-06-01

Hubble view of the Homunculus Nebula surrounding Eta Carinae [NASA Hubble Space Telescope/Jon Morse (University of Colorado)]The incredibly luminous massive star Eta Carinae has long posed a challenge for astronomers to model. New observations are now in so were our models correct?Dramatic TargetThe massive evolved star Eta Carinae, located 7,500 light-years away in the constellation Carina, is the most luminous star in the Milky Way. Eta Carinae has a quite a reputation for drama: it has been very unstable in the past, exhibiting repeated eruptions that have created the spectacular Homunculus Nebula surrounding it. Its present-day wind has the highest mass-loss rate of any hot star weve observed.Picture of Stellar WindTop panel: February 2017 observations of Eta Carinae in continuum (left) and H-alpha. Middle panel: the normalized radial profile for H-alpha and continuum emission. Bottom panel: the full width at half maximum for H-alpha and continuum emission of Eta Carinae. The H-alpha is about 2.5 to 3 milliarcseconds wider than the continuum. [Adapted from Wu et al. 2017]In our goal to understand the late evolutionary phases of very massive stars, weve developed radiative-transfer models to explain the behavior of Eta Carinae. One of the most well-known models, developed by John Hillier and collaborators in 2001, describes Eta Carinaes mass loss via stellar winds. With the right observations, this model is testable, since it predicts observable locations for different types of emission. In particular, one prediction of the Hillier et al. model is that the dense, ionized winds surrounding the star should emit in H-alpha at distances between 6 and 60 AU, with a peak around 20 AU.This nicely testable hypothesis is rendered less convenient by the fact that its hard to get resolved images of Eta Carinaes H-alpha emission. Its distance from us and the fact that its shrouded in the complex nebula it created have thus far prevented us from resolving the H-alpha emission from this star. Now, however, a team of scientists from Steward Observatory, University of Arizona have changed this.Confirming the ModelLed by Ya-Lin Wu, the team obtained diffraction-limited images of Eta Carinae using the Magellan adaptive optics system. The observations, made in both H-alpha and continuum, show that the H-alpha emitting region is significantly wider than the continuum emitting region, as predicted by the model. In fact, the measured emission implies that the H-alpha line-forming region may have a characteristic emitting radius of 2530 AU in very good agreement with the Hillier et al. stellar-wind model.This confirmation is strong support of the physical wind parameters estimated for Eta Carinae in the model, like the mass-loss rate of 10^-3 solar masses per year. These parameters are enormously helpful as we attempt to understand the physics of strong stellar-wind mass loss and the late evolutionary phases of very massive stars.CitationYa-Lin Wu et al 2017 ApJL 841 L7. doi:10.3847/2041-8213/aa70ed

Multiwavelength search for protoplanetary disks

NASA Technical Reports Server (NTRS)

Neuhaeuser, Ralph; Schmidt-Kaler, Theodor

1994-01-01

Infrared emission of circumstellar dust was observed for almost one hundred T Tauri stars. This dust is interpreted to be part of a protoplanetary disk orbiting the central star. T Tauri stars are young stellar objects and evolve into solar type stars. Planets are believed to form in these disks. The spectral energy distribution of a disk depends on its temperature profile. Different disk regions emit at different wavelengths. The disk-star boundary layer is hot and emits H(alpha) radiation. Inner disk regions at around 1 AU with a temperature of a few hundred Kelvin can be probed in near infrared wavelength regimes. Outer disk regions at around 100 AU distance from the star are colder and emit far infrared and sub-millimeter radiation. Also, X-ray emission from the stellar surface can reveal information on disk properties. Emission from the stellar surface and the boundary layer may be shielded by circumstellar gas and dust. T Tauri stars with low H(alpha) emission, i.e. no boundary layer, show stronger X-ray emission than classical T Tauri stars, because the inner disk regions of weak emission-line T Tauri stars may be clear of material. In this paper, first ROSAT all sky survey results on the X-ray emission of T Tauri stars and correlations between X-ray luminosity and properties of T Tauri disks are presented. Due to atmospheric absorption, X-ray and most infrared observations cannot be carried out on Earth, but from Earth orbiting satellites (e.g. IRAS, ROSAT, ISO) or from lunar based observatories, which would have special advantages such as a stable environment.

How fast do quasar emission lines vary? First results from a program to monitor the Balmer lines of the Palomar-Green Quasars

NASA Technical Reports Server (NTRS)

Maoz, Dan; Smith, Paul S.; Jannuzi, Buell T.; Kaspi, Shai; Netzer, Hagai

1994-01-01

We have monitored spectrophotometrically a subsample (28) of the Palomar-Green Bright Quasar Sample for 2 years in order to test for correlations between continuum and emission-line variations and to determine the timescales relevant to mapping the broad-line regions of high-luminosity active galactic nuclei (AGNs). Half of the quasars showed optical continuum variations with amplitudes in the range 20-75%. The rise and fall time for the continuum variations is typically 0.5-2 years. In most of the objects with continuum variations, we detect correlated variations in the broad H-alpha and H-beta emission lines. The amplitude of the line variations is usually 2-4 times smaller than the optical continuum fluctuations. We present light curves and analyze spectra for six of the variable quasars with 1000-10,000 A luminosity in the range 0.3-4 x 10(exp 45) ergs/s. In four of these objects the lines respond to the continuum variations with a lag that is smaller than or comparable to our typical sampling interval (a few months). Although continued monitoring is required to confirm these results and increase their accuracy, the present evidence indicates that quasars with the above luminosities have broad-line regions smaller than about 1 1t-yr. Two of the quasars monitored show no detectable line variations despite relatively large-amplitude continuum changes. This could be a stronger manifestation of the low-amplitude line-response phenomenon we observe in the other quasars.

The Northern Middle Lobe of Centaurus A: Circumgalactic Gas in a Starburst Wind

NASA Technical Reports Server (NTRS)

Neff, S. G.; Eilek, J. A.; Owen, F. N.; Schiminovich, D.; Seibert, M.; Thilker, D.

2012-01-01

We present deep ultraviolet (GALEX), radio continuum (VLA) and H-alpha (Magellan) images of the circumgalactic medium around Centaurus A (NGC5128). We focus on the Northern Middle Lobe (NML), a region extending more than 50kpc beyond the galaxy and known to host a collection of striking phenomena: emission line filaments, recent star formation, disrupted HI/molecular gas streams, and short-lived X-ray clouds. Far UV emission is tightly correlated with H-alpha emission for more than 50kpc, and loosely associated with a filament of X-ray clouds and with the radio continuum emission. The radio emission in the NML region does not appear to be an extension of the inner radio jet (10kpc) or a typical radio lobe. We speculate that the "weather" seen in the NML region is a short-lived phenomenon, caused by an outflow encountering cool gas deposited by one of the recent merger/encounter events which have characterized the history of NGC5128.

Distant intense starbursts: evidence for self-regulated star formation?

NASA Astrophysics Data System (ADS)

Lehnert, M. D.

From an analysis of the Halpha and [NII]∼λ6583 rest-frame optical emission lines in a large sample of intensely star forming galaxies at z=1.3 to 2.7 observed with SINFONI on the ESO-VLT, we have reached a number of conclusions. The galaxies all have broad optical emission lines (sigma ˜50-250 km s-1) which are a function of the underlying star formation intensity as determined from the Halpha surface brightness. These broad lines are intrinsic to the galaxies and not due to beam smearing. The velocity dispersions appear to be related to the star formation intensity (Sigma SFR, star formation rate per unit area) of the form, sigma ˜ epsilon Sigma SFR1/2. This is a simple and direct relationship between the energy injection rate and the kinetic energy of the emission line gas with a coupling efficiency of epsilon . In this contribution, we outline a simple model whereby the energy output of massive stars, both mechanical and radiative, feeds a mass and energy cycle within the interstellar media of these distant galaxies. The mass and energy cycle pushes the global ISM towards the line of stability, Toomre parameter Q˜1, but only if the molecular gas captures, to some extent, the kinematics of the warm ionized gas as probed by the optical emission lines. In such a picture, the star formation intensity is self-regulating.} This work and many of the ideas presented here were developed in collaboration with L. Le Tiran, W. van Driel, P. Di Matteo (GEPI), N. Nesvadba, and F. Boulanger (IAS, Orsay, France).

Aging jets from low-mass stars

NASA Technical Reports Server (NTRS)

Graham, J. A.; Chen, W. P.

1994-01-01

An extended faint optical jet is associated with the compact emission region plus faint star known as HH 55. HH 55 is located in the Lupus 2 cloud 2 min SW of the well studied T Tauri star RU Lupi. The HH 55 jet extends 55 sec N and 35 sec S in PA 160 deg. The HH 55 star is an emission line star of spectral type M3.5. Its image in the emission lines of H-alpha and (S II) is slightly elongated by 2 sec - 3 sec to the S but in continuum light is symmetrical and pointlike ((full width at half maximum) (FWHM) = 1.7 sec). The star and jet have several features in common with the star and jet known as Sz 102 = Th 28 in the nearby Lupus 3 cloud. We suggest that these objects are representative of the late evolutionary stage of the HH jet-outflow phenomenon and point out that such objects may be quite common although difficult to detect. With L(sub bol) approximately = 0.005 solar luminosity, and log T(sub e) approximately = 3.5, the HH 55 star is close to the main sequence and evolutionary tracks suggest an age of 3 x 10(exp 7) yr.

DUST EXTINCTION FROM BALMER DECREMENTS OF STAR-FORMING GALAXIES AT 0.75 {<=} z {<=} 1.5 WITH HUBBLE SPACE TELESCOPE/WIDE-FIELD-CAMERA 3 SPECTROSCOPY FROM THE WFC3 INFRARED SPECTROSCOPIC PARALLEL SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dominguez, A.; Siana, B.; Masters, D.

Spectroscopic observations of H{alpha} and H{beta} emission lines of 128 star-forming galaxies in the redshift range 0.75 {<=} z {<=} 1.5 are presented. These data were taken with slitless spectroscopy using the G102 and G141 grisms of the Wide-Field-Camera 3 (WFC3) on board the Hubble Space Telescope as part of the WFC3 Infrared Spectroscopic Parallel survey. Interstellar dust extinction is measured from stacked spectra that cover the Balmer decrement (H{alpha}/H{beta}). We present dust extinction as a function of H{alpha} luminosity (down to 3 Multiplication-Sign 10{sup 41} erg s{sup -1}), galaxy stellar mass (reaching 4 Multiplication-Sign 10{sup 8} M {sub Sunmore » }), and rest-frame H{alpha} equivalent width. The faintest galaxies are two times fainter in H{alpha} luminosity than galaxies previously studied at z {approx} 1.5. An evolution is observed where galaxies of the same H{alpha} luminosity have lower extinction at higher redshifts, whereas no evolution is found within our error bars with stellar mass. The lower H{alpha} luminosity galaxies in our sample are found to be consistent with no dust extinction. We find an anti-correlation of the [O III] {lambda}5007/H{alpha} flux ratio as a function of luminosity where galaxies with L {sub H{alpha}} < 5 Multiplication-Sign 10{sup 41} erg s{sup -1} are brighter in [O III] {lambda}5007 than H{alpha}. This trend is evident even after extinction correction, suggesting that the increased [O III] {lambda}5007/H{alpha} ratio in low-luminosity galaxies is likely due to lower metallicity and/or higher ionization parameters.« less

The Universe as Viewed from Star Forming Galaxies over the Past Ten Billion Years

NASA Astrophysics Data System (ADS)

Ly, Chun; Malkan, M.; Lee, J. C.; Kashikawa, N.; Hayashi, M.; Motohara, K.; Subaru Deep Field Collaboration; NEWFIRM Narrow-band H-alpha Survey Team

2010-01-01

In this dissertation talk, I will discuss my work to provide improved constraints on the star formation history of the universe by (1) using narrow-band filters to identify galaxies to z 2.2 and (2) extending the Lyman break technique to z=1.5-3. These techniques efficiently isolate a large population of star-forming galaxies and enable measurement of the star formation rate via emission line and ultraviolet indicators. With the SDF team, we have conducted a narrow-band optical survey which yields a sample of 5000 galaxies within 0.25 square degree to z 1.5 detected by H-alpha, [OIII], or [OII]. Diagnostics based on broad-band optical colors are developed to resolve ambiguities in emission-line identification. In addition, with the NEWFIRM H-alpha team, we are working to extend optical studies into the near-infrared with NEWFIRM. We target H-alpha emitting galaxies at z 0.8 and z 2.2, which probes a critical period in the history of the universe during which much of the star formation has occurred. The NEWFIRM H-alpha survey covers over 1 square degree. A total of 300 H-alpha emitting galaxies at z 0.8 has been identified for 60% of the survey volume. Preliminary results from the NEWFIRM H-alpha Survey will be discussed. Spectroscopy for both narrow-band surveys reveals a high reliability of the technique: contamination at the few percent level. Finally, I will describe the first Lyman break survey to select star-forming galaxies at z 2 (limiting magnitude of 27 AB), using deep, wide GALEX near-ultraviolet imaging. A total of 7000 LBGs was identified in 0.25 square degree. Spectroscopy indicates that the success of identifying z 2 galaxies is 80%. I will also compare different z 2 photometric techniques (BzK, DRG, BX/BM) to provide a more comprehensive view of the galaxy population, including dusty star-forming galaxies. The comparison reveals a good but imperfect ( 50%) overlap, indicating that these photometric techniques are complementary.

Spectroscopy of chromospheric lines of giants in the globular cluster

NASA Technical Reports Server (NTRS)

Dupree, A. K.; Hartmann, Lee; Smith, Graeme H.; Rodgers, A. W.; Roberts, W. H.; Zucker, D. B.

1994-01-01

Spectroscopic observations of chromospheric transitions (Mg II, H-alpha, and Ca II K) from two red giants (A31 and A59) in the globular cluster NGC 6572 were made with the Goddard High Resolution Spectrograph on the Hubble Space Telescope and the coude spectrograph of the 1.9 m telescope at the Mount Stromlo Observatory. These measurements give evidence for chromospheric activity and outward motions within the atmospheres. The surface flux of the Mg II emission is comparable to that in disk population giants of similar (B-V) color. The Mg II profiles are asymmetric, which is most likely caused by absorption in an expanding stellar atmosphere and/or by possible interstellar features. Notches are found in the core of the H-alpha line of A59, which are similar to those found in Cepheids. This suggests that shocks are present in the atmosphere of A59 and indicates that hydrodynamic phenomena are influencing the levvel of chromospheric emission and producing upper atmospheric motions which may lead to mass loss.

Evidence for explosive chromospheric evaporation in a solar flare observed with SMM

NASA Technical Reports Server (NTRS)

Zarro, D. M.; Saba, J. L. R.; Strong, K. T.; Canfield, R. C.; Metcalf, T.

1986-01-01

SMM soft X-ray data and Sacramento Peak Observatory H-alpha observations are combined in a study of the impulsive phase of a solar flare. A blue asymmetry, indicative of upflow motions, was observed in the coronal Ca XIX line during the soft X-ray rise phase. H-alpha redshifts, indicative of downward motions, were observed simultaneously in bright flare kernels during the period of hard X-ray emission. It is shown that, to within observational errors, the impulsive phase momentum transported by the upflowing soft X-ray plasma is equivalent to that of the downward moving chromospheric material.

New spectroscopic and photometric observations of CV J0644+3344

NASA Astrophysics Data System (ADS)

Hernández Santisteban, J. V.

We report photometric and simultaneous spectroscopic observations of the cataclysmic variable J0644+3344 and present calibrated Doppler tomography results of the object. We have calibrated the spectra for slit losses using simultaneous photometry. This has been used to construct reliable Doppler images in the Halpha , Hbeta and He II 4686 Å@ emission lines. We have also performed a radial velocity analysis using these emission lines to derive the primary semi-amplitude and used a cophasing method to determine the secondary K_2 best value. We have improved the ephemeris of the object based on the published and our new photometric eclipse timings to obtain HJD=254474.7927+0.26937446E. We derived a K_1=123.2±6.6 {km s}-1 and K_2=205.4±6.7. Assuming a i>76, the orbital parameters are M_1=0.91±0.04 M⊙, M_2=0.83±0.04 M⊙ and a=2.10±0.03 R⊙. Based on the Doppler tomography we conclude that J0644+3344 is a nova-like SW Sex type system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devereux, Nick, E-mail: devereux@erau.edu

Prior imaging of the lenticular galaxy, NGC 3998, with the Hubble Space Telescope revealed a small, highly inclined, nuclear ionized gas disk, the kinematics of which indicate the presence of a 270 million solar mass black hole. Plausible kinematic models are used to constrain the size of the broad emission line region (BELR) in NGC 3998 by modeling the shape of the broad H{alpha}, H{beta}, and H{gamma} emission line profiles. The analysis indicates that the BELR is large with an outer radius {approx}7 pc, regardless of whether the kinematic model is represented by an accretion disk or a spherically symmetricmore » inflow. The electron temperature in the BELR is {<=} 28,800 K consistent with photoionization by the active galactic nucleus (AGN). Indeed, the AGN is able to sustain the ionization of the BELR, albeit with a high covering factor ranging between 20% and 100% depending on the spectral energy distribution adopted for the AGN. The high covering factor favors a spherical distribution for the gas as opposed to a thin disk. If the gas density is {>=}7 x 10{sup 3} cm{sup -3} as indicated by the broad forbidden [S II] emission line ratio, then interpreting the broad H{alpha} emission line in terms of a steady state spherically symmetric inflow leads to a rate {<=} 6.5 x 10{sup -2} M{sub sun} yr{sup -1} which exceeds the inflow requirement to explain the X-ray luminosity in terms of a radiatively inefficient inflow by a factor of {<=}18.« less

The nova-like cataclysmic variable star: KUV 0859+415

NASA Astrophysics Data System (ADS)

Grauer, Albert D.; Ringwald, F. A.; Wegner, Gary; Liebert, James; Schmidt, Gary D.; Green, Richard F.

1994-07-01

KUV 0859+415 has been found to be an eclipsing, nova-like cataclysmic variable with an orbital period of 3 h and 40 min. We find that it differs from other eclipsing systems of similar period (sometimes called the SW Sex stars) in several important respects. First, the eclipses are shallow, V-shaped dips, suggesting that the inclination angle is relatively low. Also, while the excitation of the emission lines are relatively high (He II comparable to H-beta), they are relatively weak compared to the continuum. The high Balmer lines have broad absorption wings, characteristic of an optically thick accretion disk. Yet there is evidence for a 'hot spot' in the system, which reaches peak brightness near phase 0.9 before the eclipse. Perhaps the most puzzling property of this system is that the H-alpha emission line radial velocity leads rather than lags the expected position for the location of the accretion disk. We present briefly a phenomenological model for the system which has a hot spot located at the normal location for the accretion stream to first impact the disk and is the source of excess optical continuum. However, the velocity curve of the emission lines requires us to conclude that the bulk of this radiation forms on the opposite side of the disk. This also explains the fact that the peak equivalent widths of H-alpha occur at phases 0.4-0.5.

Gas kinematics of Lyman Alpha Blobs at z=2-3

NASA Astrophysics Data System (ADS)

Yang, Yujin

2015-08-01

High-redshift Lyman alpha nebulae (Ly-alpha "blobs", LABs) are the site of massive galaxy formation and their early interaction with the intergalactic medium. Research in the past decade has struggled to make progress on the question of what powers these huge Ly-alpha halos and whether the Ly-alpha-emitting gas is outflowing or infalling. First, I will present our optical and NIR spectroscopic observations for the Ly-alpha and the redshifted nebular emission lines such as [OII], [OIII] and Halpha. Using three independent measures --- the velocity offset between the Ly-alpha line and the nonresonant [O III] or Halpha line, the offset of stacked interstellar metal absorption lines, and the spectrally resolved [O III] line profile --- we study the kinematics of gas along the line of sight to galaxies within each blob center. All these kinematic measures show that there are only weak outflows, therefore excluding gas inflows and extreme hyper/superwinds as a source of the extended Ly-alpha emission. I will also present the first detection of molecular gas from a Ly-alpha blob and our on-going effort to characterize the physical conditions of its ISM. The large velocity gradient (LVG) modeling using PdBI observations of CO(3-2), CO(5-4), CO(7-6), CI(2-1) lines suggests that two-phase medium is required to explain the blob's CO SEDs and dust continuum.

A study of excess H-alpha emission in chromospherically active M dwarf

NASA Technical Reports Server (NTRS)

Young, Arthur; Skumanich, Andrew; Stauffer, John R.; Harlan, Eugene; Bopp, Bernard W.

1989-01-01

Spectroscopic observations from three observatories are combined to study the properties of the excess H-alpha emission which characterizes the most chromospherically active subset of the M dwarf stars, known as the dMe stars. It is demonstrated that the excess H-alpha luminosity from these stars is a monotonically decreasing function of their (R-I) color, and evidence is presented which suggests that the product of the mean surface brightness and the mean filling factor of the emissive regions is essentially constant with color. Another significant result of the study is a linear correlation between the excess luminosity in H-alpha and the coronal X-ray luminosity.

An atlas of H-alpha-emitting regions in M33: A systematic search for SS433 star candidates

NASA Technical Reports Server (NTRS)

Calzetti, Daniela; Kinney, Anne L.; Ford, Holland; Doggett, Jesse; Long, Knox S.

1995-01-01

We report finding charts and accurate positions for 432 compact H-alpha emitting regions in the Local Group galaxy M 33 (NGC 598), in an effort to isolate candidates for an SS433-like stellar system. The objects were extracted from narrow band images, centered in the rest-frame H-alpha (lambda 6563 A) and in the red continuum at 6100 A. The atlas is complete down to V approximately equal to 20 and includes 279 compact HII regions and 153 line emitting point-like sources. The point-like sources undoubtedly include a variety of objects: very small HII regions, early type stars with intense stellar winds, and Wolf-Rayet stars, but should also contain objects with the characteristics of SS433. This extensive survey of compact H-alpha regions in M 33 is a first step towards the identification of peculiar stellar systems like SS433 in external galaxies.

Economical Emission-Line Mapping: ISM Properties of Nearby Protogalaxy Analogs

NASA Astrophysics Data System (ADS)

Monkiewicz, Jacqueline A.

2017-01-01

Optical emission line imaging can produce a wealth of information about the conditions of the interstellar medium, but a full set of custom emission-line filters for a professional-grade telescope camera can cost many thousands of dollars. A cheaper alternative is to use commercially-produced 2-inch narrow-band astrophotography filters. In order to use these standardized filters with professional-grade telescope cameras, custom filter mounts must be manufactured for each individual filter wheel. These custom filter adaptors are produced by 3-D printing rather than standard machining, which further lowers the total cost.I demonstrate the feasibility of this technique with H-alpha, H-beta, and [OIII] emission line mapping of the low metallicity star-forming galaxies IC10 and NGC 1569, taken with my astrophotography filter set on three different 2-meter class telescopes in Southern Arizona.

Balmer line profiles for infalling T Tauri envelopes

NASA Technical Reports Server (NTRS)

Calvet, Nuria; Hartmann, Lee

1992-01-01

The possibility that the Balmer emission lines of T Tauri stars arise in infalling envelopes rather than winds is considered. Line profiles for the upper Balmer lines are presented for models with cone geometry, intended to simulate the basic features of magnetospheric accretion from a circumstellar disk. An escape probability treatment is used to determine line source functions in nonspherically symmetric geometry. Thermalization effects are found to produce nearly symmetric H-alpha line profiles at the same time the higher Balmer series lines exhibit inverse P Cygni profiles. The infall models produce centrally peaked emission line wings, in good agreement with observations of many T Tauri stars. It is suggested that the Balmer emission of many T Tauri stars may be produced in an infalling envelope, with blue shifted absorption contributed by an overlying wind. Some of the observed narrow absorption components with small blueshifts may also arise in the accretion column.

Rotation and chromospheric emission among F, G, and K dwarfs of the Pleiades

NASA Technical Reports Server (NTRS)

Soderblom, David R.; Stauffer, John R.; Hudon, J. D.; Jones, Burton F.

1993-01-01

High-resolution echelle spectra of more than 100 F, G, and K dwarfs in the Pleiades are reported. Chromospheric activity in these stars is measured via comparisons of the profiles of H-alpha and the Ca II IR triplet to chromospherically inactive field stars. Consistent dereddened colors are determined from the available photometry and temperatures are derived. Most G and K dwarfs in the Pleiades rotate slowly, but about 20 percent of the stars are ultrafast rotators (UFRs). That fraction of UFRs is independent of color, and the highest rotation rates are found among the K dwarfs. The Pleiades exhibit a broad range in the strength of chromospheric emission at any one color. Most G and K dwarfs in the Pleiades show H-alpha and the IR triple in absorption, with filling in of the line cores.

New Nova Candidates from the RSBE M31 Nova Survey

NASA Astrophysics Data System (ADS)

Lauber, Stephanie; Rector, Travis A.; Shafter, Allen W.

2015-01-01

Since 1995 the Kitt Peak National Observatory WIYN 0.9-m telescope has been used to monitor M31 for novae as part of the Research-Based Science Education Project (RBSE). The resulting images, which typically cover approximately the inner 20 arc min of M31, are taken through a broad-band H-alpha filter to isolate the strong H-alpha emission lines characteristic of novae shortly after eruption.We are in the process of reanalyzing the entire RBSE data set covering the period between September 1995 and August 2014 in order to produce an up-to-date list of novae from this survey. Here, we present coordinates and H-alpha magnitudes for 4 new nova discoveries not previous reported. Among the new nova discoveries, one system appears spatially coincident with M31N 1988-09a, and is thus a recurrent nova candidate.

The morphology of flare phenomena, magnetic fields, and electric currents in active regions. II - NOAA active region 5747 (1989 October)

NASA Technical Reports Server (NTRS)

Leka, K. D.; Canfield, Richard C.; Mcclymont, A. N.; De La Beaujardiere, J.-F.; Fan, Yuhong; Tang, F.

1993-01-01

The paper describes October 1989 observations in NOAA Active Region 5747 of the morphology of energetic electron precipitation and high-pressure coronal flare plasmas of three flares and their relation to the vector magnetic field and vertical electric currents. The H-alpha spectroheliograms were coaligned with the vector magnetograms using continuum images of sunspots, enabling positional accuracy of a few arcsec. It was found that, during the gradual phase, the regions of the H-alpha flare that show the effects of enhanced pressure in the overlying corona often encompass extrema of the vertical current density, consistent with earlier work showing a close relationship between H-alpha emission and line-of-sight currents. The data are also consistent with the overall morphology and evolution described by erupting-filament models such as those of Kopp and Pneuman (1976) and Sturrock (1989).

A study of the continuum flux and the line structure in the IUE spectrum of Beta Lyrae

NASA Technical Reports Server (NTRS)

Aydin, C.; Engin, S.; Brandi, E.; Ferrer, O. E.; Hack, M.

1988-01-01

A study of the available archival IUE images of Beta Lyrae has led to the following results: (1) for lambda in the range of 1250 - 1500 A, the eclipse depth at second conjunction is slightly larger than the eclipse depth at primary conjunction; they are equal at about 1670 A; (2) the profiles of the resonance lines of SiIV (and the same seems to be true for NV and CIV) can be described as composite, formed by the superposition of a stationary P Cygni profile that suggests a velocity of approach of -170 km/s and a broad, less strong, emission that seems to yield a velocity distribution in antiphase with the velocity curve of the B8 II component of the system; and (3) the emission lines of the intercombination doublet of semiforbidden N II at about 2140 A suggest a velocity of about -130 km/s. The interpretation of the latter composite profile appears similar to the one suggested by Sahade (1966) to describe H-alpha and He I 5876 and He I 6678, and by Batten and Sahade (1973) to describe H-alpha.

The Surprising Absence of Absorption in the Far-ultraviolet Spectrum of Mrk 231

NASA Technical Reports Server (NTRS)

Veilleux, S.; Trippe, M.; Hamann, F.; Rupke, D. S. N.; Tripp, T. M.; Netzer, H.; Lutz, D.; Sembach, K. R.; Krug, H.; Teng, Stacy H.;

Diagnostics of red-shifted H-alpha line emission from a C-class flare with full non-LTE radiative and hydrodynamic approach

NASA Astrophysics Data System (ADS)

Druett, M. K.; Zharkova, V. V.; Scullion, E.; Zharkov, S.; Matthews, S. A.

2016-12-01

We analyse H-alpha line profiles with strong redshifts during the C1.8 flare on 1st July 2012 obtained from the Swedish Solar Telescope (SST) closely resembling the previous observations (Wuelser and Marti, 1989). The flare has a magnetic field configuration with two levels of loop structures. The kernels with red shifts are observed in one of the H-alpha ribbons in the south-west location formed after the main impulse recorded in the north-east. The locations of H-alpha kernels with red shifts reveal close temporal and spatial correlation with weaker HXR signatures and coincide with the locations of coronal jets observed with AIA/SDO. For interpretation we apply a revised 1D hydrodynamic and non-LTE (NLTE) radiative model for 5 level plus continuum model hydrogen atom (Druett & Zharkova, 2016) considering radiative, thermal and non-thermal excitation and ionisation by beam electrons with the updated beam densities (Zharkova & Dobranskis, 2016) and analytical excitation/ionisation rates (Zharkova& Kobylinskijj, 1993). We find the simultaneous solutions of steady state and radiative transfer equations in all optically-thick lines and continua. The electron and ion temperatures, ambient density and macrovelocity of the ambient plasma are derived from a 1D hydrodynamic model with initial condition of the pre-flaring photosphere for the two fluid ambient plasma heated by beam electrons (Zharkova & Zharkov, 2007). We simulate distributions over precipitation depth of ionisation and departure coefficients for all the hydrogen atom transitions including the deviation of ionisation from Saha equation affected by non-thermal electron beams. We show that in the very first seconds after the beam onset Balmer line profiles are sensitive to the effect of beam electrons. The combination of the additional ionisation caused by beam electrons leading to a very strong Stark effect in Balmer lines with the hydrodynamic heating and formation of a low temperature shock in the chromosphere is shown to closely account for the visible asymmetric H-alpha line profiles with strong red shifts observed now and in the past. The interplay between the ambient plasma heating and non-thermal collisional excitation and ionisation rates by beam electrons is shown to define the Balmer line red shifts and continuum enhancements.

MASS OUTFLOW FROM RED GIANT STARS IN M13, M15, AND M92

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meszaros, Sz.; Avrett, E. H.; Dupree, A. K.

Chromospheric model calculations of the H{alpha} line for selected red giant branch and asymptotic giant branch (AGB) stars in the globular clusters M13, M15, and M92 are constructed to derive mass loss rates (MLRs). The model spectra are compared to the observations obtained with the Hectochelle on the MMT telescope. These stars show strong H{alpha} emissions and blueshifted H{alpha} cores signaling that mass outflow is present in all stars. Outflow velocities of 3-19 km s{sup -1}, larger than indicated by H{alpha} profiles, are needed in the upper chromosphere to achieve good agreement between the model spectra and the observations. Themore » resulting MLRs range from 0.6 x 10{sup -9} to 5 x 10{sup -9} M {sub sun} yr{sup -1}, which are about an order of magnitude lower than predicted from 'Reimers' law' or inferred from the infrared excess of similar stars. The MLR increases slightly with luminosity and with decreasing effective temperature. Stars in the more metal-rich M13 have higher MLRs by a factor of {approx}2 than in the metal-poor clusters M15 and M92. A fit to the MLRs is given by M-dot (M {sub sun} yr{sup -1}) = 0.092 xL {sup 0.16} x T {sup -2.02} {sub eff} x A {sup 0.37}, where A=10{sup [Fe/H]}. Multiple observations of stars revealed one object in M15, K757, in which the mass outflow increased by a factor of 6 between two observations separated by 18 months. Other stars showed changes in MLR by a factor of 1.5 or less.« less

The High-Excitation Planetary Nebula NCG 246: Optical and Near-Ultraviolet Observations and Two-dimensional Numerical Models

NASA Technical Reports Server (NTRS)

Szentgyorgyi, Andrew; Raymond, John; Franco, Jose; Villaver, Eva; Lopez-Martin, Luis

2003-01-01

We have imaged the planetary nebula (PN) NGC 246 in the near-ultraviolet wavelengths [Ne v] 342.6 nm, the Bowen fluorescence line of 0 111 at 344.4 nm, and a nearby line-free region centered on 338.6 nm, as well as H(alpha), [O III] 500.7 nm, and [S II] 673.0 and 671.5 nm. Imaging in the 344.4 nm line is necessary to deconvolve contamination of the [Ne v] images by O III 342.9 nm. The emission from the shell and inner parts of the nebula is detected in [Ne v]. The radial profiles of the [Ne v] brightness decrease with radius from the exciting star, indicating that the bulk of the emission from this ion is due to the hard UV stellar radiation field, with a (probably) marginal contribution from collisional ionization in a shock between the PN shell and the interstellar medium (ISM). In contrast, the radial profiles of the emission in H(alpha), [0 III] 500.7 nm, and [S II] are flatter and peak at the location of the shell. The emission of [S II] probably traces the interaction of the PN with the ambient ISM. We also present two-dimensional numerical simulations for this PN-ISM interaction. The simulations consider the stellar motion with respect to the ambient ISM, with a velocity of 85 km/s , and include the time evolution of the wind parameters and UV radiation field from the progenitor star.

Spectroscopic classification of AT2018aes as a supernova impostor

NASA Astrophysics Data System (ADS)

Andrews, Jennifer; Smith, Nathan; Van Dyk, Schuyler D.

2018-03-01

A visual-wavelength optical spectrum of AT2018aes obtained on UT 2018 Mar 13 (JD 2458190.84) with the Magellan Clay telescope (+ LDSS3 spectrograph, VPH-all grism) reveals a narrow H-alpha emission line with a velocity of 525 km/s, with wings extending to roughly +/-1000 km/s.

THE BALMER-DOMINATED BOW SHOCK AND WIND NEBULA STRUCTURE OF {gamma}-RAY PULSAR PSR J1741-2054

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romani, Roger W.; Shaw, Michael S.; Camilo, Fernando

2010-12-01

We have detected an H{alpha} bow shock nebula around PSR J1741-2054, a pulsar discovered through its GeV {gamma}-ray pulsations. The pulsar is only {approx}1.''5 behind the leading edge of the shock. Optical spectroscopy shows that the nebula is non-radiative, dominated by Balmer emission. The H{alpha} images and spectra suggest that the pulsar wind momentum is equatorially concentrated and implies a pulsar space velocity {approx}150 km s{sup -1}, directed 15{sup 0} {+-} 10{sup 0} out of the plane of the sky. The complex H{alpha} profile indicates that different portions of the post-shock flow dominate line emission as gas moves along themore » nebula and provide an opportunity to study the structure of this unusual slow non-radiative shock under a variety of conditions. CXO ACIS observations reveal an X-ray pulsar wind nebula within this nebula, with a compact {approx}2.''5 equatorial structure and a trail extending several arcminutes behind. Together these data support a close ({<=}0.5 kpc) distance, a spin geometry viewed edge-on, and highly efficient {gamma}-ray production for this unusual, energetic pulsar.« less

MONITORING H{alpha} EMISSION AND CONTINUUM OF UXORs: RR Tauri

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bedell, Megan; Villaume, Alexa; Weiss, Lauren

2011-11-15

The Maria Mitchell Observatory, in collaboration with the Astrokolkhoz Observatory, started a program of photometric monitoring of UX Ori-type stars (UXORs) with narrowband interference filters (IFs; augmented with the traditional broadband filters) aimed at separating the H{alpha} emission variations from those of the continuum. We present the method of separation and the first results for RR Tau obtained in two seasons, each roughly 100 days long (2010 Winter-Spring and 2010 Fall-2011 Spring). We confirm the conclusion from previous studies that the H{alpha} emission in this star is less variable than the continuum. Although some correlation between the two is notmore » excluded, the amplitude of H{alpha} variations is much smaller (factors of 3-5) than that of the continuum. These results are compatible with Grinin's model of UXORs, which postulates the presence of small obscuring circumstellar clouds as the cause of the continuum fading, as well as the presence of a circumstellar reflection/emission nebula, larger than the star and the obscuring clouds, which is responsible for H{alpha} emission and the effect of the 'color reversal' in deep minima. However, the results of both our broadband and narrowband photometry indicate that the obscuration model may be insufficient to explain all of the observations. Disk accretion, the presence of stellar or (proto) planetary companion(s), as well as the intrinsic variations of the star, may contribute to the observed light variations. We argue, in particular, that the H{alpha} emission may be more closely correlated with the intrinsic variations of the star than with the much stronger observed variations caused by the cloud obscuration. If this hypothesis is correct, the close monitoring of H{alpha} emission with IFs, accessible to small-size telescopes, may become an important tool in studying the physical nature of the UXORs' central stars.« less

COMPLEX VARIABILITY OF THE H{alpha} EMISSION LINE PROFILE OF THE T TAURI BINARY SYSTEM KH 15D: THE INFLUENCE OF ORBITAL PHASE, OCCULTATION BY THE CIRCUMBINARY DISK, AND ACCRETION PHENOMENA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamilton, Catrina M.; Johns-Krull, Christopher M.; Mundt, Reinhard

2012-06-01

We have obtained 48 high-resolution echelle spectra of the pre-main-sequence eclipsing binary system KH 15D (V582 Mon, P = 48.37 days, e {approx} 0.6, M{sub A} = 0.6 M{sub Sun }, M{sub B} = 0.7 M{sub Sun }). The eclipses are caused by a circumbinary disk (CBD) seen nearly edge on, which at the epoch of these observations completely obscured the orbit of star B and a large portion of the orbit of star A. The spectra were obtained over five contiguous observing seasons from 2001/2002 to 2005/2006 while star A was fully visible, fully occulted, and during several ingressmore » and egress events. The H{alpha} line profile shows dramatic changes in these time series data over timescales ranging from days to years. A fraction of the variations are due to 'edge effects' and depend only on the height of star A above or below the razor sharp edge of the occulting disk. Other observed variations depend on the orbital phase: the H{alpha} emission line profile changes from an inverse P-Cygni-type profile during ingress to an enhanced double-peaked profile, with both a blue and a red emission component, during egress. Each of these interpreted variations are complicated by the fact that there is also a chaotic, irregular component present in these profiles. We find that the complex data set can be largely understood in the context of accretion onto the stars from a CBD with gas flows as predicted by the models of eccentric T Tauri binaries put forward by Artymowicz and Lubow, Guenther and Kley, and de Val-Borro et al. In particular, our data provide strong support for the pulsed accretion phenomenon, in which enhanced accretion occurs during and after perihelion passage.« less

Discovery of a Possible Symbiotic Binary in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Mathew, Blesson; Reid, Warren A.; Mennickent, R. E.; Banerjee, D. P. K.

2017-12-01

We report the discovery of a possible symbiotic star, in the Large Magellanic Cloud (LMC). The object under consideration here, designated as RP 870, was detected during the course of a comprehensive H$\\alpha$ survey of the LMC by Reid & Parker (2012). The spectrum of RP 870 showed high ionization emission lines of He I, He II and [O III] and molecular absorption bands of TiO $\\lambda$$\\lambda$6180, 7100. The collective signatures of a hot component (high excitation/ionization lines) and of a cool component (TiO molecular bands) are seen in RP 870, from which we propose it as a symbiotic star. Since known symbiotic systems are rare in the LMC, possibly less than a dozen are known, we thought the present detection to be interesting enough to be reported.

A study of H-alpha velocities in NGC 1499, NGC 7000, and IC 1318B/C

NASA Technical Reports Server (NTRS)

Fountain, W. F.; Gary, G. A.; Odell, C. R.

1983-01-01

Multiple slit echelle spectrograph observations of the H-alpha emission line are used to map the radial velocities of the California Nebula (NGC 1499), the North American Nebula complex (NGC 7000 and IC 5070), and IC 1318B/C. The California Nebula is singularly constant in velocity, considering its geometry. The North American Nebula complex reflects a very simple, classical dynamical picture. The expansion discovered earlier in IC 1318B/C is confirmed, detailed, and the model refined. The new data, along with that in earlier papers of this series, show that stellar wind acceleration and champagne flow mechanisms both play important roles in determining the evolution of H II regions.

Emission-Line Galaxies from the PEARS Hubble Ultra Deep Field: A 2-D Detection Method and First Results

NASA Technical Reports Server (NTRS)

Gardner, J. P.; Straughn, Amber N.; Meurer, Gerhardt R.; Pirzkal, Norbert; Cohen, Seth H.; Malhotra, Sangeeta; Rhoads, james; Windhorst, Rogier A.; Gardner, Jonathan P.; Hathi, Nimish P.;

The formation of low-ionization emission in the halo of NGC 891

NASA Technical Reports Server (NTRS)

Sokolowski, James; Bland-Hawthorn, Jonathan

1993-01-01

Imaging and Spectroscopic study first revealed the presence of a diffuse ionized medium (DIM), having unusual excitation, pervading the lower halo of the edge-on spiral galaxy NGC 891. Emission from this DIM is strongest northeast of the nucleus, at radii between 2 and 8 kpc (hereafter region 1). The (N2)(lambda)6583/H(alpha) and (S2)(lambda) (lambda)6716,6731/H(alpha) ratios increase dramatically with z in region 1, from 0.6 and 0.5 respectively at z is approximately equal to 500 pc to 1.1 and 1.0 at z is approximately equal to 1 kpc, while nondetections of (O1)(lambda)6300 and (O3)(lambda)5007 emission yield upper limits of (O1)(lambda)6300/H(alpha) less than or equal to 0.05 and (O3)(lambda)5007/H(alpha) less than or equal to 0.15 for z less than 1 kpc. Previous photoionization models, using the radiation field from disk O and B stars, have been successful in reproducing the elevated (N2)(lambda)6583/H(alpha) and (S2)(lambda)(lambda)6716.6731/H(alpha) ratios observed. However, these radiation bounded models also produce significant (O3)(lambda)5007 emission, in conflict with the observed upper limit. Here, we report the results of new, matter bounded models for the photoionization of the DIM in region 1 of NGC 891.

FAR-ULTRAVIOLET SPECTRAL IMAGES OF THE VELA SUPERNOVA REMNANT: SUPPLEMENTS AND COMPARISONS WITH OTHER WAVELENGTH IMAGES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Il-Joong; Seon, Kwang-Il; Han, Wonyong

We present the improved far-ultraviolet (FUV) emission-line images of the entire Vela supernova remnant (SNR) using newly processed Spectroscopy of Plasma Evolution from Astrophysical Radiation/Far-Ultraviolet Imaging Spectrograph (SPEAR/FIMS) data. The incomplete C III {lambda}977 and O VI {lambda}{lambda}1032, 1038 images presented in the previous study are updated to cover the whole region. The C IV {lambda}{lambda}1548, 1551 image with a higher resolution and new images at Si IV {lambda}{lambda}1394, 1403, O IV] {lambda}1404, He II {lambda}1640.5, and O III] {lambda}{lambda}1661, 1666 are also shown. Comparison of emission-line ratios for two enhanced FUV regions reveals that the FUV emissions of themore » east-enhanced FUV region may be affected by nonradiative shocks of another very young SNR, the Vela Jr. SNR (RX J0852.0-4622, G266.6-1.2). This result is the first FUV detection that is likely associated with the Vela Jr. SNR, supporting previous arguments that the Vela Jr. SNR is close to us. The comparison of the improved FUV images with soft X-ray images shows that an FUV filamentary feature forms the boundary of the northeast-southwest asymmetrical sections of the X-ray shell. The southwest FUV features are characterized as the region where the Vela SNR is interacting with slightly denser ambient medium within the dim X-ray southwest section. From a comparison with the H{alpha} image, we identify a ring-like H{alpha} feature overlapped with an extended hot X-ray feature of similar size and two local peaks of C IV emission. Their morphologies are expected when the H{alpha} ring is in direct contact with the near or far side of the Vela SNR.« less

The nuclear superbubble of NGC 3079

NASA Technical Reports Server (NTRS)

Veilleux, S.; Cecil, G.; Bland-Hawthorn, J.; Tully, R. B.; Filippenko, A. V.; Sargent, W. L. W.

1994-01-01

We have used the Hawaii Imaging Fabry-Perot Interferometer (HIFI) at the CFH 3.6 m telescope to map H-alpha + (N II) lambda-lambda 6548, 6583 emission-line profiles across the entire edge-on, nearby SBc galaxy NGC 3079, with resolution 70 km/s and subarcsecond sampling. Blue and red long-slit spectra were obtained with the Double Spectrograph on the Palomar 5 meter telescope to provide additional emission-line diagnostics. A spectacular, line emitting bubble of diameter 13 sec (approximately 1.1 kpc) is observed immediately east of the nucleus. Its unusual gaseous excitation (e.g., (N II) lambda(6583)/H-alpha greater than 1) suggests that shocks are important. Extremely violent gas motions that range over 2000 km/s are detected across the bubble and diametrically opposite on the west side of the nucleus. Nonrotational motions are also found in the inner galaxy disk. The superbubble of NGC 3079 is the most powerful example known of a wind-blown bubble, and an excellent laboratory to study wind dynamics. The dimensions and energies of the bubble imply that is likely to be in the blowout phase and partially ruptured. The predicted rate of kinetic energy output from the central starburst appears sufficient to power most of this outflow. It is possible that a central active galactic nucleus also contributes to the outflow.

The BUSS spectrum of Beta Lyrae. [Balloon-borne Ultraviolet Stellar Spectrograph

NASA Technical Reports Server (NTRS)

Hack, M.; Sahade, J.; De Jager, C.; Kondo, Y.

1983-01-01

The spectrum of Beta Lyrae from about 1975 to 3010 A taken with the Balloon-borne ultraviolet Stellar Spectrograph experiment in May 1976 at phase 0.61 P is analyzed. Results show the presence of N II semi-forbidden emission and provide evidence for about the same location, in the outer envelope of the system, of the layers responsible for the resonance Mg II doublet emissions and for the "narrow" H-alpha emission. In addition, three sets of absorption lines, P Cygni profiles of Fe III and broad Beals Type III emissions of Mg II, are found to be present.

Spectrum of Transient ASASSN-13at

NASA Astrophysics Data System (ADS)

Garnavich, Peter; Deal, Shanel

2013-06-01

We observed the transient ASASSN-13at (ATEL 5168) on June 28.3 (UT) with the Vatican Advanced Technology Telescope (VATT) and VATTSPEC instrument. The resulting spectrum covers the wavelength range between 365 nm and 750 nm with a resolution of 1100. The spectrum of ASASSN-13at shows a blue continuum with strong Balmer absorption lines. Helium absorption at 447 nm and 588 nm is also seen. Blue-shifted emission lines are visible within the Halpha and Hbeta absorption features.

Association of X-ray arches with chromospheric neutral lines

NASA Technical Reports Server (NTRS)

Mcintosh, P. S.; Krieger, A. S.; Nolte, J. T.; Vaiana, G.

1976-01-01

Daily maps of magnetic neutral lines derived from H-alpha observations have been superimposed on solar X-ray images for the period from June 15 to 30, 1973. Nearly all X-ray-emitting structures consist of systems of arches covering chromospheric neutral lines. Areas of low emissivity, coronal holes, appear as the areas between arcades of arches. The presence of a coronal hole, therefore, is determined by the spacing between neutral lines and the scale of the arches over those neutral lines. X-ray emissivity on the solar disk extends from neutral lines in proportion to the vertical and horizontal scale of the arches over those neutral lines. Increasing scale of arches corresponds with increasing age of magnetic fields associated with the neutral line. All X-ray filament cavities coincided with neutral lines, but filaments appeared under cavities for only part of their length and for only a fraction of the disk passage.

A novel observational test of momentum balance in a solar flare

NASA Technical Reports Server (NTRS)

Canfield, Richard C.; Metcalf, Thomas R.; Strong, Keith T.; Zarro, Dominic M.

1987-01-01

A unique combination of SMM X-ray spectra and Sacramento Peak Observatory H-alpha imaging spectra has been used, for the first time, to measure and compare momentum values of upflowing and downflowing plasmas during the impulsive phase of a solar flare. The well-known blue asymmetry of X-ray spectral lines, indicative of upflow, was observed in the coronal Ca XIX line. The red asymmetry of H-alpha line profiles, indicative of downflow, was simultaneously observed in bright H-alpha kernels. It is found that, to within observational uncertainty, the momentum transported by the upflowing X-ray plasma was the same as that of the downflowing H-alpha material. Of the several physical mechanisms advanced to explain the observed blue asymmetry of X-ray lines, only explosive chromospheric evaporation predicts oppositely directed momenta of equal magnitude.

A test of the massive binary black hole hypothesis - Arp 102B

NASA Technical Reports Server (NTRS)

Helpern, J. P.; Filippenko, Alexei V.

1988-01-01

The emission-line spectra of several AGN have broad peaks which are significantly displaced in velocity with respect to the host galaxy. An interpretation of this effect in terms of orbital motion of a binary black hole predicts periods of a few centuries. It is pointed out here that recent measurements of the masses and sizes of many low-luminosity AGN imply orbital periods much shorter than this. In particular, it is found that the elliptical galaxy Arp 102B is the most likely candidate for observation of radial velocity variations; its period is expected to be about 3 yr. The H-alpha line profile of Arp 102B has been measured for 5 yr without detecting any change in velocity, and it is thus found that a rather restrictive observational test of the massive binary black hole hypothesis already exists, albeit for this one object.

The 2.8-hour flux modulation of the cataclysmic variable PG1711 + 336

NASA Astrophysics Data System (ADS)

Rosen, S. R.; Branduardi-Raymont, G.; Mason, K. O.; Murdin, P. G.

1989-04-01

High-speed optical photometry of the cataclysmic variable PG1711 + 336 is used to confirm the presence of a 2.8-hour periodic modulation in the light curve of the star and to improve its ephemeris. Pronounced flickering on time-scales between 10 and 20 minutes is found superimposed on the 2.8-hour variation. Three hours of time-resolved spectroscopy of PG1711 + 336 yields evidence for a radial velocity variation in the He II 4686-A emission line at a period consistent with the 2.8-hour photometric modulation. This is in contrast with observations of the H-alpha line reported in the literature which indicate a 15-hour radial velocity modulation period. The issue of which, if either, of these periods is the orbital period of the system remains unresolved. However, an observation made using the Exosat satellite failed to detect X-ray emission from PG1711 + 336 in the 0.1-10 keV range, which argues against this object being a member of the Intermediate Polar class of magnetic cataclysmic variables.

Simultaneous observations of Ca II K and Mg II k in T Tauri stars

NASA Technical Reports Server (NTRS)

Calvet, N.; Basri, G.; Imhoff, C. L.; Giampapa, M. S.

1985-01-01

The first simultaneous, calibrated observations of the Ca II K and Mg II k resonance lines in T Tauri stars are presented. It is found that for T Tauri stars with mass greater than 1.5 solar mass, which have radiative cores and tend to be fast rotators, the k line seems to arise in an extended region (probably also responsible for the H-alpha emission), whereas the K line apparently originates closer to the highly inhomogeneous stellar surface. The lower mass stars, which are fully convective and tend to be slow rotators, are more easily described by a largely chromospheric model, consistent with main-sequence activity structures but at greater values of the nonradiative flux. The strongest emission-line stars in the low-mass group, however, are also likely to have extended k line regions.

Dynamic evolution of recurrent mass ejections observed in H-alpha and C IV lines

NASA Technical Reports Server (NTRS)

Schmieder, B.; Mein, P.; Martres, M. J.; Tandberg-Hanssen, E.

1984-01-01

The mass ejections of 1 September, 1980 are studied from observations obtained with the MSDP spectrograph and with the Ultraviolet Spectrometer and Polarimeter aboard the Solar Maximum Mission satellite. The analysis is focused on observations in the chromospheric H-alpha line and the transition region C IV 1548 A line. It is noted that cold and hot material had the same projection, although the upward C IV velocity structure was more extended than the H-alpha one. It is shown that the observed contrast of the H-alpha absorbing structure can be interpreted in terms of a dynamic cloud model overlying the chromosphere. Radial velocities of 25-30 km/s and -40 km/s are estimated for the first and second phases of ejection, respectively.

Evolution and Activity in the Solar Corona: A Comparison of Coronal and Chromospheric Structures Seen in Soft X-Rays, White Light and H-Alpha Emission

NASA Technical Reports Server (NTRS)

Bagenal, Fran

2001-01-01

The work completed under this project, 'Evolution and Activity in the Solar Corona: A Comparison of Coronal and Chromospheric Structures Seen in Soft X-Rays, White Light and H-Alpha Emission', includes the following presentations: (1) Analysis of H-alpha Observations of High-altitude Coronal Condensations; (2) Multi-spectral Imaging of Coronal Activity; (3) Measurement and Modeling of Soft X-ray Loop Arcades; (4) A Study of the Origin and Dynamics of CMEs; and various poster presentations and thesis dissertations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan Changshuo; Wang Jianmin, E-mail: wangjm@ihep.ac.c

High spatial resolution observations show that high-redshift galaxies are undergoing intensive evolution of dynamical structure and morphologies displayed by the H{alpha}, H{beta}, [O III], and [N II] images. It has been shown that supernova explosion (SNexp) of young massive stars during the star formation epoch, as kinetic feedback to host galaxies, can efficiently excite the turbulent viscosity. We incorporate the feedback into the dynamical equations through mass dropout and angular momentum transportation driven by the SNexp-excited turbulent viscosity. The empirical Kennicutt-Schmidt law is used for star formation rates (SFRs). We numerically solve the equations and show that there can bemore » intensive evolution of structure of the gaseous disk. Secular evolution of the disk shows interesting characteristics: (1) high viscosity excited by SNexp can efficiently transport the gas from 10 kpc to {approx}1 kpc forming a stellar disk whereas a stellar ring forms for the case with low viscosity; (2) starbursts trigger SMBH activity with a lag of {approx}10{sup 8} yr depending on SFRs, prompting the joint evolution of SMBHs and bulges; and (3) the velocity dispersion is as high as {approx}100 km s{sup -1} in the gaseous disk. These results are likely to vary with the initial mass function (IMF) that the SNexp rates rely on. Given the IMF, we use the GALAXEV code to compute the spectral evolution of stellar populations based on the dynamical structure. In order to compare the present models with the observed dynamical structure and images, we use the incident continuum from the simple stellar synthesis and CLOUDY to calculate emission line ratios of H{alpha}, H{beta}, [O III], and [N II], and H{alpha} brightness of gas photoionized by young massive stars formed on the disks. The models can produce the main features of emission from star-forming galaxies. We apply the present model to two galaxies, BX 389 and BX 482 observed in the SINS high-z sample, which are bulge and disk-dominated, respectively. Two successive rings independently evolving are able to reproduce the main dynamical and emission properties of the two galaxies, such as the Baldwin-Phillips-Terlevich diagram, the relation between line ratios, and H{alpha} brightness. The observed relation between turbulent velocity and the H{alpha} brightness can be explained by the present model. High viscosity excited by SNexp is able to efficiently transport the gas into a bulge to maintain high SFRs or to form a stellar ring close enough to the bulge so that it immigrates into the bulge of its host galaxy. This leads to a fast growing bulge. Implications and future work of the present models have been extensively discussed for galaxy formation in high-z universe.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benitez, Erika; Cruz-Gonzalez, Irene; Martinez, Benoni

A sample of 10 nearby intermediate-type active galactic nuclei (AGNs) drawn from the Sloan Digital Sky Survey is presented. The aim of this work is to provide estimations of the black hole (BH) mass for the sample galaxies from the dynamics of the broad-line region. For this purpose, a detailed spectroscopic analysis of the objects was done. Using Baldwin-Phillips-Terlevich diagnostic diagrams, we have carefully classified the objects as true intermediate-type AGNs and found that 80%{sup +7.2%} {sub -17.3%} are composite AGNs. The BH mass estimated for the sample is within 6.54 {+-} 0.16 < log M {sub BH} < 7.81more » {+-} 0.14. Profile analysis shows that five objects (J120655.63+501737.1, J121607.08+504930.0, J141238.14+391836.5, J143031.18+524225.8, and J162952.88+242638.3) have narrow double-peaked emission lines in both the red (H{alpha}, [N II] {lambda}{lambda}6548,6583 and [S II] {lambda}{lambda}6716, 6731) and the blue (H{beta} and [O III] {lambda}{lambda}4959, 5007) regions of the spectra, with velocity differences ({Delta}V) between the double peaks within 114 km s{sup -1} < {Delta}V < 256 km s{sup -1}. Two of them, J121607.08+504930.0 and J141238.14+391836.5, are candidates for dual AGNs since their double-peaked emission lines are dominated by AGN activity. In searches of dual AGNs, type 1, type II, and intermediate-type AGNs should be carefully separated, due to the high serendipitous number of narrow double-peaked sources (50% {+-} 14.4%) found in our sample.« less

Molecular hydrogen and excitation in the HH 1-2 system

NASA Technical Reports Server (NTRS)

Noriega-Crespo, A.; Garnavich, P. M.

1994-01-01

We present a series of molecular hydrogen images of the Herbig-Haro 1-2 system in the 1-0 S(1) transition at 2.121 microns, with a spatial resolution of approximately 2 sec. The distribution of H2 is then compared with that of the excitation, given by the (S II) 6717+6731 to H-alpha line ratio. We find that most optical condensations in the HH 1-2 system, including the VLA 1 jet, have H2 counterparts. H2 emission is detected in most low excitation knots, as expected for low velocity shocks (50 km/s less than), but also in high excitation regions, like in HH 1F and HH 2A min. For these latter objects, the H2 emission could be due to the interaction of the preionizing flux, produced by 150-200 km/s shocks, with the surrounding interstellar matter, i.e., fluorescence. The lack fluorescent lines in the ultraviolet (UV), however, suggest a different mechanism. H2 is detected at the tip of the VLA 1 jet, where the knot morphology suggests the presence of a second bow shock. H2 is detected also SE of HH 2E and SW of HH 1F, in regions with known NH3 emission.

THE NATURE OF A GALAXY ALONG THE SIGHT LINE TO PKS 0454+039

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takamiya, Marianne; Chun, Mark; Kulkarni, Varsha P.

2012-10-01

We report on the properties of a faint blue galaxy (G1) along the line of sight to the QSO PKS 0454+039 from spectroscopic and imaging data. We measured emission lines of H{alpha}, [S II] {lambda}{lambda}6716, 6732, and [N II] {lambda}6584 in the spectrum of G1 obtained with the Gemini/GMOS instrument. The spectroscopic redshift of G1 is z = 0.0715 {+-} 0.0002. From the extinction-corrected H{alpha} flux, we determine a modest star formation rate of SFR = 0.07 M{sub Sun} yr{sup -1} and a specific SFR of log (sSFR) -8.4. Using three different abundance indicators, we determine a nebular abundance 12more » + log (O/H) ranging from 7.6 to 8.2. Based on the velocity dispersion inferred from the emission line widths and the observed surface brightness profile, we estimate the virial mass of G1 to be M{sub vir} {approx} 6.7 Multiplication-Sign 10{sup 9} M{sub Sun} with an effective radius of 2.0 kpc. We estimate the stellar mass of G1 using spectral energy distribution fitting to be M{sub *} Almost-Equal-To 1.2 Multiplication-Sign 10{sup 7} M{sub Sun} and an r'-luminosity of L{sub r'} = 1.5x10{sup 8} L{sub Sun }. Overall, G1 is a faint, low-mass, low-metallicity Im/H II galaxy. We also report on the line flux limits of another source (G3) which is the most likely candidate for the absorber system at z = 0.8596. From the spectrum of the QSO itself, we report a previously undetected Mg II {lambda}{lambda}2796, 2803 absorption line system at z = 1.245.« less

Statistical methods for astronomical data with upper limits. II - Correlation and regression

NASA Technical Reports Server (NTRS)

Isobe, T.; Feigelson, E. D.; Nelson, P. I.

1986-01-01

Statistical methods for calculating correlations and regressions in bivariate censored data where the dependent variable can have upper or lower limits are presented. Cox's regression and the generalization of Kendall's rank correlation coefficient provide significant levels of correlations, and the EM algorithm, under the assumption of normally distributed errors, and its nonparametric analog using the Kaplan-Meier estimator, give estimates for the slope of a regression line. Monte Carlo simulations demonstrate that survival analysis is reliable in determining correlations between luminosities at different bands. Survival analysis is applied to CO emission in infrared galaxies, X-ray emission in radio galaxies, H-alpha emission in cooling cluster cores, and radio emission in Seyfert galaxies.

A new Be star in an open cluster - NGC 6871-8

NASA Technical Reports Server (NTRS)

Grigsby, James A.; Morrison, Nancy D.

1988-01-01

Spectroscopic observations of H-alpha show that star eight in the open cluster NGC 6871 is a previously-undiscovered Be star. The H-alpha profile was observed to vary from clear emission to pure absorption over a period of ten days; later observations over a five-day interval show weak emission along with asymmetries and filling in of the profile.

A dynamic flare with anomalously dense flare loops

NASA Technical Reports Server (NTRS)

Svestka, Z.; Fontenla, J. M.; Machado, M. E.; Martin, S. F.; Neidig, D. F.

1986-01-01

The dynamic flare of November 6, 1980 developed a rich system of growing loops which could be followed in H-alpha for 1.5 hours. Throughout the flare, these loops, near the limb, were seen in emission against the disk. Theoretical computations of b-values for a hydrogen atom reveal that this requires electron densities in the loops to be close to 10 to the 12th per cu cm. From measured widths of higher Balmer lines the density at the tops of the loops was found to be 4 x 10 to the 12th per cu cm if no nonthermal motions were present. It is now general knowledge that flare loops are initially observed in X-rays and become visible in H-alpha only after cooling. For such a high density a loop would cool through radiation from 10 to the 7th K to 10 to the 4th K within a few minutes so that the dense H-alpha loops should have heights very close to the heights of the X-ray loops. This, however, contradicts the observations obtained by the HXIS and FCS instruments on board SMM which show the X-ray loops at much higher altitudes than the loops in H-alpha. Therefore, the density must have been significantly smaller when the loops were formed and the flare loops were apparently both shrinking and becoming denser while cooling.

WISE J233237.05-505643.5: A Double-Peaked Broad-Lined AGN with Spiral-Shaped Radio Morphology

NASA Technical Reports Server (NTRS)

Tsai, Chao Wei; Jarrett, Thomas H.; Stern, Daniel; Emonts, Bjorn; Barrows, R. Scott; Assef, Roberto J.; Norris, Ray P.; Eisenhardt, Peter R. M.; Lonsdale, Carol; Blain, Andrew W.;

X-ray and optical emission-line filaments in the cooling flow cluster 2A 0335 + 096

NASA Technical Reports Server (NTRS)

Sarazin, Craig L.; O'Connell, Robert W.; Mcnamara, Brian R.

1992-01-01

We present a new high-resolution X-ray image of the 2A 0335 + 096 cluster of galaxies obtained with the High Resolution Imager (HRI) aboard the ROSAT satellite. The presence of dense gas having a very short cooling time in the central regions confirms its earlier identification as a cooling flow. The X-ray emission from the central regions of the cooling flow shows a great deal of filamentary structure. Using the crude spectral resolution of the HRI, we show that these filaments are the result of excess emission, rather than foreground X-ray absorption. Although there are uncertainties in the pointing, many of the X-ray features in the cooling flow region correspond to features in H-alpha optical line emission. This suggests that the optical emission line gas has resulted directly from the cooling of X-ray-emitting gas. The filament material cannot be in hydrostatic equilibrium, and it is likely that other forces such as rotation, turbulence, and magnetic fields influence the dynamical state of the gas.

THE OPTICAL STRUCTURE OF THE STARBURST GALAXY M82. II. NEBULAR PROPERTIES OF THE DISK AND INNER WIND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Westmoquette, M. S.; Smith, L. J.; Konstantopoulos, I. S.

2009-12-01

In this second paper of the series, we present the results from optical Gemini-North GMOS-IFU and WIYN DensePak IFU spectroscopic observations of the starburst and inner wind zones of M82, with a focus on the state of the T approx 10{sup 4} K ionized interstellar medium. Our electron density maps show peaks of a few 1000 cm{sup -3} (implying very high thermal pressures), local small spatial-scale variations, and a falloff in the minor axis direction. We discuss the implications of these results with regards to the conditions/locations that may favor the escape of individual cluster winds that ultimately power themore » large-scale superwind. Our findings, when combined with the body of literature built up over the last decade on the state of the interstellar medium (ISM) in M82, imply that the starburst environment is highly fragmented into a range of clouds from small/dense clumps with low-filling factors (<1 pc, n {sub e} approx> 10{sup 4} cm{sup -3}) to larger filling factor, less dense gas. The most compact clouds seem to be found in the cores of the star cluster complexes, whereas the cloud sizes in the inter-complex region are larger. These dense clouds are bathed with an intense radiation field and embedded in an extensive high temperature (T approx> 10{sup 6} K), X-ray-emitting ISM that is a product of the high star formation rates in the starburst zones of M82. The near-constant state of the ionization state of the approx10{sup 4} K gas throughout the M82 starburst zone can be explained as a consequence of the small cloud sizes, which allow the gas conditions to respond quickly to any changes. In Paper I, we found that the observed emission lines are composed of multiple components, including a broad (FWHM approx 150-350 km s{sup -1}) feature that we associate with emission from turbulent mixing layers on the surfaces of the gas clouds, resulting from the interaction of the fast wind outflows from the synchrotron self-Comptons. The large number of compact clouds and wind sources provides an ideal environment for broad line emission, and explains the large observed broad/narrow-line flux ratios. We have examined in more detail the discrete outflow channel identified within the inner wind in Paper I. The channel appears as a coherent, expanding cylindrical structure of length >120 pc and width 35-50 pc. The walls maintain an approximately constant (but subsonic) expansion velocity of approx60 km s{sup -1}, and are defined by peaks and troughs in the densities of the different line components. We hypothesize that as the hot wind fluid flows down the channel cavity, it interacts with the cooler, denser walls of the channel and with entrained material within the flow to produce broad-line emission, while the walls themselves emit primarily the narrow lines. We use the channel to examine further the relationship between the narrow and broad component emitting gas within the inner wind. Within the starburst energy injection zone, we find that turbulent motions (as traced by the broad component) appear to play an increasing role with height. Finally, we have argued that a point-like knot identified in GMOS position 4, exhibiting blueshifted (by approx140 km s{sup -1}), broad (approx<350 km s{sup -1}) Halpha emission and enhanced [S II]/Halpha and [N II]/Halpha ratios, is most likely an ejected luminous blue variable-type object.« less

Mapping High-Velocity H-alpha and Lyman-alpha Emission from Supernova 1987A

NASA Technical Reports Server (NTRS)

France, Kevin; McCray, Richard; Fransson, Claes; Larsson, Josefin; Frank, Kari A.; Burrows, David N.; Challis, Peter; Kirshner, Robert P.; Chevalier, Roger A.; Garnavich, Peter;

The SAMI Galaxy Survey: Publicly Available Spatially Resolved Emission Line Data Products

NASA Astrophysics Data System (ADS)

Medling, Anne; Green, Andrew W.; Ho, I.-Ting; Groves, Brent; Croom, Scott; SAMI Galaxy Survey Team

2017-01-01

The SAMI Galaxy Survey is collecting optical integral field spectroscopy of up to 3400 nearby (z<0.1) galaxies with a range of stellar masses and in a range of environments. The first public data release contains nearly 800 galaxies from the Galaxy And Mass Assembly (GAMA) Survey. In addition to releasing the reduced data cubes, we also provide emission line fits (flux and kinematic maps of strong emission lines including Halpha and Hbeta, [OII]3726,29, [OIII]4959,5007, [OI]6300, [NII]6548,83, and [SII]6716,31), extinction maps, star formation classification masks, and star formation rate maps. We give an overview of the data available for your favorite emission line science and present a few early science results. For example, a sample of edge-on disk galaxies show enhanced extraplanar emission related to SF-driven outflows, which are correlated with a bursty star formation history and higher star formation rate surface densities. Interestingly, the star formation rate surface densities of these wind hosts are 5-100 times lower than the canonical threshold for driving winds (0.1 MSun/yr/kpc2), indicating that galactic winds may be more important in normal star-forming galaxies than previously thought.

Dynamics of a surge observed in the C IV and H alpha lines

NASA Technical Reports Server (NTRS)

Schmieder, B.; Mein, P.; Vial, J.-C.; Tandberg-Hanssen, E.

1983-01-01

Time sequences of a surge have been obtained in Active Region 2701 during a coordinated SMY program, on October 2nd, 1980, while the MSDP spectrograph operated in H-alpha at the Meudon Solar Tower and the UVSP spectrometer on SMM observed in the 1548 A C IV resonance line. The cold (H-alpha) and hot (C IV) material follow the same channel, and the event lasts about 10 min in both lines. A good correlation is found between H-alpha and C IV velocities; radial velocities along the surge are in the range 40-60 km/s in both cases. The observations are consistent with the hypothesis that a pressure gradient drives the surge. The H-alpha data seem to indicate the presence of a shock wave in the chromosphere, while the C IV quantities (velocities, accelerations) vary on a very short time scale. Their maxima occur at some locations which could be interpreted as 'pinched' zones.

Determination of the Far-Infrared Cosmic Background Using COBE/DIRBE and WHAM Data

NASA Technical Reports Server (NTRS)

Odegard, N.; Arendt, R. G.; Dwek, E.; Haffner, L. M.; Hauser, M. G.; Reynolds, R. J.

2007-01-01

Determination of the cosmic infrared background (CIB) at far infrared wavelengths using COBE/DIRBE data is limited by the accuracy to which foreground interplanetary and Galactic dust emission can be modeled and subtracted. Previous determinations of the far infrared CIB (e.g., Hauser et al. 1998) were based on the detection of residual isotropic emission in skymaps from which the emission from interplanetary dust and the neutral interstellar medium were removed. In this paper we use the Wisconsin H(alpha) Mapper (WHAM) Northern Sky Survey as a tracer of the ionized medium to examine the effect of this foreground component on determination of the CIB. We decompose the DIRBE far infrared data for five high Galactic latitude regions into HI- and H(alpha)- correlated components and a residual component. Eased on FUSE H2 absorption line observations, the contribution of a11 H2-correlated component is expected to he negligible. We find the H(alpha)-correlated component to be consistent with zero for each region, and we find that addition of an H(alpha)-correlated component in modeling the foreground emission has negligible effect on derived CIB results. Our CIB detections and 2(sigma) upper limits are essentially the same as those derived by Hauser et al. and are given by (nu)I(sub nu)(nW/sq m/sr) < 75, < 32, 25+/-8, and 13+/-3 at gamma = 60, 100, 140, and 240 microns, respectively. Our residuals have not been subjected to a detailed anisotropy test, so our CIB results do not supersede those of Hauser et al. Mie derive upper limits on the 100 micron emissivity of the ionized medium that are typically about 40% of the 100 micron emissivity of the neutral atomic medium. This low value may be caused in part by a lower dust-to-gas mass ratio in the ionized medium than in the neutral medium, and in part by a shortcoming of using H(alpha) intensity as a tracer of far infrared emission. If H(alpha) is not a reliable tracer, our analysis would underestimate the emissivity of the ionized medium, and both our analysis and the Hauser et al. analysis may slightly overestimate the CIB. We estimate the possible effect for the CIB to be only about 5%, which is much smaller than the quoted uncertainties. From a comparison of the Hauser et al. CIB results with the integrated galaxy brightness from Spitzer source counts, we obtain 2(sigma) upper limits on a possible diffuse CIB component that are 26 nW/sq m/sr at 140 microns and 8.5 nW/sq m/sr at 240 microns.

(Talk) Investigating The Star Formation Quenching Across Cosmic Time - A Methodology To Select Galaxies Just After The Quenching Of Star Formation

NASA Astrophysics Data System (ADS)

Citro, Annalisa; Pozzetti, Lucia; Quai, Salvatore; Moresco, Michele; Vallini, Livia; Cimatti, Andrea

2017-06-01

We propose a method aimed at identifing galaxies in the short evolutionary phase in which they quench their star-formation (SF). We rely on high- to low-ionization emission line ratios, which rapidly disappear after the SF halt due to the softening of the UV ionizing radiation. In particular, we focus on [O III] 5007/Halpha and [Ne III] 3869/[O II] 3727, simulating their time evolution by means of the CLOUDY photoionization code. We find that these two emission line ratios are able to trace the quenching on very short time-scales (i.e. 10-80 Myr), depending on if a sharp or a smoother SF quenching is assumed. We adopt the [N II] 6584/[O II] 3727 ratio as metallicity diagnostic to mitigate the metallicity degeneracy which affects our method. Using a Sloan Digital Sky Survey galaxy sample, we identify 11 examples of extreme quenching candidates within the [O III] 5007/Halpha vs. [N II] 6584/[O II] 3727 plane, characterized by faint [Ne III] 3869, blue dust-corrected spectra and blue (u-r) colours, as expected if the quenching occurred in the recent past. Our results also suggest that the observed fractions of quenching candidates can be used to constrain the quenching mechanism at work and its time-scales.

The Gas Content Of Protoplanetary Herbig Ae/be Discs As Seen With Herschel

NASA Astrophysics Data System (ADS)

Meeus, Gwendolyn; Herschel OTKP, GASPS; Dent, B.

2011-09-01

The mechanisms determining planet formation are not (yet) well-understood. Primordial protoplanetary discs consist 99% out of gas, and only 1% out of dust. With time, those discs are believed to evolve from a flaring geometry into a flat geometry, as the initially small dust grains grow to larger sizes and settle towards the mid-plane. In the mean time, the gas will disperse, until so little is left that giant planets no longer can form. As an important piece of the puzzle of planet formation, it is important to understand the influence of the gas heating/cooling processes on the young disc structure, its chemical composition and finally how fast gas gets dispersed. In this talk, we study the protoplanetary discs around Herbig Ae/Be stars, young objects of intermediate mass, in the context of its gas content. We present Herschel PACS spectroscopic observations for a sample that was obtained within the GASPS (Gas in Protoplanetary Systems) Open Time Key Project, concentrating on the detection and characterisation of emission lines of the [OI], [CII], and CO, tracing the disc between 5 and 500 AU. We look for correlations between the observed line fluxes and stellar properties such as effective temperature, Halpha emission, accretion rates and UV flux, as well as the disc properties: degree of flaring, presence and strength of PAH emission and disc mass. We will present a few cases to show how simultaneous modeling (using the thermo-chemical disc code ProDiMo) of the atomic fine structure lines and both molecular lines can constrain the disc gas mass, once the disc structure is derived. Finally, we compare our gas line observations with those of young debris disc stars, for which the HAEBE stars are thought to be progenitors.

Observations of the Gum Nebula with a Fabry-Perot spectrometer

NASA Technical Reports Server (NTRS)

Reynolds, R. J.

1976-01-01

Scans have been made of H-alpha, 6584-A forbidden N II, 5007-A forbidden O III, and 5876-A He I emissions in selected directions in the Gum Nebula. Analyses of the line profiles and line intensities indicate that much of the emitting gas in the Gum Nebula is confined to an expanding shell which has a radius of about 125 pc, an expansion velocity of approximately 20 km/s, an emission measure which ranges from about 15 units to about 500 units, and a temperature near 11,000 K. The ultraviolet flux from zeta Pup and gamma-2 Vel appears to be capable of producing most of the observed ionization, although the origin of the shell structure and high expansion velocity is not certain.-

Flash photoionization of gamma-ray burst environments

NASA Technical Reports Server (NTRS)

Band, David L.; Hartmann, Dieter H.

1992-01-01

The H-alpha line emission that a flash-photoionized region emits is calculated. Archival transients, as well as various theoretical predictions, suggest that there may be significant ionizing flux. The limits on the line flux which might be observable indicate that the density must be fairly high for the recombination radiation to be observable. The intense burst radiation is insufficient to melt the dust which will be present in such a dense medium. This dust may attenuate the observable line emission, but does not attenuate the ionizing radiation before it ionizes the neutral medium surrounding the burst source. The dust can also produce a light echo. If there are indeed gamma-ray bursts in dense clouds, then it is possible that the burst was triggered by Bondi-Hoyle accretion from the dense medium, although it is unlikely on statistical grounds that all bursts occur in clouds.

Long-slit optical spectroscopy of powerful far-infrared galaxies - The nature of the nuclear energy source

NASA Technical Reports Server (NTRS)

Armus, Lee; Heckman, Timothy M.; Miley, George K.

1989-01-01

Optical spectroscopic data are presented for a sample of 47 powerful far-IR galaxies chosen for IR spectral shape, and for six other IR-bright galaxies. The stellar absorption lines expected from a population of old stars are generally very weak in the nuclei of the galaxies. Very weak Mg I absorption is found in regions well off the nucleus, implying that the visible spectrum is dominated by young stars and not by an AGN. At least one, and probably five, of the galaxies have detectable WR emission features, providing additional evidence for a young stellar population. About 20 percent of the galaxies have strong Balmer absorption lines, indicating the presence of a substantial intermediate-age stellar population. The equivalent width of the H-alpha emission line can be modeled as arising from a mixture of a large young population and an intermediate-age population of stars.

Observations of H-alpha and microwave brightening caused by a distant solar flare

NASA Technical Reports Server (NTRS)

Kundu, M. R.; Bobrowsky, M.; Rust, D. M.

1983-01-01

Synthesized maps with integration times of 10 and 30 sec, based on the observation of three subflares at 6 cm and H-alpha 6563 A, indicate that most of the 6 cm burst emission originated in 10-15 arcsec features coincident with, or adjacent to, H-alpha flare kernels. During the onset of one of the subflares, 6 cm emission was discovered in a loop stretching over 100,000 km from the primary flare site in association with H-alpha flare-like brightness at the remote footpoint of the loop. Assuming a primary flare site origin for the energy of the distant brightening, about 4 x 10 to the 24th ergs/sec propagated along the connecting magnetic loop at a velocity of more than 6000 km/sec. It is suggested that the energy may have been carried by electrons originating in the high energy tail of the electron thermal velocity distribution, escaping from the primary flare site.

HET LRS2 Observations of Halpha in Old Hydrogen-deficient Supernovae

NASA Astrophysics Data System (ADS)

Wheeler, J. Craig Craig; Pooley, David A.; Vinko, Jozsef; Szalai, Tamas; Marion, Howie H.; Sand, David J.; McQueen, Phillip; Silverman, Jeffrey M.

2017-06-01

For 3 years, we have been using narrow-band filters with the DIAFI imager on the HJS 2.7 m telescope to search for evidence that hydrogen-deficient supernovae undergo delayed collision with previously ejected circumstellar material and associated excitation of Halpha (see abstract by Pooley et al.). A powerful method to determine whether detected Halpha flux is from an HII region or a supernova is to obtain spectra; broad lines (> 1000 km/s) will be a certain indicator of a supernova. We have observed about 20 events that ranged in age from about 1000 days to nearly 80 years for which we have detected Halpha in the vicinity of the supernova. So far, only SN 2014C showed the broad H that is concrete evidence of ongoing circumstellar interaction. One interesting aspect revealed by the spectra is that we often pick up the two [N II] lines that typically accompany H in H II regions. Our spectra of SN 2008ha did not show these [N II] lines. The absence of the [N II] lines might be a clue to circumstellar interaction in conditions where the shock had slowed to a point where the H is not detectably broadened.

Disc structure and variability in dwarf novae

NASA Astrophysics Data System (ADS)

Harlaftis, Emilios Theofanus

An introduction is given to dwarf novae reviewing the current research status in the field. We present IUE observations of Z Cha which support the mass transfer instability as the cause of the superoutbursts observed in SU UMa type dwarf novae. Comparison between the superoutburst and a normal outburst of Z Cha shows that the disc is flatter and has significantly less azimuthal structure than during superoutburst. Z Cha exhibits a soft x-ray deficit during superoutburst compared to OY Car. We find that the secondary star of Z Cha contributes approximately 30 percent of the infrared flux at peak of outburst. The second part of the thesis presents results from the 1988 International Time Project at the Observatorio del Roque de los Muchachos. Investigation of the behavior of SU UMa and YZ Cnc is carried out through the outburst cycle. The secular changes of the equivalent widths of both systems shows an increasing trend even during quiescence and are caused by the continuum decrease. Both systems show a low-velocity emission component which contaminates the wings of the H(alpha) profile. In addition to doppler broadening, the Stark effect is found to cause significant broadening to the line profile. The radial dependence of the emission lines is discussed in relation to other cataclysmic variables. H(alpha) emission from the secondary star of YZ Cnc is found during superoutburst, during outburst and during quiescence after outburst. Photometry during late decline of outburst shows a sinusoidal, weak variation peaking at 0.5 orbital phase and which is related to heating of the red star or to a transient disc event. During quiescence, the flickering is found to be caused by the bright spot. This modulation increases with time and is maximum before the outburst. Doppler tomography of IP Peg during quiescence reveals an emission line distribution not consistent to the standard model. We find Balmer emission from the secondary star, at a level of only 2.5 percent of the total flux during quiescence. Simultaneously to this, line emission from the outer disc decreases by approximately 70 percent 5 days before an outburst.

Chromospheres of two red giants in NGC 6752

NASA Technical Reports Server (NTRS)

Dupree, A. K.; Hartmann, L.; Harper, G. M.; Jordan, Carole; Rodgers, A. W.

1990-01-01

Two red giant stars, A31 and A59, in the globular cluster NGC 6752 exhibit Mg II (2800 A) emission with surface fluxes comparable to those observed among metal-deficient halo field giants, and among low-activity Population I giants. Optical echelle spectra of these cluster giants reveal emission in the core of the Ca II K (3933.7 A) line, and in the wing of the H-alpha (6562.8 A) profile. Asymmetries exist both in the emission profiles and the line cores. These observations demonstrate unequivocally the existence of chromospheres among old halo population giants, and the presence of mass outflow in their atmospheres. Maintenance of a relatively constant level of chromospheric activity on the red giant branch contrasts with the decay of magnetic dynamo activity exhibited by dwarf stars and younger giants. A purely hydrodynamic phenomenon may be responsible for heating the outer atmospheres of these stars, enhancing chromospheric emission, thus extending the atmospheres and facilitating mass loss.

Comparison of H-alpha synoptic charts with the large-scale solar magnetic field as observed at Stanford

NASA Technical Reports Server (NTRS)

Duvall, T. L., Jr.; Wilcox, J. M.; Svalgaard, L.; Scherrer, P. H.; Mcintosh, P. S.

1977-01-01

Two methods of observing the neutral line of the large-scale photospheric magnetic field are compared: neutral line positions inferred from H-alpha photographs (McIntosh and Nolte, 1975) and observations of the photospheric magnetic field made with low spatial resolution (three minutes) and high sensitivity using the Stanford magnetograph. The comparison is found to be very favorable.

The shell spectrum of HD 94509

NASA Astrophysics Data System (ADS)

Cowley, Charles R.; Przybilla, Norbert; Hubrig, Swetlana

2015-01-01

HD 94509 is a 9th magnitude Be star with an unusually rich metallic-lined shell. The absorption spectrum is rich, comparable to that of an A or F supergiant, but Mg II (4481A), and the Si II (4128 and 4130A), are weak, indicating a dilute radiation field, as described by Otto Struve. The H-alpha emission is double with components of equal intensity and an absorption core that dips well below the stellar continuum. H-beta is weaker, but with a similar structure. H-gamma through H-epsilon have virtually black cores, indicating that the shell covers the stellar disk. The stronger metallic absorption lines are wide near the continuum, but taper to very narrow cores. This line shape is unexplained. However, the total absorption can be modeled to reveal an overall particle densities of 10^{10}-10^{12} cm^{-3}. An electron density log(n_e) = 11.2 is obtained from the Paschen-line convergence and the Inglis-Tellar relation. Column densities are obtained with the help of curves of growth by assuming uniform conditions in the cloud. These indicate a nearly solar composition. The CLOUDY code (Ferland, et al. Rev. Mex. Astron. Astroph. 49, 137, 213) is used to produce a model that predicts matching column densities of the dominant ions, the n = 3 level of hydrogen, the H-alpha strength, and the electron density (± 0.5 dex).

Intrinsic polarization changes and the H-alpha and CA II emission features in T-Tauri stars

NASA Astrophysics Data System (ADS)

Svatos, J.; Solc, M.

1981-12-01

On the basis of the correlation between polarization and emission features observed in certain T-Tauri stars, it is concluded that flaring effects associated with UV and/or X-ray irradiation and with increased magnetic field are responsible for the intrinsic polarization changes in T-Tauri stars. The correlation between emission Ca II lines and polarization degree both in Miras and T-Tau stars is thought to support the contention that the intrinsic polarization changes are due to the irradiation of silicate-like grains. In some T-Tau stars the increase in the magnetic field can be the principal agent causing the polarization increase due to the enhanced orientation of elongated grains.

The BAT AGN Spectroscopic Survey (BASS)

NASA Astrophysics Data System (ADS)

Koss, Michael

2017-08-01

We present the Swift BAT AGN Spectroscopic Survey (BASS) and discus the first four papers. The catalog represents an unprecedented census of hard-X-ray selected AGN in the local universe, with ~90% of sources at z<0.2. Starting from an all-sky catalog of AGN detected based on their 14-195 keV flux from the 70-month Swift/BAT catalog, we analyze a total of 1279 optical spectra, taken from twelve different telescopes, for a total of 642 spectra of unique AGN. We present the absorption and emission line measurements as well as black hole masses and accretion rates for the majority of obscured and un-obscured AGN (473), representing more than a factor of 10 increase from past studies. Consistent with previous surveys, we find an increase in the fraction of un-obscured (type 1) AGN, as measured from broad Hbeta and Halpha, with increasing 14-195 keV and 2-10 keV luminosity. We find the FWHM of the emission lines to show broad agreement with the X-ray obscuration measurements. Compared to narrow line AGN in the SDSS, the X-ray selected AGN in our sample with emission lines have a larger fraction of dustier galaxies suggesting these types of galaxies are missed in optical AGN surveys using emission line diagnostics.

Strong [Fe X] Emission and Deep Optical Eclipses of the Classical Nova V5593 Sgr 2012 No. 5

NASA Astrophysics Data System (ADS)

Starrfield, Sumner; Wagner, R. Mark; Walter, Frederick M.; Woodward, Charles E.; Schwarz, Greg; Krautter, Joachim

2016-01-01

V5593 Sgr was discovered by T. Kojima on 2012 July 16.512 UT at a magnitude of ~12.6. A low-resolution spectrum obtained by M. Fujii on 2012 July 18.572 UT confirmed that the object was indeed a Classical Nova. The AAVSO V-band light curve showed that the nova peaked near 11th mag on July 23-24 UT and subsequently declined in brightness with a t_2 of about 27 days making it a moderately fast nova. We obtained optical spectroscopy of V5593 Sgr between 2012 July 26 and 2013 February 19 UT with the SMARTS/CTIO 1.5 m telescope (+RC spectrograph) and then between 2014 August 25 and 2015 June 17 UT using the MDM Observatory 2.4 m Hiltner telescope (+CCDS), the 8.4 m Large Binocular Telescope (+MODS1), and the 6.5 m MMT (+BlueChannel). The SMARTS spectra confirmed the Fe II classification but showed that by 2013 February 19 UT the Fe II lines became much weaker and strong He II 468.5 nm and [Fe VII] 608.7 nm became prominent. A spectrum obtained on 2014 August 25 UT exhibited Balmer, He II, and [Fe VII] emission lines, but also for the first time, the presence of strong [Fe X] 637.4 nm emission with an observed intensity ratio with respect to Halpha of about 1.5. Other identified emission lines in our spectra included O VI, [Ca V], [Ca VI], [Ca VII], [Fe VI], [Fe XI], and [Fe XIV]. Surprisingly, [O III] emission was weak or absent. By 2015 June, a spectrum showed that the observed [Fe X]/Halpha intensity ratio had decreased to about 0.74. Contemporaneous optical photometry was obtained with the SMARTS/CTIO 1 m telescope (+ANDICAM) between 2014 March 19 and 2015 September 28 UT in the BVRIJHK bands. In agreement with our spectra in quiescence, V5593 Sgr is very red with (B-V) ~ 1 mag and (V-K) ~ 5 mag. The photometry shows ellipsoidal-like modulations with a peak-to-peak amplitude exceeding 2 mag in R and I. The modulation is seen in B through K; however, the amplitude is lower in JHK. Brief eclipses occur at the minimum of the ellipsoidal variation with a depth of at least 5 mag in R and I. The eclipse is seen in all bands covered by our observations. Two or more candidate periods may be consistent with the data. We will discuss these results in the context of other classical novae including GQ Mus and V723 Cas.

Chromospherically active stars. IV - HD 178450 = V478 Lyr: An early-type BY Draconis type binary

NASA Technical Reports Server (NTRS)

Fekel, Francis C.

1988-01-01

It is shown that the variable star HD 178450 = V478 Lyr is a chromospherically active G8 V single-lined spectroscopic binary with a period of 2.130514 days. This star is characterized by strong UV emission features and a filled-in H-alpha absorption line which is variable in strength. Classified as an early-type BY Draconis system, it is similar to the BY Dra star HD 175742 = V775 Her. The unseen secondary of HD 178450 has a mass of about 0.3 solar masses and is believed to be an M2-M3 dwarf.

ANALYSIS OF OPTICAL Fe II EMISSION IN A SAMPLE OF ACTIVE GALACTIC NUCLEUS SPECTRA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kovacevic, Jelena; Popovic, Luka C.; Dimitrijevic, Milan S., E-mail: jkovacevic@aob.bg.ac.r

We present a study of optical Fe II emission in 302 active galactic nuclei (AGNs) selected from the Sloan Digital Sky Survey. We group the strongest Fe II multiplets into three groups according to the lower term of the transition (b{sup 4} F, a{sup 6} S, and a{sup 4} G terms). These approximately correspond to the blue, central, and red parts, respectively, of the 'iron shelf' around H{beta}. We calculate an Fe II template that takes into account transitions into these three terms and an additional group of lines, based on a reconstruction of the spectrum of I Zw 1.more » This Fe II template gives a more precise fit of the Fe II lines in broad-line AGNs than other templates. We extract Fe II, H{alpha}, H{beta}, [O III], and [N II] emission parameters and investigate correlations between them. We find that Fe II lines probably originate in an intermediate line region. We note that the blue, red, and central parts of the iron shelf have different relative intensities in different objects. Their ratios depend on continuum luminosity, FWHM H{beta}, the velocity shift of Fe II, and the H{alpha}/H{beta} flux ratio. We examine the dependence of the well-known anti-correlation between the equivalent widths of Fe II and [O III] on continuum luminosity. We find that there is a Baldwin effect for [O III] but an inverse Baldwin effect for the Fe II emission. The [O III]/Fe II ratio thus decreases with L {sub {lambda}5100}. Since the ratio is a major component of the Boroson and Green Eigenvector 1 (EV1), this implies a connection between the Baldwin effect and EV1 and could be connected with AGN evolution. We find that spectra are different for H{beta} FWHMs greater and less than {approx}3000 km s{sup -1}, and that there are different correlation coefficients between the parameters.« less

Multiwavelength analysis of a well observed flare from SMM. [Solar Maximum Mission

NASA Technical Reports Server (NTRS)

Macneice, P.; Pallavicini, R.; Mason, H. E.; Simnett, G. M.; Antonucci, E.; Shine, R. A.; Dennis, B. R.

1985-01-01

Observations of an M 1.4 flare which began at 17:00 UT on November 12, 1980, are presented and analyzed. Ground based H-alpha and magnetogram data have been combined with EUV, soft and hard X-ray observations made with instruments on-board the Solar Maximum Mission satellite. The preflare phase was marked by a gradual brightening of the flare site in O v and the disappearance of an H-alpha filament. Filament ejecta were seen in O v moving southward at a speed of about 60 km/s, before the impulsive phase. The flare loop footpoints brightened in H-alpha and the Ca XIX resonance line broadened dramatically 2 min before the impulsive phase. Nonthermal hard X-ray emission was detected from the loop footpoints during the impulsive phase, while during the same period blue-shifts corresponding to upflows of 200-250 km/s were seen in Ca XIX. Evidence was found for energy deposition in both the chromosphere and corona at a number of stages during the flare. Two widely studied mechanisms for the production of the high temperature soft X-ray flare plasma in the corona are considered, i.e. chromospheric evaporation, and a model in which the heating and transfer of material occurs between flux tubes during reconnection.

Multi-thermal observations of newly formed loops in a dynamic flare

NASA Technical Reports Server (NTRS)

Svestka, Zdenek F.; Fontenla, Juan M.; Machado, Marcos E.; Martin, Sara F.; Neidig, Donald F.

1987-01-01

The dynamic flare of November 6, 1980 (max at about 15:26 UT) developed a rich system of growing loops which could be followed in H-alpha for 1.5 hr. Throughout the flare, these loops, near the limb, were seen in emission against the disk. Theoretical computations of deviations from LTE populations for a hydrogen atom reveal that this requires electron densities in the loops close to, or in excess of 10 to the 12th/cu cm. From measured widths of higher Balmer lines the density at the tops of the loops was found to be 4 x 10 to the 12th/cu cm if no nonthermal motions were present, or 5 x 10 to the 11th/cu cm for a turbulent velocity of about 12 km/s. It is now general knowledge that flare loops are initially observed in X-rays and become visible in H-alpha only after cooling. For such a high density, a loop would cool through radiation from 10 to the 7th to 10 to the 4th K within a few minutes so that the dense H-alpha loops should have heights very close to the heights of the X-ray loops. This, however, contradicts the observations obtained by the HXIS and FCS instruments on board SMM which show the X-ray loops at much higher altitudes than the loops in H-alpha. Therefore, it is suggested that the density must have been significantly lower when the loops were formed, and that the flare loops were apparently both shrinking and increasing in density while cooling.

A Modified Kinematic Model of Neutral and Ionized Gas in Galactic Center

NASA Astrophysics Data System (ADS)

Krishnarao, Dhanesh; Benjamin, Robert A.; Haffner, L. Matthew

2018-01-01

Gas near the center of the Milky Way is very complex across all phases (cold, warm, neutral, ionized, atomic, molecular, etc.) and shows strong observational evidence for warping, lopsided orientations and strongly non-circular kinematics. Historically, the kinematic complexities were modeled with many discrete features involved with expulsive phenomena near Galactic Center. However, much of the observed emission can be explained with a single unified and smooth density structure when geometrical and perspective effects are accounted for. Here we present a new model for a tilted, elliptical disk of gas within the inner 2 kpc of Galactic center based on the series of models following Burton & Liszt (1978 - 1992, Papers I- V). Machine learning techniques such as the Histogram of Oriented Gradients image correlation statistic are used to optimize the geometry and kinematics of neutral and ionized gas in 3D observational space (position,position, velocity). The model successfully predicts emission from neutral gas as seen by HI (Hi4Pi) and explains anomalous ionized gas features in H-Alpha emission (Wisconsin H-Alpha Mapper) and UV absorption lines (Hubble Space Telescope - Space Telescope Imaging Spectrograph). The modeled distribution of this tilted gas disk along with its kinematics of elliptical x1 orbits can reveal new insight about the Galactic Bar, star formation, and high-velocity gas near Galactic Center and its relation with the Fermi Bubble.

Ram Pressure Stripping of Galaxy JO201

NASA Astrophysics Data System (ADS)

Zhong, Greta; Tonnesen, Stephanie; Jaffé, Yara; Bellhouse, Callum; Bianca Poggianti

2017-01-01

Despite the discovery of the morphology-density relation more than 30 years ago, the process driving the evolution of spiral galaxies into S0s in clusters is still widely debated. Ram pressure stripping--the removal of a galaxy's interstellar medium by the pressure of the intracluster medium through which it orbits--may help explain galactic evolution and quenching in clusters. MUSE (Multi Unit Spectroscopic Explorer) observational data of galaxy JO201 in cluster Abell 85 reveal it to be a jellyfish galaxy--one with an H-alpha emitting gas tail on only one side. We model the possible orbits for this galaxy, constrained by the cluster mass profile, line of sight velocity, and projected distance from the cluster center. Using Enzo, an adaptive mesh refinement hydrodynamics code, we simulate effects of ram pressure on this galaxy for a range of possible orbits. We present comparisons of both the morphology and velocity structure of our simulated galaxy to the observations of H-alpha emission.

TIME-DOMAIN SPECTROSCOPY OF A T TAURI STAR

NASA Astrophysics Data System (ADS)

Dupree, Andrea K.; Brickhouse, Nancy S.; Cranmer, Steven R.; Berlind, Perry L.; Strader, Jay; Smith, Graeme H.

2014-06-01

High resolution optical and near-infrared spectra of TW Hya, the nearest accreting T Tauri star, cover a decade and reveal the substantial changes in accretion and wind properties. Our spectra suggest that the broad near-IR, optical, and far-uv emission lines, centered on the star, originate in a turbulent post-shock region and can undergo scattering by the overlying stellar wind as well as absorption from infalling material. Stable absorption features appear in H-alpha, apparently caused by an accreting column silhouetted in the stellar wind. The free-fall velocity of material correlates inversely with the strength of the post-shock emission, consistent with a dipole accretion model. Terminal outflow velocities appear to be directly related to the amount of post-shock emission, giving evidence for an accretion-driven stellar wind.

Chromospherically active stars. VI - HD 136901 = UV CrB: A massive ellipsoidal K giant single-lined spectroscopic binary

NASA Technical Reports Server (NTRS)

Fekel, Francis C.; Kirkpatrick, J. Davy; Yang, Xinxing; Strassmeier, Klaus G.

1989-01-01

The variable star HD 136901 = UV CrB is a chromospherically active K2 III single-lined spectroscopic binary with an orbital period of 18.665 days. It has modest-strength Ca H and K emission and UV features, while H-alpha is a strong absorption feature containing little or no emission. The inclination of the system is 53 + or - 12 deg. The v sin i of the primary is 42 + or - 2 km/s, resulting in a minimum radius of 15.5 + or - 0.8 solar. When compared with the Roche lobe radius, this results in a mass ratio of 2.90 or larger. Additional constraints indicate that the secondary has a mass between 0.85 and 1.25 solar. Thus, the mass of the primary is at least 2.5 solar and probably is in the range 2.5-4 solar.

Interaction of NGC 2276 with the NGC 2300 group - Fabry-Perot observations of the H-alpha velocity field

NASA Technical Reports Server (NTRS)

Gruendl, Robert A.; Vogel, Stuart N.; Davis, David S.; Mulchaey, John S.

1993-01-01

We report kinematic observations of H-alpha emission from the spiral galaxy NGC 2276 obtained with a Fabry-Perot Camera. The 'bow shock' appearance and enhanced star formation in NGC 2276 have been attributed by Mulchaey et al. (1993) to a ram-pressure interaction with the dense IGM detected in ROSAT observations of the NGC 2300 group of galaxies. Along the 'bow shock' limb of the galaxy, we observe strong H-alpha emission and significant kinematic perturbations located immediately interior to an abrupt decrease in the scale length of the optical disk. Although ram-pressure forces may be important in the evolution of the outer gaseous disk, the peculiar kinematics and the truncation in the stellar disk are difficult to explain in a ram-pressure model; a more likely cause is tidal interaction, probably with the elliptical galaxy NGC 2300.

A surge observed in H alpha and C IV

NASA Technical Reports Server (NTRS)

Schmieder, B.; Mein, P.; Vial, J. C.; Tandberg-Hanssen, E.

1982-01-01

Results are presented of simultaneous measurements of H-alpha (MSDP at Meudon) and C IV (UVSP onboard SMM) of Active Region 2701 made on October 2, 1980. Isodensity and velocity maps were obtained for both lines and these maps were superimposed. Results show a good correlation between the H-alpha and C IV velocities with a surge being observed for 10 minutes. The base of the surge was determined to be located in a bright point in C IV and H-alpha, while the escaping matter followed the same channel ('absorbing' in H-alpha, 'emitting' in C IV). It was found that the velocity along the surge was about 80 km/s in H-alpha and 100 km/s in C IV. In addition, a loop appeared in C IV during the surge. It is concluded that the vertical pressure gradient was capable of driving the surge.

A qualitative interpretation of 7 August 1972 impulsive phase flare H alpha line profiles

NASA Technical Reports Server (NTRS)

Canfield, R. C.

1982-01-01

The considered investigation shows that existing models of the formation of the H-alpha line during flares appear to provide clear qualitative evidence that heating of the H-alpha forming regions of the flare chromosphere in the bright H-alpha kernels observed during the impulsive phase of solar flares is not due primarily to heating by Coulomb collisions of a power-law distribution of 10-100 keV electrons with chromospheric material. It appears rather that some shorter-range process, involving possibly conduction or optically thick radiative transfer, is favored. Such a conclusion is clearly relevant to collisionless confinement modelling. However, much work remains to be done before there will be a basis for quantitatively testing the consistency of the considered picture with chromospheric diagnostics.

STAR-FORMING GALAXIES IN THE HERCULES CLUSTER: H{alpha} IMAGING OF A2151

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cedres, Bernabe; Iglesias-Paramo, Jorge; VIlchez, Jose Manuel

2009-09-15

This paper presents the first results of an H{alpha} imaging survey of galaxies in the central regions of the A2151 cluster. A total of 50 sources were detected in H{alpha}, from which 41 were classified as secure members of the cluster and 2 as likely members based on spectroscopic and photometric redshift considerations. The remaining seven galaxies were classified as background contaminants and thus excluded from our study on the H{alpha} properties of the cluster. The morphologies of the 43 H{alpha} selected galaxies range from grand design spirals and interacting galaxies to blue compacts and tidal dwarfs or isolated extragalacticmore » H II regions, spanning a range of magnitudes of -21 {<=} M{sub B} {<=} -12.5 mag. From these 43 galaxies, 7 have been classified as active galactic nucleus (AGN) candidates. These AGN candidates follow the L(H{alpha}) versus M{sub B} relationship of the normal galaxies, implying that the emission associated with the nuclear engine has a rather secondary impact on the total H{alpha} emission of these galaxies. A comparison with the clusters Coma and A1367 and a sample of field galaxies has shown the presence of cluster galaxies with L(H{alpha}) lower than expected for their M{sub B} , a consequence of the cluster environment. This fact results in differences in the L(H{alpha}) versus EW(H{alpha}) and L(H{alpha}) distributions of the clusters with respect to the field, and in cluster-to-cluster variations of these quantities, which we propose are driven by a global cluster property as the total mass. In addition, the cluster H{alpha} emitting galaxies tend to avoid the central regions of the clusters, again with different intensity depending on the cluster total mass. For the particular case of A2151, we find that most H{alpha} emitting galaxies are located close to the regions with the higher galaxy density, offset from the main X-ray peak. Overall, we conclude that both the global cluster environment and the cluster merging history play a non-negligible role in the integral star formation properties of clusters of galaxies.« less

The great flare of 1982 June 6

NASA Technical Reports Server (NTRS)

Tanaka, K.; Zirin, H.

1985-01-01

The great soft X-ray (SXR) flare (X12) of the past solar maximum was observed by Hinotori and by Big Bear Solar Observatory (BBSO) on June 6, 1982. Hinotori data consist of hard X-ray (HXR) and SXR images in the rise and decay of the flare, high-resolution soft X-ray spectra throughout the flare, and HXR and gamma-ray data. The BBSO data include films of H-alpha, H-alpha blue wing, D3 and longitudinal magnetic field, as well as video tapes of continuum. Images in HXR, SXR, H-alpha, D3 and the continuum are compared and SXR spectra analyzed. The flare resulted from extended motion of a large spot shearing the magnetic field. D3 and white-light images exhibit a progression from fast flashes to two ribbons, while both HXR and SXR are centered on the optical kernels. The continuum emission shows the same temporal behavior as the HXR at 160 keV. In its early phases, the Fe XXV line was double-peaked, and a decreasing blueshifted (up to 400 km/sec) component was observed, from which the evaporation rate of chromospheric material was estimated. It is suggested that this upflow is adequate to supply the coronal cloud. Flare energetics are discussed in detail, and it is concluded that a significant amount of energy was deposited in the corona, and that nonthermal electrons are the major energy input.

Optical imagery and spectrophotometry of CTB 80

NASA Technical Reports Server (NTRS)

Hester, J. Jeff; Kulkarni, Shrinivas R.

1989-01-01

Narrow-band imagery and spectrophotometry of the central region of CTB 80 are presented. The images show weak forbidden O III and ubiquitous filamentary forbidden S II and H-alpha emission from the extended radio lobes in which the core is embedded. The data indicate that the extended component is shock heated. Balmer line-dominated emission is observed around the perimeter of the core. Assuming that the volume of the radio shell is similar to the volume of the thermal shell, it is found that a magnetic field of about 600 microG and a cosmic-ray proton-to-electron ratio of about 200 are required to explain the pressure and synchrotron volume emissivity in the radio shell. It is suggested that the optical emission form the core of CTB 80 arises behind shocks which are being driven into a magnetized thermal plasma by the confined relativistic wind from PSR 1951+32.

Molecules in Protoplanetary HAEBE discs as seen with Herschel.

NASA Astrophysics Data System (ADS)

Meeus, G.

2011-05-01

The discovery of planets around other stars has revealed that planet formation is ubiquitous. However, the mechanisms determining planet formation are not (yet) well-understood. Primordial protoplanetary discs consist 99% out of gas, and only 1% out of dust. With time, those discs are believed to evolve from a flaring geometry into a flat geometry, as the initially small dust grains grow to larger sizes and settle towards the mid-plane. In the mean time, the gas will disperse, until so little is left that giant planets no longer can form. It is thus important to understand the chemical composition of the disc and the influence of the gas heating/cooling processes on the disc structure, and finally how gas gets dispersed as a pieces of the puzzle of planet formation. In this contribution, we study the protoplanetary discs around Herbig Ae/Be stars, young objects of intermediate mass, in the context of gas chemistry. We present Herschel PACS spectroscopic observations for a sample that was obtained within the GASPS (Gas in Protoplanetary Systems) Open Time Key Project, concentrating on the detection and characterisation of emission lines of the molecules H20, CO and CH+ (besides [OI] and [CII]), tracing the disc between 5 and 500 AU. We look for correlations between the observed line fluxes and stellar properties such as effective temperature, Halpha emission, accretion rates and UV flux, as well as the disc properties: degree of flaring, presence and strength of PAH emission and disc mass. We will present a few cases to show how simultaneous modeling (using the thermo-chemical disc code ProDiMo) of the atomic fine structure lines and both Space Telescope and ground-based molecular lines can constrain the disc gas mass, once the disc structure is derived (here with the radiative transfer code MCFost). Finally, we compare our gas line observations with those of young debris disc stars, for which the HAEBE stars are thought to be progenitors.

Mass motions in the solar chromosphere and transition zone

NASA Technical Reports Server (NTRS)

Mein, P.; Simon, G.; Vial, J. C.; Shine, R. A.

1982-01-01

A comparison is made between H-alpha and C IV observations of Active Region 2717 on October 9, 1980. On the basis of this comparison, it is found that upward velocities are present above sunspots in the chromosphere-corona transition zone (20 km/s). The downward velocities are found to be well correlated in both lines. Doppler-shift ratios between C IV and H-alpha levels (approximately 10) are seen to be much smaller than expected from density ratio estimates. The comparison is seen as suggesting that flow lines are probably far from vertical in the transition zone. It is pointed out, however, that this depends on model densities that may not be correct. A simple method for comparing matter flows is presented. The best fit between H-alpha and C IV levels is obtained when C IV Doppler shifts are multiplied by the line intensity to the power 0.5 (approximately) in order to make allowance for density fluctuations.

Far-infrared emission and star formation in spiral galaxies

NASA Technical Reports Server (NTRS)

Trinchieri, G.; Fabbiano, G.; Bandiera, R.

1989-01-01

The correlations between the emission in the far-IR, H-alpha, and blue in a sample of normal spiral galaxies are investigated. It is found that the luminosities in these three bands are all tightly correlated, although both the strength of the correlations and their functional dependencies are a function of the galaxies' morphological types. The best-fit power laws to these correlations are different for the comparison of different quantities and deviate significantly from linearity in some cases, implying the presence of additional emission mechanisms not related to the general increase of luminosity with galactic mass. Clear evidence is found of two independent effects in the incidence of warm far-IR emission in late-type spirals. One is a luminosity effect shown by the presence of excess far-IR relative to H-alpha or optical emission in the more luminous galaxies. The other is a dependence on widespread star-formation activity.

Dust Attenuation and H(alpha) Star Formation Rates of Z Approx. 0.5 Galaxies

NASA Technical Reports Server (NTRS)

Ly, Chun; Malkan, Matthew A.; Kashikawa, Nobunari; Ota, Kazuaki; Shimasaku, Kazuhiro; Iye, Masanori; Currie, Thayne

2012-01-01

Using deep narrow-band and broad-band imaging, we identify 401 z approximately 0.40 and 249 z approximately 0.49 H-alpha line-emitting galaxies in the Subaru Deep Field. Compared to other H-alpha surveys at similar redshifts, our samples are unique since they probe lower H-alpha luminosities, are augmented with multi-wavelength (rest-frame 1000AA--1.5 microns) coverage, and a large fraction (20%) of our samples has already been spectroscopically confirmed. Our spectra allow us to measure the Balmer decrement for nearly 60 galaxies with H-beta detected above 5-sigma. The Balmer decrements indicate an average extinction of A(H-alpha)=0.7(uparrow){+1.4}_{-0.7} mag. We find that the Balmer decrement systematically increases with higher H-alpha luminosities and with larger stellar masses, in agreement with previous studies with sparser samples. We find that the SFRs estimated from modeling the spectral energy distribution (SED) is reliable---we derived an "intrinsic" H-alpha luminosity which is then reddened assuming the color excess from SED modeling. The SED-predicted H-alpha luminosity agrees with H-alpha narrow-band measurements over 3 dex (rms of 0.25 dex). We then use the SED SFRs to test different statistically-based dust corrections for H-alpha and find that adopting one magnitude of extinction is inappropriate: galaxies with lower luminosities are less reddened. We find that the luminosity-dependent dust correction of Hopkins et al. yields consistent results over 3 dex (rms of 0.3 dex). Our comparisons are only possible by assuming that stellar reddening is roughly half of nebular reddening. The strong correspondence argue that with SED modeling, we can derive reliable intrinsic SFRs even in the absence of H-alpha measurements at z approximately 0.5.

A Proper-Motion Corrected, Cross-Matched Catalog Of M Dwarfs In SDSS And FIRST

NASA Astrophysics Data System (ADS)

Arai, Erin; West, A. A.; Thyagarajan, N.; Agüeros, M.; Helfand, D.

2011-05-01

We present a preliminary analysis of M dwarfs identified in both the Sloan Digital Sky Survey (SDSS) and the Very Large Array's (VLA) Faint Images of the Radio Sky at Twenty-centimeters survey (FIRST). The presence of magnetic fields is often associated with indirect magnetic activity measurements, such as H-alpha or X-ray emission. Radio emission, in contrast, is directly proportional to the magnetic field strength in addition to being another measure of activity. We search for stellar radio emission by cross-matching the SDSS DR7 M dwarf sample with the FIRST catalog. The SDSS data allow us to examine the spectra of our objects and correlate the magnetic activity (H-alpha) with the magnetic field strength (radio emission). Accurate positions and proper motions are important for obtaining a complete list of overlapping targets. Positions in FIRST and SDSS need to be proper motion corrected in order to ensure unique target matches since nearby M dwarfs can have significant proper motions (up to 1'' per year). Some previous studies have neglected the significance of proper motions in identifying overlapping targets between SDSS and FIRST; we correct for some of these previous oversights. In addition the FIRST data were taken in multiple epochs; individual images need to be proper motion corrected before the images can be co-added. Our cross-match catalog puts important constraints on models of magnetic field generation in low-mass stars in addition to the true habitability of attending planets.

H-alpha synoptic charts of solar activity during the first year of solar cycle 20, October 1964 - August 1965. [Skylab program

NASA Technical Reports Server (NTRS)

Mcintosh, P. S.

1975-01-01

Solar activity during the period October 28, 1964 through August 27, 1965 is presented in the form of charts for each solar rotation constructed from observations made with the chromospheric H-alpha spectra line. These H-alpha synoptic charts are identical in format and method of construction to those published for the period of Skylab observations. The sunspot minimum marking the start of Solar Cycle 20 occurred in October, 1964; therefore, charts represent solar activity during the first year of this solar cycle.

The Environmental Impact of Intra-Cluster Medium on the Interstellar Medium in Early Type Galaxies

NASA Technical Reports Server (NTRS)

Trinchieri, Ginevra

1997-01-01

High resolution X-ray images of three early type galaxies observed with the ROSAT HRI are presented. Data for NGC 1553 and NGC 5846 indicate that the emission is highly irregular, with interesting features on scales from a few arcsec to a few arcmin. The gas temperatures also vary both with the galactocentric radius and in correspondence to regions of higher emission and denser material. Strikingly similar features are observed in the X-ray and H(alpha) morphologies of NGC 1553 and NGC 5846, while smoother, more regular isophotes are observed in NGC 4649 at both wavelengths. A connection between these two kinds of emission therefore seems likely. In the light of our observations we discuss possible scenarios that can and account for the connection between X-ray and H(alpha) emissions.

Spitzer c2d Legacy, Circumstellar Disks around wTT Stars

NASA Astrophysics Data System (ADS)

Wahhaj, Zahed; c2d Legacy Team

2007-05-01

The Spitzer Legacy Project From "Molecular Cores to Planet-forming Disks" conducted a 3.6 to 70um photometric survey of roughly 160 weak- line TTauri Stars (wTTs) and 20 classical TTauri stars (cTTs) in the nearby star-forming regions Chamaeleon, Lupus, Ophiuchus and Taurus. WTTs are so named because they possess weaker H-alpha emission lines signifying weaker disk accretion on to the star than cTTs. The evolution of dust disks around these young stars (Age 10 Myrs) is key to understanding planet formation. From the observed infrared excesses, we infer the presence of circumstellar disks around 12% of wTTs and 75% of cTTs. However, when considering on-cloud sources only, the wTTs disk fraction is 22%, while it is only 6% for off- cloud sources, suggesting an older age for the latter. WTTs, while not discernibly younger than cTTs in age diagnostics, in general have disks which exhibit lower fractional luminosities and larger inner clearings. However, quite a few wTTs systems have fractional disk luminosities as high as cTTs systems. In light of these findings, wTTs seem to be transitional objects between cTTs and debris disks.

THE LICK AGN MONITORING PROJECT: REVERBERATION MAPPING OF OPTICAL HYDROGEN AND HELIUM RECOMBINATION LINES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bentz, Misty C.; Walsh, Jonelle L.; Barth, Aaron J.

2010-06-20

We have recently completed a 64-night spectroscopic monitoring campaign at the Lick Observatory 3 m Shane telescope with the aim of measuring the masses of the black holes in 12 nearby (z < 0.05) Seyfert 1 galaxies with expected masses in the range {approx}10{sup 6}-10{sup 7} M{sub sun} and also the well-studied nearby active galactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including NGC 5548) showed optical variability of sufficient strength during the monitoring campaign to allow for a time lag to be measured between the continuum fluctuations and the response to these fluctuations in themore » broad H{beta} emission, which we have previously reported. We present here the light curves for the H{alpha}, H{gamma}, He II {lambda}4686, and He I {lambda}5876 emission lines and the time lags for the emission-line responses relative to changes in the continuum flux. Combining each emission-line time lag with the measured width of the line in the variable part of the spectrum, we determine a virial mass of the central supermassive black hole from several independent emission lines. We find that the masses are generally consistent within the uncertainties. The time-lag response as a function of velocity across the Balmer line profiles is examined for six of the AGNs. We find similar responses across all three Balmer lines for Arp 151, which shows a strongly asymmetric profile, and for SBS 1116+583A and NGC 6814, which show a symmetric response about zero velocity. For the other three AGNs, the data quality is somewhat lower and the velocity-resolved time-lag response is less clear. Finally, we compare several trends seen in the data set against the predictions from photoionization calculations as presented by Korista and Goad. We confirm several of their predictions, including an increase in responsivity and a decrease in the mean time lag as the excitation and ionization level for the species increases. Specifically, we find the time lags of the optical recombination lines to have weighted mean ratios of {tau}(H{alpha}):{tau}(H{beta}):{tau}(H{gamma}):{tau}(He I):{tau}(He II) = 1.54:1.00:0.61:0.36:0.25. Further confirmation of photoionization predictions for broad-line gas behavior will require additional monitoring programs for these AGNs while they are in different luminosity states.« less

RS CVn stars - Chromospheric phenomena

NASA Technical Reports Server (NTRS)

Bopp, B. W.

1983-01-01

The observational information regarding chromospheric emission features in surface-active RS CVn stars is reviewed. Three optical features are considered in detail: Ca II H and K, Balmer H-alpha and He I 10830 A. While the qualitative behavior of these lines is in accord with solar-analogy/rotation-activity ideas, the quantitative variation and scaling are very poorly understood. In many cases, the spectroscopic observations with sufficient SNR and resolution to decide these questions have simply not yet been made. The FK Com stars, in particular, present extreme examples of rotation that may well tax present understanding of surface activity to its limits.

Luminosity-velocity diagrams for Virgo Cluster spirals. I - Inner rotation curves

NASA Technical Reports Server (NTRS)

Woods, David; Fahlman, Gregory G.; Madore, Barry F.

1990-01-01

Optical rotation curves are presented for the innermost portions of nine spiral galaxies in the Virgo Cluster. The emission-line (H-alpha and forbidden N II) velocity data are to be used in combination with new CCD photometry to construct luminosity-velocity diagrams, in a continuing investigation of an apparent initial linear branch and its potential as a distance indicator. Compared to recent H I data, the present optical rotation curves generally show systematically steeper inner gradients. This effect is ascribed to the poorer resolution of the H I data and/or to holes in the gas distribution.

GBT Observations of Radio Recombination Line Emission Associated with Supernova Remnants W28 and W44

NASA Astrophysics Data System (ADS)

Hewitt, John W.; Yusef-Zadeh, F.

2006-06-01

Since the 1970's weak radio recombination line(RRL) emission has been observed toward several supernova remnants. It has remained unclear if this emission is in fact associated with these remnants or due to intervening sources such as extended HII envelopes along the line of sight. To explore the origin of this emitting gas we have recently undertaken Green Bank Telescope (GBT) observations of prominent supernova remnants W28 and W44 which are well-known to be interacting with molecular clouds. Eight alpha and beta RRL transitions were mapped at C-Band (4-6 GHz) with 2.5' resolution. Maps cover 0.5 and 0.25 square degrees of W28 and W44, respectively, permitting comparison with the distribution of X-rays, Radio, and H-alpha emission. Both remnants are observed to have a mixed-morphology: a radio-continuum shell centrally-filled by thermal X-rays. We find the observed velocity of RRL emission is near the systemic velocity of both remnants as traced by OH(1720 MHz) masers. Preliminary results are presented exploring the association of the RRL-emitting gas with these interacting supernova remants and implications for the origins of the hot thermal X-ray plasma that fills their centers. Support for this work was provided by the NSF through The GBT Student Support Program from the NRAO.

Explosive plasma flows in a solar flare

NASA Technical Reports Server (NTRS)

Zarro, Dominic M.; Canfield, Richard C.; Metcalf, Thomas R.; Strong, Keith T.

1988-01-01

Solar Maximum Mission soft X-ray data and Sacramento Peak Observatory H-alpha observations are combined in a study of the impulsive phase of a solar flare. A blue asymmetry, indicative of upflows, was observed in the coronal Ca XIX line during the soft X-ray rise phase. A red asymmetry, indicative of downflows, was observed simultaneously in chromospheric H-alpha emitted from bright flare kernels during the period of hard X-ray emission. Combining the velocity data with a measurement of coronal electron density, it is shown that the impulsive phase momentum of upflowing soft X-ray-emitting plasma equalled that of the downflowing H-alpha-emitting plasma to within one order of magnitude. In particular, the momentum of the upflowing plasma was 2 x 10 to the 21st g cm/s while that of the downflowing plasma was 7 x 10 to the 21st g cm/s, with a factor of 2 uncertainty on each value. This equality supports the explosive chromospheric evaporation model of solar flares, in which a sudden pressure increase at the footprint of a coronal loop produces oppositely directed flows in the heated plasma.

An Improved Red Spectrum of the Methane or T Dwarf SDSS 1624+0029: The Role of the Alkali Metals.

PubMed

Liebert; Reid; Burrows; Burgasser; Kirkpatrick; Gizis

2000-04-20

A Keck II low-resolution spectrum shortward of 1 µm is presented for SDSS 1624+0029, the first field methane or T dwarf discovered in the Sloan Digital Sky Survey. Significant flux is detected down to the spectrum's short-wavelength limit of 6200 Å. The spectrum exhibits a broad absorption feature centered at 7700 Å, which we interpret as the K i lambdalambda7665, 7699 resonance doublet. The observed flux declines shortward of 7000 Å, most likely owing to the red wing of the Na i doublet. Both Cs i doublet lines are detected more strongly than in an earlier red spectrum. Neither Li i absorption nor Halpha emission are detected. An exploratory model fit to the spectrum suggests that the shape of the red spectrum can be primarily accounted for by the broad wings of the K i and Na i doublets. This behavior is consistent with the argument proffered by Burrows, Marley, & Sharp that strong alkali absorption is principally responsible for depressing T dwarf spectra shortward of 1 µm. In particular, there seems no compelling reason at this time to introduce dust or an additional opacity source in the atmosphere of the Sloan object. The width of the K i and strengths of the Cs i lines also indicate that the Sloan object is warmer than Gl 229B.

An Empirically-derived non-LTE XUV-Visible Spectral Synthesis Model of the M1 V Exoplanet Host Star GJ832

NASA Astrophysics Data System (ADS)

Linsky, Jeffrey; Fontenla, Juan; Witbrod, Jesse; France, Kevin

2016-01-01

GJ832 (HD 204961) is a nearby M1 V host star with two exoplanets: a Jovian mass planet and a super-Earth. We have obtained near-UV and far-UV spectra of GJ832 with the STIS and COS instruments on HST as part of the Cycle 19 MUSCLES pilot program (France et al. 2013). Our objective is to obtain the first accurate physical model for a representative M-dwarf host star in order to understand the stellar radiative emission at all wavelengths and to infer the radiation environment of their exoplanets that drives their atmospheric photochemistry.We have calculated a full non-LTE model for GJ 832 including the photosphere, chromosphere, transition region, and corona to fit the observed emission lines formed over a wide range of temperatures and the X-ray flux. Our one-dimensional semi-empirical model uses the Solar-Stellar Physical Modelling tools that are an offspring of the tools used by Fontenla and collaborators for computing solar models. For this model of GJ832, we calculate the populations of 52 atoms and ions and 20 molecules with 2 million spectral lines. We find excellent agreement with the observed H-alpha, CaII, MgII, CII, SiIV, CIV, and NV lines. Our model for GJ832 has a temperature minimum in the lower chromosphere much cooler than the Sun and then a steep temperature rise different from the Sun. The different thermal structure of GJ832 compared to the Sun results in the formation regions of the emission lines being different for the two stars. We also compute theradiative cooling rates as a function of height and temperature in the atmosphere of GJ832.This work is supported by grants from STScI to the University of Colorado.

AGN POPULATION IN HICKSON COMPACT GROUPS. I. DATA AND NUCLEAR ACTIVITY CLASSIFICATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

MartInez, M. A.; Del Olmo, A.; Perea, J.

2010-03-15

We have conducted a new spectroscopic survey to characterize the nature of nuclear activity in Hickson compact group (HCG) galaxies and establish its frequency. We have obtained new intermediate-resolution optical spectroscopy for 200 member galaxies and corrected for underlying stellar population contamination using galaxy templates. Spectra for 11 additional galaxies have been acquired from the ESO and 6dF public archives, and emission-line ratios have been taken from the literature for 59 more galaxies. Here we present the results of our classification of the nuclear activity for 270 member galaxies, which belong to a well-defined sample of 64 HCGs. We foundmore » a large fraction of galaxies, 63%, with emission lines. Using standard diagnostic diagrams, 45% of the emission-line galaxies were classified as pure active galactic nuclei (AGNs), 23% as Transition Objects (TOs), and 32% as star-forming nuclei (SFNs). In the HCGs, the AGN activity appears as the most frequent activity type. Adopting the interpretation that in TOs a low-luminosity AGN coexists with circumnuclear star formation, the fraction of galaxies with an AGN could rise to 42% of the whole sample. The low frequency (20%) of SFNs confirms that there is no star formation enhancement in HCGs. After extinction correction, we found a median AGN H{alpha} luminosity of 7.1 x 10{sup 39} erg s{sup -1}, which implies that AGNs in HCG have a characteristically low luminosity. This result added to the fact that there is an almost complete absence of broad-line AGNs in compact groups (CGs) as found by MartInez et al. and corroborated in this study for HCGs, is consistent with very few gas left in these galaxies. In general, therefore, what may characterize the level of activity in CGs is a severe deficiency of gas.« less

THE LYMAN ALPHA REFERENCE SAMPLE: EXTENDED LYMAN ALPHA HALOS PRODUCED AT LOW DUST CONTENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, Matthew; Oestlin, Goeran; Duval, Florent

2013-03-10

We report on new imaging observations of the Lyman alpha emission line (Ly{alpha}), performed with the Hubble Space Telescope, that comprise the backbone of the Lyman alpha Reference Sample. We present images of 14 starburst galaxies at redshifts 0.028 < z < 0.18 in continuum-subtracted Ly{alpha}, H{alpha}, and the far ultraviolet continuum. We show that Ly{alpha} is emitted on scales that systematically exceed those of the massive stellar population and recombination nebulae: as measured by the Petrosian 20% radius, R{sub P20}, Ly{alpha} radii are larger than those of H{alpha} by factors ranging from 1 to 3.6, with an average ofmore » 2.4. The average ratio of Ly{alpha}-to-FUV radii is 2.9. This suggests that much of the Ly{alpha} light is pushed to large radii by resonance scattering. Defining the Relative Petrosian Extension of Ly{alpha} compared to H{alpha}, {xi}{sub Ly{alpha}} = R {sup Ly{alpha}}{sub P20}/R {sup H{alpha}}{sub P20}, we find {xi}{sub Ly{alpha}} to be uncorrelated with total Ly{alpha} luminosity. However, {xi}{sub Ly{alpha}} is strongly correlated with quantities that scale with dust content, in the sense that a low dust abundance is a necessary requirement (although not the only one) in order to spread Ly{alpha} photons throughout the interstellar medium and drive a large extended Ly{alpha} halo.« less

The BAT AGN Spectroscopic Survey (BASS)

NASA Astrophysics Data System (ADS)

Koss, Michael; Trakhtenbrot, Benny; Ricci, Claudio; Lamperti, Isabella; Oh, Kyuseok; Berney, Simon; Schawinski, Kevin; Balokovic, Mislav; Baronchelli, Linda; Gehrels, Neil; Stern, Daniel; Mushotzky, Richard; Veilleux, Sylvain; Ueda, Yoshihiro; Crenshaw, D. Michael; Harrison, Fiona; Fischer, Travis C.; Treister, Ezequiel; BASS Team; Swift BAT Team

2017-01-01

We present the Swift BAT AGN Spectroscopic Survey (BASS) and discus the first four papers. The catalog represents an unprecedented census of hard-X-ray selected AGN in the local universe, with ~90% of sources at z<0.2. Starting from an all-sky catalog of AGN detected based on their 14-195 keV flux from the 70-month Swift/BAT catalog, we analyze a total of 1279 optical spectra, taken from twelve dierent telescopes, for a total of 642 spectra of unique AGN. We present the absorption and emission line measurements as well as black hole masses and accretion rates for the majority of obscured and un-obscured AGN (473), representing more than a factor of 10 increase from past studies. Consistent with previous surveys, we find an increase in the fraction of un-obscured (type 1) AGN, as measured from broad Hbeta and Halpha, with increasing 14-195 keV and 2-10 keV luminosity. We find the FWHM of the emission lines to show broad agreement with the X-ray obscuration measurements. Compared to narrow line AGN in the SDSS, the X-ray selected AGN in our sample with emission lines have a larger fraction of dustier galaxies suggesting these types of galaxies are missed in optical AGN surveys using emission line diagnostics. Additionally, we discuss follow-on efforts to study the variation of [OIII] to Xray measurements, a new method to measure accretion rates from using line ratios, a sample of 100 AGN observed with NIR spectroscopy, and an effort to measure the accretion rates and obscuration with merger stage in a subsample of mergers.

The BAT AGN Spectroscopic Survey (BASS) DR1-Spectral Measurements, Derived Quantities, and AGN Demographics

NASA Astrophysics Data System (ADS)

Koss, Michael; BASS Team

2018-01-01

We present the first catalog and data release of the Swift-BAT AGN Spectroscopic Survey (BASS). We analyze optical spectra of the majority of AGN (77%, 641/836) detected based on their 14-195 keV emission in the 70-month Swift BAT all-sky catalog. This includes redshift determination, absorption and emission line measurements, and black hole mass and accretion rate estimates for the majority of obscured and un-obscured AGN (74%, 473/641) with 340 measured for the first time. With ~90% of sources at z<0.2, the survey represents a significant census of hard-X-ray selected AGN in the local universe. In this first catalog paper, we describe the spectroscopic observations and datasets, and our initial spectral analysis. The FWHM of the emission lines show broad agreement with the X-ray obscuration (~94%), such that Sy 1-1.8 have NH<10^21.9 cm^-2, and Seyfert 2, have NH>10^21.9 cm^-2. Seyfert 1.9 show a range of column densities. Compared to narrow line AGN in the SDSS, the X-ray selected AGN have a larger fraction of dusty host galaxies suggesting these types of AGN are missed in optical surveys. Using the most sensitive [OIII]/Hbeta and [NII]/Halpha emission line diagnostic, about half of the sources are classified as Seyferts, ~15% reside in dusty galaxies that lack an Hbeta detection, but for which the line upper limits imply either a Seyfert or LINER, ~15% are in galaxies with weak or no emission lines despite high quality spectra, and a few percent each are LINERS, composite galaxies, HII regions, or in known beamed AGN.

Bright Points and Subflares in Ultraviolet Lines and X-Rays

NASA Technical Reports Server (NTRS)

Rovira, M.; Schmieder, B.; Demoulin, P.; Simnett, G. M.; Hagyard, M. J.; Reichmann, E.; Reichmann, E.; Tandberg-Hanssen, E.

1999-01-01

We have analyzed an active region which was observed in H.alpha (Multichannel Subtractive Double Pass Spectrograph), in UV lines (SMM/UVSP), and in X-rays (SMM/HXIS). In this active region there were only a few subflares and many small bright points visible in UV and in X-rays. Using an extrapolation based on the Fourier transform, we have computed magnetic field lines connecting different photospheric magnetic polarities from ground-based magnetograms. Along the magnetic inversion lines we find two different zones: (1) a high-shear region (> 70 deg) where subflares occur, and (2) a low-shear region along the magnetic inversion line where UV bright points are observed. In these latter regions the magnetic topology is complex with a mixture of polarities. According to the velocity field observed in the Si IV lamda.1402 line and the extrapolation of the magnetic field, we notice that each UV bright point is consistent with emission from low-rising loops with downflows at both ends. We notice some hard X-ray emissions above the bright-point regions with temperatures up to 8 x 10(exp 6) K, which suggests some induced reconnection due to continuous emergence of new flux. This reconnection is also enhanced by neighboring subflares.

Geminga's tails: a pulsar bow shock probing the interstellar medium.

PubMed

Caraveo, P A; Bignami, G F; DeLuca, A; Mereghetti, S; Pellizzoni, A; Mignani, R; Tur, A; Becker, W

2003-09-05

We report the X-ray Multimirror Mission-Newton European Photon Imaging Camera observation of two elongated parallel x-ray tails trailing the pulsar Geminga. They are aligned with the object's supersonic motion, extend for approximately 2', and have a nonthermal spectrum produced by electron-synchrotron emission in the bow shock between the pulsar wind and the surrounding medium. Electron lifetime against synchrotron cooling matches the source transit time over the x-ray features' length. Such an x-ray detection of a pulsar bow shock (with no Halpha emission) allows us to gauge the pulsar electron injection energy and the shock magnetic field while constraining the angle of Geminga's motion and the local matter density.

The chromospheres of late-type stars. I - Eridani as a test case of multiline modelling

NASA Technical Reports Server (NTRS)

Thatcher, John D.; Robinson, Richard D.; Rees, David E.

1991-01-01

A new model of the lower chromosphere of the dwarf K2 star Epsilon Eridani is derived by matching flux profiles of the Ca IR triplet lines 8498 and 8542 A H-alpha and H-beta lines and the Na D lines (all observed simultaneously at the AAT), and the Ca II K line. The coupled non-LTE equations of statistical equilibrium and radiative transfer are solved under the constraint of hydrostatic equilibrium using the Carlsson (1986) code. Within the framework of the model, the Na D lines are an important photospheric diagnostic, and the Ca IR triplet lines can be used to locate the temperature minimum. The computed H-alpha and H-beta depths are highly sensitive constraints on the transition zone gradients and base pressures allowing us to derive a pressure at the base of the transition zone of 0.9 dyn/cm.

VizieR Online Data Catalog: Halpha measurements in Abell 2465 (Wegner+, 2015)

NASA Astrophysics Data System (ADS)

Wegner, G. A.; Chu, D. S.; Hwang, H. S.

2015-07-01

The wavelength of the Hα line at the redshift of Abell 2465 is near 817nm in a clear spectral region between the many telluric emission lines. A custom narrow-band filter for observing Hα was obtained from the Andover Corp. It has a peak transmission at 817.7nm (m817) and a full width at half-maximum (FWHM) of 8.77nm. The wide filter was a Gunn i (ig) filter with nearly the same central wavelength of 820nm and a FWHM of 185nm, and was manufactured by Custom Scientific. Hα observations of Abell 2465 were obtained 2012 September 19-23 using the 2.4m Hiltner telescope at the MDM Observatory on Kitt Peak. The 'Nellie' CCD was used. (1 data file).

Characterizing the population of active galactic nuclei in dwarf galaxies

NASA Astrophysics Data System (ADS)

Baldassare, Vivienne F.; Reines, Amy E.; Gallo, Elena; Greene, Jenny E.

2017-01-01

Clues to super-massive black hole (BH) formation and growth reside in the population and properties of BHs in local dwarf galaxies. The masses of BHs in these systems are our best observational constraint on the masses of the first BH "seeds" at high redshift. Moreover, present-day dwarf galaxies are unlikely to have undergone major mergers, making them a relatively pristine testbed for studying triggers of BH accretion. However, in order to find BHs in dwarf galaxies outside the Local Group, it is necessary to search for signatures of accretion, i.e., active galactic nuclei (AGN). Until recently, only a handful of dwarf galaxies were known to contain AGN. However, large surveys such as the SDSS have led to the production of samples of over a hundred dwarf galaxies with AGN signatures (see e.g., Reines et al. 2013). My dissertation work has involved in-depth, multi-wavelength follow-up of nearby (z<0.055) dwarf galaxies with optical spectroscopic AGN signatures in SDSS.I analyzed high resolution spectra of dwarf galaxies with narrow-line AGN, which led to the discovery of a 50,000 MSun BH in the nucleus of RGG 118 - the smallest BH yet reported in a galaxy nucleus (Baldassare et al. 2015). I also used multi-epoch optical spectroscopy to study the nature of broad H-alpha emission in dwarf galaxies. A characteristic signature of dense gas orbiting around a BH, broad emission can also be produced by transient stellar processes. I showed that broad H-alpha in star-forming dwarf galaxies fades over a baseline of 5-10 years, and is likely produced by e.g., a Type II SN as opposed to an AGN. However, broad emission in dwarf galaxies with AGN/composite narrow lines is persistent and consistent across observations, suggesting an AGN origin (Baldassare et al. 2016). Finally, I analyzed X-ray and UV observations of dwarf galaxies with broad and narrow-line AGN signatures. All targets had nuclear X-ray detections at levels significantly higher than expected from X-ray binaries. With BH masses of ~105-106 MSun, inferred Eddington ratios range from 0.1-50%, akin to massive broad-line AGN at higher redshift (Baldassare et al. submitted). My dissertation work provides strong confirmation that these systems are bona fide AGN.

The Disk of 48 Lib Revealed by NPOI

NASA Astrophysics Data System (ADS)

Lembryk, Ludwik; Tycner, C.; Sigut, A.; Zavala, R. T.

2013-01-01

We present a study of the disk around the Be star 48 Lib, where NLTE numerical disk models are being compared to the spectral and interferometric data to constrain the physical properties of the inner disk structure. The computational models are generated using the BEDISK code, which accounts for heating and cooling of various atoms in the disk and assumes solar chemical composition. A large set of self-consistent disk models produced with the BEDISK code is in turn used to generate synthetic spectra and images assuming a wide range of inclination angles using the BERAY code. The aim of this project is to constrain the physical properties as well as the inclination angles using both spectroscopic and interferometric data. The interferometric data were obtained using the Naval Precision Optical Interferometer (NPOI), with the focus on Hydrogen Balmer-alpha emission, which is the strongest emission line present due to the circumstellar structure. Because 48 Lib shows clear asymmetric spectral lines, we discuss how we model the asymmetric peaks of the Halpha line by combining two models computed with different density structures. The corresponding synthetic images of these combined density structures are then Fourier transformed and compared to the interferometric data. This numerical strategy has the potential to easily model the commonly observed variation of the ratio of the violet-to-red (V/R ratio) emission peaks and constrain the long-term variability associated with the disk of 48 Lib as well as other emission-line stars that show similar variability.

Line Profile of H Lyman-Beta Emission from Dissociative Excitation of H2

NASA Technical Reports Server (NTRS)

Ajello, Joseph M.; Ahmed, Syed M.; Liu, Xian-Ming

1996-01-01

A high-resolution ultraviolet spectrometer was employed for a measurement of the H Lyman-Beta(H L(sub Beta)) emission Doppler line profile at 1025.7 A from dissociative excitation of H2 by electron impact. Analysis of the deconvolved line profile reveals the existence of a narrow central peak, less than 30 mA full width at half maximum (FWHM), and a broad pedestal base about 260 mA FWHM. Analysis of the red wing of the line profile is complicated by a group of Wemer and Lyman rotational lines 160-220 mA from the line center. Analysis of the blue wing of the line profile gives the kinetic-energy distribution. There are two main kinetic-energy components to the H(3p) distribution: (1) a slow distribution with a peak value near 0 eV from singly excited states, and (2) a fast distribution with a peak contribution near 7 eV from doubly excited states. Using two different techniques, the absolute cross section of H L(sub Beta)p is found to be 3.2+/-.8 x 10(exp -19)sq cm at 100-eV electron impact energy. The experimental cross-section and line-profile results can be compared to previous studies of H(alpha) (6563.7 A) for principal quantum number n=3 and L(sub alpha)(1215.7 A) for n=2.

Present-day Galaxy Evolution through Baryon Flows in the Circumgalactic Medium of the Galactic-Magellanic System

NASA Astrophysics Data System (ADS)

Barger, Kathleen Ann

Galaxy evolution is governed by an intricate ballet of gas flows. To sustain star formation over many billions of years, more gas must inflow than outflow. Although numerous gas clouds surround the Milky Way, their attributes, origins, destinations, and responses to their surroundings need thorough investigation on an individual basis to realize how the entire population affects Galactic evolution. This dissertation hones in on two circumgalactic gas structures near the Milky Way: Complex A and the Magellanic Bridge. Complex A is an elongated gas structure that is traversing the hot Halo of the Milky Way, plummeting towards the Galaxy's disk. The Magellanic Bridge is a bridge of gas and stars that connects the Magellanic Clouds, created by galaxy interactions. In this thesis, I present the results of the highest sensitivity and kinematically resolved Halpha emission-line survey of Complex A and Halpha, [S II], and [N II] surveys of the Magellanic Bridge using the Wisconsin Halpha Mapper to explore their properties, surroundings, origins, and fates to unravel how circumgalactic structures influence galaxy evolution. I find that the observational properties of Complex A closely match with radiative transfer model predictions of a cloud ionized by the Milky Way and extragalactic background, implying a 5% escape fraction of ionizing photons from the Galactic disk. The multiline observations and modeling place the cloud's metallicity below solar. These results combined with other studies suggests the cloud has an intergalactic medium origin. I find that the global distribution of the warm ionized gas traces the neutral gas in the Magellanic Bridge. These observations place the ionized gas mass between (0.7 -- 1.6) x 108 solar masses, implying an ionization fraction of 25 -- 33% and a 5% maximum escape fraction of ionizing photons from the Magellanic Clouds. The line ratios reveal that the physical state of the the SMC-Tail and the LMC-Bridge interface regions differ from the Magellanic Bridge. The multiple component structure and line ratios reveal that at least two coherent structures with different physical properties exist throughout the Bridge.

MOPRA CO OBSERVATIONS OF THE BUBBLE H II REGION RCW 120

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, L. D.; Deharveng, L.; Zavagno, A.

2015-02-20

We use the Mopra radio telescope to test for expansion of the molecular gas associated with the bubble H II region RCW 120. A ring, or bubble, morphology is common for Galactic H II regions, but the three-dimensional geometry of such objects is still unclear. Detected near- and far-side expansion of the associated molecular material would be consistent with a three-dimensional spherical object. We map the J = 1 → 0 transitions of {sup 12}CO, {sup 13}CO, C{sup 18}O, and C{sup 17}O, and detect emission from all isotopologues. We do not detect the 0{sub 0} → 1{sub –1} E masingmore » lines of CH{sub 3}OH at 108.8939 GHz. The strongest CO emission is from the photo-dissociation region (PDR), and there is a deficit of emission toward the bubble interior. We find no evidence for expansion of the molecular material associated with RCW 120 and therefore can make no claims about its geometry. The lack of detected expansion is roughly in agreement with models for the time-evolution of an H II region like RCW 120, and is consistent with an expansion speed of ≲ 1.5 km s{sup –1}. Single-position CO spectra show signatures of expansion, which underscores the importance of mapped spectra for such work. Dust temperature enhancements outside the PDR of RCW 120 coincide with a deficit of emission in CO, confirming that these temperature enhancements are due to holes in the RCW 120 PDR. H-alpha emission shows that RCW 120 is leaking ∼5% of the ionizing photons into the interstellar medium (ISM) through PDR holes at the locations of the temperature enhancements. Hα emission also shows a diffuse 'halo' from leaked photons not associated with discrete holes in the PDR. Overall ∼25% ± 10% of all ionizing photons are leaking into the nearby ISM.« less

Young stars of low mass in the Gum nebula

NASA Technical Reports Server (NTRS)

Graham, J. A.; Heyer, Mark H.

1989-01-01

Observations are presented for four recently formed stars in the vicinity of the Gum nebula which are heavily obscured by surrounding dust and are associated with small reflection nebulae. HH46 is the only currently active star of the sample, and it is found to have a spectral type in the range of late G-early K, with superimposed emission lines of H-alpha, Ca II, Fe I, Fe II, and weak He I at near zero velocities. It is suggested that the observed scenario of low-mass stars in an older massive star environment may be analogous to the circumstances surrounding the birth of the sun.

Line Intensity Mapping during the Epoch of Reionization

NASA Astrophysics Data System (ADS)

Silva, Marta B.; Zaroubi, Saleem

2018-05-01

Characterizing the properties and the evolution of the first stars and galaxies is a challenging task for traditional galaxy surveys since they are sensitivity limited and can only detect the brightest light sources. Three-dimensional intensity mapping (IM) of transition lines can be a valuable alternative to study the high redshift Universe given that this technique avoids sensitivity limitation problems by measuring the overall emission of a line, with a low resolution, without resolving its sources. While 21cm line IM surveys probe neutral hydrogen gas and can, therefore, be used to probe the state of the IGM and the evolution of the ionization field during the Epoch of Reionization (EoR). IM surveys of other lines, such as CO, CII, Ly-alpha or H-alpha, can be used to probe the galaxies which emitted most of the ionizing radiation responsible for the EoR. These lines will trace the different ISM gas phases, the excitation state of this gas, its metallicity, etc. This study addresses IM of multiple transition lines and how it can be used to probe the EoR and to constrain the redshift evolution of galaxy properties.

Hydrogen line ratios in Seyfert galaxies and low redshift quasars

NASA Technical Reports Server (NTRS)

Kriss, G. R.

1984-01-01

New observations of the Lymal alpha radiation/hydrogen alpha radiation ratio in a set of X-ray selected active galactic nuclei and an archival study of International Ultraviolet Explorer (IUE) observations of Lymal alpha low redshift quasars and Seyfert galaxies have been used to form a large sample for studying the influence of soft X-rays on the enhancement of Balmer emission in the broad line region. In common models of broad line clouds, the Balmer lines are formed deep in the interior, largely by collisional excitation. Heating within the clouds is provided by soft X-ray radiation, while Lymal alpha is formed mainly by recombination after photoionization. The ratio Lymal alpha/Halpha is expected to depend weakly on the ratio of ionizing ultraviolet luminosity to X-ray luminosity (L sub UV/l sub x). If the Lymal alpha luminosity is used as a measure of L sub UV' a weak dependence of Lymal/H alpha on the X-ray luminosity is found similar to previous results.

The distribution of mass for spiral galaxies in clusters and in the field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forbes, D.A.; Whitmore, B.C.

1989-04-01

A comparison is made between the mass distributions of spiral galaxies in clusters and in the field using Burstein's mass-type methodology. Both the H-alpha emission-line rotation curves and more extended H I rotation curves are used. The fitting technique for determining mass types used by Burstein and coworkers has been replaced by an objective chi-sq method. Mass types are shown to be a function of both the Hubble type and luminosity, contrary to earlier results. The present data show a difference in the distribution of mass types for spiral galaxies in the field and in clusters, in the sense thatmore » mass type I galaxies, where the inner and outer velocity gradients are similar, are generally found in the field rather than in clusters. This can be understood in terms of the results of Whitmore, Forbes, and Rubin (1988), who find that the rotation curves of galaxies in the central region of clusters are generally failing, while the outer galaxies in a cluster and field galaxies tend to have flat or rising rotation curves. 15 refs.« less

Early Results from the Wisconsin H-Alpha Mapper Southern Sky Survey

NASA Astrophysics Data System (ADS)

Haffner, L. Matthew; Reynolds, R. J.; Madsen, G. J.; Hill, A. S.; Barger, K. A.; Jaehnig, K. P.; Mierkiewicz, E. J.; Percival, J. W.

2010-01-01

After a successful eleven-year campaign at Kitt Peak, we moved the Wisconsin H-Alpha Mapper (WHAM) to Cerro Tololo in early 2009. Here we present some of the early data after the first nine months under southern skies. These maps begin to complete the first all-sky, kinematic survey of the diffuse Hα emission from the Milky Way. Much of this emission arises from the Warm Ionized Medium (WIM), a significant component of the ISM that extends a few kiloparsecs above the Galactic disk. The WHAM instrument consists of a 0.6 m primary lens housed in a steerable siderostat coupled to a 15 cm dual-etalon Fabry-Perot spectrometer. The optical configuration delivers a spatially integrated spectrum from a one-degree beam on the sky covering 200 km/s with 12 km/s spectral resolution. Short, 30-second exposures allow us to cover the observable sky in about two years at sensitivity levels of about 0.1 R (EM 0.2 pc cm-6). While this first look at the data focuses on the Hα survey, WHAM is also capable of observing many other optical emission lines, revealing fascinating trends in the temperature and ionization state of the WIM. Our ongoing studies of the physical conditions of diffuse ionized gas will continue in the south following the Hα survey. In addition, future observations using our survey mode will cover the full velocity range of the Magellanic Stream, Bridge, and Clouds to trace the ionized gas associated with these neighboring systems. WHAM is supported by NSF award AST-0607512 and has made this smooth relocation south due to the excellent staff at KPNO and CTIO.

Intensity mapping the Universe

NASA Astrophysics Data System (ADS)

Croft, Rupert

Intensity mapping (IM) is the use of one or more emission lines to trace out the structure of the Universe without needing to resolve individual objects (such as galaxies or gas clouds). It is one of the most promising ways to radically extend the sky survey revolution in cosmology. By making spectra of the entire sky, rather than the one part in one million captured by current fiber spectrographs, one would be sensitive to all structure. There are potentially huge discoveries to be made in the vast majority of the sky that is currently spectrally unmapped, and also great gains in signal to noise of cosmological clustering measurements. Intensity mapping with the 21cm radio line has been explored theoretically by many and instruments are being built, particularly targeting the epoch of reionization. In the UV, visible and infrared, however other lines have enormous promise, and will be exploited by a range of future NASA missions including WFIRST, Euclid, and the proposed SPHEREx instrument, a dedicated intensity mapping satellite. The first measurement of large-scale structure outside the radio (using Lyman-alpha emission) was recently made by the PI and collaborators. The Ly-a absorption line also traces a continuous cosmological field, the Lyman-alpha forest, and the enormous recent increase in the number of observed quasar spectra have made it possible to interpolate between quasar sightlines to create three-dimensional maps. Being able to trace the same cosmic structure in emission and absorption offers huge advantages when we seek to understand the processes involved. It will help us make comprehensive maps of the Universe's contents and offer us the opportunity to create new powerful cosmological tests. In our proposed work we will explore the possibilities afforded by taking grism and integral field spectra of large volumes of the Universe, using state-of-the-art cosmological hydrodynamic simulations. We will make use of analysis techniques developed for the Lyman-alpha forest, as well as forest data itself to test them. Our aim is to develop intensity mapping as a cosmological tool and show how it can be used to answer questions about the contents of the Universe and the formation of structure that are not accessible to traditional techniques. The project will involve both direct sampling of cosmic structure and cross-correlations of line intensity and objects (including galaxies, quasars and absorption lines). Emission (e.g., H-alpha emission) and absorption (Ly alpha forest) will be viewed as continuous fields. Using large volume cosmological simulations combined with population synthesis techniques we will make simulated spectral data sets. The techniques to analyse these cosmological data cubes will be developed. The expected outcomes are the following: (a) Predictions for the large-scale structure of strong emission lines (including Ha, Hb, Lya, OII, OIII) in the Universe using hydrodynamic simulations including the contribution from all components, from quasars to diffuse emssion. (b) Simulations of realistic examples of the use of IM as a cosmological probe, including Baryon Oscillations and weak gravitational lensing. (c) Tests of techniques to detection and quantify the low surface brightness Universe, leading to a complete census of the cosmic intensity in specific lines such as OII and Ha. (d) Development of techniques to extract redshifts for individual galaxies from low angular resolution IM spectroscopy. (e) Mock catalogs for SPHEREx, Euclid and WFIRST spectroscopy of diffuse emission, as well as for the Galex grism survey and tests of analysis techniques on data from the latter.

The highly obscured nucleus of 3C 219

NASA Technical Reports Server (NTRS)

Fabbiano, G.; Willner, S. P.; Carleton, N. P; Elvis, M.

1986-01-01

The detection of a strong, and possibly broad, Paschen-alpha line from the narrow-line radio galaxy 3C 219 is reported. The detected flux is larger than predicted from the H-alpha line and the case B recombination. This implies the presence of a highly reddened line-emitting region in the nucleus.

OT2_pgolds01_6: Herschel [NII] Observations to Define the Source of [CII] Emission

NASA Astrophysics Data System (ADS)

Goldsmith, P.

2011-09-01

The 158 micron line of ionized carbon is the strongest single long-wavelength emission feature from the interstellar medium and is the most important coolant of gas in which hydrogen is in atomic form. It is a key determinant of the evolution of these largely atomic regions into denser, cooler molecular clouds in which new stars are formed, and is widely used as a tracer of star formation in the Milky Way and other galaxies. There is, however, an ongoing, serious controversy about the origin of the [CII] emission, which has been asserted to come from the extended low-density warm interstellar medium, but has more generally been associated with the primarily molecular photon dominated regions (PDRs) intimately associated with massive, young stars. We propose a combined HIFI and PACS study of the two far-infrared [NII] fine structure lines in order to resolve the important question of the fraction of CII emission that arises in ionized gas. Specifically, we will (1) utilize the fact that due to its ionization potential NII is found only in HII regions, and with PACS 122 and 205 micron observations, determine electron densities in a sample of such regions in the Galactic plane; (2) utilize available data on radio free-free and H-alpha emission to determine the NII column densities and from this the CII column densities in the HII regions; (3) use the electron densities to determine the fraction of CII emission arising in the ionized interstellar medium. These observations will be carried out at 150 of the positions in the Galactic plane observed in [CII] by the GOT-C+ project. We will also carry out HIFI observations of 10 selected positions in the 205 micron line to determine spectral characteristics of the NII emission line, which with CII, CI, and CO profiles already in hand will serve as a further discriminant among the proposed sources of CII emission.

Young stars of low mass in the Gum nebula

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, J.A.; Heyer, M.H.

1989-06-01

Observations are presented for four recently formed stars in the vicinity of the Gum nebula which are heavily obscured by surrounding dust and are associated with small reflection nebulae. HH46 is the only currently active star of the sample, and it is found to have a spectral type in the range of late G-early K, with superimposed emission lines of H-alpha, Ca II, Fe I, Fe II, and weak He I at near zero velocities. It is suggested that the observed scenario of low-mass stars in an older massive star environment may be analogous to the circumstances surrounding the birthmore » of the sun. 53 refs.« less

A polarimetric survey of symbiotic stars

NASA Technical Reports Server (NTRS)

Schulte-Ladbeck, R. E.; Aspin, C.; Magalhaes, A. M.; Schwarz, H. E.

1990-01-01

Optical and near-infrared polarization observations of 24 symbiotic stars, 14 observed with polarimetry for the first time are presented. In combination with published data, it is found that about 50 percent of the symbiotics observed polarimetrically show evidence for intrinsic polarization. The results are discussed in the light of previous observations, and comments are made on the temporal variability and wavelength dependence of the polarization. Dust scattering is identified as the dominant mechanism producing polarization in symbiotic stars. While it cannot be excluded that some symbiotic systems are completely engulfed in their dust shells, the data indicate that the H-alpha emission line may originate from outside of the dust-scattering envelopes in some systems.

X-Ray Flare Characteristics in the B2e Star Lambda Eridani (ROSAT)

NASA Technical Reports Server (NTRS)

Smith, Myron A.

1997-01-01

We document the results of a simultaneous wavelength monitoring on the B2e star (lambda) Eri. This campaign was carried out from ground stations and with the ROSAT, ASCA, IUE, and Voyager 2 space platforms during a week in February-March 1995; a smaller follow-up was conducted in September 1995. During the first of these intervals (lambda) Eri exhibited extraordinary wind and disk-ejection activity. The ROSAT/HRI X-ray light curves showed no large flares such as the one the ROSAT/PSCA observed in 1991. However, possible low level fluctuations in the February-March ROSAT data occurred at the same time as unusual activity in H(alpha) He I (lambda)6678, He II (lambda)1640, and the C IV doublet. For example, the hydrogen and helium lines exhibited an emission in the blue half of their profiles, probably lasting several hours. The C IV lines showed a strong high-velocity Discrete Absorption Component (DAC) accompanied by unusually strong absorption at lower velocities. The helium line activity suggests that a mass ejection occurred at the base of the wind while the strong C III (Voyager) and C IV (IUE) lines implies that shock interactions occurred in the wind flow. It is not clear that the X-ray elevations are directly related to the strong C IV absorptions because the former changed on a much more rapid timescale than absorptions in the C IV lines. Within hours of the mild X-ray flux variations found by ROSAT on February 28, the Voyager UVS observed a "ringing" that decayed over three 3-hr. cycles. The amplitude of these fluctuations was strong (50%) at (lambda)(lambda)950-1100, decreased rapidly with wavelength, and faded to nondetection longward of (lambda)1300. Various considerations indicate that these continuum variations were not due to an instrumental pathology in the UVS. Rather, they appear to be due to a time-dependent flux deficit in the (lambda)(lambda)950-1250 region. We outline a scenario in which a dense plasma structure over the star's surface is heated and cooled quasi-periodically to produce such flux changes. Observations of new examples of this phenomenon are badly needed. Amateur astronomers can make a significant contribution to its understanding by searching for ringing in light curves of Be stars during their outburst phases. Finally we draw attention to an increase in the emission of the H(alpha) line that occurred at about the time the FUV ringing started. This increased emission hints that approximately 50,000K plasma near the star's surface can influence the circumstellar disc at approximately 12R. by its increased Lyman continuum flux.

Hα and [SII] emission from warm Ionized GAS in the Scutum-Centaurus Arm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hill, Alex S.; Benjamin, Robert A.; Gostisha, Martin C.

2014-06-01

We present Wisconsin H-Alpha Mapper [SII] λ6716 and Hα spectroscopic maps of the warm ionized medium (WIM) in the Scutum-Centaurus Arm at Galactic longitudes 310° < l < 345°. Using extinction-corrected Hα intensities (I{sub Hα}{sup c}), we measure an exponential scale height of electron density squared in the arm of H{sub n{sub e{sup 2}}}=0.30 kpc (assuming a distance of 3.5 kpc), intermediate between that observed in the inner Galaxy and in the Perseus Arm. The [S II]/Hα line ratio is enhanced at large |z| and in sightlines with faint I{sub Hα}{sup c}. We find that the [S II]/Hα line ratiomore » has a power-law relationship with I{sub Hα}{sup c} from a value of ≈1.0 at I{sub Hα}{sup c}<0.2 R (Rayleighs) to a value of ≈0.08 at I{sub Hα}{sup c}≳100 R. The line ratio is better correlated with Hα intensity than with height above the plane, indicating that the physical conditions within the WIM vary systematically with electron density. We argue that the variation of the line ratio with height is a consequence of the decrease of electron density with height. Our results reinforce the well-established picture in which the diffuse Hα emission is due primarily to emission from in situ photoionized gas, with scattered light only a minor contributor.« less

Solar coronal magnetic field topology inferred from high resolution optical and x-ray movies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tarbell, T.; Frank, Z.; Hurlburt, N.

1993-01-01

The authors are using high resolution digital movies of solar active regions in optical and X-ray wavelengths to study solar flares and other transients. The optical movies were collected at the Swedish Solar Observatory on La Palma using the Lockheed tunable filtergraph system, in May-July, 1992. They include longitudinal and transverse magnetograms, H-alpha Doppler and intensity images at many wavelengths, Ca K, Na D, and white light images. Simultaneous X-ray images from Yohkoh are available much of the time. Several ways to establish the connectivity of some coronal magnetic field lines are being explored. Some of the clues available are:more » magnetic footpoint polarities and transverse field direction; H-alpha fibrils and loops seen in several wavelengths; proper motion and Dopper shifts of blobs moving along field lines; footprint brightening in micro-flares; spreading of flare ribbons during gradual phases of flares; X-ray morphology and correlations with H-alpha; and draining of flare loops. Examples of each of these will be shown on video.« less

The kinematics of the molecular gas in Centaurus A

NASA Technical Reports Server (NTRS)

Quillen, A. C.; De Zeeuw, P. T.; Phinney, E. S.; Phillips, T. G.

1992-01-01

The CO (2-1) emission along the inner dust lane of Centaurus A, observed with the Caltech Submillimeter Observatory on Mauna Kea, shows the molecular gas to be in a thin disk, with a velocity dispersion of only about 10 km/s. The observed line profiles are broadened considerably due to beam smearing of the gas velocity field. The profile shapes are inconsistent with planar circular and noncircular motion. However, a warped disk in a prolate potential provides a good fit to the profile shapes. The morphology and kinematics of the molecular gas is similar to that of the ionized material, seen in H-alpha. The best-fitting warped disk model not only matches the optical appearance of the dust lane but also agrees with the large-scale map of the CO emission and is consistent with H I measurements at larger radii.

A hard X-ray and gamma ray observation of the 22 November 1977 solar flare. [experimental design

NASA Technical Reports Server (NTRS)

Chambon, G.; Hurley, K.; Niel, M.; Talon, R.; Vedrenne, G.; Likine, O. B.; Kouznetsov, A. V.; Estouline, I. V.

1978-01-01

The Franco-Soviet experiment package Signe 2 MP for solar and cosmic X and gamma ray observations, launched aboard a Soviet Prognoz satellite into a highly eccentric earth orbit is described. An uncollimated NaI detector 37 mm thick by 90 mm diameter, placed on the upper surface of the satellite faced the sun. A collimated lateral NaI detector 14 mm thick by 38 mm diameter also faced the sun, and a similar lateral detector faced the anti-solar direction. Data tapes reveal an intense solar flare up to energies of up to 5 MeV, with evidence for line emission at 2.23 MeV and possibly 4.4 MeV. The event observed was associated with the Mc Math Plage Region 15031, and an H-alpha flare of importance 2B. It is not yet clear what radio emission is associated with the X-ray observation.

'Marginal' BY Draconis stars

NASA Technical Reports Server (NTRS)

Bopp, Bernard W.

1987-01-01

Spectroscopic observations of 52 dK-dM stars, obtained at 640-665 nm (with spectral resolution 70-90 pm) using CCD detectors on the coude-feed telescope at KPNO since 1982, are reported. Data for four stars found to have diluted absorption or weak emission above continuum at H-alpha are presented in tables and spectra and discussed in detail. These objects (Gliese numbers 256, 425A, 900, and 907.1) are shown to be 'marginal' BY Dra stars, single objects of age 2.5-3 Gyr with activity and rotational velocity (3-5 km/s) between those of normal dM stars and those of true BY Dra stars. An explanation based on evolution from the BY Dra stage through marginal BY Dra to inactive dM is proposed.

EUV emission, filament activation and magnetic fields in a slow-rise flare

NASA Technical Reports Server (NTRS)

Rust, D. M.; Nakagawa, Y.; Neupert, W. M.

1975-01-01

Results are reported for observations and analysis of synoptic data on a 1B flare that occurred on January 19, 1972. The observations include large-scale H-alpha movies of the flare and pre-flare developments, OSO-7 satellite data on soft X-ray and EUV developments, magnetograms, and hard X-ray observations. Theoretical force-free magnetic field configurations are compared with structures seen in the soft X-ray, EUV, and H-alpha images, and the evolution of the flare is described. The energy available for the flare is estimated from the change of magnetic field inferred from the H-alpha filtergrams and from force-free field calculations. It is suggested that the flare originated in a twisted filament where it was compressed by emerging fields, and it is shown that the flare started below the corona and appeared to derive its energy from the magnetic fields in or near the filament.

Evidence for the interaction of large scale magnetic structures in solar flares

NASA Technical Reports Server (NTRS)

Mandrini, C. H.; Demoulin, P.; Henoux, J. C.; Machado, M. E.

1991-01-01

By modeling the observed vertical magnetic field of an active region AR 2372 by the potential field of an ensemble of magnetic dipoles, the likely location of the separatrices, surfaces that separates cells of different field line connectivities, and of the separator which is the intersection of the separatrices, is derived. Four of the five off-band H-alpha kernels of a flare that occurred less than 20 minutes before obtaining the magnetogram are shown to have taken place near or at the separatrices. These H-alpha kernels are connected by field lines that pass near the separator. This indicates that the flare may have resulted from the interaction in the separator region of large scale magnetic structures.

By Draconis Stars

NASA Astrophysics Data System (ADS)

Bopp, Bernard W.

An optical spectroscopic survey of dK-M stars has resulted in the discovery of several new H-alpha emission objects. Available optical data suggest these stars have a level of chromospheric activity midway between active BY Dra stars and quiet dM's. These "marginal" BY Dra stars are single objects that have rotation velocities slightly higher than that of quiet field stars but below that of active flare/BY Dra objects. The marginal BY Dra stars provide us with a class of objects rotating very near a "trigger velocity" (believed to be 5 km/s) which appears to divide active flare/BY Dra stars from quiet dM's. UV data on Mg II emission fluxes and strength of transition region features such as C IV will serve to fix activity levels in the marginal objects and determine chromosphere and transition-region heating rates. Simultaneous optical magnetic field measures will be used to explore the connection between fieldstrength/filling-factor and atmospheric heating. Comparison of these data with published information on active and quiet dM stars will yield information on the character of the stellar dynamo as it makes a transition from "low" to "high" activity.

A Multi-wavelength Study of an Isolated MSP Bow Shock

NASA Astrophysics Data System (ADS)

Romani, Roger W.; Slane, Patrick; Green, Andrew

2017-08-01

PSR J2124-3358 is the only single MSP known to sport an Halpha bow shock. This shock, now also seen in the UV, encloses an unusual X-ray pulsar wind nebula (PWN) with a long off-axis trail. Combining the X-ray and UV images with AAT/KOALA integral field spectroscopy of the Halpha emission, we have an unusually complete picture of the pulsar's (101 km/s transverse) motion and the latitudinal distribution of its wind flux. These images reveal the 3-D orientation of a hard-spectrum PWN jet and a softer equatorial outflow. Within the context of a thin shock model, we can constrain the total energy output of the pulsar and the neutron star moment of inertia. The IFU spectra show extreme Balmer dominance, which also constrains the nature of the UV shock emission.

SEARCHING FOR YOUNG M DWARFS WITH GALEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shkolnik, Evgenya L.; Weinberger, Alycia J.; Liu, Michael C.

2011-01-20

The census of young moving groups in the solar neighborhood is significantly incomplete in the low-mass regime. We have developed a new selection process to find these missing members based on the Galaxy Evolution Explorer (GALEX) All-Sky Imaging Survey (AIS). For stars with spectral types {approx}>K5 (R - J {approx}> 1.5) and younger than {approx}300 Myr, we show that near-UV (NUV) and far-UV (FUV) emission is greatly enhanced above the quiescent photosphere, analogous to the enhanced X-ray emission of young low-mass stars seen by ROSAT but detectable to much larger distances with GALEX. By combining GALEX data with optical (HSTmore » Guide Star Catalog) and near-IR (2MASS) photometry, we identified an initial sample of 34 young M dwarf candidates in a 1000 deg{sup 2} region around the {approx}10 Myr TW Hydra Association (TWA). Low-resolution spectroscopy of 30 of these found 16 which had H{alpha} in emission, which were then followed up at high resolution to search for spectroscopic evidence of youth and to measure their radial velocities. Four objects have low surface gravities, photometric distances and space motions consistent with TWA, but the non-detection of Li indicates that they may be too old to belong to this moving group. One object (M3.5, 93 {+-} 19 pc) appears to be the first known accreting low-mass member of the {approx}15 Myr Lower Centaurus Crux OB association. Two objects exhibit all the characteristics of the known TWA members, and thus we designate them as TWA 31 (M4.2, 110 {+-} 11 pc) and TWA 32 (M6.3, 53 {+-} 5 pc). TWA 31 shows extremely broad (447 km s{sup -1}) H{alpha} emission, making it the sixth member of TWA found to have ongoing accretion. TWA 32 is resolved into a 0.''6 binary in Keck laser guide star adaptive optics imaging. Our search should be sensitive down to spectral types of at least M4-M5 in TWA and thus the small numbers of new member is puzzling. This might indicate TWA has an atypical mass function or that the presence of lithium absorption may be too restrictive a criteria for selecting young low-mass stars.« less

Deep Imaging of Extremely Metal-Poor Galaxies

NASA Astrophysics Data System (ADS)

Corbin, Michael

2006-07-01

Conflicting evidence exists regarding whether the most metal-poor and actively star-forming galaxies in the local universe such as I Zw 18 contain evolved stars. We propose to help settle this issue by obtaining deep ACS/HRC U, narrow-V, I, and H-alpha images of nine nearby {z < 0.01} extremely metal-poor {12 + O/H < 7.65} galaxies selected from the Sloan Digital Sky Survey. These objects are only marginally resolved from the ground and appear uniformly blue, strongly motivating HST imaging. The continuum images will establish: 1.} If underlying populations of evolved stars are present, by revealing the objects' colors on scales 10 pc, and 2.} The presence of any faint tidal features, dust lanes, and globular or super star clusters, all of which constrain the objects' evolutionary states. The H-alpha images, in combination with ground-based echelle spectroscopy, will reveal 1.} Whether the objects are producing "superwinds" that are depleting them of their metals; ground-based images of some of them indeed show large halos of ionized gas, and 2.} The correspondence of their nebular and stellar emission on scales of a few parsecs, which is important for understanding the "feedback" process by which supernovae and stellar winds regulate star formation. One of the sample objects, CGCG 269-049, lies only 2 Mpc away, allowing the detection of individual red giant stars in it if any are present. We have recently obtained Spitzer images and spectra of this galaxy to determine its dust content and star formation history, which will complement the proposed HST observations. [NOTE: THIS PROPOSAL WAS REDUCED TO FIVE ORBITS, AND ONLY ONE OF THE ORIGINAL TARGETS, CGCG 269-049, AFTER THE PHASE I REVIEW

A UV spectroscopic survey of periodic M dwarfs in the Hyades

NASA Astrophysics Data System (ADS)

Agueros, Marcel

2017-08-01

Because of its proximity, the 650-Myr-old Hyades open cluster is a unique resource for exploring the relationship between magnetic activity, rotation, and age in low-mass stars. While the cluster has been largely ignored in UV studies of the dependence of activity on rotation, we now have an extensive and growing set of complementary rotation period, Halpha, and X-ray measurements with which to examine in detail the rotation-activity relation at 650 Myr and to constrain theories of magnetic heating. We propose to measure Mg II line emission, the strongest NUV activity tracer, in COS spectra of 17 Hyads ranging in spectral type from M0 to M7 with known rotation periods and Halpha and X-ray measurements. These stars form a representative sample of M-dwarf Hyads with known periods and are a significant addition to, and expansion of, the sample of 20 mainly solar-mass rotators with existing (mostly low-resolution) International Ultravioled Explorer (IUE) NUV spectra. The Mg II measurements will contribute significantly to our goal of mapping out the rotation-activity relation star-by-star in this benchmark open cluster. This, in turn, will move us toward an improved understanding of the radiation environment and habitability of the exoplanets we continue to find around low-mass stars.

The Radial Distribution of Star Formation in Galaxies at z1 From The 3D-HST Survey

NASA Technical Reports Server (NTRS)

Nelson, Erica June; Dokkum, Pieter G. Van; Momcheva, Ivelina; Brammer, Gabriel; Lundgren, Britt; Skelton, Rosalind E.; Tease, Katherine Whitaker; Cunha, Elisabete Da; Schreiber, Natascha Forster; Franx, Marijn;

Optical Monitoring of Young Stellar Objects

NASA Astrophysics Data System (ADS)

Kar, Aman; Jang-Condell, Hannah; Kasper, David; Findlay, Joseph; Kobulnicky, Henry A.

2018-06-01

Observing Young Stellar Objects (YSOs) for variability in different wavelengths enables us to understand the evolution and structure of the protoplanetary disks around stars. The stars observed in this project are known YSOs that show variability in the Infrared. Targets were selected from the Spitzer Space Telescope Young Stellar Object Variability (YSOVAR) Program, which monitored star-forming regions in the mid-infrared. The goal of our project is to investigate any correlation between the variability in the infrared versus the optical. Infrared variability of YSOs is associated with the heating of the protoplanetary disk while accretion signatures are observed in the H-alpha region. We used the University of Wyoming’s Red Buttes Observatory to monitor these stars for signs of accretion using an H-alpha narrowband filter and the Johnson-Cousins filter set, over the Summer of 2017. We perform relative photometry and inspect for an image-to-image variation by observing these targets for a period of four months every two to three nights. The study helps us better understand the link between accretion and H-alpha activity and establish a disk-star connection.

Precession of the Disk in Pleione Study of the Halpha Line Profile

NASA Astrophysics Data System (ADS)

Pollmann, Ernst

2018-03-01

Medium-resolution spectroscopy of the binary system Pleione (28 Tau), obtained over the time period October 2004 (JD 2453300) to March 2018 (JD 2458185) by the ARAS Spectroscopy Group, has been used to determine the central absorption depth (CA), V/R ratio, radial velocity (RV) and equivalent width of the H emission, in order to study the disk precession as a consequence of the periastron passages of the companion. We found an exact coincidence of the CA maxima with the minima of V/R and RV as a result of the disk precession. This has never before been observed during the maximum shell phase in the years around 1980, or during the initial shell phase around August/October 1974.

The Star Formation Rate Density of the Universe at z = 0.24 and 0.4 from Halpha

NASA Astrophysics Data System (ADS)

Pascual, S.

2005-01-01

Knowledge of both the global star formation history of the universe and the nature of individual star-forming galaxies at different look-back times is essential to our understanding of galaxy formation and evolution. Deep redshift surveys suggest star-formation activity increases by an order of magnitude from z = 0 to ~1. As a direct test of whether substantial evolution in star-formation activity has occurred, we need to measure the star formation rate (SFR) density and the properties of the corresponding star-forming galaxy populations at different redshifts, using similar techniques. The main goal of this work is to extend the Universidad Complutense de Madrid (UCM) survey of emission-line galaxies to higher redshifts. (continues)

VizieR Online Data Catalog: M31 center emission-line point-like sources (Martin+, 2018)

NASA Astrophysics Data System (ADS)

Martin, T. B.; Drissen, L.; Melchior, A.-L.

2017-11-01

We present a catalogue of the point-like sources in the central 11'x11' part of M31 obtained with SITELLE. For each source we report the radial velocity as long as the spectrophotmetric flux of H-alpha, [NII]6584 and the sum of the [SII]6717,6731 doublet. The ID of the sources cross-matched with the catalogues from Merrett et al. (2006MNRAS.369..120M, J/MNRAS/369/120) and Halliday et al. (2006MNRAS.369...97H, J/MNRAS/369/97) are also indicated. We also report the detection of the sources in the images of the Local Group Galaxies Survey (Massey et al., 2006, 2006AJ....131.2478M). (1 data file).

PEARS Emission Line Galaxies

NASA Technical Reports Server (NTRS)

Pirzkal, Nor; Rothberg, Barry; Ly, Chun; Rhoads, James E.; Malhotra, Sangeeta; Grogin, Norman A.; Dahlen, Tomas; Meurer, Gerhardt R.; Walsh, Jeremy; Hathi, Nimish P.;

Soft X-ray observations of pre-main sequence stars in the chamaeleon dark cloud

NASA Technical Reports Server (NTRS)

Feigelson, Eric D.; Kriss, Gerard A.

1987-01-01

Einstein IPC observations of the nearby Chamaeleon I star forming cloud show 22 well-resolved soft X-ray sources in a 1x2 deg region. Twelve are associated with H-alpha emission line pre-main sequence (PMS) stars, and four with optically selected PMS stars. Several X-ray sources have two or more PMS stars in their error circles. Optical spectra were obtained at CTIO of possible stellar counterparts of the remaining X-ray sources. They reveal 5 probable new cloud members, K7-MO stars with weak or absent emission lines. These naked X-ray selected PMS stars are similar to those found in the Taurus-Auriga cloud. The spatial distributions and H-R diagrams of the X-ray and optically selected PMS stars in the cloud are very similar. Luminosity functions indicate the Chamaeleon stars are on average approximately 5 times more X-ray luminous than Pleiad dwarfs. A significant correlation between L sub x and optical magnitude suggests this trend may continue within the PMS phase of stellar evolution. The relation of increasing X-ray luminosity with decreasing stellar ages is thus extended to stellar ages as young as 1 million years.

Chromospherically active stars. III - HD 26337 = EI Eri: An RS CVn candidate for the Doppler-imaging technique

NASA Technical Reports Server (NTRS)

Fekel, Francis C.; Quigley, Robert; Gillies, Kim; Africano, John L.

1987-01-01

Spectroscopic observations of the chromospherically active G5 IV single-lined binary HD 26337 = EI Eri are presented. An orbital period of 1.94722 days is found for the star. It has moderately strong Ca II H and K emission and strong ultraviolet emission features, while H-alpha is a weak absorption feature that is variable in strength. The inclination of the system is 46 + or - 12 deg, and the unseen secondary is probably a late K or early M dwarf. The v sin i of the primary is 50 + or - 3 km/s, resulting in a minimum radius of 1.9 + or - 0.1 solar radius. The star is within the required limits for Doppler imaging. The primary is close to filling its Roche lobe, resulting in a strong constraint that the mass ratio is 2.6 or greater, with a primary mass of at least 1.4 solar mass. The distance to the system is estimated at 75 pc.

Constraining the Type Ia Supernova Progenitor: The Search for Hydrogen in Nebular Spectra

NASA Astrophysics Data System (ADS)

Leonard, Douglas

2006-02-01

The progenitor systems of Type Ia supernovae (SNe Ia) are observationally unconstrained. Prevailing theory invokes a carbon- oxygen white dwarf accreting matter from a companion until a thermonuclear runaway ensues that incinerates the white dwarf. While models of exploding carbon-oxygen white dwarfs faithfully reproduce the main characteristics of SNe Ia, we are ignorant about the nature of the proposed companion star. Simulations resulting from this single- degenerate binary channel, however, demand the presence of low-velocity, H(alpha) emission in spectra taken in the nebular phase (250 - 400 days after maximum light), since a portion of the companion's envelope becomes entrained in the ejecta. This hydrogen has never been detected, and only generally weak limits have heretofore been set from ~ 6 SNe Ia observed during the nebular phase at low resolution and often with a low signal-to-noise ratio (S/N). We propose to remedy this situation through high S/N observations of two nearby, nebular-phase SNe Ia, with sufficient sensitivity and resolution to detect ~ 0.01 Msun of solar abundance material in the ejecta. The detection of late- time H(alpha) emission would be considered a ``smoking gun'' for the binary scenario. If H(alpha) is not detected, the limits will effectively rule out sub-giant, red giant, and all but the most widely separated main-sequence companions.

Energetic ion, atom, and molecule reactions and excitation in low-current H2 discharges: H(alpha) Doppler profiles.

PubMed

Petrović, Z Lj; Phelps, A V

2009-12-01

Absolute spectral emissivities for Doppler broadened H(alpha) profiles are measured and compared with predictions of energetic hydrogen ion, atom, and molecule behavior in low-current electrical discharges in H2 at very high electric field E to gas density N ratios E/N and low values of Nd , where d is the parallel-plate electrode separation. These observations reflect the energy and angular distributions for the excited atoms and quantitatively test features of multiple-scattering kinetic models in weakly ionized hydrogen in the presence of an electric field that are not tested by the spatial distributions of H(alpha) emission. Absolute spectral intensities agree well with predictions. Asymmetries in Doppler profiles observed parallel to the electric field at 4

30 Dor B - A supernova remnant in a star formation region

NASA Technical Reports Server (NTRS)

Chu, You-Hua; Kennicutt, Robert C., Jr.; Schommer, Robert A.; Laff, Joshua

1992-01-01

The supernova remnant 30 Dor B is embedded in an H II region around the OB association LH 99, and has been suggested to be a Crab-type remnant. To determine the spatial extent and kinematic properties of this supernova remnant, long-slit echelle observations were obtained in the H-alpha and forbidden N II lines, along with imaging Fabry-Perot observations in the H-alpha line. It is found that 30 Dor B is partially obscured by a dark cloud with which the supernova remnant also interacts. The size of 30 Dor B is much larger than previously thought, making it much older than the Crab Nebula. If the progenitor of the supernova was formed coevally with LH 99, then it would have been more massive than the O3 members of the OB association.

Anisotropic ionizing radiation in Seyfert galaxies. I - The extended narrow-line region in Markarian 573

NASA Technical Reports Server (NTRS)

Tsvetanov, Zlatan; Walsh, J. R.

1992-01-01

The morphology, kinematics, and ionization state of the nuclear extended narrow-line region (ENLR) of the Seyfert 2 galaxy Mrk 573 are studied using narrow-band images of a grid of long-slit spectra. The entire ENLR is mapped spectroscopically, and velocity structure is studied. The velocity field map shows a typical galactic rotation picture with some important deviations. A simple geometric model, in accordance with the 'unified schemes', is employed to study the effects of various parameters of the observed picture. The best match is achieved when a biconical radiation field illuminates the ISM of the host galaxy that takes part in a normal galaxy rotation but also has radial motions close to the nucleus. The emission-line images reveal an ENLR elongated along the radio axis in the northwest-southeast direction, but a map of the flux ratio forbidden O III 5007/(H-alpha + forbidden N II) shows a different structure, with the highest excitation peak offset by about 4 arcsec along the radio axis to the southeast.

ROSAT X-ray detection of a young brown dwarf in the chamaeleon I dark cloud

PubMed

Neuhauser; Comeron

1998-10-02

Photometry and spectroscopy of the object Cha Halpha 1, located in the Chamaeleon I star-forming cloud, show that it is a approximately 10(6)-year-old brown dwarf with spectral type M7.5 to M8 and 0.04 +/- 0.01 solar masses. Quiescent x-ray emission was detected in a 36-kilosecond observation with 31.4 +/- 7.7 x-ray photons, obtained with the Rontgen Satellite (ROSAT), with 9final sigma detection significance. This corresponds to an x-ray luminosity of 2.57 x 10(28) ergs per second and an x-ray to bolometric luminosity ratio of 10(-3.44). These are typical values for late M-type stars. Because the interior of brown dwarfs may be similar to that of convective late-type stars, which are well-known x-ray sources, x-ray emission from brown dwarfs may indicate magnetic activity.

On the Naming and Dscovery of the Solar Chromosphere

NASA Astrophysics Data System (ADS)

Reardon, Kevin P.

2014-06-01

The chromosphere was discovered by Lockyer and Janssen in 1868, and named by Lockyer. It is often stated that his motivation for associating this region of the solar atmosphere with "color" was because of its bright red appearance at eclipses due to the predominance of H-alpha. However, Lockyer had never seen a total solar eclipse at the time he gave the name and does not appear to have provided this justification himself. It is more likely that the "color" refers to the plethora of different colored emission lines he saw and identified with his spectrograph.I also discuss the Padre Angelo Secchi's observation of the 1860 eclipse in Spain, His accurate description of the chromosphere as a complete, theretofore unseen layer enveloping the Sun predates Lockyer and Janssen by eight years.

VizieR Online Data Catalog: V1357 Cyg spectroscopic monitoring in 2002-04 (Karitskaya+, 2008)

NASA Astrophysics Data System (ADS)

Karitskaya, E. A.; Bochkarev, N. G.; Bondar, A. V.; Galazutdinov, G. A.; Lee, B.-K.; Musaev, F. A.; Sapar, A. A.; Shimansky, V. V.

2008-11-01

The results of Cyg X-1 = HDE 226868/V1357 Cyg optical spectral monitoring in 2002-2004 are discussed. Spectral observations were carried out on Peak Terskol Observatory (Kabardino-Balkaria, Russia, resolution R=45000 and 13000) and Bohyunsan Optical Astronomy Observatory (BOAO, Korea, R=30000, 44000). Each spectrum covers the main part of optical spectral range. During 33 observational nights 75 echelle spectra were obtained in the times of the "soft" and "hard" states of Cyg X-1. The X-ray influence on spectral line profiles was studied. The RXTE/ASM data were used for this purpose. The X-ray flare resulted in strong variations of Halpha and HeII4686{AA} emission component profiles during night. This behaviour we connect with variations of ionization structure of matter in the system. Line profile variations with the orbital phase were observed. The spectral atlas for Cyg X-1 was constructed. The contented line identification was done. There were revealed 172 lines and blends which belong to 12 chemical elements: H, He, C, N, O, Ne, Mg, Al, Si, S, Fe, Zn. The HDE 226868 spectral classification as ON star was confirmed. (2 data files).

The H-alpha/H-beta ratio in solar flares

NASA Technical Reports Server (NTRS)

Zirin, H.; Liggett, M.; Patterson, A.

1982-01-01

The present investigation involves the study of an extensive body of data accumulated of simultaneous H-alpha and H-beta cinematography of flares. The data were obtained with two telescopes simultaneously photographing flares in H-alpha and H-beta. The results of measurements in a number of flares are presented in a table. The flares were selected purely by optical quality of the data. That the measured ratios are not too different from those in stellar flares is suggested by the last two columns of the table. These columns show that a variety of possible line width ratios could give an integrated intensity ratio of less than unity.

Mass loss in HR 1040 /A0 Ia/ - Analysis of Mg II lambda 2802 and H-alpha

NASA Technical Reports Server (NTRS)

Kunasz, P. B.; Morrison, N. D.; Spressart, B.

1983-01-01

It is pointed out that International Ultraviolet Explorer (IUE) data for several early A type supergiants are now available to complement the ground-based spectroscopic data available for these bright stars. An examination of the resonance doublet of Mg II in the A type supergiants reveals that HR 1040 (HD 21389) is the only star in the observational literature in which a violet-shifted, deep absorption line is present without complete saturation. From an unsaturated profile, a good estimate of Mg(+) density can be found by means of accurate radiative transfer calculations. A relation can then be derived between mass loss rate and ionization balance. When certain velocity-related quantities can be estimated from a Mg II line profile, the H-alpha provides an estimate of the mass loss rate. The present investigation is concerned with an application of these diagnostics to HR 1040.

HIGHLY VARIABLE EXTINCTION AND ACCRETION IN THE JET-DRIVING CLASS I-TYPE YOUNG STAR PTF 10nvg (V2492 Cyg, IRAS 20496+4354)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hillenbrand, Lynne A.; Carpenter, John M.; Muirhead, Philip S.

2013-03-15

We report extensive new photometry and spectroscopy of the highly variable young stellar object PTF 10nvg (also known as IRAS 20496+4354 and V2492 Cyg), including optical and near-infrared time-series data as well as mid-infrared and millimeter data. Following the previously reported 2010 rise to R{sub PTF} {approx}<13.{sup m}5 and subsequent fade, during 2011 and 2012 the source underwent additional episodes of brightening, followed by several magnitude dimming events including prolonged faint states at R{sub PTF} {approx}> 20{sup m}. The observed high-amplitude variations are largely consistent with extinction changes ({Delta}A{sub V} up to 30 mag) having a {approx}220 day quasi-periodic signal.more » However, photometry measured when the source was near maximum brightness in mid-2010 as well as in late-2012 does not phase well to this period. Spectral evolution includes not only changes in the spectral slope but also correlated variation in the prominence of TiO/VO/CO bands and atomic line emission, as well as anti-correlated variation in forbidden line emission which, along with H{sub 2}, dominates optical and infrared spectra at faint epochs. Notably, night-to-night variations in several forbidden doublet strengths and ratios are observed. High-dispersion spectra were obtained in a variety of photometric states and reveal time-variable line profiles. Neutral and singly ionized atomic species are likely formed in an accretion flow and/or impact while the origin of zero-velocity atomic Li I {lambda}6707 in emission is unknown. Forbidden lines, including several rare species, exhibit blueshifted emission profiles and likely arise from an outflow/jet. Several of these lines are also seen spatially offset from the continuum source position, presumably in a shocked region of an extended jet. Blueshifted absorption components of the Na I D doublet, K I {lambda}{lambda}7665, 7669 doublet, and the O I 7774 triplet, as well as blueshifted absorption components seen against the broad H{alpha} and Ca II triplet emission lines, similarly are formed in the outflow. CARMA maps resolve on larger scales a spatially extended outflow in millimeter-wavelength CO. We attribute the recently observed photometric and spectroscopic behavior to rotating circumstellar disk material located at separation a Almost-Equal-To 0.7(M{sub *}/M{sub Sun }){sup 1/3} AU from the continuum source, causing the semi-periodic dimming. Occultation of the central star as well as the bright inner disk and the accretion/outflow zones renders shocked gas in the inner part of the jet amenable to observation at the faint epochs. We discuss PTF 10nvg as a source exhibiting both accretion-driven (perhaps analogous to V1647 Ori) and extinction-driven (perhaps analogous to UX Ori or GM Cep) high-amplitude variability phenomena.« less

Spectro-imagerie optique a faible flux et comparaison de la cinematique Halpha et HI d'un echantillon de galaxies proches

NASA Astrophysics Data System (ADS)

Daigle, Olivier

A new EMCCD (Electron multiplying Charge Coupled Device) controller is presented. It allows the EMCCD to be used for photon counting by drastically taking down its dominating source of noise: the clock induced charges. A new EMCCD camera was built using this controller. It has been characterized in laboratory and tested at the observatoire du mont Megantic. When compared to the previous generation of photon counting cameras based on intensifier tubes, this new camera renders the observation of the galaxies kinematics with an integral field spectrometer with a Fabry-Perot interferometer in Halpha light much faster, and allows fainter galaxies to be observed. The integration time required to reach a given signal-to-noise ratio is about 4 times less than with the intensifier tubes. Many applications could benefit of such a camera: fast, faint flux photometry, high spectral and temporal resolution spectroscopy, earth-based diffraction limited imagery (lucky imaging), etc. Technically, the camera is dominated by the shot noise for flux higher than 0.002 photon/pixel/image. The 21 cm emission line of the neutral hydrogen (HI) is often used to map the galaxies kinematics. The extent of the distribution of the neutral hydrogen in galaxies, which goes well beyond the optical disk, is one of the reasons this line is used so often. However, the spatial resolution of such observations is limited when compared to their optical equivalents. When comparing the HI data to higher resolution ones, some differences were simply attributed to the beam smearing of the HI caused by its lower resolution. The THINGS (The H I Nearby Galaxy Survey) project observed many galaxies of the SINGS (Spitzer Infrared Nearby Galaxies Survey) project. The kinematics of THINGS will be compared to the kinematic data of the galaxies obtained in Halpha light. The comparison will try to determine whether the sole beam smearing is responsible of the differences observed. The results shows that intrinsic dissimilarities between the kinematical tracers used are responsible of some of the observed disagreements. The understanding of theses differences is of a high importance as the dark matter distribution, inferred from the rotation of the galaxies, is a test to some cosmological models. Keywords: Astronomical instrumentation - Photon counting - EMCCD - Clock Induced Charges - Galaxies - Kinematics - Dark matter - Fabry-Perot interferometry - 3D spectroscopy - SINGS.

Solar H-alpha features with hot onsets. III. Long fibrils in Lyman-alpha and with ALMA

NASA Astrophysics Data System (ADS)

Rutten, R. J.

2017-02-01

In H-alpha most of the solar surface is covered by dense canopies of long opaque fibrils, but predictions for quiet-Sun observations with ALMA have ignored this fact. Comparison with Ly-alpha suggests that the extraordinary opacity of H-alpha fibrils is caused by hot precursor events. Application of a recipe that assumes momentary Saha-Boltzmann extinction during their hot onset to millimeter wavelengths suggests that ALMA will observe H-alpha-like fibril canopies, not acoustic shocks underneath, and will yield data more interesting than if these canopies were transparent. An additional file is available at the end of the PDF file of this article.This study is offered as compliment to M.W.M. de Graauw. Our ways, objects, instruments and spectral domains parted after the 1970 eclipse but converge here.

Observations and analysis of O(1D) and NH2 line profiles for the coma of comet P/Halley

NASA Technical Reports Server (NTRS)

Smyth, William H.; Combi, Michael R.; Roesler, Fred L.; Scherb, Frank

1995-01-01

A set of high-resolution Fabry-Perot measurements of the coma of comet P/Halley was acquired in the (O I) 6300 A and NH2 6298.62 A emission lines. These high-resolution measurements provide the first optical observations capable of studying directly the photochemical kinetics and dynamic outflow of the coma. The observations were analyzed by a Monte Carlo Particle Trajectory Model. The agreement of the model and observed line profiles was excellent and verified the underlying dynamics, exothermic photodissociative chemistry, and collisional thermalization in the coma. The somewhat wider intrinsic line profile width for the O(1D) emission in 1986 January compared to 1986 May, is, for example, produced by the larger outflow speeds and gas temperatures nearer perihelion in January. The January O(1D) profile, which is wider than the January NH2 profile, is indicative of the photochemical kinetics in the dissociation of the parent molecules H2O and OH in the coma. The absolute calibration of the observations in 1986 January allowed the production rates for H2O and the NH2-parent molecules to be determined. The average daily water production rates derived from the O(1D) emission data for January 16 and 17 are presented. These very large water production rates are consistent with the extrapolated (and 7.6 day time variable) water production rates determined from the analysis of lower spectral resolution observations for O(1D) and H-alpha emissions that covered the time period up to January 13. The large production rates on January 16 and 17 establish that the maximum water production rate for comet Halley accurred pre-perihelion in January. Implications drawn from comparison with 18 cm radio emission data in January suggest that the peak water production rate was even larger. The average production rate for NH3 determined from the NH2 emission data for January 17 was (1.48 +/- 0.10) x 10(exp 28) molecules/s, yielding an NH3/H2O production rate ratio of 0.55%.

Multicolor eclipse studies of UU Aquarii. 1: Observations and system parameters

NASA Technical Reports Server (NTRS)

Baptista, R.; Steiner, J. E.; Cieslinski, D.

1994-01-01

A study of the eclipses in UU Aqr from multicolor high-speed photometry is presented. A revised ephemeris for the times of minimum and an upper limit for orbital period variations are obtained. We use measurements of contact phases in the eclipse light curve to derive the binary geometry and to estimate masses and relevant dimensions. We find a mass ratio of q = 0.30 +/- 0.07 and an inclination of i = 78 deg +/- 2 deg. The masses of the component stars are M(sub 1) = 0.67 +/- 0.14 solar mass and M(sub 2) = 0.20 +/- 0.07 solar mass. Our photometric model predicts K(sub 1) = 84 +/- 26 km/s, which is approximately 30% smaller than the velocity amplitude obtained from the emission lines. From the white dwarf fluxes we estimate T(sub wd) approximately = 34,000 K and a distance of d = 270 +/- 50 pc if the inner disk is opaque. UU Aqr has long term brightness variations of approximately = 0.3 m on timescales of approximately 4 yr. The system was in a 'high' state in 1989 and 1990 and in a 'low' state in 1988 and 1992. The high state results from an increase in the brightness of the outer and cooler parts of the disk, mainly due to the appearance of a bright spot at disk rim. Based on the smooth and gradual eclipse shape and on the absence of a prominent hump in the light curve we suggest that UU Aqr is a high mass-transfer nova-like system with a relatively bright and optically thick accretion disk. We find no perceptible eclipse in the H-alpha emission line. The fluxes at mid-eclipse can be fitted by a compostion of a late-type spectrum plus an optically thin hydrogen emission-line spectrum. These evidences suggest that the emission lines are formed in an extended region only partially occulted during eclipse.

Non-LTE line-blanketed model atmospheres of hot stars. 2: Hot, metal-rich white dwarfs

NASA Technical Reports Server (NTRS)

Lanz, T.; Hubeny, I.

1995-01-01

We present several model atmospheres for a typical hot metal-rich DA white dwarf, T(sub eff) = 60,000 K, log g = 7.5. We consider pure hydrogen models, as well as models with various abundances of two typical 'trace' elements-carbon and iron. We calculte a number of Local Thermodynamic Equilibrium (LTE) and non-LTE models, taking into account the effect of numerous lines of these elements on the atmospheric structure. We demostrate that while the non-LTE effects are notvery significant for pure hydrogen models, except for describing correctly the central emission in H-alpha they are essential for predicting correctly the ionization balance of metals, such as carbon and iron. Previously reported discrepancies in LTE abundances determinations using C III and C IV lines are easily explained by non-LTE effects. We show that if the iron abundance is larger than 10(exp -5), the iron line opacity has to be considered not only for the spectrum synthesis, but also in the model construction itself. For such metal abundances, non-LTE metal line-blanketed models are needed for detailed abundance studies of hot, metal-rich white dwarfs. We also discuss the predicted Extreme Ultraviolet (EUV) spectrum and show that it is very sensitive to metal abundances, as well as to non-LTE effects.

The ALMA and HST Views of the Molecular Gas and Star Formation in the Prototypical Barred Spiral Galaxy NGC 1097

NASA Astrophysics Data System (ADS)

Sheth, Kartik; Regan, Michael W.; Kim, Taehyun; Kohno, Kotaro; Martin, Sergio; Villard, Eric; Onishi, Kyoko

2016-01-01

We mapped the entire inner disk of NGC 1097 (the circumnuclear ring, bar ends, the bar and inner spiral arms) using ALMA in the CO J=1-0 line at resolution of 1" (~65 pc). We also mapped the northern half of the bar in every other common molecular gas tracer at 3mm (HCN, HCO+, C18O, 13CO, C34S). Together these data provide the most detailed and highest resolution map of the molecular gas distribution and kinematics in a nearby barred spiral, rivalling the incredible maps seen for galaxies like M51 in the northern hemisphere. The data show the impact of the different environments in the galaxy as well as evidence for a multi-phased molecular medium. The data also evidence how the shear induced by the bar shock completely inhibits the star formation activity in the inner ends of the bar (clearly showing an anti-correlation between the strength of the CO line emission and Halpha emission). We will also present multiwavelength HST observations of the galaxy which are used to identify and map star clusters across the inner disk of the galaxy. We use these data to understand how star formation proceeds from one environment to the next across the galaxy.

Isolated Star-Forming Cloud Discovered in Intracluster Space

NASA Astrophysics Data System (ADS)

2003-01-01

Subaru and VLT Join Forces in New Study of Virgo Galaxy Cluster [1] Summary At a distance of some 50 million light-years, the Virgo Cluster is the nearest galaxy cluster. It is located in the zodiacal constellation of the same name (The Virgin) and is a large and dense assembly of hundreds of galaxies. The "intracluster" space between the Virgo galaxies is permeated by hot X-ray emitting gas and, as has become clear recently, by a sparse "intracluster population of stars". So far, stars have been observed to form in the luminous parts of galaxies. The most massive young stars are often visible indirectly by the strong emission from surrounding cocoons of hot gas, which is heated by the intense radiation from the embedded stars. These "HII regions" (pronounced "Eitch-Two" and so named because of their content of ionized hydrogen) may be very bright and they often trace the beautiful spiral arms seen in disk galaxies like our own Milky Way. New observations by the Japanese 8-m Subaru telescope and the ESO Very Large Telescope (VLT) have now shown that massive stars can also form in isolation, far from the luminous parts of galaxies. During a most productive co-operation between astronomers working at these two world-class telescopes, a compact HII region has been discovered at the very boundary between the outer halo of a Virgo cluster galaxy and Virgo intracluster space. This cloud is illuminated and heated by a few hot and massive young stars. The estimated total mass of the stars in the cloud is only a few hundred times that of the Sun. Such an object is rare at the present epoch. However, there may have been more in the past, at which time they were perhaps responsible for the formation of a fraction of the intracluster stellar population in clusters of galaxies. Massive stars in such isolated HII regions will explode as supernovae at the end of their short lives, and enrich the intracluster medium with heavy elements. Observations of two other Virgo cluster galaxies, Messier 86 and Messier 84, indicate the presence of other isolated HII regions, thus suggesting that isolated star formation may occur more generally in galaxies. If so, this process may provide a natural explanation to the current riddle why some young stars are found high up in the halo of our own Milky Way galaxy, far from the star-forming clouds in the main plane. The Virgo Cluster ESO PR Photo 04a/03 ESO PR Photo 04a/03 [Preview - JPEG: 400 x 428 pix - 74k [Normal - JPEG: 800 x 855 pix - 408k] [Hi-Res - JPEG: 4252 x 4544 pix - 10.3M] ESO PR Photo 04b/03 ESO PR Photo 04b/03 [Preview - JPEG: 433 x 400 pix - 60k [Normal - JPEG: 865 x 800 pix - 456k] [Hi-Res - JPEG: 3077 x 2847 pix - 4.2M] Captions: PR Photo 04a/03 displays a sky field near some of the brighter galaxies in the Virgo Cluster. It was obtained in April 2000 with the Wide Field Imager (WFI) at the La Silla Observatory (exposure 6 x 5 min; red R-band; seeing 1.3 arcsec). The large elliptical galaxy at the centre is Messier 84; the elongated image of NGC 4388 (an active spiral galaxy, seen from the side) is in the lower left corner. The field measures 16.9 x 15.7 arcmin2. PR Photo 04b/03 shows a larger region of the Virgo cluster, with the galaxies Messier 86 (at the upper edge of the field, to the left of the centre), as well as Messier 84 (upper right) and NGC 4388 (just below the centre) that are also seen in PR Photo 04a/03. It is reproduced from a long-exposure Subaru Suprime-Cam image, obtained in the red light of ionized hydrogen (the H-alpha spectral line at wavelength 656.2 nm). In order to show the faintest possible hydrogen emitting objects embedded in the outskirts of bright galaxies, their smooth envelopes have been "subtracted" during the image processing. The field measures 34 x 27 arcmin2. Part of this sky field is shown in colour in PR Photo 04c/03. Captions: PR Photo 04a/03 displays a sky field near some of the brighter galaxies in the Virgo Cluster. It was obtained in April 2000 with the Wide Field Imager (WFI) at the La Silla Observatory (exposure 6 x 5 min; red R-band; seeing 1.3 arcsec). The large elliptical galaxy at the centre is Messier 84; the elongated image of NGC 4388 (an active spiral galaxy, seen from the side) is in the lower left corner. The field measures 16.9 x 15.7 arcmin2. PR Photo 04b/03 shows a larger region of the Virgo cluster, with the galaxies Messier 86 (at the upper edge of the field, to the left of the centre), as well as Messier 84 (upper right) and NGC 4388 (just below the centre) that are also seen in PR Photo 04a/03. It is reproduced from a long-exposure Subaru Suprime-Cam image, obtained in the red light of ionized hydrogen (the H-alpha spectral line at wavelength 656.2 nm). In order to show the faintest possible hydrogen emitting objects embedded in the outskirts of bright galaxies, their smooth envelopes have been "subtracted" during the image processing. The field measures 34 x 27 arcmin2. Part of this sky field is shown in colour in PR Photo 04c/03. The galaxies in the Universe are rarely isolated - they prefer company. Many are found within dense structures, referred to as galaxy clusters, cf. e.g., ESO PR Photo 16a/99. The galaxy cluster nearest to us is seen in the direction of the zodiacal constellation Virgo (The Virgin), at a distance of approximately 50 million light-years. PR Photo 04a/03 (from the Wide Field Imager camera at the ESO La Silla Observatory) shows a small sky region near the centre of this cluster with some of the brighter cluster galaxies. PR Photo 04b/03 displays an image of a larger field (partially overlapping Photo 04a/03) in the light of ionized hydrogen - it was obtained by the Japanese 8.2-m Subaru telescope on Mauna Kea (Hawaii, USA). The field includes some of the large galaxies in this cluster, e.g., Messier 86, Messier 84 and NGC 4388. In order to show the faintest possible hydrogen emitting objects embedded in the outskirts of bright galaxies, their smooth envelopes have been "subtracted" during the image processing. This is why they look quite different in the two photos. Clusters of galaxies are believed to have formed because of the strong gravitational pull from dark and luminous matter. The Virgo cluster is considered to be a relatively young cluster, because studies of the distribution of its member galaxies and X-ray investigations of hot cluster gas have revealed small "subclusters of galaxies" around the major galaxies Messier 87, Messier 86 and Messier 49. These subclusters are yet to merge to form a dense and smooth galaxy cluster. The Virgo cluster is apparently cigar-shaped, with its longest dimension of about 10 million light-years near the line-of-sight direction - we see it "from the end". Stars in intracluster space Galaxy clusters are dominated by dark matter. The largest fraction of the luminous (i.e. "visible") cluster mass is made up of the hot gas that permeates all of the cluster. Recent observations of "intracluster" stars have confirmed that, in addition to the individual galaxies, the Virgo cluster also contains a so-called "diffuse stellar component", which is located in the space between the cluster galaxies. The first hint of this dates back to 1951 when Swiss astronomer Fritz Zwicky (1898-1974), working at the 5-m telescope at Mount Palomar in California (USA), claimed the discovery of diffuse light coming from the space between the galaxies in another large cluster of galaxies, the Coma cluster. The brightness of this intracluster light is 100 times fainter than the average night-sky brightness on the ground (mostly caused by the glow of atoms in the upper terrestrial atmosphere) and its measurement is difficult even with present technology. We now know that this intracluster glow comes from individual stars in that region. Planetary nebulae More recently, astronomers have undertaken a new and different approach to detect the elusive intracluster stars. They now search for Sun-like stars in their final dying phase during which they eject their outer layers into surrounding space. At the same time they unveil their small and hot stellar core which appears as a "white dwarf star". Such objects are known as "planetary nebulae" because some of those nearby, e.g. the "Dumbbell Nebula" (cf. ESO PR Photo 38a/98) resemble the disks of the outer solar system planets when viewed in small telescopes. The ejected envelope is illuminated and heated by the very hot star at its centre. This nebula emits strongly in characteristic emission lines of oxygen (green; at wavelengths 495.9 and 500.7 nm) and hydrogen (red; the H-alpha line at 656.2 nm). Planetary nebulae may be distinguished from other emission nebulae by the fact that their main green oxygen line at 500.7 nm is normally about 3 to 5 times brighter than the red H-alpha line. Search for intracluster planetary nebulae An international team of astronomers [2] is now carrying out a very challenging research programme, aimed at finding intracluster planetary nebulae. For this, they observe the regions between cluster galaxies with specially designed, narrow-band optical filters tuned to the wavelength of the green oxygen lines. The main goal is to study the overall properties of the diffuse stellar component in the nearby Virgo cluster. How much diffuse light comes from the intracluster space, how is it distributed within the cluster, and what is its origin? Because the stars in this region are apparently predominantly old, the most likely explanation of their presence in this region is that they formed inside individual galaxies, which were subsequently stripped of many of their stars during close encounters with other galaxies during the initial stages of cluster formation. These "lost" stars were then dispersed into intracluster space where we now find them. The Subaru observations ESO PR Photo 04c/03 ESO PR Photo 04c/03 [Preview - JPEG: 471 x 400 pix - 62k [Normal - JPEG: 941 x 800 pix - 776k] [Hi-Res - JPEG: 3028 x 2573 pix - 4.4M] ESO PR Photo 04d/03 ESO PR Photo 04d/03 [Preview - JPEG: 444 x 400 pix - 92k [Normal - JPEG: 888 x 800 pix - 600k] Captions: PR Photo 04c/03 shows the general location of the newly discovered compact HII region with respect to a previously published Subaru Suprime-Cam image of NGC 4388. The image combines H-alpha narrow-band (hydrogen), O[III] narrow-band (oxygen), and broad-band optical V-band data. The extended pink filamentary structure in this image is due to gas ionized by the radiation from the nucleus of the galaxy. The vertical lines are caused by detector saturation of bright objects. The field of view is 11.6 x 5.0 arcmin2. The outlined region indicates the sky field shown in PR Photo 04d/03 which is an H-alpha image of a 4 x 3 arcmin2 region in the Virgo intracluster region. This is part of the area selected for spectroscopic follow-up observations with the FORS2 multimode instrument at the 8.2-m VLT YEPUN telescope. The image shows the confirmed compact HII region (in blue circle to the left) and the confirmed intracluster planetary nebula (in yellow and red circle at the top). The two other objects (in red circles) are additional planetary nebulae candidates, which will soon be observed spectroscopically. North is up, and East is left. The newly discovered HII-region (blue circle) is well visible on PR Photo 04c/03 and faintly on the high-resolution versions of PR Photo 04a/03 and PR Photo 04b/03. Captions: PR Photo 04c/03 shows the general location of the newly discovered compact HII region with respect to a previously published Subaru Suprime-Cam image of NGC 4388. The image combines H-alpha narrow-band (hydrogen), O[III] narrow-band (oxygen), and broad-band optical V-band data. The extended pink filamentary structure in this image is due to gas ionized by the radiation from the nucleus of the galaxy. The vertical lines are caused by detector saturation of bright objects. The field of view is 11.6 x 5.0 arcmin2. The outlined region indicates the sky field shown in PR Photo 04d/03 which is an H-alpha image of a 4 x 3 arcmin2 region in the Virgo intracluster region. This is part of the area selected for spectroscopic follow-up observations with the FORS2 multimode instrument at the 8.2-m VLT YEPUN telescope. The image shows the confirmed compact HII region (in blue circle to the left) and the confirmed intracluster planetary nebula (in yellow and red circle at the top). The two other objects (in red circles) are additional planetary nebulae candidates, which will soon be observed spectroscopically. North is up, and East is left. The newly discovered HII-region (blue circle) is well visible on PR Photo 04c/03 and faintly on the high-resolution versions of PR Photo 04a/03 and PR Photo 04b/03. Japanese and European astronomers used the Suprime-Cam wide-field mosaic camera at the 8-m Subaru telescope (Mauna Kea, Hawaii, USA) to search for intracluster planetary nebulae in one of the densest regions of the Virgo cluster, cf. PR Photo 04b/03. They needed a telescope of this large size in order to select such objects and securely discriminate them from the thousands of foreground stars in the Milky Way and background galaxies. In particular, by observing in two narrow-band filters sensitive to oxygen and hydrogen, respectively, the planetary nebulae visible in this field could be "separated" from distant (high-redshift) background galaxies, which do not have strong emission in both the green and red band. It is very time-consuming to observe the weak H-alpha emission and this can only be done with a big telescope. Some 40 intracluster planetary nebulae candidates were found in this field which had the expected oxygen/H-alpha line intensity ratios of 3 - 5, such as those depicted PR Photo 04d/03. Unexpectedly, however, the data also showed a small number of star-like emission objects with oxygen/H-alpha line ratios of about 1. This is more typical of a cloud of ionized gas around young, massive stars - like the so-called HII regions in our own galaxy, the Milky Way. However, it would be very unusual to find such star formation regions in the intracluster region, so follow-up spectroscopic observations were clearly needed for confirmation. THE VLT MEASUREMENTS ESO PR Photo 04e/03 ESO PR Photo 04e/03 [Preview - JPEG: 506 x 400 pix - 35k [Normal - JPEG: 1011 x 800 pix - 128k] Captions: PR Photo 04e/03 displays the emission spectrum (in the visible/near-IR spectral region) of the compact HII region in the Virgo intracluster field, as obtained with the FORS2 multi-mode instrument of the 8.2-m VLT YEPUN telescope on Paranal. Emission lines from oxygen ([OIII]) and hydrogen (H-alpha, H-beta, H-gamma) atoms as well as ionized sulphur ([SII], [SIII]) are identified. The only way to make sure that these unusual objects are actually powered by young stars is by a detailed spectroscopical study, analyzing the emitted light over a wide range of wavelengths. One of the objects was observed in this way in April 2002 with the FORS2 multi-mode instrument at the 8.2-m VLT YEPUN telescope at the ESO Paranal Observatory (Chile). This was a most challenging observation, even for this very powerful facility, requiring several hours of exposure time. The brightness of the faint object (the flux of the oxygen [OIII 500.7]-line) was comparable to that of a 60-Watt light bulb at a distance of about 6.6 million km, i.e., about 17 times farther than the Moon. The recorded (long-slit) spectrum (PR Photo 04e/03) is indeed that of an HII region, with characteristic emission lines from hydrogen, oxygen and sulphur, and with underlying blue "continuum" emission from hot, young stars. This is the first concrete evidence that some of the ionized hydrogen gas in the intracluster medium near NGC 4388 is heated by massive stars, rather than radiation from the nucleus of the galaxy. Comparing the spectrum with simple starburst models showed that this HII region is "powered" by one or two hot and massive (O-type) stars. The best-fitting starburst model implies an estimated total mass of young stars of some 400 solar masses with an age of about 3 million years. The object is obviously very compact - it is indeed unresolved in all the images. The inferred radius of the HII region is about 11 light-years. Young stars form far from galaxies This compact star-forming region is located about 3.4 arcmin north and 0.9 arcmin west of the galaxy NGC 4388, corresponding to a distance of some 82,000 light-years (projected) from the main star-forming regions in this galaxy. The small cloud is moving away from us with an observed velocity of 2670 km/sec. This is considerably faster than the mean velocity of the Virgo cluster (about 1200 km/sec) but similar to that of NGC 4388 (2520 km/sec), indicating that it is probably falling through the Virgo cluster core together with NGC 4388, but it cannot have moved far during the comparatively short lifetime of its massive stars. It is not known whether it once was or still is bound to NGC 4388, or whether it only belonged to the surroundings that fell into the Virgo cluster with this galaxy. In any case, the existence of this HII region is a clear demonstration that stars can form in the "diffuse" outskirts of galaxies, if not in intracluster space. Because of internal dynamical processes, the stars in this object cannot remain forever in a dense cluster. Within a few hundred million years they will disperse and mix with the diffuse stellar population nearby. This isolated star formation is therefore likely to contribute to the intracluster stellar population, either directly, or after having moved away from the halo of NGC 4388. This mode of isolated star formation does not contribute much to the total intracluster light emission - at the current rate it can explain only a small fraction of the diffuse light now observed in this region. However, it may have been more significant in the past, when protogalaxies and proto-galaxy groups, rich in neutral gas and with gas clouds at large distances from their centers, fell into the forming Virgo cluster for the first time. Prospects The existence of isolated compact HII regions like this one is important as a very different site of star formation than those normally seen in galaxies. The massive stars born in such isolated clouds will explode as supernovae and enrich the Virgo intracluster medium with metals. Other possible - but not yet spectroscopically verified - compact HII regions in the halos of both Messier 86 and Messier 84 have been detected during this work. This finding thus also calls into question the current use of emission-line planetary nebulae luminosities as a distance indicator; to obtain the best possible accuracy, it will henceforth be necessary to weed out possible HII regions in the samples. If compact HII regions exist generally in galaxies, they may possibly be the birthplaces of some of the young stars now observed in the halo of our Milky Way galaxy, high above the main plane. Observational programmes with both the Subaru and VLT telescopes are now planned to discover more of these interesting objects and to explore their properties.

Analysis of X-ray observations of the 15 June 1973 flare in active region NOAA 131

NASA Technical Reports Server (NTRS)

Krall, K. R.; Reichmann, E. J.; Wilson, R. M.; Henze, W., Jr.; Smith, J. B., Jr.

1978-01-01

Observations and analyses of the 1B/M3 flare of 15 June, 1973 in active region NOAA 131 (McMath 12379) are presented. The X-ray observations, consisting of broadband photographs and proportional counter data from the Skylab/ATM NASA-MSFC/Aerospace S-056 experiment, are used to infer temperatures, emission measures, and densities for the flaring plasma. The peak temperature from the spatially resolved photographs is 25,000,000 K, while the temperature from the full-disk proportional counter data is approximately 15,000,000 K. The density is 3 times 10 to the 10th/cu cm. The X-ray flare emission appears to come primarily from two low-lying curvilinear features lying perpendicular to and centered on the line where the photospheric longitudinal magnetic field is zero. Similarities in the preflare and postflare X-ray emission patterns indicate that no large-scale relaxation of the coronal magnetic configuration was observed. Also discussed are H-alpha and magnetic field observations of the flare and the active region. Finally, results of numerical calculations, including thermal conduction, radiative loss, and chromospheric evaporation, are in qualitative agreement with the decay phase observations.

The MagAO Giant Accreting Protoplanet Survey (GAPlanetS): Recent Results

NASA Astrophysics Data System (ADS)

Follette, Katherine; Close, Laird; Males, Jared; Morzinski, Katie; Leonard, Clare; MagAO

2018-01-01

I will summarize recent results of the MagAO Giant Accreting Protoplant Survey (GAPlanetS), a search for accreting protoplanets at H-alpha inside of transitional disk gaps. These young, centrally-cleared circumstellar disks are often hosted by stars that are still actively accreting, making it likely that any planets that lie in their central cavities will also be actively accreting. Through differential imaging at Hydrogen-alpha using Magellan's visible light adaptive optics system, we have completed the first systematic search for H-alpha emission from accreting protoplanets in fifteen bright Southern hemisphere transitional disks. I will present results from this survey, including a second epoch on the LkCa 15 system that shows several accreting protoplanet candidates.

Flares observed by the normal incidence X-ray telescope on 1989 September 11

NASA Technical Reports Server (NTRS)

Herant, M.; Pardo, F.; Spiller, E.; Golub, L.

1991-01-01

Two solar flare events have been observed in soft X-rays during a sounding-rocket flight of the Normal-Incidence X-ray Telescope payload on September 11, 1989. The flare in X-rays involves a single bright loop crossing the neutral line, and having its footpoints at the southern ends of the ribbons; this loop accounts for more than 66 percent of the emission. Within the remainder of each of the flare ribbons, a complex coronal structure is also observed to be interacting with the main flare loop. A second event, in an active region at the limb, has a strong correlation with H-alpha images obtained at the same time. This indicates the coexistence, and indeed the close proximity, of coronal and chromospheric temperature material. Interpretations of this phenomenon are discussed.

Preliminary results on an H-alpha map of the Gum nebula obtained with the D-z-A satellite

NASA Technical Reports Server (NTRS)

Blamont, J. E.; Levasseur, A. C.

1971-01-01

Hydrogen emissions, including telluric H alpha, in the terrestrial atmosphere were studied. The H alpha experiment was designed to use a monochromatic photometer that would provide measurements of weak H alpha emission originating at altitudes of a few hundred or thousand km, free of contamination by other telluric emissions. The Gum nebula was recorded by the instrument as a much more intense feature than the geocoronal emission. The spacecraft employed and the optical onboard equipment are described. Field of view, spectral response, absolute calibration, linearity, and inflight performance are discussed.

Development of the prototype data management system of the solar H-alpha full disk observation

NASA Astrophysics Data System (ADS)

Wei, Ka-Ning; Zhao, Shi-Qing; Li, Qiong-Ying; Chen, Dong

2004-06-01

The Solar Chromospheric Telescope in Yunnan Observatory generates about 2G bytes fits format data per day. Huge amounts of data will bring inconvenience for people to use. Hence, data searching and sharing are important at present. Data searching, on-line browsing, remote accesses and download are developed with a prototype data management system of the solar H-alpha full disk observation, and improved by the working flow technology. Based on Windows XP operating system and MySQL data management system, a prototype system of browse/server model is developed by JAVA and JSP. Data compression, searching, browsing, deletion need authority and download in real-time have been achieved.

H-alpha observations of Sh2-190, Sh2-222, Sh2-229, Sh2-236 HII regions

NASA Astrophysics Data System (ADS)

Sahan, Muhittin

2018-02-01

Hα spectral line (6563Å) profiles of four northern HII regions in the our galaxy (Sh2-190, Sh2-222, Sh2-229, Sh2-236) have been obtained using DEFPOS spectrometer, located at coude focus of 150 cm RTT150 telescope at TUBITAK National Observatory (TUG, Antalya, Turkey). Observations were carried out at nights of 2015 December 24-27 with long exposure times ranging from 900s to 3600s. The LSR velocities and the linewidths (Full Width Half Maximum: FWHM) of the Hα emission lines were found to be in the range of -45.46 kms-1 to +3.57 kms-1 and 38.50 kms-1 to 44.10 kms-1, respectively. The Sh2-229 HII region is the faintest one (211.16 R), while the Sh2-236 HII region (IC410) is brightest source (535.75 R). The LSR velocity and the line width (FWHM) results of the DEFPOS/RTT150 system were compared with the data by several authors given in literature and results of DEFPOS data were found to be in good agreement with data given in literature.

Abundance Variations and Flows in Plage Regions Observed with CDS/SOHO

NASA Astrophysics Data System (ADS)

Rank, G.; Bagalá, L. G.; Czaykowska, A.; Haerendel, G.

1999-10-01

We present results from CDS/SOHO observations of the spotless active region NOAA-8208, obtained on 28th April 1998 near disk center. MDI images show a bipolar magnetic configuration. The regions of enhanced He I emission correspond to the areas with strong magnetic flux and also with bright plage areas seen in Ca II and H-alpha images. A high correlation is found between intensity maps of the transition region lines He I (logTmax = 4.3), O III (logTmax = 5.0), and O V (logTmax = 5.4). The line-of-sight velocities of He I reveal a strong downflow in the plage areas. Further, the line-of-sight velocities of He I, O III, and O V are well correlated, showing that the downflow pattern exists up to temperatures of about 0.25 MK. At higher temperatures (Mg VIII at logTmax = 5.8) this flow is not detected, suggesting that material streams into the plage region from sideways in the high transition region. Maps of the electron density in the transition region have been constructed from several line ratios yielding densities of about 9.0 cm-3 in the plage regions, about dex 0.5 cm-3 higher compared to the surrounding. To study the spatial variation of the first ionization potential (FIP) effect, the abundance ratio has been mapped for the ion ratio MgVI/NeVI. The ratio is highly variable on spatial scales down to a few arcsec from photospheric values to enhancements of a factor of 10. The strongest FIP enhancements are not correlated with transition region line emission, but are found outside of the plage regions. Some areas of strong FIP enhancement appear stretched and elongated, suggesting that the material is confined in loop-like structures.

Laser-induced breakdown spectroscopy for in-cylinder equivalence ratio measurements in laser-ignited natural gas engines.

PubMed

Joshi, Sachin; Olsen, Daniel B; Dumitrescu, Cosmin; Puzinauskas, Paulius V; Yalin, Azer P

2009-05-01

In this contribution we present the first demonstration of simultaneous use of laser sparks for engine ignition and laser-induced breakdown spectroscopy (LIBS) measurements of in-cylinder equivalence ratios. A 1064 nm neodynium yttrium aluminum garnet (Nd:YAG) laser beam is used with an optical spark plug to ignite a single cylinder natural gas engine. The optical emission from the combustion initiating laser spark is collected through the optical spark plug and cycle-by-cycle spectra are analyzed for H(alpha)(656 nm), O(777 nm), and N(742 nm, 744 nm, and 746 nm) neutral atomic lines. The line area ratios of H(alpha)/O(777), H(alpha)/N(746), and H(alpha)/N(tot) (where N(tot) is the sum of areas of the aforementioned N lines) are correlated with equivalence ratios measured by a wide band universal exhaust gas oxygen (UEGO) sensor. Experiments are performed for input laser energy levels of 21 mJ and 26 mJ, compression ratios of 9 and 11, and equivalence ratios between 0.6 and 0.95. The results show a linear correlation (R(2) > 0.99) of line intensity ratio with equivalence ratio, thereby suggesting an engine diagnostic method for cylinder resolved equivalence ratio measurements.

Observations of two peculiar emission objects in the Large Magellanic Cloud

NASA Technical Reports Server (NTRS)

Kafatos, M.; Michalitsianos, A. G.; Allen, D. A.; Stencel, R. E.

1983-01-01

Ultraviolet and visual wavelength spectra were obtained of two peculiar emission objects, Henize S63 and Sanduleak's star in the Large Magellanic Cloud. Previously not observed in the near- or far-ultraviolet, both objects exhibit strong permitted and semiforbidden line emissions. Estimates based on the absolute continuum flux of the hot companion star in Hen S63 indicate that it rivals the luminosity of the carbon star primary. The emission-line profile structure in both objects does not suggest Wolf-Rayet type emission. Carbon in Sanduleak's star (LMC anonymous) is conspicuously absent, while N V, semiforbidden N IV, and semiforbidden N III dominate the UV emission-line spectrum. Nitrogen is overabundant with respect to carbon and oxygen in both objects. The large overabundance of nitrogen in Sanduleak's star suggests evidence for CNO processes material similar to that seen in Nu Car.

Galaxy bachelors, couples, spouses: Star formation in interacting galaxies

NASA Astrophysics Data System (ADS)

Sun, Jing; Barger, Kathleen; Richstein, Hannah; SDSS-IV/MaNGA

2017-01-01

We investigate the star formation activity in three galaxy systems in different stages of interaction to determine how the environment of galaxies affects their star forming ability and potential. These systems include an isolated galaxy, a pair of interacting galaxies, and a pair of merging galaxies. All of the target galaxies in these systems have similar stellar masses and similar radii and are at similar redshifts. We trace the star formation activity over the past 1-2 Gyr using spatially and kinematically resolved H-alpha emission, H-alpha equivalent width, and 4000-Angstrom break maps. This work is based on data from the fourth-generation Sloan Digital Sky Survey (SDSS-IV)/Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), and is part of the Project No.0285 in SDSS-IV.

The Kanzelhöhe Observatory

NASA Astrophysics Data System (ADS)

Pötzi, Werner; Temmer, Manuela; Veronig, Astrid; Hirtenfellner-Polanec, Wolfgang; Baumgartner, Dietmar

2013-04-01

Kanzelhöhe Observatory (KSO; kso.ac.at) located in the South of Austria is part of the Institute of Physics of the University of Graz. Since the early 1940s, the Sun has been observed in various layers and wavelengths. Currently, KSO provides high-cadence full-disk observations of the solar disk in three wavelengths: H-alpha line, Ca II K line, white light. Real-time images are published online. For scientific use, the data is processed, and immediately available to the scientific community after each observing day via the Kanzelhöhe Online Data Archive archive (KODA; kanzelhohe.uni-graz.at). KSO is part of the Global H-Alpha Network and is also one of the contributing stations for the international sunspot number. In the frame of ESA's Space Situational Awareness program, methods are currently under development for near-real image recognition with respect to solar flares and filaments. These data products will give valuable complementary information for the solar sources of space weather.

VizieR Online Data Catalog: Diffuse ionized gas database DIGEDA (Flores-Fajardo+ 2009)

NASA Astrophysics Data System (ADS)

Flores-Fajardo, N.; Morisset, C.; Binette, L.

2009-09-01

DIGEDA is a comprehensive database comprising 1061 DIG and HII region spectroscopic observations of 29 different galaxies (25 spiral galaxies and 4 irregulars) from 18 bibliographic references. This survey contains galaxies with significant spread in star formation rates, Halpha luminosities, distances, disk inclinations, slit positions and slit orientations. The 1061 observations obtained from these references were extracted by digitalization of published figures or tables. The data were subsequently normalized and incorporated in DIGEDA. This resulted in a table of 26 columns containing 1061 data lines or records (DIGEDA.dat file). We have not performed any reddening by dust correction or for the presence of underlying absorption lines, although we did use the reddening corrected ratios when made available by the authors. Missing entries are represented by (-1) in the corresponding data field. In DIGEDA the observed areas are classificated in three possible emission region types: HII region, transition zones or DIG. When this classification was not reported (no matter the criterion) for the authors, we introduce our own classification taking into account the value of |z| as described in the paper. (4 data files).

Pre-main-sequence stars in the young cluster IC 2391

NASA Technical Reports Server (NTRS)

Stauffer, John; Hartmann, Lee W.; Jones, Burton F.; Mcnamara, Brian R.

1989-01-01

Seven or eight new, late-type members of the poor open cluster IC 2391 are identified, and membership is confirmed for two other stars. The new members fall approximately along a 3 x 10 to the 7th yr isochrone, which is the age estimated for the cluster on the basis of it super main-seqence turnoff. Echelle spectra were obtained for the most probable cluster members. Most show H-alpha in emission and a strong Li 6707 A absorption line, and a few are rapid rotators. The Li abundances for cluster stars cooler than the sun are considerably less than the primordial Li abundance, providing the first direct evidence for substantial premain-sequence Li burning. The rotational velocities show a range from about 15 to 150 km/s, with a distribution of rotational velocities not significantly different from that observed for low-mass stars in the Pleiades.

Large-scale solar magnetic fields and H-alpha patterns

NASA Technical Reports Server (NTRS)

Mcintosh, P. S.

1972-01-01

Coronal and interplanetary magnetic fields computed from measurements of large-scale photospheric magnetic fields suffer from interruptions in day-to-day observations and the limitation of using only measurements made near the solar central meridian. Procedures were devised for inferring the lines of polarity reversal from H-alpha solar patrol photographs that map the same large-scale features found on Mt. Wilson magnetograms. These features may be monitored without interruption by combining observations from the global network of observatories associated with NOAA's Space Environment Services Center. The patterns of inferred magnetic fields may be followed accurately as far as 60 deg from central meridian. Such patterns will be used to improve predictions of coronal features during the next solar eclipse.

International Ultraviolet Explorer (IUE)

NASA Technical Reports Server (NTRS)

Boehm, Karl-Heinz

1992-01-01

The observation, data reduction, and interpretation of ultraviolet spectra (obtained with the International Ultraviolet Explorer) of Herbig-Haro objects, stellar jets, and (in a few cases) reflection nebulae in star-forming regions is discussed. Intermediate results have been reported in the required semi-annual reports. The observations for this research were obtained in 23 (US1) IUE shifts. The spectra were taken in the low resolution mode with the large aperture. The following topics were investigated: (1) detection of UV spectra of high excitation Herbig-Haro (HH) objects, identification of emission lines, and a preliminary study of the energy distribution of the ultraviolet continuum; (2) details of the continuum energy distribution of these spectra and their possible interpretation; (3) the properties of the reddening (extinction) of HH objects; (4) the possible time variation of strong emission lines in high excitation HH objects; (5) the ultraviolet emission of low excitation HH objects, especially in the fluorescent lines of the H2 molecule; (6) the ultraviolet emission in the peculiar object HH24; (7) the spatial emission distribution of different lines and different parts of the continuum in different HH objects; and (8) some properties of reflection nebula, in the environment of Herbig-Haro objects. Each topic is discussed.

Shocked molecular hydrogen emission from Herbig-Haro objects and their exciting stars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilking, B.A.; Schwartz, R.D.; Mundy, L.G.

1990-01-01

The results of an H2 emission-line survey of the 1-0 S(1) transition from 33 Herbig-Haro objects and suspected Herbig-Haro objects are presented. The survey focuses on Herbig-Haro objects that have been recently identified and/or lie at southern declinations. Data are also presented for the 2-1 S(3), 1-0 Q(1), and 1-0 Q(3) transitions of H2 for a subset of the sample. H2 emission has been detected toward 16 Herbig-Haro or nebulous objects; published optical spectra of 13 of these objects suggest that they are low-excitation nebulae associated with low-velocity shocks. H2 has also been detected toward the emission-line stars RU Lupmore » and LkH-alpha 234. Extended 1-0 S(1) emission has been mapped in the vicinity of gas outflows associated with the emission-line stars R CrA and LkH-alpha 234 and appears to delineate the blueshifted molecular gas in these bipolar outflows. A comparison of the data, in combination with the atomic line data from these HHs, is made with current C- and J-type shock models. 41 refs.« less

EZ Pegasi - The last pieces of the puzzle

NASA Technical Reports Server (NTRS)

Howell, S. B.; Williams, W. M.; Barden, S. C.; Bopp, B. W.

1986-01-01

Based on UBV differential photometric observations carried out at the Braeside Observatory between October 19, 1984 and January 11, 1985, it is shown that EZ Peg is in synchronous rotation with a photometric period of 11.6626 days. The orbital solution of Griffin (1985) is in good agreement with the present results, and it is employed to analyze the emission properties of the Ca II and H-alpha emission in the system. It is suggested that the emission of the system is almost entirely associated with the primary component, and the two stars appear to be similar in size and luminosity.

Mystery spot in supernova 1987A - Reflection or fluorescence by an interstellar cloud?

NASA Technical Reports Server (NTRS)

Felten, James E.; Dwek, Eli; Viegas-Aldrovandi, Sueli M.

1989-01-01

This paper explores fluorescence and reflection models of the companion to SN 1987A obseved by speckle interferometry, recalling a 1901 precedent. The apparent small angular size of the companion is a severe constraint. A fluorescence model cannot reach the observed brightness unless the ultraviolet burst from the supernova contained as many as 2 x 10 to the 58th ionizing photons. This is about 25 times stronger than generous current models. Even then, the expected line ratios and widths do not fit the observations. The absence of narrow H-alpha and H-beta lines in the supernova spectrum, the ratio of fluxes of the companion in H-alpha and forbidden N II line filters, the invisibility of the companion at 4861 (H-beta), and its detection at 5330 fail to agree with theory. A dust-reflection model is more promising, and the color can be reddened by the evaporation of small grains, but the model still falls more than about 1 mag short in brightness. Furthermore, a dust reflection should have increased in relative brightness in May-June 1987, rather than disappearing as the mystery spot did. If all the observations are correct, neither model is likely to work.

The Analysis of Emission Lines; A Meeting in Honour of the 70th Birthdays of D. E. Osterbrock and M. J. Seaton

NASA Technical Reports Server (NTRS)

Williams, Robert (Editor); Livio, Mario (Editor); Dufour, Reginald J.

1994-01-01

A review of the field of astronomical spectroscopy with emphasis on emission lines in astrophysical plasmas is presented. A brief history of UV spectroscopy instruments is given, following by a discussion and tabulation of major atlases of UV emission-line objects to date (mid-1994). A discussion of the major diagnostic UV emission lines in the approx. 912-3200 A spectral region that are useful for determining electron densities, temperatures, abundances, and extinction in low- to moderate density plasmas is given, with examples of applications to selected objects. The review concludes by presenting some recent results from HST, HUT, and IUE on UV emission-line spectroscopy of nebulae and active galaxies.

In Tarantula Territory

NASA Astrophysics Data System (ADS)

2002-06-01

The largest emission nebula in the sky, the Tarantula Nebula (also known as NGC 2070 or 30 Doradus ) is located in the Large Magellanic Cloud (LMC) , one of the satellite galaxies to our own Milky Way system. Seen far down in the southern sky at a distance of about 170,000 light-years, this beautiful nebula measures more than 1000 light-years across and extends over more than one third of a degree, almost, but not quite the size of the full moon. It received its descriptive name because of the unusual shape. It is a splendid object with a central cluster of hot and luminous young stars that powers strong emission from hydrogen and oxygen gas, making the Tarantula Nebula an easy and impressive target for observations, even with the unaided eye. It is well visible from ESO's mountain observatories at La Silla and Paranal in Chile and it has been the object of innumerable research programmes with many different telescopes. The present images of the Tarantula Nebula were obtained with the Wide-Field Imager (WFI) on the MPG/ESO 2.2-m telescope at the La Silla Observatory. This advanced digital camera has already produced many impressive pictures, cf. the WFI Photo Gallery [1]. As the name indicates, the WFI has a comparatively large field-of-view, 34 x 34 arcmin 2 , and it is therefore well suited to show the full extent of this stunning nebula. The WFI image PR Photo 14a/02 has been produced from 15 individual WFI-exposures obtained in September 2000. Details are available below about the way it was made. A large number of different and colourful objects are seen in this amazing image. The very complex nebulosity is prominent in most of the field; it predominantly emits red light from hydrogen atoms (the H-alpha spectral line at wavelength 656.2 nm) and green-blue light from hydrogen atoms (H-beta line at 486.2 nm) and oxygen ions (two [O III] lines at 495.7 and 500.7 nm). This emission is excited by the strong ultraviolet (UV) radiation emitted by hot young stars in the central cluster (known as "R136") which were born 2-3 million years ago at the heart of the Tarantula Nebula . Throughout the field, there are several other smaller, young open stellar clusters that are still embedded in nebulosity. Two globular clusters can also be seen, NGC 2100 at the very left of the field-of-view (see PR Photo 14d/01 below), and KMHK 1137 at the upper right ( PR Photo 14e/01 ) [2]. Note the very different colours of these two globular clusters: the stars in NGC 2100 appear blue and bright, indicating their relative youth, whereas those in KMHK 1137 are fainter and much redder, due to their older age and possibly also the reddening effect of dust in this area. The entire field is full of stars of very different colours and luminosity - most of them belong to the LMC, but some are foreground objects in our own galaxy, the Milky Way. A gallery of selected objects Below are shown a number of typical objects and their immediate surroundings, all located in the field of the large WFI photo ( PR Photo 14a/02 ) and illustrating the great diversity present in this rich area.

TIDAL TAILS OF MINOR MERGERS. II. COMPARING STAR FORMATION IN THE TIDAL TAILS OF NGC 2782

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knierman, Karen A.; Scowen, Paul; Veach, Todd

2013-09-10

The peculiar spiral NGC 2782 is the result of a minor merger with a mass ratio {approx}4: 1 occurring {approx}200 Myr ago. This merger produced a molecular and H I-rich, optically bright eastern tail and an H I-rich, optically faint western tail. Non-detection of CO in the western tail by Braine et al. suggested that star formation had not yet begun. However, deep UBVR and H{alpha} narrowband images show evidence of recent star formation in the western tail, though it lacks massive star clusters and cluster complexes. Using Herschel PACS spectroscopy, we discover 158 {mu}m [C II] emission at themore » location of the three most luminous H{alpha} sources in the eastern tail, but not at the location of the even brighter H{alpha} source in the western tail. The western tail is found to have a normal star formation efficiency (SFE), but the eastern tail has a low SFE. The lack of CO and [C II] emission suggests that the western tail H II region may have a low carbon abundance and be undergoing its first star formation. The western tail is more efficient at forming stars, but lacks massive clusters. We propose that the low SFE in the eastern tail may be due to its formation as a splash region where gas heating is important even though it has sufficient molecular and neutral gas to make massive star clusters. The western tail, which has lower gas surface density and does not form high-mass star clusters, is a tidally formed region where gravitational compression likely enhances star formation.« less

Disk Accretion in the 10 Myr Old T Tauri Stars TW Hydrae and Hen 3-600A.

PubMed

Muzerolle; Calvet; Briceño; Hartmann; Hillenbrand

2000-05-20

We have found that two members of the TW Hydrae association, TW Hydrae and Hen 3-600A, are still actively accreting, based on the ballistic infall signature of their broad Halpha emission profiles. We present the first quantitative analysis of accretion in these objects and conclude that the same accretion mechanisms which operate in the well-studied 1 Myr old T Tauri stars can and do occur in older (10 Myr) stars. We derive the first estimates of the disk mass accretion rate in TW Hya and Hen 3-600A, which are 1-2 orders of magnitude lower than the average rates in 1 Myr old objects. The decrease in accretion rates over 10 Myr, as well as the low fraction of TW Hya association objects still accreting, points to significant disk evolution, possibly linked to planet formation. Given the multiplicity of the Hen 3-600 system and the large UV excess of TW Hya, our results show that accretion disks can be surprisingly long lived in spite of the presence of companions and significant UV ionizing flux.

Tracing Interactions of a Protoplanet with its Circumstellar Disk

NASA Astrophysics Data System (ADS)

Stapelfeldt, Karl

2017-08-01

A candidate companion to a very young star has been discovered in HST snapshot optical images. The object is projected at the outer radius of an edge-on protoplanetary disk and is aligned with the disk plane. Keck LGS photometry results indicate the object has the same temperature as brown dwarf GQ Lupi b but with 10x less luminosity - consistent with a planetary mass companion. Because the edge-on disk suppresses the light of the central star, the companion is uniquely accessible to follow-up studies with minimal starlight residuals. We propose HST/WFC3 imaging and spectroscopy of the system to 1) fully define the morphology of the disk scattered light, particularly at the disk outer edge near the companion; 2) search for Halpha emission from the companion as evidence that it is actively accreting; and 3) complete spectral characterization of the companion using G141 spectroscopy. Confirmation of a substellar spectrum, accretion, and disk interaction action would establish this object as a leading example of an accreting protoplanet at 100 AU and offer support to models for planet formation by gravitational instability.

Emission line galaxies and active galactic nuclei in WINGS clusters

NASA Astrophysics Data System (ADS)

Marziani, P.; D'Onofrio, M.; Bettoni, D.; Poggianti, B. M.; Moretti, A.; Fasano, G.; Fritz, J.; Cava, A.; Varela, J.; Omizzolo, A.

2017-03-01

We present the analysis of the emission line galaxies members of 46 low-redshift (0.04 < z < 0.07) clusters observed by WINGS (WIde-field Nearby Galaxy cluster Survey). Emission line galaxies were identified following criteria that are meant to minimize biases against non-star-forming galaxies and classified employing diagnostic diagrams. We examined the emission line properties and frequencies of star-forming galaxies, transition objects, and active galactic nuclei (AGNs: LINERs and Seyferts), unclassified galaxies with emission lines, and quiescent galaxies with no detectable line emission. A deficit of emission line galaxies in the cluster environment is indicated by both a lower frequency, and a systematically lower Balmer emission line equivalent width and luminosity with respect to control samples; this implies a lower amount of ionized gas per unit mass and a lower star formation rate if the source is classified as Hii region. A sizable population of transition objects and of low-luminosity LINERs (≈ 10-20% of all emission line galaxies) are detected among WINGS cluster galaxies. These sources are a factor of ≈1.5 more frequent, or at least as frequent, as in control samples with respect to Hii sources. Transition objects and LINERs in clusters are most affected in terms ofline equivalent width by the environment and appear predominantly consistent with so-called retired galaxies. Shock heating can be a possible gas excitation mechanism that is able to account for observed line ratios. Specific to the cluster environment, we suggest interaction between atomic and molecular gas and the intracluster medium as a possible physical cause of line-emitting shocks. The data whose description is provided in Table B.1, and emission line catalog of the WINGS database are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/599/A83

Ultraviolet and Radio Emission from the Northern Middle Lobe of Centaurus A

NASA Technical Reports Server (NTRS)

Neff, Susan

2009-01-01

We present deep GALEX ultraviolet (135 - 280 nm) images of the Northern Middle Lobe (NML) of the nearby radio galaxy Centaurus A. We find that the ultraviolet emission appears to have a complex interaction with soft X-ray, H-alpha emission, and radio emission, which should help constrain various models of energy transport in the NML. We also present new 90cm VLA images of the NML. The radio morphology at this wavelength is indicative of a more complex system than either a straightforward flaring jet (Morganti et al. 1999) or a bubble with trailing stem (Saxton et al. 2001). New limits are placed on the lack of radio emission from any corresponding southern counterpart to the NML.

ON THE COMPACT H II GALAXY UM 408 AS SEEN BY GMOS-IFU: PHYSICAL CONDITIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lagos, Patricio; Telles, Eduardo; Munoz-Tunon, Casiana

2009-06-15

We present Integral Field Unit GMOS-IFU data of the compact H II galaxy UM 408, obtained at the Gemini South telescope, in order to derive the spatial distribution of emission lines and line ratios, kinematics, plasma parameters, and oxygen abundances as well the integrated properties over an area of 3''x4.''4 equivalent with {approx}750 pc x 1100 pc located in the central part of the galaxy. The starburst in this area is resolved into two giant regions of about 1.''5 and 1'' ({approx}375 and {approx}250 pc) diameter, respectively and separated 1.5-2'' ({approx}500 pc). The extinction distribution concentrate its highest values closemore » but not coincident with the maxima of H{alpha} emission around each one of the detected regions. This indicates that the dust has been displaced from the exciting clusters by the action of their stellar winds. The ages of these two regions, estimated using H{beta} equivalent widths, suggest that they are coeval events of {approx}5 Myr with stellar masses of {approx}10{sup 4} M {sub sun}. We have also used [O III]/H{beta} and [S II]/H{alpha} ratio maps to explore the excitation mechanisms in this galaxy. Comparing the data points with theoretical diagnostic models, we found that all of them are consistent with excitation by photoionization by massive stars. The H{alpha} emission line was used to measure the radial velocity and velocity dispersion. The heliocentric radial velocity shows an apparent systemic motion where the east part of the galaxy is blueshifted, while the west part is redshifted, with a relative motion of {approx}10 km s{sup -1}. The velocity dispersion map shows supersonic values typical for extragalactic H II regions. We derived an integrated oxygen abundance of 12+log(O/H) = 7.87 summing over all spaxels in our field of view. An average value of 12+log(O/H) = 7.77 and a difference of {delta}(O/H) = 0.47 between the minimum and maximum values (7.58 {+-} 0.06-8.05 {+-} 0.04) were found, considering all data points where the oxygen abundance was measured. The spatial distribution of oxygen abundance does not show any significant gradient across the galaxy. On the other hand, the bulk of data points are lying in a region of {+-}2{sigma} dispersion (with {sigma} = 0.1 dex) around the average value, confirming that this compact H II galaxy, like other previously studied dwarf irregular galaxies, is chemically homogeneous. Therefore, the new metals processed and injected by the current star formation episode are possibly not observed and reside in the hot gas phase, whereas the metals from previous events are well mixed and homogeneously distributed through the whole extent of the galaxy.« less

Bright Points and Subflares in UV Lines and in X-Rays

NASA Technical Reports Server (NTRS)

Rovira, M.; Schmieder, B.; Demoulin, P.; Simnett, G. M.; Hagyard, M. J.; Reichmann, E.; Tandberg-Hanssen, E.

1998-01-01

We have analysed an active region which was observed in Halpha (MSDP), UV lines (SMM/UVSP), and in X rays (SMM/HXIS). In this active region there were only a few subflares and many small bright points visible in UV and in X rays. Using an extrapolation based on the Fourier transform we have computed magnetic field lines connecting different photospheric magnetic polarities from ground-based magnetograms. Along the magnetic inversion lines we find 2 different zones: 1. a high shear region (less than 70 degrees) where subflares occur 2. a low shear region along the magnetic inversion line where UV bright points are observed.

Spectroscopic CCD surveys for quasars at large redshift. 3: The Palomar Transit Grism Survey catalog

NASA Technical Reports Server (NTRS)

Schneider, Donald P.; Schmidt, Maarten; Gunn, James E.

1994-01-01

This paper reports the initial results of the Palomar Transit Grism Survey (PTGS). The PTGS was designed to produce a sample of z greater than 2.7 quasars that were identified by well-defined selection criteria. The survey consists of six narrow (approximately equal to 8.5 min wide) strips of sky; the total effective area is 61.47 sq deg. Low-resolution slitless spectra, covering the wavelength range from 4400 to 7500 A, were obtained for approximately 600 000 objects. The wavelength- and flux-calibrated spectra were searched for emission lines with an automatic software algorithm. A total to 1655 emission features in the grism data satisfied our signal-to-noise ratio and equivalent width selection criteria; subsequent slit spectroscopy of the candidates confirmed the existence of 1052 lines (928 different objects). Six groups of emission lines were detected in the survey: Lyman alpha + N V, C IV, C III1, Mg II, H Beta + (O III), and H alpha + (S II). More than two-thirds of the candidates are low-redshift (z less than 0.45) emission-line galaxies; ninety objects are high-redshift quasars (z greater than 2.7) detected via their Lyman alpha + N V emission lines. The survey contains three previously unknown quasars brighter than 17th magnitude; all three have redshifts of approximately equal to 1.3. In this paper we present the observational properties of the survey, the algorithms used to select the emission-line candidates, and the catalog of emission-line objects.

X-ray-emitting gas surrounding the spiral galaxy NGC 891

NASA Astrophysics Data System (ADS)

Bregman, Joel N.; Pildis, Rachel A.

1994-01-01

We observed the edge-on spiral galaxy NGC 891 with the Position Sensitive Proportional Counter (PSPC) on Roentgen Satellite (ROSAT) to search for how extraplanar gas expected in the galactic fountain model. Diffuse X-ray emission surrounds the disk with a Half Width at Half Maximum (HWHM) for the surface brightness perpendicular to the disk of 50 sec (2.4 kpc) and a radial extent of approximately 6.5 kpc, both of which are similar in extent to the extended H(alpha) and radio halo component; the implied density scale height for the hot gas is 7 kpc. The spectrum is best fitted with a hard stellar component and a soft diffuse gas component of temperature 3.6 x 106 K. The density of this gas is 2 x 10-3/cu cm, the luminosity is 4.4 x 1039 ergs/s, the mass is 1 x 108 solar mass, and the pressure (P/k) is 1.4 104 K/cu cm. These data are consistent with this gas participating in a galactic fountain, where the material approaches hydrostatic equilibrium before cooling at a rate of 0.12 solar mass/yr. The cooled material may be responsible for some of the H(alpha) emission.

Be Star Monitoring Using a Small Aperture Telescope and Fiber-fed Spectrograph

NASA Astrophysics Data System (ADS)

Austin, S. J.

2003-12-01

Initial results are reported from a Be star monitoring project developed for undergraduate student research involvement at a small undergraduate university using a small aperture telescope and a custom-built fiber-fed spectrograph. Beginning in 2003 June, 0.8 Angstrom/pixel resolution spectra of the H-alpha line for over forty Be stars (Omi Aqr, 4 Aql, V923 Aql, V1294 Aql, Nu 2 Boo, 24 CVn, Gamma Cas, 4 CrB, Beta Cyg, 11 Cyg, 28 Cyg, 55 Cyg, 59 Cyg, 66 Cyg, V2136 Cyg, 1 Del, CX Dra, Omi Her, Sigma Her, 4 Her, 11 Her, 88 Her, 48 Lib, Chi Oph, Zeta Oph, 51 Oph, 66 Oph, Eta PsA, V4024 Sgr, 64 Ser, Delta Sco, QR Vul, 12 Vul, 20 Vul, 25 Vul, HD142184, HD165174, HD169033, HD170235, HD174179, HD181615, HD184279, HD195554, HD201733) have been obtained. H-alpha line profile velocities and evolution are shown. Funding has been provided by the UCA University Research Council and the Arkansas Space Grant Consortium.

ELLERMAN BOMBS AT HIGH RESOLUTION. I. MORPHOLOGICAL EVIDENCE FOR PHOTOSPHERIC RECONNECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watanabe, Hiroko; Kitai, Reizaburo; Vissers, Gregal

2011-07-20

High-resolution imaging-spectroscopy movies of solar active region NOAA 10998 obtained with the Crisp Imaging Spectropolarimeter at the Swedish 1-m Solar Telescope show very bright, rapidly flickering, flame-like features that appear intermittently in the wings of the Balmer H{alpha} line in a region with moat flows and likely some flux emergence. They show up at regular H{alpha} blue-wing bright points that outline the magnetic network, but flare upward with much larger brightness and distinct 'jet' morphology seen from aside in the limbward view of these movies. We classify these features as Ellerman bombs and present a morphological study of their appearancemore » at the unprecedented spatial, temporal, and spectral resolution of these observations. The bombs appear along the magnetic network with footpoint extents up to 900 km. They show apparent travel away from the spot along the pre-existing network at speeds of about 1 km s{sup -1}. The bombs flare repetitively with much rapid variation at timescales of seconds only, in the form of upward jet-shaped brightness features. These reach heights of 600-1200 km and tend to show blueshifts; some show bi-directional Doppler signature and some seem accompanied with an H{alpha} surge. They are not seen in the core of H{alpha} due to shielding by overlying chromospheric fibrils. The network where they originate has normal properties. The morphology of these jets strongly supports deep-seated photospheric reconnection of emergent or moat-driven magnetic flux with pre-existing strong vertical network fields as the mechanism underlying the Ellerman bomb phenomenon.« less

THE MISSING GOLIATH'S SLINGSHOT: MASSIVE BLACK HOLE RECOIL AT M83

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dottori, Horacio; Diaz, Ruben J.; Facundo Albacete-Colombo, Juan

2010-07-01

The Fanaroff-Riley II radio source J133658.3-295105, which is also an X-ray source, appears to be projected onto the disk of the barred-spiral galaxy M83 at about 60'' from the galaxy's optical nucleus. J133658.3-295105 and its radio lobes are aligned with the optical nucleus of M 83 and two other radio sources, neither of which are supernova remnants or H II regions. Due to this peculiar on-the-sky projection, J133658.3-295105 was previously studied by Gemini+GMOS optical spectroscopy, which marginally revealed the presence of H{alpha} in emission receding at 130 km s{sup -1} with respect to the optical nucleus. In this Letter, wemore » reanalyze the Chandra spectroscopy carried out in 2000. We show that J133658.3-295105 presents an Fe K{alpha} emission line at a redshift of z = 0.018. This redshift is compatible with a black hole at the distance of M 83. We discuss similarities to the recently reported micro-quasar in NGC 5408. This finding reinforces the kicked-off black hole scenario for J133658.3-295105.« less

Do Lyman-alpha photons escape from star-forming galaxies through dust holes?

NASA Astrophysics Data System (ADS)

France, Kevin; Wofford, A.; Leitherer, C.; Fleming, B.; McCandliss, S. R.; Nell, N.

2014-01-01

H I Lyman-alpha (LyA) is commonly used as a signpost for the entire galaxy at redshifts z>2, and yet spatially and kinematically resolved views of the local conditions within galaxies that determine the integrated properties of this line are scarce. We obtained Hubble Space Telescope (HST) images in continuum-subtracted LyA, H-alpha, H-beta, and far-UV continuum of three low-inclination spiral star-forming galaxies located at redshifts z=0.02, 0.03, and 0.05. This was accomplished using the UVIS and SBC channels of the Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS), respectively. Previous HST spectroscopy obtained by our team with the Cosmic Origins Spectrograph (COS) showed that the galaxies display different integrated LyA profiles within their central few kiloparsecs, i.e., pure absorption, single emission, and double emission, which are representative of what is observed between redshifts 0-3. This data is useful for establishing the relative importance of starburst phase, dust content, and gas kinematics in determining the LyA escape. We present preliminary results that combine our spectroscopic and imaging observations.

Hydrogen leak detection using laser-induced breakdown spectroscopy.

PubMed

Ball, A J; Hohreiter, V; Hahn, D W

2005-03-01

Laser-induced breakdown spectroscopy (LIBS) is investigated as a technique for real-time monitoring of hydrogen gas. Two methodologies were examined: The use of a 100 mJ laser pulse to create a laser-induced breakdown directly in a sample gas stream, and the use of a 55 mJ laser pulse to create a laser-induced plasma on a solid substrate surface, with the expanding plasma sampling the gas stream. Various metals were analyzed as candidate substrate surfaces, including aluminum, copper, molybdenum, stainless steel, titanium, and tungsten. Stainless steel was selected, and a detailed analysis of hydrogen detection in binary mixtures of nitrogen and hydrogen at atmospheric pressure was performed. Both the gaseous plasma and the plasma initiated on the stainless steel surface generated comparable hydrogen emission signals, using the 656.28 Halpha emission line, and exhibited excellent signal linearity. The limit of detection is about 20 ppm (mass) as determined for both methodologies, with the solid-initiated plasma yielding a slightly better value. Overall, LIBS is concluded to be a viable candidate for hydrogen sensing, offering a combination of high sensitivity with a technique that is well suited to implementation in field environments.

Planetary Nebulae in the Solar Neighbourhood: Statistics, Distance Scale and Luminosity Function

NASA Astrophysics Data System (ADS)

Frew, David J.

2008-07-01

An accurate census of the nearest planetary nebulae (PNe) is needed for calculations of the total number, space density, scale height, and birth rate of PNe in the Galaxy, to understand the dynamics of an evolving nebula and its relationship to the cooling history of the central star, and also to provide an unbiased sample to investigate the frequency of binary central stars and their role in the formation and shaping of these objects. This study presents the most refined volume-limited survey of PNe known to date. Integrated H-alpha fluxes for over 400 mostly evolved PNe are presented, based primarily on data from the Southern H-alpha Sky Survey Atlas (SHASSA) and the Virginia Tech Spectral-Line Survey (VTSS). Aperture photometry on the digital images was performed to extract H-alpha+[NII] fluxes. The [NII] contribution was then de-convolved using literature data, new data from slit spectra, or spectrophotometric data from the Wisconsin H-Alpha Mapper (WHAM) also obtained as part of this project. Comparison with previous work shows that the flux scale presented here has no significant zero-point error. The H-alpha fluxes are used to determine new Zanstra temperatures for those PNe with accurate central star photometry, calculating surface-brightness distances for each PN in the sample, and in conjunction with accurate [OIII] fluxes, new absolute PN magnitudes for delineating the faint end of the PN luminosity function. A spectroscopic survey of a range of MASH PNe is also presented. New emission-line intensities for 60 PNe are given, including a preliminary discussion of the chemical abundances of this sample. New distances have been determined for a large number of PNe, by either critically examining the literature, or by deriving new extinction and kinematic distances where suitable. For all PNe not amenable to these approaches, distances were estimated from a new H-alpha surface brightness-radius (SB-r) relation. The Hα SB-r relation covers >6 dex in SB, and while the spread in SB is ∼1 dex at a given radius, optically thick (mainly bipolar and bipolar-core) PNe tend to populate the upper bound of the trend, while common-envelope PNe and high-excitation PNe fall along the lower boundary in SB-r space. Using sub-trends has allowed more precision in the determination of distances, as good as ±22% in the case of high-excitation PNe. The adopted SB-r zero point, set from 122 galactic calibrators, recovers the distances to the LMC, SMC and the Sagittarius dSph galaxy to within 5%. With distances to all nearby PNe, I have generated the most accurate volume-limited sample of PNe (D ≤ 1.0 kpc) yet considered, containing ∼56 PNe. An extension sample to 2.0 kpc contains ∼210 PNe. An accurate database of parameters for nearly all of these objects is presented, providing integrated fluxes, diameters, morphological classifications, distances, ionized masses, expansion velocities, kinematic ages, chemical abundances, and central star properties for each PN in this volume-limited sample.Details are also given on a number of misclassified 'PNe' which contaminate the local volume, including, amongst others, Abell 35, DHW 5, Sh 2-68, Sh 2-174, Hewett 1, RE J1738+665, PG 0108+101, PG 0109+111, PHL 932 and EGB 5. The observation that known close-binary PNe fall on a particular trend in SB-r space, is suggestive that these form a separate population to the majority of PNe. Recent conclusions that the great majority (or all) PNe go through a common-envelope phase are not supported at this point in time, though there is no doubt a modest frequency of common-envelope events has occurred in the solar neighbourhood. The exact number awaits a full multiplicity census of all objects within this volume. A preliminary estimate of the binary frequency of PN central stars in the solar neighbourhood is ∼52-58% and hence I conclude that it is possible for single stars to produce PNe. A deep local PN luminosity function is presented, extending to 10 magnitudes below the bright PN cutoff magnitude, M*. The local [OIII] PNLF is seen to be much more bottom-heavy than previously recognised, with up to half of all PNe being fainter than 7 mag below M*. An exponential increase in PN numbers occurs to ∼8.3 mag below M*, where a marked turnover in the PNLF is seen. The very faintest PNe may represent a population of low-mass objects with low-luminosity central stars. New estimates for the number density, scale height, birth rate, and total number of Galactic PNe, as extrapolated from the solar neighbourhood sample, are also given. The total Galactic population is estimated to be 24,000 ± 4000 PNe with r < 1.5 pc, and 13,000 ± 2000 PNe with r < 0.9 pc. The MW/LMC luminosity ratio implies a total LMC PN population of ∼2400. Evidently many more PNe remain to be discovered in this system. The observed Galactic population leads to a PN birthrate of 0.8 ± 0.3 × 10^-12 pc^-3yr^-1, fully consistent within the errors with the birthrate of white dwarfs. A remarkable bow-shock nebula around a previously unnoticed, bright, nova-like cataclysmic variable, V341 Ara, has also been discovered as part of this study. The star has a high space motion, leading to the formation of the parabolic bow-shock at the interaction of the disk wind and the ISM. The proximity of this nebula to the Sun suggests the space density of such objects may quite high. Similar nebulae might be found through a narrowband search around other CVs with significant proper motion.

Infrared and Optical Spectroscopy of Protostars in the Elephant Trunk Nebula

NASA Astrophysics Data System (ADS)

Faied, Dohy; Reach, W. T.; Tappe, A.; Rho, J.

2006-12-01

We present Spitzer Space Telescope observations of the optically dark globule IC1396A. We have identified red objects located within the molecular globule to be Class I protostars, and objects scattered near the globule are found to be Class II T-Tauri stars surrounded by warm, luminous disks. We obtained simultaneous optical and infrared spectra (5.5 40 microns) with the Palomar Hale 200 inch telescope. The Class I sources were observed to have extremely red continua, rising at 24 microns, with deep silicate absorption at 9-11 microns, and weaker silicate absorption at around 12 microns. Some of these sources also display weak ice features such as CO2 and H2O. In contrast, the Class II sources have strong H-alpha emission and silicate emission features at 9-11 microns, indicative of circumstellar disks. These results all suggest that star formation within this globule is occurring at two different stages the first stage, leading to the Class II sources located in the center of the globule, and a second, very recent one (less than 100,000 yr ago) that is occurring within the globule. This second phase was likely triggered by the wind and radiation of the central O-type star of the IC 1396 H II region.

Database of emission lines

NASA Astrophysics Data System (ADS)

Binette, L.; Ortiz, P.; Joguet, B.; Rola, C.

1998-11-01

A widely accessible data bank (available through Netscape) and consiting of all (or most) of the emission lines reported in the litterature is being built. It will comprise objects as diverse as HII regions, PN, AGN, HHO. One of its use will be to define/refine existing diagnostic emission line diagrams.

EVIDENCE FOR AN FU ORIONIS-LIKE OUTBURST FROM A CLASSICAL T TAURI STAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Adam A.; Poznanski, Dovi; Silverman, Jeffrey M.

2011-04-01

We present pre- and post-outburst observations of the new FU Orionis-like young stellar object PTF 10qpf (also known as LkH{alpha} 188-G4 and HBC 722). Prior to this outburst, LkH{alpha} 188-G4 was classified as a classical T Tauri star (CTTS) on the basis of its optical emission-line spectrum superposed on a K8-type photosphere and its photometric variability. The mid-infrared spectral index of LkH{alpha} 188-G4 indicates a Class II-type object. LkH{alpha} 188-G4 exhibited a steady rise by {approx}1 mag over {approx}11 months starting in August 2009, before a subsequent more abrupt rise of >3 mag on a timescale of {approx}2 months. Observationsmore » taken during the eruption exhibit the defining characteristics of FU Orionis variables: (1) an increase in brightness by {approx}>4 mag, (2) a bright optical/near-infrared reflection nebula appeared, (3) optical spectra are consistent with a G supergiant and dominated by absorption lines, the only exception being H{alpha} which is characterized by a P Cygni profile, (4) near-infrared spectra resemble those of late K-M giants/supergiants with enhanced absorption seen in the molecular bands of CO and H{sub 2}O, and (5) outflow signatures in H and He are seen in the form of blueshifted absorption profiles. LkH{alpha} 188-G4 is the first member of the FU Orionis-like class with a well-sampled optical to mid-infrared spectral energy distribution in the pre-outburst phase. The association of the PTF 10qpf outburst with the previously identified CTTS LkH{alpha} 188-G4 (HBC 722) provides strong evidence that FU Orionis-like eruptions represent periods of enhanced disk accretion and outflow, likely triggered by instabilities in the disk. The early identification of PTF 10qpf as an FU Orionis-like variable will enable detailed photometric and spectroscopic observations during its post-outburst evolution for comparison with other known outbursting objects.« less

Pharmacologic study of C-terminal fragments of frog skin calcitonin gene-related peptide.

PubMed

Ladram, Ali; Besné, Isabelle; Breton, Lionel; de Lacharrière, Olivier; Nicolas, Pierre; Amiche, Mohamed

2008-07-01

The calcitonin gene-related peptide from the skin of the frog Phyllomedusa bicolor (pbCGRP) is a 37-residue neuropeptide that differs from human alpha CGRP (halphaCGRP) at 16 positions. The affinities of the C-terminal fragments of pbCGRP and halphaCGRP were evaluated in SK-N-MC cells: pbCGRP(8-37) (K(i)=0.2nM) and pbCGRP(27-37) (K(i)=95nM) were, respectively, 3 times and 20 times more potent than the human fragments halphaCGRP(8-37) and halphaCGRP(27-37). Their antagonistic potencies were measured in SK-N-MC and Col 29 cells, and the rat vas deferens. pbCGRP(8-37) inhibited the halphaCGRP-stimulated production of cAMP by SK-N-MC and Col 29 cells 3 to 4 times more strongly than halphaCGRP(8-37). Thus pbCGRP(8-37) is the most potent CGRP-1 competitive antagonist of all the natural sequences reported to date. pbCGRP(27-37) was also as potent as [D(31), A(34), F(35)] halphaCGRP(27-37), a prototypic antagonist analog derived from structure-activity relationship studies of halphaCGRP(8-37).

A Diffraction-limited Survey for Direct Detection of Halpha Emitting/Accreting ExtraSolar Planets with the 6.5m Magellan Telescope and the MagAO Visible AO system

NASA Astrophysics Data System (ADS)

Close, Laird

TECHNICAL BACKGROUND: An advanced adaptive secondary mirror (ASM) with 585 actuators was commissioned at the 6.5-m Magellan Telescope at one of the world’s best sites (Las Campanas Observatory; LCO) in Chile. By the end of the commissioning run (April 2013) the MagAO system was regularly producing the highest spatial resolution deep images to date (0.023” deep images at Halpha (0.656 microns); Close et al. 2013). This is due to its 378 corrective modes at 1kHz on a 6.5-m telescope. Strehl ratis>20% at Halpha were obtained in 75% of the seeing statistics at the site. We propose here to utilize MagAO’s absolutely unique ability to take Halpha, continuum (0.643 microns), and L’ (3.8 microns) thermal images (all simultaneously) to carry out a novel survey to: Discover a population of the lowest mass young accreting extrasolar planets imaged to date. to characterize the spatial distribution, and estimate accretion rates, of young extrasolar planets >5AU, to understand the influence of planets on transitional disk gaps. THEORY BACKGROUND: Extrasolar planets are very difficult to image directly since planets become very faint below ~8 Mjup (Jupiter masses) for ages >1 Myr and such massive planets are rare. There is a class of young stars that are still accreting yet have SED (and often imaging) evidence of a lack of dust and gas inside a r=5-140 AU “gap”. These “transitional disks” are believed to be transitioning into “disk free” stars. These gaps are believed to be maintained by planets that continuously clear (though scattering or accretion) the optically thin gaps. Indeed large >10 AU gaps (>few Hill spheres) must be maintained by multiple ~1 Mjup planets (Dodson-Robinson & Salyk 2011). Since gas must pass through each of these gaps to continuously supply the accreting star, simulations suggest that these “gap planets” are also crossing points for these gas streamers on their way to the star. These streamers “force-feed” these planets a steady diet of hydrogen gas. Such planets should then be quite bright in Halpha accretion emission. The key point is that: instead of a steep drop off in the luminosity of the planet’s atmosphere, the accretion luminosity of these planets will just linearly decrease with decreasing mass. At an accretion rate=6e-10 Msun/yr we find low mass (~1 Mjup) accreting gap planets are much (50-1000x) brighter (for 0-3.4 mag of Halpha extinction) in Halpha than at H band. PROOF-OF_CONCEPT: A 3 hour MagAO observation at Halpha of a transitional disk in April 2013 was made. The resulting deep diffraction-limited images discovered (at 10.5 sigma) an Halpha source that was 295% above the continuum just 0.083” from the star (edge of the inner 10 AU disk gap). We also detected (at 5 sigma) an excellent (though much fainter) ~1 Mjup mass Halpha planet candidate located auspiciously at the outer edge (145 AU) of the gap. If confirmed by our “second epoch” follow-up as common proper motion then this would be the lowest mass (~1 Mjup) planet ever imaged. SURVEY: Scaling off of this exciting success we propose to deeply image (120 min) all 14 nearby (D<250pc), bright (R<11 mag) , not edge-on (i<80 deg) , young (~5 Myr) transitional disks with MagAO simultaneously at Halpha and L’. In addition, we will use BrGamma instead of Halpha for 8 additional fainter (111 Mjup in mass, we integrate across our target list and find that, in the worst case of minimal masses (1+/-0.5 Mjup), and 3.4 mag extinction, at least seven ~1 Mjup planets should be discovered by this survey --meeting all three of our science goals above.

Detection of a very bright source close to the LMC supernova SN 1987A

NASA Technical Reports Server (NTRS)

Nisenson, P.; Papaliolios, C.; Karovska, M.; Noyes, R.

1987-01-01

High angular resolution observations of the supernova in the Large Magellanic Cloud, SN 1987A, have revealed a bright source separated from the SN by approximately 60 mas with a magnitude difference of 2.7 at 656 nm (H-alpha). Speckle imaging techniques were applied to data recorded with the CfA two-dimensional photon counting detector on the CTIO 4 m telescope on March 25 and April 2 to allow measurements in H-alpha on both nights and at 533 nm and 450 nm on the second night. The nature of this object is as yet unknown, though it is almost certainly a phenomenon related to the SN.

Star formation across galactic environments

NASA Astrophysics Data System (ADS)

Young, Jason

I present here parallel investigations of star formation in typical and extreme galaxies. The typical galaxies are selected to be free of active galactic nuclei (AGN), while the extreme galaxies host quasars (the most luminous class of AGN). These two environments are each insightful in their own way; quasars are among the most violent objects in the universe, literally reshaping their host galaxies, while my sample of AGN-free star-forming galaxies ranges from systems larger than the Milky Way to small galaxies which are forming stars at unsustainably high rates. The current paradigm of galaxy formation and evolution suggests that extreme circumstances are key stepping stones in the assembly of galaxies like our Milky Way. To test this paradigm and fully explore its ramifications, this dual approach is needed. My sample of AGN-free galaxies is drawn from the KPNO International Spectroscopic Survey. This Halpha-selected, volume-limited survey was designed to detect star-forming galaxies without a bias toward continuum luminosity. This type of selection ensures that this sample is not biased toward galaxies that are large or nearby. My work studies the KISS galaxies in the mid- and far-infrared using photometry from the IRAC and MIPS instruments aboard the Spitzer Space Telescope. These infrared bands are particularly interesting for star formation studies because the ultraviolet light from young stars is reprocessed into thermal emission in the far-infrared (24mum MIPS) by dust and into vibrational transitions features in the mid-infrared (8.0mum IRAC) by polycyclic aromatic hydrocarbons (PAHs). The work I present here examines the efficiencies of PAH and thermal dust emission as tracers of star-formation rates over a wide range of galactic stellar masses. I find that the efficiency of PAH as a star-formation tracer varies with galactic stellar mass, while thermal dust has a highly variable efficiency that does not systematically depend on galactic stellar mass. Complementing this study of normal star-forming galaxies, my study of quasar host galaxies utilizes narrow- and medium-band images of eight Palomar-Green (PG) quasars from the WFPC2 and NICMOS instruments aboard the Hubble Space Telescope. Using images of a point-spread function (PSF) star in the same filters, I subtract the PSF of the quasar from each of the target images. The residual light images clearly show the host galaxies of the respective quasars. The narrow-band images were chosen to be centered on the Hbeta, [O II ], [O III], and Paalpha emission lines, allowing the use of line ratios and luminosities to create extinction and star formation maps. Additionally, I utilize the line-ratio maps to distinguish AGN-powered line emission from star formation powered line emission with line-diagnostic diagrams. I find star formation in each of the eight quasar host galaxies in my study. The bulk star-formation rates are lower than expected, suggesting that quasar host galaxies may be dynamically more advanced than previously believed. Seven of the eight quasar host galaxies in this study have higher-than-typical mass-specific star-formation rates. Additionally, I see evidence of shocked gas, supporting the hypotheses presented in earlier works that suggest that AGN activity quenches star formation in its host galaxy by disrupting its gas reservoir.

Imaging Spectrophotometry of the Jet/ISM Interaction in IC5063

NASA Technical Reports Server (NTRS)

Cecil, G.; Schuft, B.; Morse, J.; Bland-Hawthorn, J.

2004-01-01

IC5063 is a somewhat dusty z=0.0110 S0 galaxy with a Seyfert 2 nucleus. It has a triple radio source that spans 3 arcsec, mostly blueshifted H I absorption that spans 700 km/s, and ionization cones that extend for more than 2 arcmins. We obtained fully sampled [O III]\\lambda5007 grids at 0."9 and 70 km/s FWHM resolution using the Rutgers Fabry-Perot system on the Blanco 4m telescope. Complementary long-slit spectra using the RC spectrograph on the Blanco, and Taurus Tunable Filter spectral images in H\\alpha and [N II]\\lambda6583, were also obtained to assess gaseous ionization conditions. We present the results of our analysis, and correlate spectral structures to those visible in archival WFPC2 images. We find that, in the region near the radio triple, gaseous ionization and line velocity width is tightly correlated, in excellent quantitative agreement with the high-velocity shock regime in the diagnostic emission-line ratio diagrams of Dopita & Sutherland. We separate kinematically gas in normal disk rotation that is illuminated by the AGN in the ionization cones from that agitated mechanically by the jet, and assess the energy input from both processes.

Comportamiento de la cromósfera solar en la línea H-alpha durante el ciclo 23

NASA Astrophysics Data System (ADS)

Davoli, D.; Aquilano, R.; Missio, H.

Using the instrumental of the Observatorio Astronómico Municipal de Rosario (OAMR), we analyze the solar chromospheric activity during an approximate period of 11 years. The instrument is a Carl Zeiss refractor telescope of 150 mm aperture and 2250 mm of focal distance with monochromatic filter in the H-alpha line. We take as proxy for the solar activity the area covered by chromospheric plages. Simultaneously, we determine the relative wolf number from observations of the solar photosphere. We describe our technique and the results obtained. We observe 2 maxima of solar activity in the years 2000 and 2001 respectively, and a later decrease of this activity with low average values starting around 2006 that corresponds to the end of cycle 23. FULL TEXT IN SPANISH

The Spitzer/IRAC Star Formation Reference Survey

NASA Astrophysics Data System (ADS)

Fazio, Giovanni; Ashby, Matthew; Ashby, Matthew L. N.; Barmby, Pauline; Chakrabarti, Sukanya; Gonzalez-Alfonso, Eduardo; Huang, Jia-Sheng; Madden, Suzanne; Noeske, Kai; Pahre, Michael; Papovich, Casey; Robitaille, Thomas; Smith, Howard; Sturm, Eckhard; Surace, Jason; Wang, Zhong; Whitney, Barbara; Willner, Steven; Wu, Hong; Zezas, Andreas

2008-03-01

We propose a statistically robust study of 380 nearby, bright star-forming galaxies of all types to better understand the nature of star formation. The goal of this IRAC reference survey will be to measure total star formation rates via 8.0 micron PAH emission, with an emphasis on quantitative comparisons of multiple global star formation indicators including ultraviolet emission, H-alpha, and radio continuum measurements. The sample is selected to be fully representative of the entire ranges of infrared luminosity, dust temperature, and stellar mass exhibited by star-forming galaxies in the local universe: the sample galaxies exhibit all existing combinations of these properties with the minimum overall number, selected in a manner that allows results to be applied to the entire local galaxy population. Here we propose four-band Spitzer/IRAC photometry for the 275 out of 380 objects which lack suitable observations in the Spitzer archive. All sample galaxies already have extensive complementary data available including global ugrizJHK photometry plus radio continuum intensities. Most also have GALEX imaging; in addition we have already begun a ground-based campaign to acquire global H-alpha imaging for the complete sample. We are submitting this IRAC proposal in the context of a larger campaign that includes a GTO proposal to complete the MIPS 24 micron imaging, and a GO proposal to acquire the IRS low-resolution spectroscopy. Although these companion proposals will significantly increase the scientific return of our survey program, the success of this proposal is not contingent in any way on any other Spitzer proposal. Our international team is dedicated, experienced, and has adequate manpower and institutional resources, with expertise in all the relevant disciplines to ensure the success of this undertaking. PI Fazio believes this proposal to be the most important element of his extragalactic GTO program, and requests that it be assigned first priority.

Extreme ultraviolet and X-ray spectroheliograph for OSO-H

NASA Technical Reports Server (NTRS)

Sterk, A. A.; Kieser, F.; Peck, S.; Knox, E.

1972-01-01

A complex scientific instrument was designed, fabricated, tested, and calibrated for launch onboard OSO-H. This instrument consisted of four spectroheliographs and an X-ray polarimeter. The instrument is designed to study solar radiation at selected wavelengths in the X-ray and the extreme ultraviolet ranges, make observations at the H-alpha wavelength, and measure the degree of polarization of X-ray emissions.

A Narrowband Imaging Search for [O III] Emission from Galaxies at z > 3

NASA Astrophysics Data System (ADS)

Teplitz, Harry I.; Malkan, Matthew A.; McLean, Ian S.

1999-03-01

We present the results of a narrowband survey of quasi-stellar-object (QSO) fields at redshifts that place the [O III] (5007 Å) emission line in the Δλ/λ~1% 2.16 μm filter. We have observed 3 arcmin2 and detected one emission-line candidate object in the field around PC 1109+4642. We discuss the possibilities that this object is a star-forming galaxy at the QSO redshift, zem=3.313, or a Seyfert galaxy. In the former case, we infer a star formation rate of 170 Msolar yr-1 for this K'=21.3 object. The galaxy has a compact but resolved morphology, with an FWHM=0.6" or 4.2 kpc at z=3.313 (H0=50 km s-1 Mpc-1 and q0=0.5). The comoving density of such objects in QSO environments appears to be 0.0033 Mpc-3, marginally lower (<=3 σ) than the density observed for Hα-emitters in absorption-line fields at z~2.5 but similar to the density of Lyman-break galaxies at z~3. If, on the other hand, most of the line emission is [O III] from a Seyfert 2 nucleus at z=3.31, then the high inferred volume density could imply a large evolution in the Seyfert 2 luminosity function from the current epoch. We find the field containing the object to also contain many faint extended objects in the K' image but little significant excess over the expected number-magnitude relation. We discuss the implication of the emission line being a longer wavelength line at a lower redshift.

VizieR Online Data Catalog: HD 50138 short-term variability (Borges Fernandes+, 2012)

NASA Astrophysics Data System (ADS)

Borges Fernandes, M.; Kraus, M.; Nickeler, D. H.; De Cat, P.; Lampens, P.; Pereira, C. B.; Oksala, M. E.

2012-10-01

A total of 72 files related to the optical spectra taken within 8 observing nights with HERMES spectrograph, covering the photospheric HeI 4026Å and SiII 4128Å and 4131Å lines, the circumstellar [OI] 6364Å line, and the lines formed in the upper layers of the stellar atmosphere or very close to the stellar surface: SiII 6347Å and 6371Å, HeI 6678Å, H10, H9 and Halpha lines. The data were reduced by automated data reduction pipeline and cosmic ray and heliocentric velocity corrected (but not telluric corrected). (2 data files).

Galaxy interactions and star formation: Results of a survey of global H-alpha emission in spiral galaxies in 8 clusters

NASA Technical Reports Server (NTRS)

Moss, C.

1990-01-01

Kennicutt and Kent (1983) have shown that the global H alpha emission from a spiral galaxy is an indicator of the formation rate of massive stars. Moss, Whittle and Irwin (1988) have surveyed two clusters (Abell 347 and 1367) for galaxies with H alpha emission using a high dispersion objective prism technique. The purpose of the survey is to investigate environmental effects on star formation in spiral galaxies, and in particular to ascertain whether star formation is enhanced in cluster spirals. Approximately 20 percent of CGCG galaxies were detected in emission. Two plates of excellent quality were obtained for each of the two clusters, and galaxies were only identified to have emission if this was detected on both plates of a plate pair. In this way, plate flaws and other spurious identifications of emission could be rejected, and weak emission confirmed. The results of this survey have been discussed by Moss (1987). The detected galaxies are of types SO-a and later. The frequency with which galaxies are detected in emission increases towards later morphological type as expected (cf. Kennicutt and Kent 1983). There is no evidence of any dependence of the frequency of detected emission on the absolute magnitude of the galaxy (cf. Moss and Whittle 1990), but there is a strong correlation between a disturbed morphological appearance of the galaxy and the detection of emission. Furthermore it is found that the emission is more centrally concentrated in those galaxies which show a disturbed morphology. It may be noted that the objective prism plate gives a spectrum of a 400 A region around rest wavelength H alpha, but superposed on this is the H alpha emission from the galaxy which, because the light is essentially monochromatic, results in a true two-dimensional image of the H alpha distribution. The visual appearance of the emission on the prism plates was classified according to its diffuseness on a 5 point scale (very diffuse, diffuse, intermediate, compact, and very compact). In tabular form, the relation is shown between this classification and a morphologically disturbed appearance for the galaxy.

The nature of 50 Palermo Swift-BAT hard X-ray objects through optical spectroscopy

NASA Astrophysics Data System (ADS)

Rojas, A. F.; Masetti, N.; Minniti, D.; Jiménez-Bailón, E.; Chavushyan, V.; Hau, G.; McBride, V. A.; Bassani, L.; Bazzano, A.; Bird, A. J.; Galaz, G.; Gavignaud, I.; Landi, R.; Malizia, A.; Morelli, L.; Palazzi, E.; Patiño-Álvarez, V.; Stephen, J. B.; Ubertini, P.

2017-06-01

We present the nature of 50 hard X-ray emitting objects unveiled through an optical spectroscopy campaign performed at seven telescopes in the northern and southern hemispheres. These objects were detected with the Burst Alert Telescope (BAT) instrument onboard the Swift satellite and listed as of unidentified nature in the 54-month Palermo BAT catalogue. In detail, 45 sources in our sample are identified as active galactic nuclei of which, 27 are classified as type 1 (with broad and narrow emission lines) and 18 are classified as type 2 (with only narrow emission lines). Among the broad-line emission objects, one is a type 1 high-redshift quasi-stellar object, and among the narrow-line emission objects, one is a starburst galaxy, one is a X-ray bright optically normal galaxy, and one is a low ionization nuclear emission line region. We report 30 new redshift measurements, 13 confirmations and 2 more accurate redshift values. The remaining five objects are galactic sources: three are Cataclismic Variables, one is a X-ray Binary probably with a low mass secondary star, and one is an active star. Based on observations obtained from the following observatories: Cerro Tololo Interamerican Observatory (Chile); Astronomical Observatory of Bologna in Loiano (Italy); Observatorio Astronómico Nacional (San Pedro Mártir, Mexico); Radcliffe telescope of the South African Astronomical Observatory (Sutherland, South Africa); Sloan Digital Sky Survey; Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (Canary Islands, Spain) and New Technology Telescope (NTT) of La Silla Observatory, Chile.

A FIVE-YEAR SPECTROSCOPIC AND PHOTOMETRIC CAMPAIGN ON THE PROTOTYPICAL {alpha} CYGNI VARIABLE AND A-TYPE SUPERGIANT STAR DENEB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richardson, N. D.; Morrison, N. D.; Kryukova, E. E.

2011-01-15

Deneb is often considered the prototypical A-type supergiant and is one of the visually most luminous stars in the Galaxy. A-type supergiants are potential extragalactic distance indicators, but the variability of these stars needs to be better characterized before this technique can be considered reliable. We analyzed 339 high-resolution echelle spectra of Deneb obtained over the five-year span of 1997 through 2001 as well as 370 Stroemgren photometric measurements obtained during the same time frame. Our spectroscopic analysis included dynamical spectra of the H{alpha} profile, H{alpha} equivalent widths, and radial velocities measured from Si II {lambda}{lambda} 6347, 6371. Time-series analysismore » reveals no obvious cyclic behavior that proceeds through multiple observing seasons, although we found a suspected 40 day period in two, non-consecutive observing seasons. Some correlations are found between photometric and radial velocity data sets and suggest radial pulsations at two epochs. No correlation is found between the variability of the H{alpha} profiles and that of the radial velocities or the photometry. Lucy found evidence that Deneb was a long-period single-lined spectroscopic binary star, but our data set shows no evidence for radial velocity variations caused by a binary companion.« less

Far-Infrared Line Emission from High Redshift Quasars

NASA Technical Reports Server (NTRS)

Benford, D. J.; Cox, P.; Hunter, T. R.; Malhotra, S.; Phillips, T. G.; Yun, M. S.

2002-01-01

Recent millimeter and submillimeter detections of line emission in high redshift objects have yielded new information and constraints on star formation at early epochs. Only CO transitions and atomic carbon transitions have been detected from these objects, yet bright far-infrared lines such as C+ at 158 microns and N+ at 205 microns should be fairly readily detectable when redshifted into a submillimeter atmospheric window. We have obtained upper limits for C+ emission &om two high redshift quasars, BR1202-0725 at z=4.69 and BRI1335-0415 at z=4.41. These limits show that the ratio of the C+ line luminosity to the total far-infrared luminosity is less than 0.0l%, ten times smaller than has been observed locally. Additionally, we have searched for emission in the N+ 205 micron line from the Cloverleaf quasar, H1413+117, and detected emission in CO J=7-6. The N+ emission is found to be below the amount predicted based on comparison to the only previous detection of this line, in the starburst galaxy M82.

Skylab

NASA Image and Video Library

1973-01-01

This chart describes the Hydrogen-Alpha (H-Alpha) #2 Telescope, one of eight major solar study facilities on the Skylab Apollo Telescope Mount (ATM). There were two H-Alpha telescopes on the ATM that were used primarily to point the ATM and keep a continuous photographic record during solar observation periods. Both telescopes gave the Skylab astronauts a real-time picture of the Sun in the red light of the H-Alpha spectrum through a closed-circuit television. The H-Alpha #1 telescope provided simultaneous photographic and ultraviolet (UV) pictures, while the #2 telescope operated only in the TV mode. The Marshall Space Flight Center was responsible for development of the H-Alpha Telescopes.

Skylab

NASA Image and Video Library

1973-01-01

This chart describes the Hydrogen-Alpha (H-Alpha) #1 Telescope, one of eight major solar study facilities on the Skylab Apollo Telescope Mount (ATM). There were two H-Alpha telescopes on the ATM that were used primarily to point the ATM and keep a continuous photographic record during the solar observation periods. Both telescopes gave the Skylab astronauts a real-time picture of the Sun in the red light of the H-Alpha spectrum through a closed-circuit television. The H-Alpha #1 Telescope provided simultaneous photographic and ultraviolet (UV) pictures, while the #2 Telescope operated only in the TV mode. The Marshall Space Flight Center was responsible for development of the H-Alpha Telescopes.

The Late-Time Evolution of SN 2002hh

NASA Astrophysics Data System (ADS)

Clayton, G. C.; Welch, D. L.

2005-12-01

We present new spectroscopic and photometric observations of the interesting Type II-P supernova, SN 2002hh, in NGC 6946. Gemini/GMOS-N has been used to acquire visible spectra and also g'r'i' photometry covering 5 epochs between August 2004 and October 2005, following the evolution of the supernova from 650 to 1050 d since its initial explosion. Supernova spectra obtained 3 years after outburst are rare. In addition, data have been obtained at several epochs in the JHK bands using the Steward 90" with the 256x256 imager and with Gemini/NIRI. Dust emission from SN 2002hh has been detected at mid-infrared wavelengths by SST/IRAC and confirmed by higher angular resolution Gemini/Michelle observations (Barlow et al. 2005, ApJ, 627, L113). There is a pre-existing optically thick dust shell having a mass of ˜0.1 Msun, suggesting a massive M supergiant or luminous blue variable precursor. However, the formation of new dust in the ejecta of SN 2002hh has not been ruled out. The IR emission from any such new dust would be swamped by the emission from the existing circumstellar dust. The new data, presented here, are being used to investigate the late-time evolution of SN 2002hh and whether new dust has been formed in its ejecta. In particular, we are looking for changes in the H-alpha emission line profiles and for variations in brightness due to changes in the extinction and emission due to dust. This study is partially supported by the Natural Sciences and Engineering Research Council of Canada (NSERC).

Multi-Wavelength Implications of the Companion Star in eta Carinae

NASA Technical Reports Server (NTRS)

Madura, Thomas I.; Gull, Theodore R.; Groh, Jose H.; Owocki, Stanley P.; Okazaki, Atsuo; Hillier, D. John; Russell, Christopher

2012-01-01

Eta-Carinae is considered to be a massive colliding wind binary system with a highly eccentric (e approximately 0.9), 5.54-yr orbit. However, the companion star continues to evade direct detection as the primary dwarfs its emission at most wavelengths. Using three-dimensional (3-D) SPH simulations of eta-Car's colliding winds and radiative transfer codes, we are able to compute synthetic observables across multiple wavebands for comparison to the observations. The models show that the presence of a companion star has a profound influence on the observed HST/STIS UV spectrum and H-alpha line profiles, as well as the ground-based photometric monitoring. Here, we focus on the Bore Hole effect, wherein the fast wind from the hot secondary star carves a cavity in the dense primary wind, allowing increased escape of radiation from the hotter/deeper layers of the primary's extended wind photosphere. The results have important implications for interpretations of eta-Car's observables at multiple wavelengths.

Imaging accretion sources and circumbinary disks in young brown dwarfs

NASA Astrophysics Data System (ADS)

Reiners, Ansgar

2010-09-01

We propose to obtain deep WFC3/UVIS imaging observations of two accreting, nearby, young brown dwarf binaries. The first, 2M1207, is a brown dwarf with a planetary mass companion that became a benchmark in low-mass star formation and low-mass evolutionary models. The second, 2M0041, is a nearby young brown dwarf with clear evidence for accretion, but its space motion suggests a slightly higher age than the canonical accretion lifetime of 5-10 Myr. It has recently been discovered to be a binary and is likely to become a second benchmark object in this field. With narrow band images centered on the Halpha line that is indicative of accretion, we aim to determine the accretion ratio between the two components in each system. Halpha was observed in both systems but so far not spatially resolved. In particular, we want to search for accretion in the planetary mass companion of 2M1207. The evidence for accretion in 2M0041 and the possibility that it is in fact older than 10Myr suggests that the accretion lifetime is longer in brown dwarfs than in stars, and in particular that it is longer in brown dwarf binaries. Accretion could be sustained for a longer time if the accreting material is replenished by a circumbinary disk that might exist in both systems. We propose deep WFC/UVIS observations in the optical to search for circumbinary disks, similar to the famous disk around the binary TTauri system GG Tau.

Large-area imager of hydrogen leaks in fuel cells using laser-induced breakdown spectroscopy.

PubMed

Hori, M; Hayano, R S; Fukuta, M; Koyama, T; Nobusue, H; Tanaka, J

2009-10-01

We constructed a simple device, which utilized laser-induced breakdown spectroscopy to image H2 gas leaking from the surfaces of hydrogen fuel cells to ambient air. Nanosecond laser pulses of wavelength lambda=532 nm emitted from a neodymium-doped yttrium aluminum garnet laser were first compressed to a pulse length Deltat<1 ns using a stimulated Brillouin backscattering cell. Relay-imaging optics then focused this beam onto the H(2) leak and initiated the breakdown plasma. The Balmer-alpha (H-alpha) emission that emerged from this was collected with a 2-m-long macrolens assembly with a 90-mm-diameter image area, which covered a solid angle of approximately 1 x 10(-3)pi steradians seen from the plasma. The H-alpha light was isolated by two 100-mm-diameter interference filters with a 2 nm bandpass, and imaged by a thermoelectrically cooled charge-coupled device camera. By scanning the position of the laser focus, the spatial distribution of H2 gas over a 90-mm-diameter area was photographed with a spatial resolution of < or = 5 mm. Photoionization of the water vapor in the air caused a strong H-alpha background. By using pure N2 as a buffer gas, H2 leaks with rates of <1 cc/min were imaged. We also studied the possibilities of detecting He, Ne, or Xe gas leaks.

He I lines in B stars - Comparison of non-local thermodynamic equilibrium models with observations

NASA Technical Reports Server (NTRS)

Heasley, J. N.; Timothy, J. G.; Wolff, S. C.

1982-01-01

Profiles of He gamma-gamma 4026, 4387, 4471, 4713, 5876, and 6678 have been obtained in 17 stars of spectral type B0-B5. Parameters of the nonlocal thermodynamic equilibrium models appropriate to each star are determined from the Stromgren index and fits to H-alpha line profiles. These parameters yield generally good fits to the observed He I line profiles, with the best fits being found for the blue He I lines where departures from local thermodynamic equilibrium are relatively small. For the two red lines it is found that, in the early B stars and in stars with log g less than 3.5, both lines are systematically stronger than predicted by the nonlocal thermodynamic equilibrium models.

Study of Two Successive Three-ribbon Solar Flares Using BBSO/NST Observations

NASA Astrophysics Data System (ADS)

Wang, Haimin; Liu, Chang; Deng, Na; Zeng, Zhicheng; Xu, Yan; Jing, Ju; Cao, Wenda

2014-06-01

We studied two rarely observed three-ribbon flares (M1.9 and C9.2) on 2012 July 6 in NOAA AR 11515, which we found using Hα observations of 0.1 arcsec resolution from the New Solar Telescope and Ca II H images from Hinode. The flaring site is characterized by an intriguing "fish-bone-like" morphology evidenced by both Halpha images and a nonlinear force-free field (NLFFF) extrapolation, where two semi-parallel rows of low-lying, sheared loops connect an elongated, parasitic negative field with the sandwiching positive fields. The NLFFF model also shows that the two rows of loops are asymmetric in height and have opposite twists, and are enveloped by large-scale field lines including open fields. The two flares occurred in succession within half an hour and are located at the two ends of the flaring region. The three ribbons of each flare run parallel to the magnetic polarity inversion line, with the outer two lying in the positive field and the central one in the negative field. Both flares show surge-like flows in Halpha apparently toward the remote region, while the C9.2 flare is also accompanied by EUV jets possibly along the open field lines. Interestingly, the 12-25 keV hard X-ray sources of the C9.2 flare first line up with the central ribbon then shift to concentrate on the top of the higher branch of loops. These results are discussed in favor of reconnection along the coronal null line, producing the three flare ribbons and the associated ejections.

FIREBall, CHaS, and the diffuse universe

NASA Astrophysics Data System (ADS)

Hamden, Erika Tobiason

The diffuse universe, consisting of baryons that have not yet collapsed into structures such as stars, galaxies, etc., has not been well studied. While the intergalactic and circumgalactic mediums (IGM & CGM) may contain 30-40% of the baryons in the universe, this low density gas is difficult to observe. Yet it is likely a key driver of the evolution of galaxies and star formation through cosmic time. The IGM provides a reservoir of gas that can be used for star formation, if it is able to accrete onto a galaxy. The CGM bridges the IGM and the galaxy itself, as a region of both inflows from the IGM and outflows from galactic star formation and feedback. The diffuse interstellar medium (ISM) gas and dust in the galaxy itself may also be affected by the CGM of the galaxy. Careful observations of the ISM of our own Galaxy may provide evidence of interaction with the CGM. These three regions of low density, the IGM, CGM, and ISM, are arbitrary divisions of a continuous flow of low density material into and out of galaxies. My thesis focuses on observations of this low density material using existing telescopes as well as on the development of technology and instruments that will increase the sensitivity of future missions. I used data from the Galaxy Evolution Explorer (GALEX) to create an all sky map of the diffuse Galactic far ultraviolet (FUV) background, probing the ISM of our own galaxy and comparing to other Galactic all sky maps. The FUV background is primarily due to dust scattered starlight from bright stars in the Galactic plane, and the changing intensity across the sky can be used to characterize dust scattering asymmetry and albedo. We measure a consistent low level non-scattered isotropic component to the diffuse FUV, which may be due in small part to an extragalactic component. There are also several regions of unusually high FUV intensity given other Galactic quantities. Such regions may be the location of interactions between Galactic super-bubbles and the CGM. Other ways of probing the CGM including direct detection via emission lines. I built a proto-type of the Circumgalactic Halpha Spectrograph (CHalphaS), a wide-field, low-cost, narrow-band integral field unit (IFU) that is designed to observe Halpha emission from the CGM of nearby, low-z galaxies. This proto-type has had two recent science runs, with preliminary data on several nearby galaxies. Additional probes of the CGM are emission lines in the rest ultra-violet. These include OVI, Lyalpha, CIV, SiIII, CIII, CII, FeII, and MgII. Such lines are accessible for low redshift galaxies in the space UV, historically a difficult wavelength range in which to work due in part to low efficiency of the available detectors. I have worked with NASA's Jet Propulsion Laboratory to develop advanced anti-reflection (AR) coatings for use on thinned, delta-doped charge coupled device (CCD) detectors. These detectors have achieved world record quantum efficiency (QE) at UV wavelengths (>50% between 130 nm and 300nm), with the potential for even greater QE with a more complex coating. One of these AR coated detectors will be used on the Faint Intergalactic Redshifted Emission Balloon (FIREBall-2), a balloon-born UV spectrograph designed to observe the CGM at 205 nm via redshifted Lyalpha (at z=0.7), CIV (at z=0.3), and OVI (at z=1.0). FIREBall-2 will launch in the fall of 2015.

X-ray-emitting gas surrounding the spiral galaxy NGC 891

NASA Technical Reports Server (NTRS)

Bregman, Joel N.; Pidis, Rachel A.

1994-01-01

We observed the edge-on spiral galaxy NGC 891 with the Position Sensitive Proportional Counter (PSPC) on Roentgen Satellite (ROSAT) to search for how extraplanar gas expected in the galactic fountain model. Diffuse X-ray emission surrounds the disk with a Half Width at Half Maximum (HWHM) for the surface brightness perpendicular to the disk of 50 sec (2.4 kpc) and a radial extent of approximately 6.5 kpc, both of which are similar in extent to the extended H(alpha) and radio halo component; the implied density scale height for the hot gas is 7 kpc. The spectrum is best fitted with a hard stellar component and a soft diffuse gas component of temperature 3.6 x 10(exp 6) K. The density of this gas is 2 x 10(exp -3)/cu cm, the luminosity is 4.4 x 10(exp 39) ergs/s, the mass is 1 x 10(exp 8) solar mass, and the pressure (P/k) is 1.4 10(exp 4) K/cu cm. These data are consistent with this gas participating in a galactic fountain, where the material approaches hydrostatic equilibrium before cooling at a rate of 0.12 solar mass/yr. The cooled material may be responsible for some of the H(alpha) emission.

Magnetic field and electric current structure in the chromosphere

NASA Technical Reports Server (NTRS)

Dravins, D.

1974-01-01

The three-dimensional vector magnetic field structure in the chromosphere above an active region is deduced by using high-resolution H-alpha filtergrams together with a simultaneous digital magnetogram. An analog model of the field is made with 400 metal wires representing field lines that outline the H-alpha structure. The height extent of the field is determined from vertical field-gradient observations around sunspots, from observed fibril heights, and from an assumption that the sources of the field are largely local. The computed electric currents (typically 10 mA/sq m) are found to flow in patterns not similar to observed features and not parallel to magnetic fields. Force structures correspond to observed solar features; the dynamics to be expected include: downward motion in bipolar areas in the lower chromosphere, an outflow of the outer chromosphere into the corona with radially outward flow above bipolar plage regions, and motion of arch filament systems.

Differential expression of chicken dimerization cofactor of hepatocyte nuclear factor-1 (DcoH) and its novel counterpart, DcoHalpha.

PubMed Central

Kim, H; You, S; Foster, L K; Farris, J; Choi, Y J; Foster, D N

2001-01-01

We have used differential display PCR to study altered gene expression in immortalized chicken embryo fibroblasts (CEFs) that have been established in our laboratory. This technique resulted in the cloning of a novel counterpart of the previously cloned chicken dimerization cofactor of hepatocyte nuclear factor (HNF)-1 (cDcoH), which was identified as cDcoHalpha. The steady-state mRNA levels of cDcoHalpha were up-regulated in all immortal CEFs tested compared with primary CEF cells. cDcoH and cDcoHalpha showed opposite patterns of mRNA expression due to differential regulation of transcription rates, but not mRNA half-lives, in primary and immortal CEFs. Expression of cDcoHalpha increased in the late G1 and early S phases of the cell cycle, while cDcoH mRNA increased in the late S and G2/M phases. In contrast with consistent expression of both genes in primary quiescent cells, cDcoH mRNA, but not cDcoHalpha mRNA, was dramatically decreased in primary senescent cells. The highest levels of cDcoHalpha mRNA were found in the kidney, liver, heart and ovarian follicles, while the major tissues expressing cDcoH were hypothalamus, kidney and liver. cDcoH and cDcoHalpha probes did not cross-hybridize to human hepatocyte mRNA. When transfected into human HepG2 cells, both cDcoH and cDcoHalpha showed similar functional activity as measured by increased expression of a reporter gene, as well as alpha-fetoprotein and albumin genes that both contain HNF-1 binding elements in their promoters. Our results suggest that the novel chicken DcoHalpha might function as a transcriptional cofactor for HNF-1 in specific cellular-environmental states. PMID:11237869

STRUCTURE IN THE ROTATION MEASURE SKY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stil, J. M.; Taylor, A. R.; Sunstrum, C.

2011-01-01

An analysis of structure in rotation measure (RM) across the sky based on the RM catalog of Taylor et al. is presented. Several resolved RM structures are identified with structure in the local interstellar medium, including radio loops I, II, and III, the Gum nebula, and the Orion-Eridanus superbubble. Structure functions (SFs) of RM are presented for selected areas, and maps of SF amplitude and slope across the sky are compared with H{alpha} intensity and diffuse polarized intensity. RM variance on an angular scale of 1{sup 0} is correlated with length of the line of sight through the Galaxy, withmore » a contribution from local structures. The slope of the SFs is less concentrated to the Galactic plane and less correlated with length of the line of sight through the Galaxy, suggesting a more local origin for RM structure on angular scales {approx}10{sup 0}. The RM variance is a factor of {approx}2 higher toward the South Galactic Pole than toward the North Galactic Pole, reflecting a more wide-spread asymmetry between the northern and southern Galactic hemispheres. Depolarization of diffuse Galactic synchrotron emission at latitudes <30{sup 0} can be explained largely by Faraday dispersion related to small-scale variance in RM, but the errors allow a significant contribution from differential Faraday rotation along the line of sight.« less

Surveys, Fields, and Collections in the Astronomical Photographic Data Archive at PARI

NASA Astrophysics Data System (ADS)

Cline, J. D.; Castelaz, M. W.; Barker, T.

2014-01-01

A diverse set of photometric, astrometric, spectral and surface brightness data exist on more than 100 years of photographic glass plates. About 20 percent of the plates in North America are located in the Astronomical Photographic Data Archive (APDA) at the Pisgah Astronomical Research Institute (PARI). APDA was established in November 2007 and is dedicated to the task of collecting, restoring, preserving and storing astronomical photographic data and PARI continues to accept collections. APDA is also tasked with scanning each image and establishing a database of images that can be accessed via the Internet by the global community of scientists, researchers and students. APDA is a new type of astronomical observatory - one that harnesses analog data of the night sky taken for more than a century and making that data available in a digital format. APDA currently has 50 collections with more than 250,000 plates taken for QSO identification, parallax measurements, spectral classification and monitoring, Magellanic Cloud studies, H-alpha emission star surveys, novae evolution, and astrometry of asteroids, outer planet satellites and Pluto. Some examples of collections include the complete set of the Henize H-alpha Southern Survey plates taken between 1949 and 1952 (Henize 1954, AJ, 59, 325), the Case Western Objective Prism All Sky Survey from 1958-1976 (e.g. Pesch, Sanduleak, and Stephenson 1996, ApJS, 103, 513), and QSO Survey from 1980 to 1991 (e.g. Pesch and Stephenson 1983, ApJS, 51, 171). We feature the contents of the APDA collections to provide the opportunity to the astronomical community to advance new and established areas of study.

An Optical Study of the Circumstellar Environment Around the Crab Nebula

NASA Technical Reports Server (NTRS)

Fesen, Robert A.; Shull, J. Michael; Hurford, Alan P.

1997-01-01

Long-slit spectra of two peripheral regions around the Crab Nebula show no H(alpha) emission down to a flux level of 1.5 x 10(exp -7)erg/sq cm s sr (0.63 Rayleigh), corresponding to an emission measure limit of 4.2 cm(sup - 6) pc (3(sigma)) assuming A(sub V)= 1.6(sup m) and T(sub e)=7000 K. This is below the flux levels reported by Murdin & Clark (Nature, 294, 543 (198 1)) for an H(alpha) halo around the Crab. Narrow H(beta) emission as described by Murdin (MNRAS, 269, 89 (1994)) is detected but appears to be Galactic emission unassociated with the remnant. A review of prior searches indicates no convincing observational evidence to support either a high- or low-velocity envelope around the remnant. Spectral scans confirm a well-organized, N-S expansion asymmetry of the filaments with a approx. 500 km/s central velocity constriction as described by MacAlpine et al. (ApJ, 342, 364 (1989)) and Lawrence et (it. (AJ, 109, 2635 (1995)] but questioned by Hester et al. (ApJ, 448, 240 (1995)). The velocity pinching appears to coincide with an cast-west chain of bright [O III] and helium-rich filaments. This expansion asymmetry might be the result of ejecta interaction with a disk of circumstellar matter, but such a model may be inconsistent with H and He filament abundances in the velocity constriction zone. A re-analysis of the remnant's total mass suggests that the filaments contain 4.6 +/- 1.8 M(solar) in ionized and neutral cas, about twice that of earlier estimates. For a 10M(solar) progenitor, this suggests that approx.equals 4M(solar) remains to be detected in an extended halo or wind.

Observations of emission in bright, low redshift quasars

NASA Technical Reports Server (NTRS)

1983-01-01

Ultraviolet, infrared, and optical spectra were combined to obtain a data set sample as broad as possible in the range of hydrogen lines in individual quasars. From the measured Lyman fluxes, coupled with Balmer and Paschen line fluxes measured in these same objects, an effort was made to establish observational constraints that would guide models of the broad emission line regions of quasars. It was found that IUE spectra were generally of sufficiently high quality to derive line profiles of the ultraviolet lines Lyman alpha and CIV 1550 A, which were compared to the Balmer line profiles. The objects observed and the line fluxes are tabulated. Plots of line profiles are included.

Latitude dependence of solar wind velocity observed at not less than 1 AU

NASA Technical Reports Server (NTRS)

Mitchell, D. G.; Roelof, E. C.; Wolfe, J. H.

1981-01-01

The large-scale solar wind velocity structure in the outer heliosphere has been systematically analyzed for Carrington rotations 1587-1541 (March 1972 to April 1976). Spacecraft data were taken from Imp 7/8 at earth, Pioneer 6, 8, and 9 near 1 AU, and Pioneer 10 and 11 between 1.6 and 5 AU. Using the constant radial velocity solar wind approximation to map all of the velocity data to its high coronal emission heliolongitude, the velocity structure observed at different spacecraft was examined for latitudinal dependence and compared with coronal structure in soft X-rays and H-alpha absorption features. The constant radial velocity approximation usually remains self-consistent in decreasing or constant velocity solar wind out to 5 AU, enabling us to separate radial from latitudinal propagation effects. Several examples of sharp nonmeridional stream boundaries in interplanetary space (about 5 deg latitude in width), often directly associated with features in coronal X-rays and H-alpha were found.

Lyman continuum observations of solar flares

NASA Technical Reports Server (NTRS)

Machado, M. E.; Noyes, R. W.

1978-01-01

A study is made of Lyman continuum observations of solar flares, using data obtained by the EUV spectroheliometer on the Apollo Telescope Mount. It is found that there are two main types of flare regions: an overall 'mean' flare coincident with the H-alpha flare region, and transient Lyman continuum kernels which can be identified with the H-alpha and X-ray kernels observed by other authors. It is found that the ground level hydrogen population in flares is closer to LTE than in the quiet sun and active regions, and that the level of Lyman continuum formation is lowered in the atmosphere from a mass column density .000005 g/sq cm in the quiet sun to .0003 g/sq cm in the mean flare, and to .001 g/sq cm in kernels. From these results the amount of chromospheric material 'evaporated' into the high temperature region is derived, which is found to be approximately 10 to the 15th g, in agreement with observations of X-ray emission measures.

Ultraviolet continuum and H2 fluorescent emission in Herbig-Haro objects 43 and 47

NASA Technical Reports Server (NTRS)

Schwartz, R. D.

1983-01-01

IUE short wavelength spectra are presented for the low excitation Herbig-Haro objects HH 43 and HH 47. In the former, several emission lines in the Lyman band of H2 from an excited state are observed which are due to fluorescence from the H Ly-alpha line pumping a lower state (that is in turn excited by a low-velocity shock wave). No evidence of highly ionized gas emission is found in the UV spectra, and both objects exhibit a UV continuum which peaks in the vicinity of 1500 A and is probably caused by H two-photon emission enhanced by low velocity shock collisional excitation.

New upper limits on the local metagalactic ionizing radiation density

NASA Technical Reports Server (NTRS)

Vogel, Stuart N.; Weymann, Ray; Rauch, Michael; Hamilton, Tom

1995-01-01

We have obtained H-alpha observations with the Maryland-Caltech Fabry-Perot Spectrometer attached to the Cassegrain focus of the 1.5 m telescope at Palomer Observatory in order to set limits on the number of ionizing photons from the local metagalactic radiation field. We have observed the SW component of the Haynes-Giovanelli cloud H I 1225+01, an intergalactic cloud which should be optimum for measuring the metagalactic flux because it is nearly opaque to ionizing photons, it does not appear to be significantly shielded from the metagalactic radiation field, and the limits on embedded or nearby ionizing sources are unusually low. For the area of the cloud with an H I column density greater than 10(exp 19)/sq cm we set a 2 sigma limit of 1.1 x 10(exp -19) ergs/sq cm/s/sq arcsec (20 mR) for the surface brightness of diffuse H-alpha. This implies a 2 sigma upper limit on the incident one-sided ionizing flux of Phi(sub ex) is less than 3 x 10(exp 4)/sq cm/s. For a radiation field of the form J(sub nu) is approximately nu(exp -1.4), this yields a firm 2 sigma upper limit on the local metagalactic photoionization rate of Gamma is less than 2 x 10(exp -13)/s, and an upper limit for the radiation field J(sub nu) at the Lyman limit of J(sub nu0) is less than 8 x 10(exp -23) ergs/sq cm/Hz/sr. We discuss previous efforts to constrain the metagalactic ionizing flux using H-alpha surface brightness observations and also other methods, and conclude that our result places the firmest upper limit on this flux. We also observed the 7 min diameter region centered on 3C 273 in which H-alpha emission at a velocity of approximately 1700 km/s was initially reported by Williams and Schommer. In agreement with T. B. Williams (private communication) we find the initial detection was spurious. We obtain a 2 sigma upper limit of 1.8 x 10(exp -19) ergs/sq cm/s/sq arcsec (32 mR) for the mean surface brightness of diffuse H-alpha, about a factor of 6 below the published value.

Investigating the Near-Infrared Properties of Planetary Nebulae II. Medium Resolution Spectra. 2; Medium Resolution Spectra

NASA Technical Reports Server (NTRS)

Hora, Joseph L.; Latter, William B.; Deutsch, Lynne K.

1998-01-01

We present medium-resolution (R approximately 700) near-infrared (lambda = 1 - 2.5 micrometers) spectra of a sample of planetary nebulae (PNe). A narrow slit was used which sampled discrete locations within the nebulae; observations were obtained at one or more positions in the 41 objects included in the survey. The PN spectra fall into one of four general categories: H1 emission line-dominated PNe, H1 and H2 emission line PNe, H2 emission line-dominated PNe, and continuum-dominated PNe. These categories correlate with morphological type, with the elliptical PNe falling into the first group, and the bipolar PNe primarily in the H2 and continuum emission groups. The categories also correlate with C/O ratio, with the O-rich objects falling into the first group and the C-rich objects in the groups. Other spectral features were observed in all catagories, such as continuum emission from the central star, and warm dust continuum emission towards the long wavelength end of the spectra. H2 was detected in four PNe in this survey for the first time. An analysis was performed using the H2 line ratios in all of the PN spectra in the survey where a sufficient number of lines were observed to determine the ortho-to-para ratio and the rotational and vibrational excitation temperatures of the H-2 in those objects. One unexpected result from this analysis is that the H-2 is excited by absorption of ultraviolet photons in most of the PNe, although there are several PNe in which collisional excitation plays an important role. The correlation between bipolar morphology and H2 emission has been strengthened with the new detections of H2 in this survey.

A search for optical pulsations from GX 1+4 at H-alpha

NASA Technical Reports Server (NTRS)

Krzeminski, W.; Priedhorsky, W. C.

1978-01-01

H-alpha observations of the binary-star candidate for the slowly pulsating hard X-ray source GX 1+4 are reported which were undertaken to search for pulsations in the H-alpha flux that are synchronous with the X-ray period of about 2 min. No significant periodic variation of the candidate star was detected in the frequency band searched. Three-sigma upper limits of 1.7% (sinusoidal pulse shape) and 0.7% (X-ray pulse shape) are set for the pulsed fraction of the H-alpha flux. It is noted that because of possible diffusion from a cloud that is optically thick to Balmer radiation, the observed lack of pulsations in the H-alpha flux need not compromise the identification of GX 1+4 with the candidate star.

VLT/X-shooter Spectroscopy of a dusty planetary nebula discovered with Spitzer/IRS

NASA Astrophysics Data System (ADS)

Oliveira, I.; Overzier, R. A.; Pontoppidan, K. M.; van Dishoeck, E. F.; Spezzi, L.

2011-02-01

As part of a mid-infrared spectroscopic survey of young stars with the Spitzer Space Telescope, an unclassified red emission line object was discovered. Based on its high ionization state indicated by the Spitzer spectrum, this object could either be a dusty supernova remnant (SNR) or a planetary nebula (PN). In this research note, the object is classified and the available spectroscopic data are presented to the community for further analysis. UV/optical/NIR spectra were obtained during the science verification run of the VLT/X-shooter. A large number of emission lines are identified allowing the determination of the nature of this object. The presence of strong, narrow (Δv ~8 - 74 km s-1) emission lines, combined with very low line ratios of, e.g., [N ii]/Hα and [S ii]/Hα show that the object is a PN that lies at an undetermined distance behind the Serpens Molecular Cloud. This illustrates the potential of X-shooter as an efficient tool for constraining the nature of faint sources with unknown spectral properties or colors.

DISSECTING THE POWER SOURCES OF LOW-LUMINOSITY EMISSION-LINE GALAXY NUCLEI VIA COMPARISON OF HST-STIS AND GROUND-BASED SPECTRA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Constantin, Anca; Castillo, Christopher A.; Shields, Joseph C.

Using a sample of ∼100 nearby line-emitting galaxy nuclei, we have built the currently definitive atlas of spectroscopic measurements of Hα and neighboring emission lines at subarcsecond scales. We employ these data in a quantitative comparison of the nebular emission in Hubble Space Telescope (HST) and ground-based apertures, which offer an order-of-magnitude difference in contrast, and provide new statistical constraints on the degree to which transition objects and low-ionization nuclear emission-line regions (LINERs) are powered by an accreting black hole at ≲10 pc. We show that while the small-aperture observations clearly resolve the nebular emission, the aperture dependence in themore » line ratios is generally weak, and this can be explained by gradients in the density of the line-emitting gas: the higher densities in the more nuclear regions potentially flatten the excitation gradients, suppressing the forbidden emission. The transition objects show a threefold increase in the incidence of broad Hα emission in the high-resolution data, as well as the strongest density gradients, supporting the composite model for these systems as accreting sources surrounded by star-forming activity. The narrow-line LINERs appear to be the weaker counterparts of the Type 1 LINERs, where the low accretion rates cause the disappearance of the broad-line component. The enhanced sensitivity of the HST observations reveals a 30% increase in the incidence of accretion-powered systems at z ≈ 0. A comparison of the strength of the broad-line emission detected at different epochs implies potential broad-line variability on a decade-long timescale, with at least a factor of three in amplitude.« less

GAS MOTION STUDY OF Ly{alpha} EMITTERS AT z {approx} 2 USING FUV AND OPTICAL SPECTRAL LINES {sup ,}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hashimoto, Takuya; Shimasaku, Kazuhiro; Nakajima, Kimihiko

2013-03-01

We present the results of Magellan/MMIRS and Keck/NIRSPEC spectroscopy for five Ly{alpha} emitters (LAEs) at z {approx_equal} 2.2 for which high-resolution FUV spectra from Magellan/MagE are available. We detect nebular emission lines including H{alpha} on the individual basis and low-ionization interstellar (LIS) absorption lines in a stacked FUV spectrum, and measure average offset velocities of the Ly{alpha} line, {Delta}v {sub Ly{alpha}}, and LIS absorption lines, {Delta}v {sub abs}, with respect to the systemic velocity defined by the nebular lines. For a sample of eight z {approx} 2-3 LAEs without active galactic nucleus from our study and the literature, we obtainmore » {Delta}v {sub Ly{alpha}} = 175 {+-} 35 km s{sup -1}, which is significantly smaller than that of Lyman-break Galaxies (LBGs), {Delta}v {sub Ly{alpha}} {approx_equal} 400 km s{sup -1}. The stacked FUV spectrum gives {Delta}v {sub abs} = -179 {+-} 73 km s{sup -1}, comparable to that of LBGs. These positive {Delta}v {sub Ly{alpha}} and negative {Delta}v {sub abs} suggest that LAEs also have outflows. In contrast to LBGs, however, the LAEs' {Delta}v {sub Ly{alpha}} is as small as |{Delta}v {sub abs}|, suggesting low neutral hydrogen column densities. Such a low column density with a small number of resonant scattering may cause the observed strong Ly{alpha} emission of LAEs. We find an anti-correlation between Ly{alpha} equivalent width (EW) and {Delta}v {sub Ly{alpha}} in a compilation of LAE and LBG samples. Although its physical origin is not clear, this anti-correlation result appears to challenge the hypothesis that a strong outflow, by means of a reduced number of resonant scattering, produces a large EW. If LAEs at z > 6 have similarly small {Delta}v {sub Ly{alpha}} values, constraints on the reionization history derived from the Ly{alpha} transmissivity may need to be revised.« less

An x-ray nebula associated with the millisecond pulsar B1957+20.

PubMed

Stappers, B W; Gaensler, B M; Kaspi, V M; van der Klis, M; Lewin, W H G

2003-02-28

We have detected an x-ray nebula around the binary millisecond pulsar B1957+20. A narrow tail, corresponding to the shocked pulsar wind, is seen interior to the known Halpha bow shock and proves the long-held assumption that the rotational energy of millisecond pulsars is dissipated through relativistic winds. Unresolved x-ray emission likely represents the shock where the winds of the pulsar and its companion collide. This emission indicates that the efficiency with which relativistic particles are accelerated in the postshock flow is similar to that for young pulsars, despite the shock proximity and much weaker surface magnetic field of this millisecond pulsar.

Performance of spectral MSE diagnostic on C-Mod and ITER

NASA Astrophysics Data System (ADS)

Liao, Ken; Rowan, William; Mumgaard, Robert; Granetz, Robert; Scott, Steve; Marchuk, Oleksandr; Ralchenko, Yuri; Alcator C-Mod Team

2015-11-01

Magnetic field was measured on Alcator C-mod by applying spectral Motional Stark Effect techniques based on line shift (MSE-LS) and line ratio (MSE-LR) to the H-alpha emission spectrum of the diagnostic neutral beam atoms. The high field of Alcator C-mod allows measurements to be made at close to ITER values of Stark splitting (~ Bv⊥) with similar background levels to those expected for ITER. Accurate modeling of the spectrum requires a non-statistical, collisional-radiative analysis of the excited beam population and quadratic and Zeeman corrections to the Stark shift. A detailed synthetic diagnostic was developed and used to estimate the performance of the diagnostic at C-Mod and ITER parameters. Our analysis includes the sensitivity to view and beam geometry, aperture and divergence broadening, magnetic field, pixel size, background noise, and signal levels. Analysis of preliminary experiments agree with Kinetic+(polarization)MSE EFIT within ~2° in pitch angle and simulations predict uncertainties of 20 mT in | B | and <2° in pitch angle. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Fusion Energy Sciences under Award Number DE-FG03-96ER-54373 and DE-FC02-99ER54512.

A SOLAR TORNADO OBSERVED BY AIA/SDO: ROTATIONAL FLOW AND EVOLUTION OF MAGNETIC HELICITY IN A PROMINENCE AND CAVITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xing; Morgan, Huw; Leonard, Drew

During 2011 September 24, as observed by the Atmospheric Imaging Assembly instrument of the Solar Dynamic Observatory and ground-based H{alpha} telescopes, a prominence and associated cavity appeared above the southwest limb. On 2011 September 25 8:00 UT, material flows upward from the prominence core along a narrow loop-like structure, accompanied by a rise ({>=}50,000 km) of the prominence core and the loop. As the loop fades by 10:00, small blobs and streaks of varying brightness rotate around the top part of the prominence and cavity, mimicking a cyclone. The most intense and coherent rotation lasts for over three hours, withmore » emission in both hot ({approx}1 MK) and cold (hydrogen and helium) lines. We suggest that the cyclonic appearance and overall evolution of the structure can be interpreted in terms of the expansion of helical structures into the cavity, and the movement of plasma along helical structures which appears as a rotation when viewed along the helix axis. The coordinated movement of material between prominence and cavity suggests that they are structurally linked. Complexity is great due to the combined effect of these actions and the line-of-sight integration through the structure which contains tangled fields.« less

Nova Mus 2008 = QY Mus

NASA Astrophysics Data System (ADS)

Templeton, Matthew R.

2008-10-01

Nova Mus 2008 = QY Mus was discovered by William Liller, Vina del Mar, Chile, on 2008 September 28.998 UT at magnitude 8.6 (Tech Pan film + orange filter). The position is RA = 13h 16m 36.44s , Dec = -67d 36m 47.8s (from P. Nelson). This object was announced as a nova in IAU Circular 8990 (Daniel W.E. Green, editor). The nova classification was determined using low-resolution spectra by W. Liller indicating the presence of broad H-alpha lines at least 2300 angstroms wide. Several observers confirmed the nova and provided photometry. The position above was provided by Peter Nelson (Ellinbank, Vic., Aus.), and is averaged from four separate exposures (rms error approx. 0.4 arcseconds). The GCVS team have formally designated Nova Mus 2008 as QY MUS. Observations should be reported to the AAVSO International Database as QY MUS.

The Development of New Atmospheric Models for K and M DwarfStars with Exoplanets

NASA Astrophysics Data System (ADS)

Linsky, Jeffrey L.

2018-01-01

The ultraviolet and X-ray emissions of host stars play critical roles in the survival and chemical composition of the atmospheres of their exoplanets. The need to measure and understand this radiative output, in particular for K and M dwarfs, is the main rationale for computing a new generation of stellar models that includes magnetically heated chromospheres and coronae in addition to their photospheres. We describe our method for computing semi-empirical models that includes solutions of the statistical equilibrium equations for 52 atoms and ions and of the non-LTE radiative transfer equations for all important spectral lines. The code is an offspring of the Solar Radiation Physical Modelling system (SRPM) developed by Fontenla et al. (2007--2015) to compute one-dimensional models in hydrostatic equilibrium to fit high-resolution stellar X-ray to IR spectra. Also included are 20 diatomic molecules and their more than 2 million spectral lines. Our-proof-of-concept model is for the M1.5 V star GJ 832 (Fontenla et al. ApJ 830, 154 (2016)). We will fit the line fluxes and profiles of X-ray lines and continua observed by Chandra and XMM-Newton, UV lines observed by the COS and STIS instruments on HST (N V, C IV, Si IV, Si III, Mg II, C II, and O I), optical lines (including H$\\alpha$, Ca II, Na I), and continua. These models will allow us to compute extreme-UV spectra, which are unobservable but required to predict the hydrodynamic mass-loss rate from exoplanet atmospheres, and to predict panchromatic spectra of new exoplanet host stars discovered after the end of the HST mission.This work is supported by grant HST-GO-15038 from the Space Telescope Science Institute to the Univ. of Colorado

GEOMETRIC OFFSETS ACROSS SPIRAL ARMS IN M51: NATURE OF GAS AND STAR FORMATION TRACERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Louie, Melissa; Koda, Jin; Egusa, Fumi, E-mail: melissa.louie@stonybrook.edu

We report measurements of geometric offsets between gas spiral arms and associated star-forming regions in the grand-design spiral galaxy M51. These offsets are a suggested measure of the star formation timescale after the compression of gas at spiral arm entry. A surprising discrepancy, by an order of magnitude, has been reported in recent offset measurements in nearby spiral galaxies. Measurements using CO and H{alpha} emission find large and ordered offsets in M51. On the contrary, small or non-ordered offsets have been found using the H I 21 cm and 24 {mu}m emissions, possible evidence against gas flow through spiral arms,more » and thus against the conventional density-wave theory with a stationary spiral pattern. The goal of this paper is to understand the cause of this discrepancy. We investigate potential causes by repeating those previous measurements using equivalent data, methods, and parameters. We find offsets consistent with the previous measurements and conclude that the difference of gas tracers, i.e., H I versus CO, is the primary cause. The H I emission is contaminated significantly by the gas photodissociated by recently formed stars and does not necessarily trace the compressed gas, the precursor of star formation. The H I gas and star-forming regions coincide spatially and tend to show small offsets. We find mostly positive offsets with substantial scatter between CO and H{alpha}, suggesting that gas flow through spiral arms (i.e., density wave) though the spiral pattern may not necessarily be stationary.« less

A Chandra X-ray Study of Cygnus A. 2; The Nucleus

NASA Technical Reports Server (NTRS)

Young, Andrew J.; Wilson, Andrew; Terashima, Yuichi; Arnaud, Keith A.; Smith, David A.; White, Nicholas E. (Technical Monitor)

2002-01-01

We report Chandra Advanced CCD Imaging Spectrometer and quasi-simultaneous Rossi X-Ray Timing Explorer (RXTE) observations of the nearby, powerful radio galaxy Cygnus A, with the present paper focusing on the properties of the active nucleus. In the Chandra observation, the hard (less than a few keV) X-ray emission is spatially unresolved with a size is approximately 1" (1.5 kpc, H(sub 0) = 50 km/s/Mpc) and coincides with the radio and near-infrared nuclei. In contrast, the soft (less than 2 keV) emission exhibits a bipolar nebulosity that aligns with the optical bipolar continuum and emission-line structures and approximately with the radio jet. In particular, the soft X-ray emission corresponds very well with the [O III] (lambda)5007 and H(alpha) + [N II] lambda(lambda)6548, 6583 nebulosity imaged with Hubble Space Telescope. At the location of the nucleus, there is only weak soft X-ray emission, an effect that may be intrinsic or result from a dust lane that crosses the nucleus perpendicular to the source axis. The spectra of the various X-ray components have been obtained by simultaneous fits to the six detectors. The compact nucleus is detected to 100 keV and is well described by a heavily absorbed power-law spectrum with Gamma(sub h) = 1.52(sup + 0.12, sub -0.12) (similar to other 0.12 narrow-line radio galaxies) and equivalent hydrogen column N(sub H)(nuc) = 2.0(sup +0.1, sub -0.1) x 10(exp 23)/sq cm. This 0.2 column is compatible with the dust obscuration to the near-infrared source for a normal gas-to-dust ratio. The soft (less than 2 keV) emission from the nucleus may be described by a power-law spectrum with the same index (i.e., Gamma(sub l) = Gamma(sub h), although direct fits suggest a slightly larger value for Gamma(sub l). Narrow emission lines from highly ionized neon and silicon, as well as a "neutral" Fe K(alpha) line, are detected in the nucleus and its vicinity (r approximately less than 2 kpc). The equivalent width (EW) of the Fe K(alpha) line (182(sup +40, sub -54) eV) is in good agreement with theoretical predictions for the EW versus N(sub H)(nuc) relationship in various geometries. An Fe K edge is also seen. The RXTE observations indicate a temperature of kT = 6.9(sup +0., sub -1.0) keV for the cluster gas (discussed in Paper III of this series) and cluster emission lines of Fe K(alpha) and Fe K(beta) and/or Ni K(alpha). We consider the possibility that the extended soft X-ray emission is electron-scattered nuclear radiation. Given that 1% of the unabsorbed 2 - 10 keV nuclear radiation would have to be scattered, the necessary gas column [N(sub H)(Scattering) approx. = 3.5 x 10(exp 22)/sq cm] would absorb the X-rays rather than scatter them if the gas is cold. Thus, the scattering plasma must be highly ionized. If this ionization is achieved through photoionization by the nucleus, the ionization parameter zeta greater than 1 ergs cm/s and the electron density n(sub e) approx. = 6 cc given the observed distance of the soft X-ray emission from the nucleus. The electron column density inferred from the X-ray observations is much too low to account for the extended optical scattered light, strongly suggesting that the polarized optical light is scattered by dust. The presence of highly ionized Ne lines in the soft X-ray spectrum requires 20 ergs cm/s approximately less than zeta approximately less than 300 ergs cm/s these lines may originate closer to the nucleus than the extended soft continuum or in a lower density gas. A collisionally ionized thermal model of the extended soft X-rays cannot be ruled out but is unattractive in view of the low metal abundance required (Z = 0.03 Z(mass)). The hard X-ray to far-infrared ratio for the nucleus of Cygnus A is similar to that seen in Seyfert 1 and unobscured radio galaxies. By means of the correlation between hard X-ray luminosity and nuclear optical absolute magnitude for these classes of object, we estimate M(sub B) = -22.4 for Cygnus A, near the .borderline between Seyfert galaxies and QSOs.

The Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey III. Optical Identifications and New Redshifts

NASA Technical Reports Server (NTRS)

Pursimo, Tapio; Ojha, Roopesh; Jauncey, David L.; Rickett, Barney J.; Dutka, Michael S.; Koay, Jun Yi; Lovell, James E. J.; Bignall, Hayley E.; Kedziora-Chudczer, Lucyna; Macquart, Jean-Pierre

2013-01-01

Intraday variability (IDV) of the radio emission from active galactic nuclei is now known to be predominantly due to interstellar scintillation (ISS). The MASIV (The Microarcsecond Scintillation Induced Variability) survey of 443 at spectrum sources revealed that the IDV is related to the radio flux density and redshift. A study of the physical properties of these sources has been severely handicapped by the absence of reliable redshift measurements for many of these objects. This paper presents 79 new redshifts and a critical evaluation of 233 redshifts obtained from the literature. We classify spectroscopic identifications based on emission line properties, finding that 78% of the sources have broad emission lines and are mainly FSRQs. About 16% are weak lined objects, chiefly BL Lacs, and the remaining 6% are narrow line objects. The gross properties (redshift, spectroscopic class) of the MASIV sample are similar to those of other blazar surveys. However, the extreme compactness implied by ISS favors FSRQs and BL Lacs in the MASIV sample as these are the most compact object classes. We confirm that the level of IDV depends on the 5 GHz flux density for all optical spectral types. We find that BL Lac objects tend to be more variable than broad line quasars. The level of ISS decreases substantially above a redshift of about two. The decrease is found to be generally consistent with ISS expected for beamed emission from a jet that is limited to a fixed maximum brightness temperature in the source rest frame.

Bayesian Redshift Classification of Emission-line Galaxies with Photometric Equivalent Widths

NASA Astrophysics Data System (ADS)

Leung, Andrew S.; Acquaviva, Viviana; Gawiser, Eric; Ciardullo, Robin; Komatsu, Eiichiro; Malz, A. I.; Zeimann, Gregory R.; Bridge, Joanna S.; Drory, Niv; Feldmeier, John J.; Finkelstein, Steven L.; Gebhardt, Karl; Gronwall, Caryl; Hagen, Alex; Hill, Gary J.; Schneider, Donald P.

2017-07-01

We present a Bayesian approach to the redshift classification of emission-line galaxies when only a single emission line is detected spectroscopically. We consider the case of surveys for high-redshift Lyα-emitting galaxies (LAEs), which have traditionally been classified via an inferred rest-frame equivalent width (EW {W}{Lyα }) greater than 20 Å. Our Bayesian method relies on known prior probabilities in measured emission-line luminosity functions and EW distributions for the galaxy populations, and returns the probability that an object in question is an LAE given the characteristics observed. This approach will be directly relevant for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), which seeks to classify ˜106 emission-line galaxies into LAEs and low-redshift [{{O}} {{II}}] emitters. For a simulated HETDEX catalog with realistic measurement noise, our Bayesian method recovers 86% of LAEs missed by the traditional {W}{Lyα } > 20 Å cutoff over 2 < z < 3, outperforming the EW cut in both contamination and incompleteness. This is due to the method’s ability to trade off between the two types of binary classification error by adjusting the stringency of the probability requirement for classifying an observed object as an LAE. In our simulations of HETDEX, this method reduces the uncertainty in cosmological distance measurements by 14% with respect to the EW cut, equivalent to recovering 29% more cosmological information. Rather than using binary object labels, this method enables the use of classification probabilities in large-scale structure analyses. It can be applied to narrowband emission-line surveys as well as upcoming large spectroscopic surveys including Euclid and WFIRST.

Thermodynamics of the Solar Corona and Evolution of the Solar Magnetic Field as Inferred from the Total Solar Eclipse Observations of 11 July 2010

NASA Technical Reports Server (NTRS)

Habbal, Shadia Rifai; Druckmueller, Miloslav; Morgan, Huw; Ding, Adalbert; Johnson, Judd; Druckmuellerova, Hana; Daw, Adrian; Arndt, Martina B.; Dietzel, Martin; Saken, Jon

2011-01-01

We report on multi-wavelength observations of the corona taken simultaneously in broadband white light, and in seven spectral lines, H-alpha 656.3 nm, Fe IX 435.9 nm, Fe X 637.4 nm, Fe XI 789.2 nm, Fe XIII 1074.7 nm, Fe XIV 530.3 nm and Ni XV 670.2 nm. The observations were made during the total solar eclipse of 11 July 2010 from the atoll of Tatakoto in French Polynesia. Simultaneous imaging with narrow bandpass filters in each of these spectral lines and in their corresponding underlying continua maximized the observing time during less than ideal observing conditions and yielded outstanding quality data. The application of two complementary image processing techniques revealed the finest details of coronal structures at 1" resolution in white light, and 6.5" in each of the spectral lines. This comprehensive wavelength coverage confirmed earlier eclipse findings that the solar corona has a clear two-temperature structure: The open field lines, expanding outwards from the solar surface, are characterized by electron temperatures near 1 X 10(exp 6) K, while the hottest plasma around 2X 10(exp 6) K resides in loop-like structures forming the bulges of streamers. The first images of the corona in the forbidden lines of Fe IX and Ni XV, showed that there was very little coronal plasma at temperatures below 5 X 10(exp 5) K and above 2.5X 10(exp 6) K. The data also enabled temperature differentiations as low as 0:2 X 10(exp 6) K in different density structures. These observations showed how the passage of CMEs through the corona, prior to totality, produced large scale ripples and very sharp streaks, which could be identified with distinct temperatures for the first time. The ripples were most prominent in emission from spectral lines associated with temperatures around 10(exp 6) K. The most prominent streak was associated with a conical-shaped void in the emission from the coolest line of Fe IX and from the hottest line of Ni XV. A prominence, which erupted prior to totality, appeared in the shape of a hook in the cooler lines of Fe X and Fe XI, spanning 0.5 R(solar) in extent starting at a heliocentric distance of 1.3 R(solar), with a complex trail of hot and cool twisted structures connecting it to the solar surface. Simultaneous Fe X 17.4 nm observations from space by Proba2/SWAP provided an ideal opportunity for comparing emission from a coronal forbidden line, namely Fe X 637.4 nm, with a space-based EUV allowed line. Comparison of the Fe X 17.4 nm and 637.4 nm emission provided the first textbook example of the role of radiative excitation in extending the detectability of coronal emission to much larger heliocentric distances than its collisionally excited component. These eclipse observations demonstrate the unique capabilities of coronal forbidden lines for exploring the evolution of the coronal magnetic field in the heliocentric distance range of 1 - 3 R(solar), which is currently inaccessible to any space-borne or ground-based observatory.

The RMS survey: near-IR spectroscopy of massive young stellar objects

NASA Astrophysics Data System (ADS)

Cooper, H. D. B.; Lumsden, S. L.; Oudmaijer, R. D.; Hoare, M. G.; Clarke, A. J.; Urquhart, J. S.; Mottram, J. C.; Moore, T. J. T.; Davies, B.

2013-04-01

Near-infrared H- and K-band spectra are presented for 247 objects, selected from the Red MSX Source (RMS) survey as potential young stellar objects (YSOs). 195 (˜80 per cent) of the targets are YSOs, of which 131 are massive YSOs (LBOL > 5 × 103 L⊙, M > 8 M⊙). This is the largest spectroscopic study of massive YSOs to date, providing a valuable resource for the study of massive star formation. In this paper, we present our exploratory analysis of the data. The YSOs observed have a wide range of embeddedness (2.7 < AV < 114), demonstrating that this study covers minimally obscured objects right through to very red, dusty sources. Almost all YSOs show some evidence for emission lines, though there is a wide variety of observed properties. The most commonly detected lines are Brγ, H2, fluorescent Fe II, CO bandhead, [Fe II] and He I 2-1 1S-1P, in order of frequency of occurrence. In total, ˜40 per cent of the YSOs display either fluorescent Fe II 1.6878 μm or CO bandhead emission (or both), indicative of a circumstellar disc; however, no correlation of the strength of these lines with bolometric luminosity was found. We also find that ˜60 per cent of the sources exhibit [Fe II] or H2 emission, indicating the presence of an outflow. Three quarters of all sources have Brγ in emission. A good correlation with bolometric luminosity was observed for both the Brγ and H2 emission line strengths, covering 1 < LBOL < 3.5 × 105 L⊙. This suggests that the emission mechanism for these lines is the same for low-, intermediate- and high-mass YSOs, i.e. high-mass YSOs appear to resemble scaled-up versions of low-mass YSOs.

SFR bulge-to-disk ratios from the CALIFA IFS nearby galaxies survey

NASA Astrophysics Data System (ADS)

Catalán-Torrecilla, Cristina; Gil de Paz, Armando; Castillo-Morales, Africa; Iglesias Páramo, Jorge; Sanchez, Sebastian

2015-08-01

Our ultimate aim is to study the evolution of the Star Formation Rate (SFR) by components (nuclei, bulges, disks) as a key constraint for the models of galaxy formation and evolution. In order to provide a local benchmark, we start from the analysis of a sample of nearby galaxies from the CALIFA Integral Field Spectroscopy (IFS) survey. Prior to this study, we have verified that the extinction-corrected Halpha luminosity provided by CALIFA IFS data recovers the total SFR by means of comparing measurements from this estimator with single-band (22μm, TIR and FUV) and hybrid tracers (FUV+22μm, FUV+TIR, Halpha+22μm, Halpha+TIR) for our sample of 272 CALIFA galaxies (Catalán-Torrecilla et al. 2015). We focus here on the study of the SFR bulge-to-disk ratio in nearby galaxies, something achievable in large numbers thanks to the good spatial resolution of our optical stellar-absorption and extinction corrected IFS-based Halpha maps. The results of the photometric decomposition of SDSS images of our sample is used as a prior is this analysis. The CALIFA objects analyzed range from galaxies that have all the SFR concentrated in the nuclear part to cases in which the SFR is spread over the disk and include both barred and unbarred galaxies. In summary, we are able to explore the distribution of the SFR in scales of 0.3-1.6 kpc for a rather large and well-characterized galaxy sample in the Local Universe.This and similar studies at higher redshifts will be key to understand how and at what rate galaxies assemble their stellar masses, either through mergers and/or secular processes.

Molecular hydrogen line ratios in four regions of shock-excited gas

NASA Technical Reports Server (NTRS)

Burton, M. G.; Brand, P. W. J. L.; Geballe, T. R.; Webster, A. S.

1989-01-01

Five emission lines of molecular hydrogen, with wavelengths in the ranges of 2.10-2.25 and 3.80-3.85 microns, have been observed in four objects of different type in which the line emission is believed to be excited by shocks. The relative intensities of the lines 1 - 0 S(1):1 - 0 S(O):2 - 1 S(1) are approximately 10.5:2.5:1.0 in all four objects. The 0 - 0 S(13):1 - 0 O(7) line ratio, however, varies from 1.05 in OMC-1 to about 2.3 in the Herbig-Haro object HH 7. The excitation temperature derived from the S(13) and O(7) lines is higher than that derived from the 1 - 0 and 2 - 1 S(1) lines in all four objects, so the shocked gas in these objects cannot be characterized by a single temperature. The constancy of the (1-0)/(2-1) S(1) line ratio between sources suggests that the post-shock gas is 'thermalized' in each source. The S(13)/O(7) ratio is particularly sensitive to the density and temperature conditions in the gas.

The VIRUS Emission Line Detection Recipe

NASA Astrophysics Data System (ADS)

Gössl, C. A.; Hopp, U.; Köhler, R.; Grupp, F.; Relke, H.; Drory, N.; Gebhardt, K.; Hill, G.; MacQueen, P.

2007-10-01

HETDEX, the Hobby-Eberly Telescope Dark Energy Experiment, will measure the imprint of the baryonic acoustic oscillations on the galaxy population at redshifts of 1.8 < z < 3.7 to constrain the nature of dark energy. The survey will be performed over at least 200 deg^2. The tracer population for this blind search will be Ly-α emitting galaxies through their most prominent emission line. The data reduction pipeline will extract these emission line objects from ˜35,000 spectra per exposure (5 million per night, i.e. 500 million in total) while performing astrometric, photometric, and wavelength calibration fully automatically. Here we will present our ideas how to find and classify objects even at low signal-to-noise ratios.

Observations of the 63 micron forbidden O I line in Herbig-Haro objects

NASA Technical Reports Server (NTRS)

Cohen, Martin; Hollenbach, David J.; Haas, Michael R.; Erickson, Edwin F.

1988-01-01

The paper presents observations of the 63 micron forbidden O I line from Herbig-Haro objects and their exciting stars. Forbidden O I 63 micron emission is detected toward the HH-exciting stars T Tau, DG Tau, L1551 IRS 5, and toward the HH objects HH 7-11, HH 42A, and HH 43 which are displaced from their exciting stars. The forbidden O I emission is associated with these flows on the basis of its spatial coincidence and its negative radial velocities. If the exciting stars drive bipolar flows in which the 63 micron emission follows that at 6300 A, the absence of redshifted 63 micron lines from the three exciting stars might indicate that the disks hypothesized to overlie the receding lobes of these flows are still optically thick in the far-infrared.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plotkin, Richard M.; Gallo, Elena; Shemmer, Ohad

Over the past 15 yr, examples of exotic radio-quiet quasars with intrinsically weak or absent broad emission line regions (BELRs) have emerged from large-scale spectroscopic sky surveys. Here, we present spectroscopy of seven such weak emission line quasars (WLQs) at moderate redshifts (z = 1.4–1.7) using the X-shooter spectrograph, which provides simultaneous optical and near-infrared spectroscopy covering the rest-frame ultraviolet (UV) through optical. These new observations effectively double the number of WLQs with spectroscopy in the optical rest-frame, and they allow us to compare the strengths of (weak) high-ionization emission lines (e.g., C iv) to low-ionization lines (e.g., Mg ii,more » Hβ, Hα) in individual objects. We detect broad Hβ and Hα emission in all objects, and these lines are generally toward the weaker end of the distribution expected for typical quasars (e.g., Hβ has rest-frame equivalent widths ranging from 15–40 Å). However, these low-ionization lines are not exceptionally weak, as is the case for high-ionization lines in WLQs. The X-shooter spectra also display relatively strong optical Fe ii emission, Hβ FWHM ≲ 4000 km s{sup −1}, and significant C iv blueshifts (≈1000–5500 km s{sup −1}) relative to the systemic redshift; two spectra also show elevated UV Fe ii emission, and an outflowing component to their (weak) Mg ii emission lines. These properties suggest that WLQs are exotic versions of “wind-dominated” quasars. Their BELRs either have unusual high-ionization components, or their BELRs are in an atypical photoionization state because of an unusually soft continuum.« less

Search with Copernicus for ultraviolet emission lines in the planetary nebula NGC 3242

NASA Technical Reports Server (NTRS)

Schwartz, R. D.; Snow, T. P., Jr.; Upson, W. L., II

1978-01-01

The high-excitation planetary nebula NGC 3242 has been observed with the ultraviolet telescope-spectrometer aboard Copernicus. Wavelength intervals corresponding to the emission lines of O VI at 1032 A, He II at 1085 A, Si III at 1206 A, and N V at 1239 A have been scanned. Upper limits to the observed fluxes are reported and compared with predicted emission-line fluxes from this object.

A SIMPLE CONNECTION BETWEEN THE NEAR- AND MID-INFRARED EMISSION OF GALAXIES AND THEIR STAR FORMATION RATES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mentuch, Erin; Abraham, Roberto G.; Zibetti, Stefano

2010-12-20

We have measured the near-infrared colors and the fluxes of individual pixels in 68 galaxies common to the Spitzer Infrared Nearby Galaxies Survey and the Large Galaxy Atlas Survey. Pixels from each galaxy are grouped into regions of increasingly red near-infrared colors. As expected, the majority of pixels are shown to have relatively constant NIR flux ratios (log{sub 10} I{sub 3.6}/I{sub 1.25} = -0.30 {+-} 0.07 and log{sub 10} I{sub 4.5}/I{sub 3.6} = -0.19 {+-} 0.02), representing the blackbody continuum emission of main sequence stars. However, pixels with red NIR colors correspond to pixels with higher H{sub {alpha}} emission andmore » dust extinction. We show that the NIR colors are correlated to both quantities, with the strongest correlation to the intrinsic H{sub {alpha}} emission. In addition, in regions of high star formation, the average intensity of pixels in red-excess regions (at 1.25 {mu}m, 3.6 {mu}m, 4.5 {mu}m, 5.6 {mu}m, 8.0 {mu}m and 24 {mu}m) scales linearly with the intrinsic intensity of H{alpha} emission, and thus with the star formation rate (SFR) within the pixel. This suggests that most NIR-excess regions are not red because their light is being depleted by absorption. Instead, they are red because additional infrared light is being contributed by a process linked to star formation. This is surprising because the shorter wavelength bands in our study (1.25 {mu}m-5.6 {mu}m) do not probe emission from cold (10-20 K) and warm (50-100 K) dust associated with star formation in molecular clouds. However, emission from hot dust (700-1000 K) and/or polycyclic aromatic hydrocarbon (PAH) molecules can explain the additional emission seen at the shorter wavelengths in our study. The contribution from hot dust and/or PAH emission at 2 {mu}m-5 {mu}m and PAH emission at 5.6 {mu}m and 8.0 {mu}m scales linearly with warm dust emission at 24 {mu}m and the intrinsic H{alpha} emission. Since both are tied to the SFR, our analysis shows that the NIR excess continuum emission and PAH emission at {approx}1-8 {mu}m can be added to spectral energy distribution models in a very straightforward way, by simply adding an additional component to the models that scales linearly with SFR.« less

A support vector machine for spectral classification of emission-line galaxies from the Sloan Digital Sky Survey

NASA Astrophysics Data System (ADS)

Shi, Fei; Liu, Yu-Yan; Sun, Guang-Lan; Li, Pei-Yu; Lei, Yu-Ming; Wang, Jian

2015-10-01

The emission-lines of galaxies originate from massive young stars or supermassive blackholes. As a result, spectral classification of emission-line galaxies into star-forming galaxies, active galactic nucleus (AGN) hosts, or compositions of both relates closely to formation and evolution of galaxy. To find efficient and automatic spectral classification method, especially in large surveys and huge data bases, a support vector machine (SVM) supervised learning algorithm is applied to a sample of emission-line galaxies from the Sloan Digital Sky Survey (SDSS) data release 9 (DR9) provided by the Max Planck Institute and the Johns Hopkins University (MPA/JHU). A two-step approach is adopted. (i) The SVM must be trained with a subset of objects that are known to be AGN hosts, composites or star-forming galaxies, treating the strong emission-line flux measurements as input feature vectors in an n-dimensional space, where n is the number of strong emission-line flux ratios. (ii) After training on a sample of emission-line galaxies, the remaining galaxies are automatically classified. In the classification process, we use a 10-fold cross-validation technique. We show that the classification diagrams based on the [N II]/Hα versus other emission-line ratio, such as [O III]/Hβ, [Ne III]/[O II], ([O III]λ4959+[O III]λ5007)/[O III]λ4363, [O II]/Hβ, [Ar III]/[O III], [S II]/Hα, and [O I]/Hα, plus colour, allows us to separate unambiguously AGN hosts, composites or star-forming galaxies. Among them, the diagram of [N II]/Hα versus [O III]/Hβ achieved an accuracy of 99 per cent to separate the three classes of objects. The other diagrams above give an accuracy of ˜91 per cent.

Are some BL Lac objects artefacts of gravitational lensing?

NASA Technical Reports Server (NTRS)

Ostriker, J. P.; Vietri, M.

1985-01-01

It is proposed here that a significant fraction of BL Lac objects are optically violently variable quasars whose continuum emission has been greatly amplified, relative to the line emission, by pointlike gravitational lenses in intervening galaxies. Several anomalous physical and statistical properties of BL Lacs can be understood on the basis of this model, which is immediately testable on the basis of absorption line studies and by direct imaging.

Time-resolved spectrophotometry of the AM Herculis system E2003 + 225

NASA Technical Reports Server (NTRS)

Mccarthy, Patrick; Bowyer, Stuart; Clarke, John T.

1986-01-01

Time-resolved, medium-resolution photometry is reported for the binary system E2003 + 225 over a complete orbital period in 1984. The object was 1.5-2 mag fainter than when viewed earlier in 1984. The fluxes, equivalent widths and full widths at FWHM for dominant lines are presented for four points in the cycle. A coincidence of emission lines and a 4860 A continuum line was observed for the faster component, which had a 500 km/sec velocity amplitude that was symmetric around the zero line. An aberrant emission line component, i.e., stationary narrow emission lines displaced about 9 A from the rest wavelengths, is modeled as Zeeman splitting of emission from material close to the primary.

Solar radio bursts of spectral type II, coronal shocks, and optical coronal transients

NASA Technical Reports Server (NTRS)

Maxwell, A.; Dryer, M.

1981-01-01

An examination is presented of the association of solar radio bursts of spectral type II and coronal shocks with solar flare ejecta observed in H-alpha, the green coronal line, and white-light coronagraphs. It is suggested that fast-moving optical coronal transients should for the most part be identified with piston-type phenomena well behind the outward-traveling shock waves that generate type II radio bursts. A general model is presented which relates type II radio bursts and coronal shocks to optically observed ejecta and consists of three main velocity regimes: (1) a quasi-hemispherical shock wave moving outward from the flare at speeds of 1000-2000 km/sec and Alfven Mach number of about 1.5; (2) the velocity of the piston driving the shock, on the order of 0.8 that of the shock; and (3) the regime of the slower-moving H-alpha ejecta, with velocities of 300-500 km/sec.

The nuclear region of low luminosity flat radio spectrum sources. II. Emission-line spectra

NASA Astrophysics Data System (ADS)

Gonçalves, A. C.; Serote Roos, M.

2004-01-01

We report on the spectroscopic study of 19 low luminosity Flat Radio Spectrum (LL FRS) sources selected from Marchã's et al. (\\cite{March96}) 200 mJy sample. In the optical, these objects are mainly dominated by the host galaxy starlight. After correcting the data for this effect, we obtain a new set of spectra clearly displaying weak emission lines; such features carry valuable information concerning the excitation mechanisms at work in the nuclear regions of LL FRS sources. We have used a special routine to model the spectra and assess the intensities and velocities of the emission lines; we have analyzed the results in terms of diagnostic diagrams. Our analysis shows that 79% of the studied objects harbour a Low Ionization Nuclear Emission-line Region (or LINER) whose contribution was swamped by the host galaxy starlight. The remaining objects display a higher ionization spectrum, more typical of Seyferts; due to the poor quality of the spectra, it was not possible to identify any possible large Balmer components. The fact that we observe a LINER-type spectrum in LL FRS sources supports the idea that some of these objects could be undergoing an ADAF phase; in addition, such a low ionization emission-line spectrum is in agreement with the black hole mass values and sub-Eddington accretion rates published for some FRS sources. Based on observations collected at the Multiple Mirror Telescope on Mt. Hopkins. Full Fig. 1 is only available in electronic form at http://www.edpsciences.org

Time dependent emission line profiles in the radially streaming particle model of Seyfert galaxy nuclei and quasi-stellar objects

NASA Technical Reports Server (NTRS)

Hubbard, R.

1974-01-01

The radially-streaming particle model for broad quasar and Seyfert galaxy emission features is modified to include sources of time dependence. The results are suggestive of reported observations of multiple components, variability, and transient features in the wings of Seyfert and quasi-stellar emission lines.

Searching for Dwarf H Alpha Emission-line Galaxies within Voids III: First Spectra

NASA Astrophysics Data System (ADS)

Moody, J. Ward; Draper, Christian; McNeil, Stephen; Joner, Michael D.

2017-02-01

The presence or absence of dwarf galaxies with {M}r\\prime > -14 in low-density voids is determined by the nature of dark matter halos. To better understand what this nature is, we are conducting an imaging survey through redshifted Hα filters to look for emission-line dwarf galaxies in the centers of two nearby galaxy voids called FN2 and FN8. Either finding such dwarfs or establishing that they are not present is a significant result. As an important step in establishing the robustness of the search technique, we have observed six candidates from the survey of FN8 with the Gillett Gemini telescope and GMOS spectrometer. All of these candidates had emission, although none was Hα. The emission in two objects was the [O III]λ4959, 5007 doublet plus Hβ, and the emission in the remaining four was the [O II]λ3727 doublet, all from objects beyond the void. While no objects were within the void, these spectra show that the survey is capable of finding emission-line dwarfs in the void centers that are as faint as {M}r\\prime ˜ -12.4, should they be present. These spectra also show that redshifts estimated from our filtered images are accurate to several hundred km s-1 if the line is identified correctly, encouraging further work in finding ways to conduct redshift surveys through imaging alone.

Emission Lines in the Near-infrared Spectra of the Infrared Quintuplet Stars in the Galactic Center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Najarro, F.; Geballe, T. R.; Figer, D. F.

We report the detection of a number of emission lines in the 1.0–2.4 μ m spectra of four of the five bright-infrared dust-embedded stars at the center of the Galactic center’s (GC) Quintuplet Cluster. Spectroscopy of the central stars of these objects is hampered not only by the large interstellar extinction that obscures all of the objects in the GC, but also by the large amounts of warm circumstellar dust surrounding each of the five stars. The pinwheel morphologies of the dust observed previously around two of them are indicative of Wolf–Rayet colliding wind binaries; however, infrared spectra of eachmore » of the five have until now revealed only dust continua steeply rising to long wavelengths and absorption lines and bands from interstellar gas and dust. The emission lines detected, from ionized carbon and from helium, are broad and confirm that the objects are dusty late-type carbon Wolf–Rayet stars.« less

Centaurus X-3. [early x-ray binary star spectroscopy

NASA Technical Reports Server (NTRS)

Hutchings, J. B.; Cowley, A. P.; Crampton, D.; Van Paradus, J.; White, N. E.

1979-01-01

Spectroscopic observations of Krzeminski's star at dispersions 25-60 A/mm are described. The primary is an evolved star of type O6-O8(f) with peculiarities, some of which are attributable to X-ray heating. Broad emission lines at 4640A (N III), 4686 A(He II) and H-alpha show self-absorption and do not originate entirely from the region near the X-ray star. The primary is not highly luminous (bolometric magnitude about -9) and does not show signs of an abnormally strong stellar wind. The X-ray source was 'on' at the time of optical observations. Orbital parameters are presented for the primary, which yield masses of 17 + or - 2 and 1.0 + or - 3 solar masses for the stars. The optical star is undermassive for its luminosity, as are other OB-star X-ray primaries. The rotation is probably synchronized with the orbital motion. The distance to Cen X-3 is estimated to be 10 + or - 1 kpc. Basic data for 12 early-type X-ray primaries are discussed briefly

MULTI-COMPONENT ANALYSIS OF POSITION-VELOCITY CUBES OF THE HH 34 JET

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez-Gonzalez, A.; Esquivel, A.; Raga, A. C.

We present an analysis of H{alpha} spectra of the HH 34 jet with two-dimensional spectral resolution. We carry out multi-Gaussian fits to the spatially resolved line profiles and derive maps of the intensity, radial velocity, and velocity width of each of the components. We find that close to the outflow source we have three components: a high (negative) radial velocity component with a well-collimated, jet-like morphology; an intermediate velocity component with a broader morphology; and a positive radial velocity component with a non-collimated morphology and large linewidth. We suggest that this positive velocity component is associated with jet emission scatteredmore » in stationary dust present in the circumstellar environment. Farther away from the outflow source, we find only two components (a high, negative radial velocity component, which has a narrower spatial distribution than an intermediate velocity component). The fitting procedure was carried out with the new AGA-V1 code, which is available online and is described in detail in this paper.« less

Spectral Analysis Flare ribbons by NST and IRIS

NASA Astrophysics Data System (ADS)

Huang, Nengyi; Xu, Yan; Wang, Haimin; Jing, Ju

2017-08-01

As one of the most powerful phenomena of solar activities, flares have long been observed and studied extensively. Taking advantages of observing capabilities of modern solar telescopes and focal-plane instruments such as the Interface Region Imaging Spectrograph (IRIS) and the 1.6 m New Solar Telescope (NST) at Big Bear Solar observatory (BBSO), we are able to obtain high resolution imaging spectroscopic data in UV, visible and near-infrared (NIR) wavelengths. Here we present the spectral analysis of an M6.5 flare (SOL2015-06-22T18:23) which was well covered by the joint observation of IRIS and NST. In the visible wavelengths H-alpha and TiO, we can separate the flare ribbon into a very narrow leading front and faint trailing component, of which the former is characterized by the intense emission and significant Doppler signals. In the IRIS UV spectra, the ribbon front shows distinct properties, such as the line broadening, Doppler shifts and central reversal pattern, which are consistent with the visible observations. These characteristics suggest that the ribbon front to be the p

Evaporation of Accretion Disks around Black Holes: The Disk-Corona Transition and the Connection to the Advection-dominated Accretion Flow.

PubMed

Liu; Yuan; Meyer; Meyer-Hofmeister; Xie

1999-12-10

We apply the disk-corona evaporation model (Meyer & Meyer-Hofmeister) originally derived for dwarf novae to black hole systems. This model describes the transition of a thin cool outer disk to a hot coronal flow. The mass accretion rate determines the location of this transition. For a number of well-studied black hole binaries, we take the mass flow rates derived from a fit of the advection-dominated accretion flow (ADAF) model to the observed spectra (for a review, see Narayan, Mahadevan, & Quataert) and determine where the transition of accretion via a cool disk to a coronal flow/ADAF would be located for these rates. We compare this with the observed location of the inner disk edge, as estimated from the maximum velocity of the Halpha emission line. We find that the transition caused by evaporation agrees with this determination in stellar disks. We also show that the ADAF and the "thin outer disk + corona" are compatible in terms of the physics in the transition region.

EMISSION-LINE OBJECTS PROJECTED UPON THE GALACTIC BULGE*

PubMed Central

Herbig, G. H.

1969-01-01

Low-dispersion slit spectrograms have been obtained of 34 faint objects that lie in the direction of the galactic bulge and have the Hα line in emission upon a detectable continuum. Eleven of these are certain or probable symbiotic stars. A rough comparison with R CrB stars in the same area suggests that these brightest symbiotics in the bulge have in the mean Mv ≈ -3 to -4, which suggest Population II red giants rather than conventional Population I M-type objects. The sample also contains a number of hot stars having H and [O II] or [O III] in emission, as well as four conventional Be stars, and six certain or possible planetary nebulae. Images PMID:16578699

An X-ray image of the violent interstellar medium in 30 Doradus

NASA Technical Reports Server (NTRS)

Wang, Q.; Helfand, D. J.

1991-01-01

A detailed analysis of the X-ray emission from the largest H II region complex in the Local Group, 30 Dor, is presented. Applying a new maximum entropy deconvolution algorithm to the Einstein Observatory data, reveals striking correlations among the X-ray, radio, and optical morphologies of the region, with X-ray-emitting bubbles filling cavities surrounded by H-alpha shells and coextensive diffuse X-ray and radio continuum emission from throughout the region. The total X-ray luminosity in the 0.16-3.5 keV band from an area within 160 pc of the central cluster R136 is about 2 x 10 to the 37th ergs/sec.

Periodic spectrum variations in helium-rich stars

NASA Technical Reports Server (NTRS)

Walborn, N. R.

1982-01-01

Spectroscopic observations of four helium-rich stars are presented. In HD 37776, antiphase variations of Si III and He I have been found, which represent another point of similarity to the Ap phenomenon. The remarkable H-alpha emission variations in Sigma Ori E are illustrated with uniform phase coverage, and strict periodicity over a five-year interval is shown. A radial-velocity study of HD 64740 shows constancy to within the accuracy of the observations. Finally, Delta Ori B is confirmed as a helium-rich star.

THE MICRO-ARCSECOND SCINTILLATION-INDUCED VARIABILITY (MASIV) SURVEY. III. OPTICAL IDENTIFICATIONS AND NEW REDSHIFTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pursimo, Tapio; Ojha, Roopesh; Jauncey, David L.

2013-04-10

Intraday variability (IDV) of the radio emission from active galactic nuclei is now known to be predominantly due to interstellar scintillation (ISS). The MASIV (The Micro-Arcsecond Scintillation-Induced Variability) survey of 443 flat spectrum sources revealed that the IDV is related to the radio flux density and redshift. A study of the physical properties of these sources has been severely handicapped by the absence of reliable redshift measurements for many of these objects. This paper presents 79 new redshifts and a critical evaluation of 233 redshifts obtained from the literature. We classify spectroscopic identifications based on emission line properties, finding thatmore » 78% of the sources have broad emission lines and are mainly FSRQs. About 16% are weak lined objects, chiefly BL Lacs, and the remaining 6% are narrow line objects. The gross properties (redshift, spectroscopic class) of the MASIV sample are similar to those of other blazar surveys. However, the extreme compactness implied by ISS favors FSRQs and BL Lacs in the MASIV sample as these are the most compact object classes. We confirm that the level of IDV depends on the 5 GHz flux density for all optical spectral types. We find that BL Lac objects tend to be more variable than broad line quasars. The level of ISS decreases substantially above a redshift of about two. The decrease is found to be generally consistent with ISS expected for beamed emission from a jet that is limited to a fixed maximum brightness temperature in the source rest frame.« less

Ultraviolet Observations of M-Type Symbiotic Stars

NASA Astrophysics Data System (ADS)

Michalitsianos, Andrew G.

The significant differences revealed in high dispersion short wavelength spectra of two M-type symbiotic stars RW Hya (gM2 + pec) and RX Pup (M5 + pec) observed previously with IUE emphasizes the need for high resolution observations of a wide range of similar objects. The anomalies observed in high excitation lines in RX Pup of He II, N III], N IV], O III], C III], C IV and Si III] that show split line profiles, multiple component Doppler displaced components, and broadened blue wing emission structure in N III] and N IV] suggest motion in circumstellar material. In contrast, high dispersion UV spectra of RW Hya reveal narrow high excitation emission lines that give no suggestion of macroscopic motions in the circumstellar gas. We wish to extend observations of a selected number of symbiotic stars observed previously but in low resolution, to high dispersion in order to determine if particular M-type symbiotic stars exhibit anomalies in their line profile. As such, symbiotic stars exhibiting velocity structure in emission lines may form a subset of objects that are characterized by mass motions in their circumstellar envelops that create high excitation emission. UV line and continuum emission from other M-type symbiotics may arise from mainly photo-excitation processes that results from the intense radiation field associated with the hot secondary companion.

Ultraviolet Fe VII absorption and Fe II emission lines of central stars of planetary nebulae

NASA Technical Reports Server (NTRS)

Cheng, Kwang-Ping; Feibelman, Walter A.; Bruhweiler, Frederick C.

1991-01-01

The SWP camera of the IUE satellite was used in the high-dispersion mode to search for Fe VII absorption and Fe II high-excitation emission lines in five additional very hot central stars of planetary nebulae. Some of the Fe VII lines were detected at 1208, 1239, and 1332 A in all the objects of this program, LT 5, NGC 6058, NGC 7094, A43, and Lo 1 (= K1-26), as well as some of the Fe II emission lines at A 1360, 1776, 1869, 1881, 1884, and 1975 A. Two additional objects, NGC 2867 and He 2-131, were obtained from the IUE archive and were evaluated. The present study probably exhausts the list of candidates that are sufficiently bright and hot to be reached with the high-dispersion mode of the IUE.

High-cadence observations of spicular-type events and their wave-signatures

NASA Astrophysics Data System (ADS)

Shetye, Juie

2016-05-01

We present, a statistical study of spectral images, taken from the CRISP instrument at the Swedish 1-m Solar Telescope in H-alpha 656.28 nm of fast spicules with Doppler velocities in the range of -41km/s to +41 km/s. Remarkably, many of these spicules display apparent velocities above 500 km/s, very short lifetimes of up to 20 s combined with width or thickness of 100 km and apparent lengths of around 3500 km. Here we present, the other spectral properties of these events in the H-alpha line scan. Most features showed signature in multiple line position as we scan along the line scan. In around 89 % of the cases, there is temporal offset by 3.7 s to 5 s between the red-wing and blue-wing signatures. Another result is that 25% of cases are repetitive i.e. appear at the same location but they are not co-temporal or necessarily periodic in nature. Putting all the evidence together, we interpret the observations as mass motions (of flux tubes) that appear in the field-of-view of CRISP’s 0.0060 nm filters in the line of sight, along their projection as we scan. Further we observed transverse motion associated with these structures, which in some cases could be related to high-frequency kink-waves. We describe some cases showing this motion and the energies associated with them. The current work presented already tests the limits of current telescopes in terms of the temporal and spatial resolution. DKIST VTF instrument, having 3 times more spatial resolution than CRISP and much higher temporal resolution, we can being to understand the nature of such fine-scale transient phenomena in greater details.

EC 19314 - 5915 - A bright, eclipsing cataclysmic variable from the Edinburgh-Cape Blue Object Survey

NASA Technical Reports Server (NTRS)

Buckley, D. A. H.; O'Donoghue, D.; Kilkenny, D.; Stobie, R. S.; Remillard, R. A.

1992-01-01

A deeply eclipsing cataclysmic variable, with an orbital period of 4.75 hr, has been discovered in the southern Edinburgh-Cape Blue Object Survey. The star, EC 19314 - 5915, lies close to the positional constraints of a previously unidentified HEAO-1 hard X-ray source, 1H1930 - 5989. Its optical spectrum is unusual in that it shows, apart from the emission lines characteristic of a novalike, or dwarf nova cataclysmic variable (Balmer, He I and He II), metallic absorption lines typical of a late-G star. The individual time-resolved spectra, with the tertiary absorption lines removed, show absorption reversals in the Balmer emission lines, increasing in strength for the higher series. The Balmer emission radial velocities are therefore severely distorted in comparison to the He II 4686-A emission and He I 4471-A absorption radial velocity curves. An independent distance estimate of about 600 pc is derived for EC19314 - 5915, from the spectroscopic parallax of the third star.

X-shooter spectroscopy of young stellar objects. VI. H I line decrements

NASA Astrophysics Data System (ADS)

Antoniucci, S.; Nisini, B.; Giannini, T.; Rigliaco, E.; Alcalá, J. M.; Natta, A.; Stelzer, B.

2017-03-01

Context. Hydrogen recombination emission lines commonly observed in accreting young stellar objects represent a powerful tracer for the gas conditions in the circumstellar structures (accretion columns, and winds or jets). Aims: Here we perform a study of the H I decrements and line profiles, from the Balmer and Paschen H I lines detected in the X-shooter spectra of a homogeneous sample of 36 T Tauri objects in Lupus, the accretion and stellar properties of which were already derived in a previous work. We aim to obtain information on the H I gas physical conditions to delineate a consistent picture of the H I emission mechanisms in pre-main sequence low-mass stars (M∗< 2 M⊙). Methods: We have empirically classified the sources based on their H I line profiles and decrements. We identified four Balmer decrement types (which we classified as 1, 2, 3, and 4) and three Paschen decrement types (A, B, and C), characterised by different shapes. We first discussed the connection between the decrement types and the source properties and then compared the observed decrements with predictions from recently published local line excitation models. Results: We identify a few groups of sources that display similar H I properties. One third of the objects show lines with narrow symmetric profiles, and present similar Balmer and Paschen decrements (straight decrements, types 2 and A). Lines in these sources are consistent with optically thin emission from gas with hydrogen densities of order 109 cm-3 and 5000 < T < 15 000 K. These objects are associated with low mass accretion rates. Type 4 (L-shaped) Balmer and type B Paschen decrements are found in conjunction with very wide line profiles and are characteristic of strong accretors, with optically thick emission from high-density gas (log nH > 11 cm-3). Type 1 (curved) Balmer decrements are observed only in three sub-luminous sources viewed edge-on, so we speculate that these are actually type 2 decrements that are reddened because of neglecting a residual amount of extinction in the line emission region. About 20% of the objects present type 3 Balmer decrements (bumpy), which, however, cannot be reproduced with current models. Based on observations collected at the European Southern Observatory at Paranal, Chile, under programmes 084.C-0269(A), 085.C-238(A), 086.C-0173(A), 087.C-0244(A), and 089.C-0143(A).

ESTIMATING THE STAR FORMATION RATE AT 1 kpc SCALES IN NEARBY GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leroy, Adam K.; Munoz-Mateos, Juan-Carlos; Bigiel, Frank

2012-07-15

Using combinations of H{alpha}, ultraviolet (UV), and infrared (IR) emission, we estimate the star formation rate (SFR) surface density, {Sigma}{sub SFR}, at 1 kpc resolution for 30 disk galaxies that are targets of the IRAM HERACLES CO survey. We present a new physically motivated IR spectral-energy-distribution-based approach to account for possible contributions to 24 {mu}m emission not associated with recent star formation. Considering a variety of 'reference' SFRs from the literature, we revisit the calibration of the 24 {mu}m term in hybrid (UV+IR or H{alpha}+IR) tracers. We show that the overall calibration of this term remains uncertain at the factormore » of two level because of the lack of wide-field, robust reference SFR estimates. Within this uncertainty, published calibrations represent a reasonable starting point for 1 kpc-wide areas of star-forming disk galaxies, but we re-derive and refine the calibration of the IR term in these tracers to match our resolution and approach to 24 {mu}m emission. We compare a large suite of {Sigma}{sub SFR} estimates and find that above {Sigma}{sub SFR} {approx} 10{sup -3} M{sub Sun} yr{sup -1} kpc{sup -2} the systematic differences among tracers are less than a factor of two across two orders of magnitude dynamic range. We caution that methodology and data both become serious issues below this level. We note from simple model considerations that when focusing on a part of a galaxy dominated by a single stellar population, the intrinsic uncertainty in H{alpha}- and FUV-based SFRs is {approx}0.3 and {approx}0.5 dex.« less

The WHAM Hα Magellanic Stream Survey: Progress and Early Results

NASA Astrophysics Data System (ADS)

Smart, Brianna; Haffner, L. Matthew; Barger, Kat; Krishnarao, Dhanesh

2017-01-01

We present early analysis of the Hα survey of the Magellanic Stream using the Wisconsin H-Alpha Mapper (WHAM). The neutral component of the Stream extends some 200° across the sky (Nidever et al. 2010). However, the full extent of the ionized gas has not been mapped in detail. Previous studies (e.g., Putman et al. 2003; Weiner & Williams 1996) suggest that ionized gas is likely to be found all along the length of the Stream, and may extend beyond the current neutral boundaries as traced by 21 cm. Barger et al. (2013) used WHAM to map ionized gas throughout the Magellanic Bridge between the Magellanic Clouds. Although ionized emission tracks the neutral emission for the most part, it often spans a few degrees away from the H I at slightly offset velocities. Additionally, Fox et al. (2014) find evidence in an absorption line study that the tidal debris in the Magellanic System contains twice as much ionized gas as neutral material and may extend 30° away from 21-cm sensitivity boundaries. We are now compiling the first comprehensive picture of the ionized component of the Magellanic Stream using WHAM's unprecedented sensitivity to trace diffuse emission (~tens of mR), its velocity resolution (12 km/s) to separate the Stream from the Milky Way, and its multiwavelength capabilities (e.g., [S II] and [N II]) to examine the physical conditions of the gas. Much of the data along the primary axis of the Stream has been collected for the first phase of this extensive study, a complete kinematic Hα survey of the Stream. We present survey progress, challenges in extracting Stream emission, and first-look kinematic maps at select positions along the Stream.

An XMM-Newton Observation of the Lagoon Nebula and the Very Young Open Cluster NGC 6530

NASA Technical Reports Server (NTRS)

Rauw, G.; Naze, Y.; Gosset, E.; Stevens, I. R.; Blomme, R.; Corcoran, M. F.; Pittard, J. M.; Runacres, M. C.

2002-01-01

We report the results of an XMM-Newton observation of the Lagoon Nebula (M 8). Our EPIC images of this region reveal a cluster of point sources, most of which have optical counterparts inside the very young open cluster NGC 6530. The bulk of these X-ray sources are probably associated with low and intermediate mass pre-main sequence stars. One of the sources experiences a flare-like increase of its X-ray flux making it the second brightest source in M 8 after the O4 star 9 Sgr. The X-ray spectra of most of the brightest sources can be fitted with thermal plasma models with temperatures of kT approximately a few keV. Only a few of the X-ray selected PMS candidates are known to display H(alpha) emission and were previously classified as classical T Tauri stars. This suggests that most of the X-ray emitting PMS stars in NGC 6530 are weak line T Tauri stars. In addition to 9 Sgr, our EPIC field of view contains also a few early-type stars. The X-ray emission from HD 164816 is found to be typical for an O9.5III-IV star. At least one of the known Herbig Be stars in NGC 6530 (LkH(alpha) 115) exhibits a relatively strong X-ray emission, while most of the main sequence stars of spectral type B1 and later are not detected. We also detect (probably) diffuse X-ray emission from the Hourglass Region that might reveal a hot bubble blown by the stellar wind of Herschel 36, the ionizing star of the Hourglass Region.

Spectroscopic Observations of Nearby Low Mass Stars

NASA Astrophysics Data System (ADS)

Vican, Laura; Zuckerman, B. M.; Rodriguez, D.

2014-01-01

Young low-mass stars are known to be bright in X-ray and UV due to a high level of magnetic activity. By cross-correlating the GALEX Catalog with the WISE and 2MASS Point Source Catalogs, we have identified more than 2,000 stars whose UV excesses suggest ages in the 10-100 Myr range. We used the Shane 3-m telescope at Lick Observatory on Mount Hamilton, California to observe some of these 2,000 stars spectroscopically. We measured the equivalent width of lithium at 6708 A absorption and H-alpha emission lines. Out of a total of 122 stars observed with the Kast grating spectrometer, we find that roughly 10% have strong lithium absorption features. The high percentage of stars with lithium present is further evidence of the importance of UV emission as a youth indicator for low-mass stars. In addition, we used high-resolution spectra obtained with the Hamilton echelle spectrograph to determine radial velocities for several UV-bright stars. These radial velocities will be useful for the calculation of Galactic UVW space velocities for determination of possible moving group membership. This work is supported by NASA Astrophysics Data Analysis Program award NNX12AH37G to RIT and UCLA and Chilean FONDECYT grant 3130520 to Universidad de Chile. This submission presents work for the GALNYSS project and should be linked to abstracts submitted by David Rodriguez, Laura Vican, and Joel Kastner.

Anomalous Temporal Behaviour of Broadband Ly Alpha Observations During Solar Flares from SDO/EVE

NASA Technical Reports Server (NTRS)

Milligan, Ryan O.; Chamberlin, Phillip C.

2016-01-01

Although it is the most prominent emission line in the solar spectrum, there has been a notable lack of studies devoted to variations in Lyman-alpha (Ly-alpha) emission during solar flares in recent years. However, the few examples that do exist have shown Ly-alpha emission to be a substantial radiator of the total energy budget of solar flares (of the order of 10 percent). It is also a known driver of fluctuations in the Earth's ionosphere. The EUV (Extreme Ultra-Violet) Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO) now provides broadband, photometric Ly-alpha data at 10-second cadence with its Multiple EUV Grating Spectrograph-Photometer (MEGS-P) component, and has observed scores of solar flares in the 5 years since it was launched. However, the MEGS-P time profiles appear to display a rise time of tens of minutes around the time of the flare onset. This is in stark contrast to the rapid, impulsive increase observed in other intrinsically chromospheric features (H-alpha, Ly-beta, LyC, C III, etc.). Furthermore, the emission detected by MEGS-P peaks around the time of the peak of thermal soft X-ray emission and not during the impulsive phase when energy deposition in the chromosphere (often assumed to be in the form of non-thermal electrons) is greatest. The time derivative of Ly-alpha lightcurves also appears to resemble that of the time derivative of soft X-rays, reminiscent of the Neupert effect. Given that spectrally-resolved Ly-alpha observations during flares from SORCE / SOLSTICE (Solar Radiation and Climate Experiment / Solar Stellar Irradiance Comparison Experiment) peak during the impulsive phase as expected, this suggests that the atypical behaviour of MEGS-P data is a manifestation of the broadband nature of the observations. This could imply that other lines andor continuum emission that becomes enhanced during flares could be contributing to the passband. Users are hereby urged to exercise caution when interpreting broadband Ly-alpha observations of solar flares. Comparisons have also been made with other broadband Ly-alpha photometers such as PROBA2 (Project for On-Board Autonomy-2) / LYRA (Lyman Alpha Radiometer) and GOES (Geostationary Operational Environmental Satellite) / EUVE (Extreme Ultraviolet Explorer).

SPATIALLY RESOLVED SPECTROSCOPY AND CHEMICAL HISTORY OF STAR-FORMING GALAXIES IN THE HERCULES CLUSTER: THE EFFECTS OF THE ENVIRONMENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petropoulou, V.; Vilchez, J.; Iglesias-Paramo, J.

2011-06-10

Spatially resolved spectroscopy has been obtained for a sample of 27 star-forming (SF) galaxies selected from our deep H{alpha} survey of the Hercules cluster. We have applied spectral synthesis models to all emission-line spectra of this sample using the population synthesis code STARLIGHT and have obtained fundamental parameters of stellar components such as mean metallicity and age. The emission-line spectra were corrected for underlying stellar absorption using these spectral synthesis models. Line fluxes were measured and O/H and N/O gas chemical abundances were obtained using the latest empirical calibrations. We have derived the masses and total luminosities of the galaxiesmore » using available Sloan Digital Sky Survey broadband photometry. The effects of cluster environment on the chemical evolution of galaxies and on their mass-metallicity (MZ) and luminosity-metallicity (LZ) relations were studied by combining the derived gas metallicities, the mean stellar metallicities and ages, the masses and luminosities of the galaxies, and their existing H I data. Our Hercules SF galaxies are divided into three main subgroups: (1) chemically evolved spirals with truncated ionized-gas disks and nearly flat oxygen gradients, demonstrating the effect of ram-pressure stripping; (2) chemically evolved dwarfs/irregulars populating the highest local densities, possible products of tidal interactions in preprocessing events; and (3) less metallic dwarf galaxies that appear to be 'newcomers' to the cluster and are experiencing pressure-triggered star formation. Most Hercules SF galaxies follow well-defined MZ and LZ sequences (for both O/H and N/O), though the dwarf/irregular galaxies located at the densest regions appear to be outliers to these global relations, suggesting a physical reason for the dispersion in these fundamental relations. The Hercules cluster appears to be currently assembling via the merger of smaller substructures, providing an ideal laboratory where the local environment has been found to be a key parameter in understanding the chemical history of galaxies.« less

OPTICAL SPECTROSCOPY OF SDSS J004054.65-0915268: THREE POSSIBLE SCENARIOS FOR THE CLASSIFICATION. A z ∼ 5 BL LACERTAE, A BLUE FSRQ, OR A WEAK EMISSION LINE QUASAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landoni, M.; Zanutta, A.; Bianco, A.

2016-02-15

The haunt of high-redshift BL Lacerate objects is day by day more compelling to firmly understand their intrinsic nature and evolution. SDSS J004054.65-0915268 is, at the moment, one of the most distant BL Lac candidates, at z ∼ 5. We present a new optical-near-IR spectrum obtained with ALFOSC-NOT with a new, custom designed dispersive grating aimed to detect broad emission lines that could disprove this classification. In the obtained spectra, we do not detect any emission features and we provide an upper limit to the luminosity of the C iv broad emission line. Therefore, the nature of the object is then discussed,more » building the overall spectral energy distribution (SED) and fitting it with three different models. Our fits, based on SED modeling with different possible scenarios, cannot rule out the possibility that this source is indeed a BL Lac object, though the absence of optical variability and the lack of strong radio flux seem to suggest that the observed optical emission originates from a thermalized accretion disk.« less

Optical Spectroscopy of SDSS J004054.65-0915268: Three Possible Scenarios for the Classification. A z ˜ 5 BL Lacertae, a Blue FSRQ, or a Weak Emission Line Quasar

NASA Astrophysics Data System (ADS)

Landoni, M.; Zanutta, A.; Bianco, A.; Tavecchio, F.; Bonnoli, G.; Ghisellini, G.

2016-02-01

The haunt of high-redshift BL Lacerate objects is day by day more compelling to firmly understand their intrinsic nature and evolution. SDSS J004054.65-0915268 is, at the moment, one of the most distant BL Lac candidates, at z ˜ 5. We present a new optical-near-IR spectrum obtained with ALFOSC-NOT with a new, custom designed dispersive grating aimed to detect broad emission lines that could disprove this classification. In the obtained spectra, we do not detect any emission features and we provide an upper limit to the luminosity of the C IV broad emission line. Therefore, the nature of the object is then discussed, building the overall spectral energy distribution (SED) and fitting it with three different models. Our fits, based on SED modeling with different possible scenarios, cannot rule out the possibility that this source is indeed a BL Lac object, though the absence of optical variability and the lack of strong radio flux seem to suggest that the observed optical emission originates from a thermalized accretion disk.

Detection of 1612 MHz OH emission in the semiregular variable stars RT Vir, R Crt and W Hya

NASA Astrophysics Data System (ADS)

Etoka, S.; Le Squeren, A. M.; Gerard, E.

2003-05-01

We present evidence of 1612 MHz emission in SR variable stars. The two SRb, RT Vir and R Crt, as well as the SRa W Hya have been monitored with the upgraded Nançay radio telescope since February 2001. All three objects have shown a weak 1612 MHz emission occuring in the velocity range of the strongest emission observed in the main-lines. Such a detection is the second observational evidence for emission in the 1612 MHz OH maser satellite line from SRb stars. It also confirms the presence of 1612 MHz emission in the SRa W Hya discovered by Etoka et al. (\\cite{etoka01}). Such a finding strongly suggests that the shell properties of those three objects are quite similar to those of the Mira stars with similar IR characteristics.

THE DUST SUBLIMATION RADIUS AS AN OUTER ENVELOPE TO THE BULK OF THE NARROW Fe Kα LINE EMISSION IN TYPE 1 AGNs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gandhi, Poshak; Hönig, Sebastian F.; Kishimoto, Makoto

2015-10-20

The Fe Kα emission line is the most ubiquitous feature in the X-ray spectra of active galactic nuclei (AGNs), but the origin of its narrow core remains uncertain. Here, we investigate the connection between the sizes of the Fe Kα core emission regions and the measured sizes of the dusty tori in 13 local Type 1 AGNs. The observed Fe Kα emission radii (R{sub Fe}) are determined from spectrally resolved line widths in X-ray grating spectra, and the dust sublimation radii (R{sub dust}) are measured either from optical/near-infrared (NIR) reverberation time lags or from resolved NIR interferometric data. This directmore » comparison shows, on an object-by-object basis, that the dust sublimation radius forms an outer envelope to the bulk of the Fe Kα emission. R{sub Fe} matches R{sub dust} well in the AGNs, with the best constrained line widths currently. In a significant fraction of objects without a clear narrow line core, R{sub Fe} is similar to, or smaller than, the radius of the optical broad line region. These facts place important constraints on the torus geometries for our sample. Extended tori in which the solid angle of fluorescing gas peaks at well beyond the dust sublimation radius can be ruled out. We also test for luminosity scalings of R{sub Fe}, finding that the Eddington ratio is not a prime driver in determining the line location in our sample. We also discuss in detail potential caveats of data analysis and instrumental limitations, simplistic line modeling, uncertain black hole masses, and sample selection, showing that none of these is likely to bias our core result. The calorimeter on board Astro-H will soon vastly increase the parameter space over which line measurements can be made, overcoming many of these limitations.« less

Molecular line emission models of Herbig-Haro objects. II - HCO(+) emission

NASA Technical Reports Server (NTRS)

Wolfire, Mark G.; Koenigl, Arieh

1993-01-01

We present time-dependent models of the chemistry and temperature of interstellar molecular gas clumps that are exposed to the radiation from propagating stellar-jet shocks. The X-ray, EUV, and FUV radiation from the shock initiates ion chemistry and also heats the gas in the clumps. Using representative parameters, we show that, on the shock transit time between the clumps, the abundances of the ionized molecular species that are produced in the clumps can exceed the values determined from steady state models by several orders of magnitude. Collisional excitation by the heated gas can lead to measurable line emission from several ionized species; as in previous investigations of X-ray-irradiated molecular gas, we find that electron impacts contribute significantly to this process. We apply these results to the interpretation of the HCO(+) line emission that has already been detected in several Herbig-Haro objects. We demonstrate that this picture provides a natural explanation of the fact that the line intensity typically peaks ahead of the associated shock, as well as of the reported low line-center velocities and narrow line widths. We tabulate several diagnostic line intensities of HCO(+) and other molecular species that may be used to infer the physical conditions in the emitting gas.

Ultraviolet Fe VII absorption and Fe II emission lines of central stars of planetary nebulae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Kwang-Ping; Feibelman, W.A.; Bruhweiler, F.C.

1991-08-01

The SWP camera of the IUE satellite was used in the high-dispersion mode to search for Fe VII absorption and Fe II high-excitation emission lines in five additional very hot central stars of planetary nebulae. Some of the Fe VII lines were detected at 1208, 1239, and 1332 A in all the objects of this program, LT 5, NGC 6058, NGC 7094, A43, and Lo 1 (= K1-26), as well as some of the Fe II emission lines at A 1360, 1776, 1869, 1881, 1884, and 1975 A. Two additional objects, NGC 2867 and He 2-131, were obtained from themore » IUE archive and were evaluated. The present study probably exhausts the list of candidates that are sufficiently bright and hot to be reached with the high-dispersion mode of the IUE. 17 refs.« less

STAR FORMATION ON SUBKILOPARSEC SCALE TRIGGERED BY NON-LINEAR PROCESSES IN NEARBY SPIRAL GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Momose, Rieko; Koda, Jin; Donovan Meyer, Jennifer

We report a super-linear correlation for the star formation law based on new CO(J = 1-0) data from the CARMA and NOBEYAMA Nearby-galaxies (CANON) CO survey. The sample includes 10 nearby spiral galaxies, in which structures at sub-kpc scales are spatially resolved. Combined with the star formation rate surface density traced by H{alpha} and 24 {mu}m images, CO(J = 1-0) data provide a super-linear slope of N = 1.3. The slope becomes even steeper (N = 1.8) when the diffuse stellar and dust background emission is subtracted from the H{alpha} and 24 {mu}m images. In contrast to the recent resultsmore » with CO(J = 2-1) that found a constant star formation efficiency (SFE) in many spiral galaxies, these results suggest that the SFE is not independent of environment, but increases with molecular gas surface density. We suggest that the excitation of CO(J = 2-1) is likely enhanced in the regions with higher star formation and does not linearly trace the molecular gas mass. In addition, the diffuse emission contaminates the SFE measurement most in regions where the star formation rate is law. These two effects can flatten the power-law correlation and produce the apparent linear slope. The super-linear slope from the CO(J = 1-0) analysis indicates that star formation is enhanced by non-linear processes in regions of high gas density, e.g., gravitational collapse and cloud-cloud collisions.« less

Propagating Waves Transverse to the Magnetic Field in a Solar Prominence

NASA Astrophysics Data System (ADS)

Kucera, Therese A.; Knizhnik, K.; Lopez Ariste, A.; Luna Bennasar, M.; Schmieder, B.; Toot, D.

2013-07-01

We have observed a quiescent prominence with the Hinode Solar Optical Telescope (SOT, in Ca II and H-alpha lines), Sacramento Peak Observatory (in H-alpha, H-beta and Sodium-D lines), and THEMIS/MTR (Télescope Héliographique pour l'Étude du Magnétisme et des Instabilités Solaires/MulTi Raies, providing vector magnetograms), and SDO/AIA (Solar Dynamics Observatory Atmospheric Imaging Assembly, in EUV) over a 4 hour period on 2012 October 10. The small fields of view of SOT, Sac Peak and THEMIS are centered on a large pillar-like prominence footpoint extending towards the surface. This feature appears in the larger field of view of the 304 Å band, as a large, quasi-vertical column with material flowing horizontally on each side. The THEMIS/MTR data indicate that the magnetic field in the pillar is essentially horizontal and the observations in the optical wavelengths show a large number of horizontally aligned features on a much smaller scale than the pillar as a whole. The data are consistent with a model of cool prominence plasma trapped in the dips of horizontal field lines. The SOT and Sac Peak data show what appear to be moving wave pulses. These pulses, which include a Doppler signature, move vertically, perpendicular to the field direction, along quasi-vertical columns. The pulses have a velocity of propagation of about 10 km/s, a period about 260 sec, and a wavelength around 2000 km. We interpret these waves in terms of fast magneto-sonic waves and discuss possible wave drivers.

Spectral properties of X-ray selected narrow emission line galaxies

NASA Astrophysics Data System (ADS)

Romero-Colmenero, E.

1998-03-01

This thesis reports a study of the X-ray and optical properties of two samples of X-ray selected Narrow Emission Line Galaxies (NELGs), and their comparison with the properties of broad line Active Galactic Nuclei (AGN). One sample (18 NELGs) is drawn from the ROSAT International X-ray Optical Survey (RIXOS), the other (19 NELGs and 33 AGN) from the ROSAT UK Deep Survey. ROSAT multi-channel X-ray spectra have been extracted and fitted with power-law, bremsstrahlung and black body models for the brighter RIXOS sources. In most cases, power-law and bremsstrahlung models provide the best results. The average spectral energy index, alpha, of the RIXOS NELGs is 0.96 +/- 0.07, similar to that of AGN (alpha~1). For the fainter RIXOS NELGs, as well as for all the UK Deep Survey sources, counts in three spectral bands have been extracted and fitted with a power-law model, assuming the Galactic value for N_H. The brighter RIXOS sources demonstrated that the results obtained by these two different extraction and fitting procedures provide consistent results. Two average X-ray spectra, one for the NELGs and another for the AGN, were created from the UK Deep Survey sources. The power-law slope of the average NELG is alpha = 0.45 +/- 0.09, whilst that of the AGN is alpha = 0.96 +/- 0.03. ROSAT X-ray surveys have shown that the fractional surface density of NELGs increases with respect to AGN at faint fluxes (<= 2e-15 ergs cm-2 s-1), thus suggesting that NELGs are important contributors to the residual soft (<2 keV) X-ray background (XRB). Moreover, the spectral slope of this background (alpha~0.4, 1-10 keV) is harder than that of AGN (alpha~1), which are known to contribute most of the XRB at higher flux levels. The work presented in this thesis shows unequivocally for the first time that the integrated spectrum of the faintest NELGs (alpha~0.4) is consistent with that of the soft X-ray background, finally reconciling it with the properties of the sources that are thought to constitute it. Furthermore, by combining both samples of NELGs, I find a tendency for sources at lower fluxes to display harder slopes (95% confidence level), further strengthening the case for NELGs to be major contributors to the XRB at the fainter fluxes. The analysis of optical spectroscopy, obtained on La Palma and Hawaii, shows that NELGs form a very heterogeneous group, made up of a mixture of Seyfert 2, LINER and HII-region like galaxies. Seyfert 2 galaxies are found to possess in general the steepest X-ray slopes. Ways to explain this in the context of the unified model of AGN are discussed. The FWHM of some emission lines (Halpha, Hbeta, [NII]) in the NELGs appears to increase with steepening X-ray spectral slope. In the case of the Balmer lines, this is at variance with what is observed in broad line AGN. The FWHM of the Balmer lines is also correlated to the FWHM of the forbidden lines, indicating that they must originate in regions of similar velocity fields. Unfortunately, the number of sources uniquely classified is not sufficient to investigate these relationships on a source type basis. The optical emission line ratios of a bright RIXOS source (aka Arp 185, NGC 6217), classified as a starburst galaxy in the literature, indicate that this is in fact a weak-[OI] LINER, powered either by emission from hot O stars or by hot stars together with a non-stellar continuum. Spatially resolved spectroscopic analysis suggests that the Balmer emission lines are concentrated in the inner regions of the nucleus, while the forbidden lines arise from a more extended region. Line ratios do not indicate a change in the ionizing continuum of this source with distance from the centre.

Spitzer IRS Observations of Low-Mass Seyfert Galaxies

NASA Astrophysics Data System (ADS)

Thornton, Carol E.; Barth, A. J.; Ho, L. C.; Greene, J. E.

2010-01-01

We present results from Spitzer IRS observations of a sample of 41 Seyfert galaxies with estimated black hole masses below 106 solar masses, including objects from the SDSS-selected samples of Seyfert 1 galaxies from Greene & Ho (2004) and Seyfert 2 galaxies from Barth et al. (2008), as well as NGC 4395 and POX 52. We use the IDL code PAHFIT (Smith et al. 2007) to derive measurements of continuum shapes and narrow emission line and PAH luminosities from the low-resolution spectra in order to examine the dust emission properties of these objects and investigate the relationship between Type 1 and Type 2 AGNs at low luminosities and low masses, to search for evidence of star formation, and to use emission-line diagnostics to constrain physical conditions within the narrow-line regions.

Medium-resolution échelle spectroscopy of the Red Square Nebula, MWC 922

NASA Astrophysics Data System (ADS)

Wehres, N.; Ochsendorf, B. B.; Tielens, A. G. G. M.; Cox, N. L. J.; Kaper, L.; Bally, J.; Snow, T. P.

2017-05-01

Context. Medium-resolution échelle spectra of the Red Square Nebula surrounding the star MWC 922 are presented. The spectra have been obtained in 2010 and 2012 using the X-shooter spectrograph mounted on the Very Large Telescope (VLT) in Paranal, Chile. The spectrum covers a wavelength range between 300 nm-2.5 μm and shows that the nebula is rich in emission lines. Aims: We aim to identify the emission lines and use them as a tool to determine the physical and chemical characteristics of the nebula. The emission lines are also used to put constraints on the structure of the nebula and on the nature of the central stars. Methods: We analyzed and identified emission lines that indicated that the Red Square Nebula consists of a low density bipolar outflow, eminent in the broad emission component seen in [Fe II], as well as in P Cygni line profiles indicative of fast outflowing material. The narrow component in the [Fe II] lines is most likely formed in the photosphere of a surrounding disk. Some of the emission lines show a pronounced double peaked profile, such as Ca II, indicating an accretion disk in Keplerian rotation around the central star. [O I] emission lines are formed in the neutral atomic zone separating the ionized disk photosphere from the molecular gas in the interior of the disk, which is prominent in molecular CO emission in the near-IR. [N II] and [S II] emission clearly originates in a low density but fairly hot (7 000-10 000 K) nebular environment. H I recombination lines trace the extended nebula as well as the photosphere of the disk. Results: These findings put constraints on the evolution of the central objects in MWC 922. The Red Square shows strong similarities to the Red Rectangle Nebula, both in morphology and in its mid-IR spectroscopic characteristics. As for the Red Rectangle, the observed morphology of the nebula reflects mass-loss in a binary system. Specifically, we attribute the biconical morphology and the associated rung-like structure to the action of intermittent jets blown by the accreting companion in a dense shell, which has been created by the primary. We stress, though, that despite the morphological similarities, these two objects represent very different classes of stellar objects. The data-reduced spectra are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A69

The Cambridge-Cambridge x-ray serendipity survey. 2: Classification of x-ray luminous galaxies

NASA Technical Reports Server (NTRS)

Boyle, B. J.; Mcmahon, R. G.; Wilkes, B. J.; Elvis, Martin

1994-01-01

We present the results of an intermediate-resolution (1.5 A) spectroscopic study of 17 x-ray luminous narrow emission-line galaxies previously identified in the Cambridge-Cambridge ROSAT Serendipity Survey and the Einstein Extended Medium Sensitivity Survey. Emission-line ratios reveal that the sample is composed of ten Seyfert and seven starburst galaxies. Measured linewidths for the narrow H alpha emission lines lie in the range 170 - 460 km s(exp -1). Five of the objects show clear evidence for asymmetry in the (OIII) lambda 5007 emission-line profile. Broad H alpha emission is detected in six of the Seyfert galaxies, which range in type from Seyfert 1.5 to 2. Broad H beta emission is only detected in one Seyfert galaxy. The mean full width at half maximum for the broad lines in the Seyfert galaxies is FWHM = 3900 +/- 1750 km s(exp -1). Broad (FWHM = 2200 +/- 600 km s(exp -1) H alpha emission is also detected in three of the starburst galaxies, which could originate from stellar winds or supernovae remnants. The mean Balmer decrement for the sample is H alpha / H beta = 3, consistent with little or no reddening for the bulk of the sample. There is no evidence for any trend with x-ray luminosity in the ratio of starburst galaxies to Seyfert galaxies. Based on our previous observations, it is therefore likely that both classes of object comprise approximately 10 percent of the 2 keV x-ray background.

Emission-line maps with OSIRIS-TF: The case of M101

NASA Astrophysics Data System (ADS)

Méndez-Abreu, J.

2013-05-01

We investigate the suitability of GTC/OSIRIS Tunable Filters (TFs) for obtaining emission-line maps of extended objects. We developed a technique to reconstruct an emission-line image from a set of images taken at consecutive central wavelengths. We demonstrate the feasibility of the reconstruction method by generating a flux calibrated Hα image of the well-known spiral galaxy M101. We tested our emission-line fluxes and ratios by using data present in the literature. We found that the differences in both Hα fluxes and N II/Hα line ratios are ~15% and ~50%, respectively. These results are fully in agreement with the expected values for our observational setup. The proposed methodology will allow us to use OSIRIS/GTC to perform accurate spectrophotometric studies of extended galaxies in the local Universe.

Suzaku Observation of Strong Fluorescent Iron Line Emission from the Young Stellar Object V1647 Ori during Its New X-ray Outburst

NASA Technical Reports Server (NTRS)

Hamaguchi, Kenji; Grosso, Nicolas; Kastner, Joel H.; Weintraub, David A.; Richmond, Michael

2009-01-01

The Suzaku X-ray satellite observed the young stellar object V1647 Ori on 2008 October 8 during the new mass accretion outburst reported in August 2008. During the 87 ksec observation with a net exposure of 40 ks, V1647 Ori showed a. high level of X-ray emission with a gradual decrease in flux by a factor of 5 and then displayed an abrupt flux increase by an order of magnitude. Such enhanced X-ray variability was also seen in XMM-Newton observations in 2004 and 2005 during the 2003-2005 outburst, but has rarely been observed for other young stellar objects. The spectrum clearly displays emission from Helium-like iron, which is a signature of hot plasma (kT approx.5 keV). It also shows a fluorescent iron Ka line with a remarkably large equivalent width of approx. 600 eV. Such a, large equivalent width indicates that a part of the incident X-ray emission that irradiates the circumstellar material and/or the stellar surface is hidden from our line of sight. XMM-Newton spectra during the 2003-2005 outburst did not show a strong fluorescent iron Ka line ; so that the structure of the circumstellar gas very close to the stellar core that absorbs and re-emits X-ray emission from the central object may have changed in between 2005 and 2008. This phenomenon may be related to changes in the infrared morphology of McNeil's nebula between 2004 and 2008.

Spectroscopic Peculiarity of the Herbig Be Star HD 259431

NASA Astrophysics Data System (ADS)

Pogodin, M. A.; Pavlovskij, S. E.; Drake, N. A.; Beskrovnaya, N. G.; Kozlova, O. V.; Alekseev, I. Yu.; Borges Fernandes, M.; Pereira, C. B.; Valyavin, G.

2017-06-01

High-resolution spectra of the Herbig Be star HD 259431 obtained in 2010-2016 at three observatories (Crimean AO, ESO in Chile, and OAN SPN in Mexico) are analysed. The object demonstrates a very rich emission line profile spectrum. The bulk of the lines exhibit double-peaked emission profiles and originate in the gaseous disk. The atmospheric lines are unusually shallow, and majority of them are distorted by the circumstellar (CS) contribution. Moreover, we have revealed that they are overlapped with an additional continuum emission. Using the observed ratio of the equivalent widths of two He I λ 4009 and 4026 lines, we estimated the spectral type of the object as B5 V. We also constructed the spectral energy distribution of the additional continuum using wide wings of the atmospheric Hβ-Hɛ lines free of the CS contribution. The continuum corresponds to the blue part of the black body spectrum. The Hβ - Hɛ Balmer emission lines show very variable profiles looking as either of P Cyg-type or a double-peaked emission line with a depression of the red wing. We found the period of this variability P = 2.630d and interpreted it as a sign of a rotating magnetosphere of the star with the magnetic axis inclined to the rotation axis. At different phases of rotation, the observer can see either an accretion flow at high magnetic latitudes or a wind zone at lower latitudes. We also estimated the inclination of the rotation axis i = 52°±1°.

High-Resolution Spectroscopy of some very Active Southern Stars

NASA Technical Reports Server (NTRS)

Soderblom, David R.; King, Jeremy R.; Henry, Todd J.

1998-01-01

We have obtained high-resolution echelle spectra of 18 solar-type stars that an earlier survey showed to have very high levels of Ca II H and K emission. Most of these stars belong to close binary systems, but five remain as probable single stars or well-separated binaries that are younger than the Pleiades on the basis of their lithium abundances and H.alpha emission. Three of these probable single stars also lie more than 1 mag above the main sequence in a color-magnitude diagram, and appear to have ages of 10 to 15 Myr. Two of them, HD 202917 and HD 222259, also appear to have a kinematic association with the pre-main-sequence multiple system HD 98800.

Nova-driven winds in globular clusters

NASA Technical Reports Server (NTRS)

Scott, E. H.; Durisen, R. H.

1978-01-01

Recent sensitive searches for H-alpha emission from ionized intracluster gas in globular clusters have set upper limits that conflict with theoretical predictions. It is suggested that nova outbursts heat the gas, producing winds that resolve this discrepancy. The incidence of novae in globular clusters, the conversion of kinetic energy of the nova shell to thermal energy of the intracluster gas, and the characteristics of the resultant winds are discussed. Calculated emission from the nova-driven models does not conflict with any observations to date. Some suggestions are made concerning the most promising approaches for future detection of intracluster gas on the basis of these models. The possible relationship of nova-driven winds to globular cluster X-ray sources is also considered.

The Environmental Impact of Intra-Cluster Medium on the Interstellar Medium in Early Type Galaxies

NASA Technical Reports Server (NTRS)

Trinchieri, Ginevra

1993-01-01

Draft versions of three articles submitted for publication are presented. The first two articles address high resolution X-ray images of early type galaxies observed with the ROSAT HRI and PSPC. Data for NGC 1553 and NGC 5846 indicate that the emission is highly irregular, with interesting features at different scales. The gas temperatures also vary both with the galactocentric radius and in correspondence to regions of higher emission and denser material. Strikingly similar features are observed in the X-ray and H-alpha morphologies of NGC 1553 and NGC 5846, while smooth, regular isophotes are observed in NGC 4649 at both wavelengths. The third article addresses ROSAT PSPC observations of 5 X-ray bright early type galaxies.

Spectral and photometric studies of the polar USNO-A2.0 0825-18396733

NASA Astrophysics Data System (ADS)

Gabdeev, M. M.; Borisov, N. V.; Shimansky, V. V.; Spiridonova, O. I.

2015-03-01

Results of photometric and spectral studies of the new magnetic cataclysmic variable (polar) USNO-A2.0 0825-18396733 are presented. Photometric data in the B, V, and R c filters show that this object exhibits a red excess of R c - V = 1 m . A red continuum with superposed strong single-peaked Balmer emission lines and HeII λ4686 Å emission, weak lines of neutral helium, and lines of heavy elements are observed in the object's spectra. Doppler maps constructed using the hydrogen and ionized-helium lines indicate that these lines form near the inner Lagrangian point, and that their formation is associated with an accretion stream. The spectra and radial-velocity curves indicate the eclipse of the white dwarf in the system to be partial. Radial-velocity curves derived for emission lines are used to estimate the component masses. The mass of the white dwarf is estimated to be 0.71-0.78 M ⊙, and the mass of the red dwarf to be 0.18-0.20 M ⊙.

The diagnostic capability of iron limes

NASA Astrophysics Data System (ADS)

Giannini, Teresa; Nisini, Brunella; Antoniucci, Simone; Alcala, Juan; Bacciotti, Francesca; Bonito, Rosaria; Podio, Linda; Stelzer, Beate; Whelan, Emma

2013-07-01

We present the VLT/X-Shooter spectrum of two jets from young protostars of different luminosity and mass, ESO-Halpha 574 and Par-Lup 3-4. In the covered spectral range (350-2500 nm) we detected more than 100 [FeII] and [FeIII] lines, which are used to precisely probe the key physical parameters of the gas (electron density and temperature, ionization degree, visual extinction). These quantities have been compared with shock-model predictions, which suggest that only the higher luminosity source (ESO-Ha 574) is able to drive a high-velocity and dissociative shock. The diagnostic capability of Iron, proven on the presented objects, represents a unique tool for the following reasons: 1) the large number of lines in the uv-infrared range makes possible to trace the physical conditions in a very large range of the parameter space; 2) at variance with the diagnostic commonly performed with other species, such as Oxygen, Nitrogen, and Sulphur, no assumption on the relative abundance is needed, since all the parameters are derived from line ratios of the same species; 3) in the unperturbed ISM, Iron is locked on the grain surfaces, while it is released in gas-phase if gas-grain or grain-grain collisions occur within a shock. Therefore the Iron abundance (derivable from ratios of Iron lines with those of other volatile species) is a direct probe of the presence of dust in the jet beam, an information crucial to understand whether jets originate close to the star or in the circumstellar disk.

Asymmetric Stokes-V Profiles at the Penumbral Boundary of a Sunspot

NASA Technical Reports Server (NTRS)

Choudhary, Debi Prasad; Balasubramanaim, K. S.; Suematsu, Yoshinori

2003-01-01

We present the spectropolarimetric measurements of a sunspot in the active region NOAA 6958 (15S03W), situated near the central meridian disk passage. The follower polarity sunspot was somewhat symmetrically round shaped with an elongated penumbra. There were several opposite polarity magnetic elements at, and beyond the penumbral boundary. The H-alpha images of the sunspot show the bright emission regions near the penumbral boundary towards the sun-center, which was of opposite polarity with respect to the main spot. The net-circular polarization (NCP) map shows that NCP is negative in the inner part of the spot and positive at the penumbral boundary and near the H-alpha plage. The Doppler velocities were determined by measuring the center-of-gravity (COG) of the Stokes-I profile and zero-crossing (ZC) wavelength of the Stokes-V profiles. The COG velocity map in general agrees with the Evershed flow. In addition, it shows the up flow in the penumbral region. The ZC velocities show the strong down flow at the penumbral boundary. Double-lobed Stokes-V profiles are observed at the locations, where the penumbral fibrils terminate coinciding the H-alpha plage. The Double lobed profiles had an unshifted component similar to the Stokes-V profiles of the sunspot penumbra and a shifted component with a velocity of about 5 km/s. The amplitude of the second component increases along the penumbral fibril as a function of the distance from the center of the sunspot. In this paper we discuss the role of emerging flux in generating the observed double lobed profiles. Based on our present observations, we propose to observe with the Solar-B Spectropolarimeter for understanding the nature of emerging flux near the sunspots.

A Magnified View of the Kinematics and Morphology of RCSGA 032727-132609: Zooming in on a Merger at z = 1.7

NASA Technical Reports Server (NTRS)

Wuyts, Eva; Rigby, Jane R.; Gladders, Michael D.; Sharon, Keren

2014-01-01

We present a detailed analysis of multi-wavelength Hubble Space Telescope/Wide Field Camera 3 (WFC3) imaging and Keck/OSIRIS near-infrared adaptive optics-assisted integral field spectroscopy for a highly magnified lensed galaxy at z = 1.70. This young starburst is representative of ultraviolet-selected star-forming galaxies (SFGs) at z approx. 2 and contains multiple individual star-forming regions. Due to the lensing magnification, we can resolve spatial scales down to 100 pc in the source plane of the galaxy. The velocity field shows disturbed kinematics suggestive of an ongoing interaction and there is a clear signature of a tidal tail. We constrain the age, reddening, star formation rate, and stellar mass of the star-forming clumps from spectral energy distribution (SED) modeling of the WFC3 photometry and measure their H(alpha) luminosity, metallicity, and outflow properties from the OSIRIS data.With strong star-formation-driven outflows in four clumps, RCSGA0327 is the first high-redshift SFG at stellar mass <10(exp 10) Stellar Mass with spatially resolved stellar winds. We compare the H(alpha) luminosities, sizes, and dispersions of the star-forming regions with other high-z clumps as well as local giant H(II) regions and find no evidence for increased clump star formation surface densities in interacting systems, unlike in the local universe. Spatially resolved SED modeling unveils an established stellar population at the location of the largest clump and a second mass concentration near the edge of the system that is not detected in H(alpha) emission. This suggests a picture of an equal-mass mixed major merger, which has not triggered a new burst of star formation or caused a tidal tail in the gas-poor component.

The Discovery of a High-Redshift Quasar without Emission Lines from Sloan Digital Sky Survey Commissioning Data.

PubMed

Fan; Strauss; Gunn; Lupton; Carilli; Rupen; Schmidt; Moustakas; Davis; Annis; Bahcall; Brinkmann; Brunner; Csabai; Doi; Fukugita; Heckman; Hennessy; Hindsley; Ivezic; Knapp; Lamb; Munn; Pauls; Pier; Rockosi; Schneider; Szalay; Tucker; York

1999-12-01

We report observations of a luminous unresolved object at redshift z=4.62, with a featureless optical spectrum redward of the Lyalpha forest region, discovered from Sloan Digital Sky Survey commissioning data. The redshift is determined by the onset of the Lyalpha forest at lambda approximately 6800 Å and a Lyman limit system at lambda=5120 Å. A strong Lyalpha absorption system with weak metal absorption lines at z=4.58 is also identified in the spectrum. The object has a continuum absolute magnitude of -26.6 at 1450 Å in the rest frame (h0=0.5, q0=0.5) and therefore cannot be an ordinary galaxy. It shows no radio emission (the 3 sigma upper limit of its flux at 6 cm is 60 µJy), indicating a radio-to-optical flux ratio at least as small as that of the radio-weakest BL Lacertae objects known. It is also not linearly polarized to a 3 sigma upper limit of 4% in the observed I band. Therefore, it is either the most distant BL Lac object known to date, with very weak radio emission, or a new type of unbeamed quasar, whose broad emission line region is very weak or absent.

On the SW Sex-type eclipsing cataclysmic variable SDSS0756+0858

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tovmassian, Gagik; Hernandez, Mercedes Stephania; González-Buitrago, Diego

We conducted a spectroscopic and photometric study of SDSS J075653.11+085831. X-ray observations were also attempted. We determined the orbital period of this binary system to be 3.29 hr. It is a deep eclipsing system, whose spectra show mostly single-peaked, Balmer emission lines and a rather intense He II line. There is also the presence of faint (often double-peaked) He I emission lines as well as several absorption lines, Mg I being the most prominent. All of these features point toward the affiliation of this object with the growing number of SW Sex-type objects. We developed a phenomenological model of anmore » SW Sex system to reproduce the observed photometric and spectral features.« less

Topology and convection of a northward interplanetary magnetic field reconnection event

NASA Astrophysics Data System (ADS)

Wendel, Deirdre E.

>From observations and global MHD simulations, we deduce the local and global magnetic topology and current structure of a northward IMF reconnection event in the dayside magnetopause. The ESA four-satellite Cluster suite crossed the magnetopause at a location mapping along field lines to an ionospheric H-alpha emission observed by the IMAGE spacecraft. Therefore, we seek reconnection signatures in the Cluster data. From the four-point Cluster observations, we develop a superposed epoch method to find the instantaneous x-line, its associated current sheet, and the nature of the reconnecting particle flows. This method is unique in that it removes the motion of the hyperbolic structure and the magnetopause relative to the spacecraft. We detect singular field line reconnection--planar hyperbolic reconnecting fields superposed on an out-of- plane field. We also detect the non-ideal electric field that is required to certify reconnection at locations where the magnetic field does not vanish, and estimate a reconnection electric field of - 4 mV/m. The current sheet appears bifurcated, embedding a 30 km current sheet of opposite polarity within a broader current sheet about 130 km thick. Using a resistive MHD simulation and ionospheric satellite data, we examine the same event at global length scales. This gives a 3D picture of where reconnection occurs on the magnetopause for northward IMF with B x and B y components and a tilted dipole field. It also demonstrates that northward IMF 3D reconnection couples the reconnection electric field and field-aligned currents to the ionosphere, driving sunward convection in a manner that agrees with satellite measurements of sunward flows. We find singular field line reconnection of the IMF with both open and closed field lines near nulls in both hemispheres. The reconnection in turn produces both open and closed field lines. We discuss for the first time how line-tying in the ionosphere and draping of open and IMF field lines produce a torsion of the reconnecting singular magnetic field lines within the magnetopause. The simulation and data show that magnetopause reconnection topology is three-dimensional in a way that challenges accepted models of neutral lines and x-lines with guide fields.

Investigating the 3D Structure of the Winds of Hot Supergiants

NASA Astrophysics Data System (ADS)

Klement, Robert

2018-04-01

An observational effort targeting supergiant stars of spectral classes B and A has been started using the VEGA high spectral resolution visible beam combiner at the CHARA array. The H-alpha emission from the structured stellar winds was resolved with respect to the surrounding continuum, showing signs of inhomogenities in the circumstellar environments as well as temporal variability on different time scales. We have begun a radiative transfer modelling effort to investigate the clumpy structure of the stellar winds and the origin of the inhomogenities, probably linked to the stellar photosphere features.

Goddard X-ray astronomy contributions to the IAU/COSPAR (1982)

NASA Technical Reports Server (NTRS)

Holt, S. S.; Petre, R.; Shafer, R. A.; Urry, C. M.; Mushotzky, R. F.

1982-01-01

The relation of X-ray flux to both the continuum flux in the optical and radio bands, and to the line emission properties of these objects were studied. The Einstein Observatory, because of increased sensitivity and improved angular resolution, increased substantially the number of known X-ray emitting active galactic nuclei. The Einstein imaging instruments detected morphology in AGN X-ray emission, in particular from jetlike structures in Cen-A, M87, and 3C273. The improved energy resolution and sensitivity of the spectrometers onboard the Observatory provide information on the geometry and ionization structure of the region responsible for the broad optical emission lines in a few AGN's. This information, combined with theoretical modeling and IUE and optical observations, allows the construction of a moderately detailed picture of the broad line region in these objects.

Early evolution of an X-ray emitting solar active region

NASA Technical Reports Server (NTRS)

Wolfson, C. J.; Acton, L. W.; Leibacher, J. W.; Roethig, D. T.

1977-01-01

The birth and early evolution of a solar active region has been investigated using X-ray observations from the mapping X-ray heliometer on board the OSO-8 spacecraft. X-ray emission is observed within three hours of the first detection of H-alpha plage. At that time, a plasma temperature of four million K in a region having a density on the order of 10 to the 10th power per cu cm is inferred. During the fifty hours following birth almost continuous flares or flare-like X-ray bursts are superimposed on a monotonically increasing base level of X-ray emission produced by the plasma. If the X-rays are assumed to result from heating due to dissipation of current systems or magnetic field reconnection, it may be concluded that flare-like X-ray emission soon after active region birth implies that the magnetic field probably emerges in a stressed or complex configuration.

On the origin of the 40-120 micron emission of galaxy disks: A comparison with H-alpha fluxes

NASA Technical Reports Server (NTRS)

Persson, Carol J. Lonsdale; Helou, George

1987-01-01

A comparison of 40 to 120 micron Infrared Astronomy Satellite (IRAS) fluxes with published H alpha and UBV photometry shows that the far infrared emission of galaxy disks consists of at least two components: a warm one associated with OB stars in HII-regions and young star-forming complexes, and a cooler one from dust in the diffuse, neutral interstellar medium, heated by the more general interstellar radiation field of the old disk population (a cirrus-like component). Most spiral galaxies are dominated by emission from the cooler component in this model. A significant fraction of the power for the cool component must originate with non-ionizing stars. For a normal spiral disk there is a substantial uncertainty in a star formation rate derived using either the H alpha or the far infrared luminosity.

Pre-flare association of magnetic fields and millimeter-wave radio emission

NASA Technical Reports Server (NTRS)

Mayfield, E. B.; White, K. P., III

1976-01-01

Observations of radio emission at 3.3 mm wavelength associated with magnetic fields in active regions are reported. Results of more than 200 regions during the years 1967-1968 show a strong correlation between peak enhanced millimeter emission, total flux of the longitudinal component of photospheric magnetic fields and the number of flares produced during transit of active regions. For magnetic flux greater than (10 to the 21st power) maxwells flares will occur and for flux of (10 to the 23rd power) maxwells the sum of the H-alpha flare importance numbers is about 40. The peak millimeter enhancement increases with magnetic flux for regions which subsequently flared. Estimates of the magnetic energy available and the correlation with flare production indicate that the photospheric fields and probably chromospheric currents are responsible for the observed pre-flare heating and provide the energy of flares.

A Multi-Wavelength Study of the X-Ray Sources in the NGC 5018

NASA Technical Reports Server (NTRS)

Ghosh, Kajal K.; Swartz, Douglas A.; Tennant, Allyn F.; Wu, Kinwah; Saripalli, Lakshmi

2004-01-01

The E3 giant elliptical galaxy NGC-5018 was observed with the cxo X-ray Observatory's Advanced CCD Imaging Spectrometer for 30-h on 14 April 2001. Results of analysis of these X-ray data as well as of complementary optical, infrared, and radio data are reported. Seven X-ray point sources, including the nucleus, were detected. If they are intrinsic to NGC-5018, then all six non-nuclear sources have luminosities exceeding 10(exp 39)-ergl in the 0.5-8.0-keV energy band; placing them in the class of Ultra- luminous X-ray sources. Comparison of X-ray source positions to archival Hubble Space Telescope/Wide Field Planetary Camera 2 (hst/WFPC2) images reveal four of the six non-nuclear sources are spatially--coincident with bright, M$(sub V)LA -8.6 mag, objects. These four objects have optical magnitudes and (V-I) colors consistent with globular clusters in NGC-5018. However, one of these objects was observed to vary by siml mag in both V and I between observations taken 28 July 1997 and 04 Feb 1999 indicating this source is a background active galactic nucleus (AGN). The nature of the other three optically-bright objects cannot be determined from the available optical data but all have X-ray-to-optical flux ratios consistent with background AGNs. Strong, unpolarized, radio emission has been detected from another of the optically-bright counterparts. It displays an inverted radio spectrum and is the most absorbed of the seven sources in the X-ray band. It, too, is most readily explained as a background AGN, though alternative explanations cannot be ruled out. Extended X-ray emission is detected within a siml5 arcsec radius of the galaxy center at a luminosity of sim lO(exp 40)-ergl in the X-ray band. Its thermal X-ray spectrum (kT sim0.4-keV) and its spatial coincidence with strong H(alpha) emission are consistent with a hot gas origin. The nucleus itself is a weak X-ray source, LA-5 times 10(exp 39)-ergl, but displays a radio spectrum typical of AGN.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Downes, R.A.

Galactic plane ultraviolet-excess (uv-excess) objects covering about 1000 square degrees of sky were surveyed. Photographic plates were obtained with both uv and blue filters, to select the uv-excess candidates, which were then observed spectroscopically to determine their classification. Most of the objects selected were nearby early-type stars with low interstellar reddening; however, a collection of hot white dwarfs, subdwarf O (sdO) stars, subdwarf B (sdB) stars, and cataclysmic variables was also found. Photoelectric photometry was obtained for these stars and a statistical analysis was performed to determine the space densities and scale heights for the four classes of objects. Severalmore » interesting objects (or class of objects) were discovered, and data for some of these stars are presented. Among the peculiar objects found are an emission-line white dwarf similar to the pulsating PG 1159 stars, a Population II Wolf-Rayet star, a previously catalogued object with a strong Fe II emission-line spectrum, and a new class of object, resembling the sdB stars, that shows variable strength H..cap alpha.. absorption, with the H..cap alpha.. line sometimes completely filled in.« less

Comparisons of measured and calculated potential magnetic fields. [in solar corona

NASA Technical Reports Server (NTRS)

Hagyard, M. J.; Teuber, D.

1978-01-01

Photospheric line-of-sight and transverse-magnetic-field data obtained, with a vector magnetograph system for an isolated sunspot are described. A study of the linear polarization patterns and of the calculated transverse field lines indicates that the magnetic field of the region is very nearly potential. The H-alpha fibril structures of this region as seen in high-resolution photographs corroborate this conclusion. Consequently, a potential-field calculation is described using the measured line-of-sight fields together with assumed Neumann boundary conditions; both are necessary and sufficient for a unique solution. The computed transverse fields are then compared with the measured transverse fields to verify the potential-field model and assumed boundary values. The implications of these comparisons for the validity of magnetic-field extrapolations using potential theory are discussed.

The structure of the white-light corona and the large-scale solar magnetic field

NASA Technical Reports Server (NTRS)

Sime, D. G.; Mccabe, M. K.

1990-01-01

The large-scale density structure of the white-light solar corona is compared to the organization of the solar magnetic field as identified by the appearance of neutral lines in the photosphere to examine whether any consistent relationship exists between the two. During the period covering Carrington rotations 1717 to 1736 brightness enhancements in the low corona tend to lie over the global neutral sheet identified in the photospheric magnetic field. The brightest of these enhancements are associated with neutral lines throguh active regions. These associations are not 1-1, but do hold both in stable and evolving conditions of the corona. A significant number of long-lived neutral lines is found, including filaments seen in H-alpha, for which there are not coronal enhancements.

THE NATURE OF ACTIVE GALACTIC NUCLEI WITH VELOCITY OFFSET EMISSION LINES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Müller-Sánchez, F.; Comerford, J.; Stern, D.

We obtained Keck/OSIRIS near-IR adaptive optics-assisted integral-field spectroscopy to probe the morphology and kinematics of the ionized gas in four velocity-offset active galactic nuclei (AGNs) from the Sloan Digital Sky Survey. These objects possess optical emission lines that are offset in velocity from systemic as measured from stellar absorption features. At a resolution of ∼0.″18, OSIRIS allows us to distinguish which velocity offset emission lines are produced by the motion of an AGN in a dual supermassive black hole system, and which are produced by outflows or other kinematic structures. In three galaxies, J1018+2941, J1055+1520, and J1346+5228, the spectral offsetmore » of the emission lines is caused by AGN-driven outflows. In the remaining galaxy, J1117+6140, a counterrotating nuclear disk is observed that contains the peak of Pa α emission 0.″2 from the center of the galaxy. The most plausible explanation for the origin of this spatially and kinematically offset peak is that it is a region of enhanced Pa α emission located at the intersection zone between the nuclear disk and the bar of the galaxy. In all four objects, the peak of ionized gas emission is not spatially coincident with the center of the galaxy as traced by the peak of the near-IR continuum emission. The peaks of ionized gas emission are spatially offset from the galaxy centers by 0.″1–0.″4 (0.1–0.7 kpc). We find that the velocity offset originates at the location of this peak of emission, and the value of the offset can be directly measured in the velocity maps. The emission-line ratios of these four velocity-offset AGNs can be reproduced only with a mixture of shocks and AGN photoionization. Shocks provide a natural explanation for the origin of the spatially and spectrally offset peaks of ionized gas emission in these galaxies.« less

THE MULTIPHASE STRUCTURE AND POWER SOURCES OF GALACTIC WINDS IN MAJOR MERGERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rupke, David S. N.; Veilleux, Sylvain, E-mail: drupke@gmail.com

2013-05-01

Massive, galaxy-scale outflows are known to be ubiquitous in major mergers of disk galaxies in the local universe. In this paper, we explore the multiphase structure and power sources of galactic winds in six ultraluminous infrared galaxies (ULIRGs) at z < 0.06 using deep integral field spectroscopy with the Gemini Multi-Object Spectrograph (GMOS) on Gemini North. We probe the neutral, ionized, and dusty gas phases using Na I D, strong emission lines ([O I], H{alpha}, and [N II]), and continuum colors, respectively. We separate outflow motions from those due to rotation and tidal perturbations, and find that all of themore » galaxies in our sample host high-velocity flows on kiloparsec scales. The properties of these outflows are consistent with multiphase (ionized, neutral, and dusty) collimated bipolar winds emerging along the minor axis of the nuclear disk to scales of 1-2 kpc. In two cases, these collimated winds take the form of bipolar superbubbles, identified by clear kinematic signatures. Less collimated (but still high-velocity) flows are also present on scales up to 5 kpc in most systems. The three galaxies in our sample with obscured QSOs host higher velocity outflows than those in the three galaxies with no evidence for an active galactic nucleus. The peak outflow velocity in each of the QSOs is in the range 1450-3350 km s{sup -1}, and the highest velocities (2000-3000 km s{sup -1}) are seen only in ionized gas. The outflow energy and momentum in the QSOs are difficult to produce from a starburst alone, but are consistent with the QSO contributing significantly to the driving of the flow. Finally, when all gas phases are accounted for, the outflows are massive enough to provide negative feedback to star formation.« less

Young Stellar Object Candidates in the Aquila Rift Region

NASA Astrophysics Data System (ADS)

Zhang, Miao-miao; Wang, Hong-chi; Stecklum, B.

2010-10-01

Using the 2m telescope of the Turingia State Observatory at Tauten-berg (TLS), imaging observations in 3 wavebands (H α, R and I) are performed in the 16 fields in the Aquila Rift region. The observed fields cover about 7 square degrees. Excluding the 3 fields with unqualified data, the photometrical analysis is made for the remaining 13 fields, from which point sources are identified, and finally 7 H α emission-line star candidates are identified by color-color diagrams. The 7 candidates are located in five fields. Three of them are located near the Galactic plane, while the galactic latitudes of the rest are greater than 4°. The 2 M ASS counterparts of the point sources are identified, and the properties of the 7 H α emission-line star candidates are further analyzed by using the two-color diagrams. It is found that the near-infrared radiation from these H α emission-line star candidates has no obvious infrared excess, one of them even falls on the main-sequence branch. This indicates that the H α-emissive young stellar objects (YSOs) are not always accompanied with the infrared excess, and that the results of the H α emission line observation and the infrared excess observation are mutually supplemented. If the 7 H α emission-line star candidates are regarded as YSO candidates, then the number of YSOs in the Aquila Rift region is quite small. The further confirmation of these candidates needs subsequent spectral observations.

Molecular line emission models of Herbig-Haro objects. I - H2 emission

NASA Technical Reports Server (NTRS)

Wolfire, Mark G.; Konigl, Arieh

1991-01-01

A comprehensive model for molecular hydrogen emssion in Herbig-Haro objects that are associated with the heads of radiative stellar jets is presented by using a simple representation of the jet head as a comprising a leading bow shock and a trailing jet shock, separated by a dense layer of cool shocked gas. Attention is given to collisional excitation in a nondissociative shock and formation pumping in the molecular reformation zone behind a dissociative shock, employing detailed shock and photodissociation-region emission models that incorporate most of the relevant atomic physics and chemistry. The conditions under which each of these excitation mechanisms may be expected to contribute to the observed emission are discussed, and a general diagnostic scheme for discriminating among them is constructed. Applying this scheme to the HH 1-2 system, strong evidence for excitation by the radiation field of a fast shock is found. It is inferred that FUV pumping contributes a significant fraction of the H2 line emission, and it is shown that this can occur only if the UV pump lines are not strongly self-shielded.

Hubble Space Telescope Images and Spectra of Objects Around an Optically Violent Variable QSO

NASA Astrophysics Data System (ADS)

Burbidge, E. M.; Beaver, E. A.; Cohen, R. D.; Hamann, F.; Junkkarinen, V. T.; Lyons, R. W.; Zuo, L.

1995-12-01

The Arecibo Occultation radio source AO 0235+164 is a rapidly and violently variable QSO with ze = 0.94. It was originally designated as a BL Lac object since no emission lines were detected in its spectrum; two absorption redshifts at 0.524 and 0.851 were measured some years before weak emission lines at z = 0.94 were detected by Cohen et al. (ApJ,318,577,1987). A point-like companion (Smith et al., ApJ,218,611,1977) was found 2 arc sec south with an emission line redshift at 0.524. It was designated object A by Yanny et al. (ApJ,338,735,1989). This object has sometimes been called a ``normal'' galaxy, presumably giving rise to the absorption at 0.524 in the QSO. Recent observations of the surrounding field, using the post-repair WFPC 2 on the Hubble Space Telescope, have been analyzed and the nature of the companion object 2 arc sec south, and of a second companion 1.3 arc sec east of AO, have been studied. Spectra of companion object A have been obtained with the Faint Object Spectrograph with gratings G160L and G270H, and 1.0 arc sec aperture, and these show that it is an AGN or QSO with BAL-type broad absorption lines shortward of CIVlambda 1549, SiIVlambda 1397, and NVlambda 1240, also broad CIII]lambda 1909 emission. The second object, A1, 1.3 arc sec east of the QSO, originally identified by Yanny et al. (1989) and shown to have [0II]lambda 3727 at z=0.524, is slightly extended. The physical properties and nature of this remarkable configuration will be discussed. This research has been supported in part by NASA NAS5-29293 and NAG5-1630.

IDENTIFYING NEARBY, YOUNG, LATE-TYPE STARS BY MEANS OF THEIR CIRCUMSTELLAR DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, Adam; Song, Inseok; Melis, Carl

2012-10-01

It has recently been shown that a significant fraction of late-type members of nearby, very young associations (age {approx}<10 Myr) display excess emission at mid-IR wavelengths indicative of dusty circumstellar disks. We demonstrate that the detection of mid-IR excess emission can be utilized to identify new nearby, young, late-type stars including two definite new members ('TWA 33' and 'TWA 34') of the TW Hydrae Association (TWA). Both new TWA members display mid-IR excess emission in the Wide-field Infrared Survey Explorer catalog and they show proper motion and youthful spectroscopic characteristics-namely, H{alpha} emission, strong lithium absorption, and low surface gravity featuresmore » consistent with known TWA members. We also detect mid-IR excess-the first unambiguous evidence of a dusty circumstellar disk-around a previously identified UV-bright, young, accreting star (2M1337) that is a likely member of the Lower-Centaurus Crux region of the Scorpius-Centaurus Complex.« less

Multi-wave band SMM-VLA observations of an M2 flare and an associated coronal mass ejection

NASA Technical Reports Server (NTRS)

Willson, Robert F.; Lang, Kenneth R.; Schmelz, Joan T.; Gonzalez, Raymond D.; Smith, Kermit L.

1991-01-01

Results are presented of observations of an M2 flare and an associated coronal mass ejection CME by instruments on the SMM as well as by the VLA and other ground-based observatories on September 30, 1988. The multiwave band data show a gradual slowly changing event which lasted several hours. The microwave burst emission was found to originate in compact moderately circularly polarized sources located near the sites of bright H-alpha and soft X-ray emission. These data are combined with estimates of an electron temperature of 1.5 x 10 to the 7th K and an emission measure of about 2.0 x 10 to the 49th/cu cm obtained from Ca XIX and Fe XXV spectra to show that the microwave emission can be attributed to thermal gyrosynchrotron radiation in regions where the magnetic field strength is 425-650 G. The CME acceleration at low altitudes is measured on the basis of ground- and space-based coronagraphs.

Infrared fine-structure line diagnostics of shrouded active galactic nuclei

NASA Technical Reports Server (NTRS)

Voit, G. M.

1993-01-01

Far-infrared spectroscopy of celestial objects will improve dramatically in the coming decade, allowing astronomers to use fine-structure line emission to probe photoionized regions obscured in the optical band by thick clouds of dust. The ultraluminous far-IR galaxies revealed by IRAS, quasar-like in luminosity but smothered in molecular gas, probably conceal either immense starbursts or luminous active nuclei. In both scenarios, these objects ought to produce copious infrared fine-structure emission with several lines comparable to H(beta) in luminosity. This paper shows how these lines, if detected, can be used to determine the electron densities and far-IR obscurations of shrouded photoionized regions and to constrain the shape and ionization parameter of the ionizing spectra. The presence of (Ne V) emission in particular will distinguish shrouded AGN's from shrouded starbursts. Since all active galaxies photoionize at least some surrounding material, these diagnostics can also be applied to active galaxies in general and will aid in studying how an active nucleus interacts with the interstellar medium of its host galaxy.

Successful "First Light" for VLT High-Resolution Spectrograph

NASA Astrophysics Data System (ADS)

1999-10-01

Great Research Prospects with UVES at KUEYEN A major new astronomical instrument for the ESO Very Large Telescope at Paranal (Chile), the UVES high-resolution spectrograph, has just made its first observations of astronomical objects. The astronomers are delighted with the quality of the spectra obtained at this moment of "First Light". Although much fine-tuning still has to be done, this early success promises well for new and exciting science projects with this large European research facility. Astronomical instruments at VLT KUEYEN The second VLT 8.2-m Unit Telescope, KUEYEN ("The Moon" in the Mapuche language), is in the process of being tuned to perfection before it will be "handed" over to the astronomers on April 1, 2000. The testing of the new giant telescope has been successfully completed. The latest pointing tests were very positive and, from real performance measurements covering the entire operating range of the telescope, the overall accuracy on the sky was found to be 0.85 arcsec (the RMS-value). This is an excellent result for any telescope and implies that KUEYEN (as is already the case for ANTU) will be able to acquire its future target objects securely and efficiently, thus saving precious observing time. This work has paved the way for the installation of large astronomical instruments at its three focal positions, all prototype facilities that are capable of catching the light from even very faint and distant celestial objects. The three instruments at KUEYEN are referred to by their acronyms UVES , FORS2 and FLAMES. They are all dedicated to the investigation of the spectroscopic properties of faint stars and galaxies in the Universe. The UVES instrument The first to be installed is the Ultraviolet Visual Echelle Spectrograph (UVES) that was built by ESO, with the collaboration of the Trieste Observatory (Italy) for the control software. Complete tests of its optical and mechanical components, as well as of its CCD detectors and of the complex control system, cf. ESO PR Photos 44/98 , were made in the laboratories of the ESO Headquarters in Garching (Germany) before it was fully dismounted and shipped (some parts by air, others by ship) to the ESO Paranal Observatory, 130 km south of Antofagasta (Chile). Here, the different pieces of UVES (with a total weight of 8 tons) were carefully reassembled on the Nasmyth platform of KUEYEN and made ready for real observations (see ESO PR Photos 36p-t/99 ). UVES is a complex two-channel spectrograph that has been built around two giant optical (echelle diffraction) gratings, each ruled on a 84 cm x 21 cm x 12 cm block of the ceramic material Zerodur (the same that is used for the VLT 8.2-m main mirrors) and weighing more than 60 kg. These echelle gratings finely disperse the light from celestial objects collected by the telescope into its constituent wavelengths (colours). UVES' resolving power (an optical term that indicates the ratio between a given wavelength and the smallest wavelength difference between two spectral lines that are clearly separated by the spectrograph) may reach 110,000, a very high value for an astronomical instrument of such a large size. This means for instance that even comparatively small changes in radial velocity (a few km/sec only) can be accurately measured and also that it is possible to detect the faint spectral signatures of very rare elements in celestial objects. One UVES channel is optimized for the ultraviolet and blue, the other for visual and red light. The spectra are digitally recorded by two highly efficient CCD detectors for subsequent analysis and astrophysical interpretation. By optimizing the transmission of the various optical components in its two channels, UVES has a very high efficiency all the way from the UV (wavelength about 300 nm) to the near-infrared (1000 nm or 1 µm). This guarantees that only a minimum of the precious light that is collected by KUEYEN is lost and that detailed spectra can be obtained of even quite faint objects, down to about magnitude 20 (corresponding to nearly one million times fainter than what can be perceived with the unaided eye). The possibility of doing simultaneous observations in the two channels (with a dichroic mirror) ensures a further gain in data gathering efficiency. First Observations with UVES In the evening of September 27, 1999, the ESO astronomers turned the KUEYEN telescope and - for the first time - focussed the light of stars and galaxies on the entrance aperture of the UVES instrument. This is the crucial moment of "First Light" for a new astronomical facility. The following test period will last about three weeks. Much of the time during the first observing nights was spent by functional tests of the various observation modes and by targeting "standard stars" with well-known properties in order to measure the performance of the new instrument. They showed that it is behaving very well. This marks the beginning of a period of progressive fine-tuning that will ultimately bring UVES to peak performance. The astronomers also did a few "scientific" observations during these nights, aimed at exploring the capabilities of their new spectrograph. They were eager to do so, also because UVES is the first spectrograph of this type installed at a telescope of large diameter in the southern hemisphere . Many exciting research possibilities are now opening with UVES . They include a study of the chemical history of many galaxies in the Local Group, e.g. by observing the most metal-poor (oldest) stars in the Milky Way Galaxy and by obtaining the first, extremely detailed spectra of their brightest stars in the Magellanic Clouds. Quasars and distant compact galaxies will also be among the most favoured targets of the first UVES observers, not least because their spectra carry crucial information about the density, physical state and chemical composition of the early Universe. UVES First Light: SN 1987A One of the first spectral test exposures with UVES at KUEYEN was of SN 1987A , the famous supernova that exploded in the Large Magellanic Cloud (LMC) in February 1987, and the brightest supernova of the last 400 years. ESO PR Photo 37a/99 ESO PR Photo 37a/99 [Preview - JPEG: 400 x 455 pix - 87k] [Normal - JPEG: 645 x 733 pix - 166k] Caption to ESO PR Photo 37a/99 : This is a direct image of SN1987A, flanked by two nearby stars. The distance between these two is 4.5 arcsec. The slit (2.0 arcsec wide) through which the echelle spectrum shown in PR Photo 37b/99 was obtained, is outlined. This reproduction is from a 2-min exposure through a R(ed) filter with the FORS1 multi-mode instrument at VLT ANTU, obtained in 0.55 arcsec seeing on September 20, 1998. North is up and East is left. ESO PR Photo 37b/99 ESO PR Photo 37b/99 [Preview - JPEG: 400 x 459 pix - 130k] [Normal - JPEG: 800 x 917 pix - 470k] [High-Res - JPEG: 3000 x 3439 pix - 6.5M] Caption to ESO PR Photo 37b/99 : This shows the raw image, as read from the CCD, with the recorded echelle spectrum of SN1987A. With this technique, the supernova spectrum is divided into many individual parts ( spectral orders , each of which appears as a narrow horizontal line) that together cover the wavelength interval from 479 to 682 nm (from the bottom to the top), i.e. from blue to red light. Many bright emission lines from different elements are visible, e.g. the strong H-alpha line from hydrogen near the centre of the fourth order from the top. Emission lines from the terrestrial atmosphere are seen as vertical bright lines that cover the full width of the individual horizontal bands. Since this exposure was done with the nearly Full Moon above the horizon, an underlying, faint absorption-line spectrum of reflected sunlight is also visible. The exposure time was 30 min and the seeing conditions were excellent (0.5 arcsec). ESO PR Photo 37c/99 ESO PR Photo 37c/99 [Preview - JPEG: 400 x 355 pix - 156k] [Normal - JPEG: 800 x 709 pix - 498k] [High-Res - JPEG: 1074 x 952 pix - 766k] Caption to ESO PR Photo 37c/99 : This false-colour image has been extracted from another UVES echelle spectrum of SN 1987A, similar to the one shown in PR Photo 37b/99 , but with a slit width of 1 arcsec only. The upper part shows the emission lines of nitrogen, sulfur and hydrogen, as recorded in some of the spectral orders. The pixel coordinates (X,Y) in the original frame are indicated; the red colour indicates the highest intensities. Below is a more detailed view of the complex H-alpha emission line, with the corresponding velocities and the position along the spectrograph slit indicated. Several components of this line can be distinguished. The bulk of the emission (here shown in red colour) comes from the ring surrounding the supernova; the elongated shape here is due to the differential velocity exhibited by the near (to us) and far sides of the ring. The two bright spots on either side are emission from two outer rings (not immediately visible in PR Photo 37a/99 ). The extended emission in the velocity direction originates from material inside the ring upon which the fastest moving ejecta from the supernova have impacted (As seen in VLT data obtained previously with the ANTU/ISAAC combination (cf. PR Photo 11/99 ), exciting times now lie ahead for SN 1987A. The ejecta moving at 30,000 km/s (1/10th the speed of light) have now, 12 years after the explosion, reached the ring of material and the predicted "fireworks" are about to be ignited.) Finally, there is a broad emission extending all along the spectrograph slit (here mostly yellow) upon which the ring emission is superimposed. This is not associated with the supernova itself, but is H-alpha emission by diffuse gas in the Large Magellanic Cloud (LMC) in which SN 1987A is located. UVES First Light: QSO HE2217-2818 The power of UVES is demonstrated by this two-hour test exposure of the southern quasar QSO HE2217-2818 with U-magnitude = 16.5 and a redshift of z = 2.4. It was discovered a few years ago during the Hamburg-ESO Quasar Survey , by means of photographic plates taken with the 1-m ESO Schmidt Telescope at La Silla, the other ESO astronomical site in Chile. ESO PR Photo 37d/99 ESO PR Photo 37d/99 [Preview - JPEG: 400 x 309 pix - 92k] [Normal - JPEG: 800x 618 pix - 311k] [High-Res - JPEG: 3000 x 2316 pix - 5.0M] ESO PR Photo 37e/99 ESO PR Photo 37e/99 [Preview - JPEG: 400 x 310 pix - 43k] [Normal - JPEG: 800 x 619 pix - 100k] [High-Res - JPEG: 3003 x 2324 pix - 436k] Caption to ESO PR Photo 37d/99 : This UVES echelle spectrum QSO HE2217-2818 (U-magnitude = 16.5) is recorded in different orders (the individual horizontal lines) and altogether covers the wavelength interval between 330 - 450 nm (from the bottom to the top). It illustrates the excellent capability of UVES to work in the UV-band on even faint targets. Simultaneously with this observation, UVES also recorded the adjacent spectral region 465 - 660 nm in its other channel. The broad Lyman-alpha emission from ionized hydrogen associated with the powerful energy source of the QSO is seen in the upper half of the spectrum at wavelength 413 nm. At shorter wavelengths, the dark regions in the spectrum are Lyman-alpha absorption lines from intervening, neutral hydrogen gas located along the line-of-sight at different redshifts (the so-called Lyman-alpha forest ) in the redshift interval z = 1.7 - 2.4. Note that since this exposure was done with the nearly Full Moon above the horizon, an underlying, faint absorption-line spectrum of reflected sunlight is also visible. Caption to ESO PR Photo 37e/99 : A tracing of one spectral order, corresponding to one horizontal line in the echelle spectrum displayed in PR Photo 37d/99 . It shows part of the Lyman-alpha forest in the ultraviolet spectrum of the southern quasar QSO HE2217-2818 . The absorption lines are caused by intervening, neutral hydrogen gas located at different distances along the line-of-sight towards this quasar. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

AN X-RAY INVESTIGATION OF THREE SUPERNOVA REMNANTS IN THE LARGE MAGELLANIC CLOUD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klimek, Matthew D.; Points, S. D.; Smith, R. C.

2010-12-20

We have investigated three supernova remnants (SNRs) in the LMC using multi-wavelength data. These SNRs are generally fainter than the known sample (see Section 4) and may represent a previously missed population. One of our SNRs is the second LMC remnant analyzed which is larger than any Galactic remnant for which a definite size has been established. The analysis of such a large remnant contributes to the understanding of the population of highly evolved SNRs. We have obtained X-ray images and spectra of three of these recently identified SNRs using the XMM-Newton observatory. These data, in conjunction with pre-existing opticalmore » emission-line images and spectra, were used to determine the physical conditions of the optical- and X-ray-emitting gas in the SNRs. We have compared the morphologies of the SNRs in the different wavebands. The physical properties of the warm ionized shell were determined from the H{alpha} surface brightness and the SNR expansion velocity. The X-ray spectra were fit with a thermal plasma model and the physical conditions of the hot gas were derived from the model fits. Finally, we have compared our observations with simulations of SNR evolution.« less

The rotating wind of the quasar PG 1700+518.

PubMed

Young, S; Axon, D J; Robinson, A; Hough, J H; Smith, J E

2007-11-01

It is now widely accepted that most galaxies undergo an active phase, during which a central super-massive black hole generates vast radiant luminosities through the gravitational accretion of gas. Winds launched from a rotating accretion disk surrounding the black hole are thought to play a critical role, allowing the disk to shed angular momentum that would otherwise inhibit accretion. Such winds are capable of depositing large amounts of mechanical energy in the host galaxy and its environs, profoundly affecting its formation and evolution, and perhaps regulating the formation of large-scale cosmological structures in the early Universe. Although there are good theoretical grounds for believing that outflows from active galactic nuclei originate as disk winds, observational verification has proven elusive. Here we show that structures observed in polarized light across the broad Halpha emission line in the quasar PG 1700+518 originate close to the accretion disk in an electron scattering wind. The wind has large rotational motions (approximately 4,000 km s(-1)), providing direct observational evidence that outflows from active galactic nuclei are launched from the disks. Moreover, the wind rises nearly vertically from the disk, favouring launch mechanisms that impart an initial acceleration perpendicular to the disk plane.

Sodium Atoms in the Lunar Exotail: Observed Velocity and Spatial Distributions

NASA Technical Reports Server (NTRS)

Line, Michael R.; Mierkiewicz, E. J.; Oliversen, R. J.; Wilson, J. K.; Haffner, L. M.; Roesler, F. L.

2011-01-01

The lunar sodium tail extends long distances due to radiation pressure on sodium atoms in the lunar exosphere. Our earlier observations determined the average radial velocity of sodium atoms moving down the lunar tail beyond Earth along the Sun-Moon-Earth line (i.e., the anti-lunar point) to be 12.4 km/s. Here we use the Wisconsin H-alpha Mapper to obtain the first kinematically resolved maps of the intensity and velocity distribution of this emission over a 15 x times 15 deg region on the sky near the anti-lunar point. We present both spatially and spectrally resolved observations obtained over four nights around new moon in October 2007. The spatial distribution of the sodium atoms is elongated along the ecliptic with the location of the peak intensity drifting 3 degrees east along the ecliptic per night. Preliminary modeling results suggest that the spatial and velocity distributions in the sodium exotail are sensitive to the near surface lunar sodium velocity distribution and that observations of this sort along with detailed modeling offer new opportunities to describe the time history of lunar surface sputtering over several days.

Circumstellar Disks Around Rapidly Rotating Be-type Stars

NASA Astrophysics Data System (ADS)

Touhami, Yamina

2012-01-01

Be stars are rapidly rotating B-type stars that eject large amounts of gaseous material into a circumstellar equatorial disk. The existence of this disk has been confirmed through the presence of several observational signatures such as the strong hydrogen emission lines, the IR flux excess, and the linear polarization detected from these systems. Here we report simultaneous near-IR interferometric and spectroscopic observations of circumstellar disks around Be stars obtained with the CHARA Array long baseline interferometer and the Mimir spectrograph at Lowell observatory. The goal of this project was to measure precise angular sizes and to characterize the fundamental geometrical and physical properties of the circumstellar disks. We were able to determine spatial extensions, inclinations, and position angles, as well as the gas density profile of the circumstellar disks using an elliptical Gaussian model and a physical thick disk model, and we show that the K-band interferometric angular sizes of the circumstellar disks are correlated with the H-alpha angular sizes. By combining the projected rotational velocity of the Be star with the disk inclination derived from interferometry, we provide estimates of the equatorial rotational velocities of these rapidly rotating Be stars.

Three-Dimensional Distribution of Ejecta in Supernova 1987A at 10,000 Days

NASA Technical Reports Server (NTRS)

Larsson, J.; Fransson, C.; Spyromilio, J.; Leibundgut, B.; Challis, P.; Chevalier, R. A.; France, K.; Jerkstrand, A.; Kirshner, R. P.; Lundqvist, P.;

Explained: Why many surveys of distant galaxies miss 90% of their targets

NASA Astrophysics Data System (ADS)

2010-03-01

Astronomers have long known that in many surveys of the very distant Universe, a large fraction of the total intrinsic light was not being observed. Now, thanks to an extremely deep survey using two of the four giant 8.2-metre telescopes that make up ESO's Very Large Telescope (VLT) and a unique custom-built filter, astronomers have determined that a large fraction of galaxies whose light took 10 billion years to reach us have gone undiscovered. The survey also helped uncover some of the faintest galaxies ever found at this early stage of the Universe. Astronomers frequently use the strong, characteristic "fingerprint" of light emitted by hydrogen known as the Lyman-alpha line, to probe the amount of stars formed in the very distant Universe [1]. Yet there have long been suspicions that many distant galaxies go unnoticed in these surveys. A new VLT survey demonstrates for the first time that this is exactly what is happening. Most of the Lyman-alpha light is trapped within the galaxy that emits it, and 90% of galaxies do not show up in Lyman-alpha surveys. "Astronomers always knew they were missing some fraction of the galaxies in Lyman-alpha surveys," explains Matthew Hayes, the lead author of the paper, published this week in Nature, "but for the first time we now have a measurement. The number of missed galaxies is substantial." To figure out how much of the total luminosity was missed, Hayes and his team used the FORS camera at the VLT and a custom-built narrowband filter [2] to measure this Lyman-alpha light, following the methodology of standard Lyman-alpha surveys. Then, using the new HAWK-I camera, attached to another VLT Unit Telescope, they surveyed the same area of space for light emitted at a different wavelength, also by glowing hydrogen, and known as the H-alpha line. They specifically looked at galaxies whose light has been travelling for 10 billion years (redshift 2.2 [3]), in a well-studied area of the sky, known as the GOODS-South field. "This is the first time we have observed a patch of the sky so deeply in light coming from hydrogen at these two very specific wavelengths, and this proved crucial," says team member Göran Östlin. The survey was extremely deep, and uncovered some of the faintest galaxies known at this early epoch in the life of the Universe. The astronomers could thereby conclude that traditional surveys done using Lyman-alpha only see a tiny part of the total light that is produced, since most of the Lyman-alpha photons are destroyed by interaction with the interstellar clouds of gas and dust. This effect is dramatically more significant for Lyman-alpha than for H-alpha light. As a result, many galaxies, a proportion as high as 90%, go unseen by these surveys. "If there are ten galaxies seen, there could be a hundred there," Hayes says. Different observational methods, targeting the light emitted at different wavelengths, will always lead to a view of the Universe that is only partially complete. The results of this survey issue a stark warning for cosmologists, as the strong Lyman-alpha signature becomes increasingly relied upon in examining the very first galaxies to form in the history of the Universe. "Now that we know how much light we've been missing, we can start to create far more accurate representations of the cosmos, understanding better how quickly stars have formed at different times in the life of the Universe," says co-author Miguel Mas-Hesse. The breakthrough was made possible thanks to the unique camera used. HAWK-I, which saw first light in 2007, is a state-of-the-art instrument. "There are only a few other cameras with a wider field of view than HAWK-I, and they are on telescopes less than half the size of the VLT. So only VLT/HAWK-I, really, is capable of efficiently finding galaxies this faint at these distances," says team member Daniel Schaerer. Notes [1] Lyman-alpha light corresponds to light emitted by excited hydrogen (more specifically, when the electron around the nucleus jumps from the first excited level to the fundamental, or ground, level). This light is emitted in the ultraviolet, at 121.6 nm. The Lyman-alpha line is the first in the so-called Lyman series, named after its discoverer, Theodore Lyman. The Balmer series, named after Johann Balmer, also corresponds to light emitted by excited hydrogen. In this case, the electron falls into the first excited level. The first line in this series is the H-alpha line, emitted at 656.3 nm. As most hydrogen atoms present in a galaxy are in the ground level, Lyman-alpha light is more efficiently absorbed than H-alpha light, which requires atoms having an electron in the second level. As this is very uncommon in the cold interstellar hydrogen permeating galaxies, the gas is almost perfectly transparent to H-alpha light. [2] A narrowband filter is an optical filter designed to let pass only a narrow bandwidth of light, centred on a specific wavelength. Traditional narrowband filters include those centred on the lines of the Balmer series, such as H-alpha. [3] Because the Universe expands, the light of a distant object is redshifted by an amount depending on its distance. This means its light is moved towards longer wavelengths. A redshift of 2.2 - corresponding to galaxies whose light has taken approximately 10 billion years to reach us - means that the light is stretched by a factor 3.2. Thus the Lyman-alpha light is now seen at about 390 nm, near the visible domain, and can be observed with the FORS instrument on ESO's VLT, while the H-alpha line is moved towards 2.1 microns, in the near-infrared. It can thus be observed with the HAWK-I instrument on the VLT. More information This research was presented in a paper to appear in Nature ("Escape of about five per cent of Lyman-a photons from high-redshift star-forming galaxies", by M. Hayes et al.). The team is composed of Matthew Hayes, Daniel Schaerer, and Stéphane de Barros (Observatoire Astronomique de l'Université de Genève, Switzerland), Göran Östlin and Jens Melinder (Stockholm University, Sweden), J. Miguel Mas-Hesse (CSIC-INTA, Madrid, Spain), Claus Leitherer (Space Telescope Science Institute, Baltimore, USA), Hakim Atek and Daniel Kunth (Institut d'Astrophysique de Paris, France), and Anne Verhamme (Oxford Astrophysics, U.K.). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

The galaxy NGC 1566 - Distribution and kinematics of the ionized gas

NASA Astrophysics Data System (ADS)

Comte, G.; Duquennoy, A.

1982-10-01

H-alpha narrowband observations are the basis of a study of ionized hydrogen in the large spiral galaxy NGC 1566 which has yielded a catalog of 418 H II regions covering the main body of the galaxy, supplemented by 59 positions and estimated H-alpha luminosities for regions located in the pseudo-outer ring where no H-alpha plate is available. A discussion of luminosity function, diameter distribution and spiral structure notes evidence for a double two-armed spiral pattern. The plane of the galaxy appears warped, and the efficiency of the two different spiral patterns in star formation is different. A preliminary radial velocity field is determined from three interferograms in H-alpha light, and is found to be acceptably fitted by a simple bulge-plus-disk dynamical model in which the apparent disk mass-to-light ratio sharply increases from center to edge.

Star Formation Driven Outflows In Edge-On Spiral Galaxies Based on HST/ACS Observations

NASA Astrophysics Data System (ADS)

Rossa, Joern; Dahlem, M.; Dettmar, R.; van der Marel, R. P.

2007-12-01

We present new results on extraplanar diffuse ionized gas (eDIG) in four late-type, actively star-forming edge-on spirals. The high spatial resolution narrowband imaging observations were obtained with ACS on-board HST. Our H-alpha observations reveal a multitude of structures on both small and large scales. Whereas all four galaxies have been studied with ground-based telescopes before, here the small scale structure of the extended emission line gas is presented for the very first time at a spatial resolution of 0.05", corresponding to 5 pc at the mean distance to our galaxies. The eDIG morphology is very different for all four targets, as a result of their different star formation activity and galaxy mass. There is a very smooth DIG morphology observed in two of the galaxies (NGC4634 and NGC5775), whereas the other two (NGC4700 and NGC7090) show a much more complex morphology with intricate filaments, bubbles and supershells. We discuss how the morphology of the eDIG, in particular the break-up of diffuse emission into filaments in galaxy halos, depends on physical parameters such as galaxy mass and SF activity and other tracers as well as the galactic environment. Support for proposal 10416 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

MAGNETIZED GAS IN THE SMITH HIGH VELOCITY CLOUD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hill, Alex S.; McClure-Griffiths, Naomi M.; Mao, S. A.

2013-11-01

We report the first detection of magnetic fields associated with the Smith High Velocity Cloud. We use a catalog of Faraday rotation measures toward extragalactic radio sources behind the Smith Cloud, new H I observations from the Robert C. Byrd Green Bank Telescope, and a spectroscopic map of Hα from the Wisconsin H-Alpha Mapper Northern Sky Survey. There are enhancements in rotation measure (RM) of ≈100 rad m{sup –2} which are generally well correlated with decelerated Hα emission. We estimate a lower limit on the line-of-sight component of the field of ≈8 μG along a decelerated filament; this is amore » lower limit due to our assumptions about the geometry. No RM excess is evident in sightlines dominated by H I or Hα at the velocity of the Smith Cloud. The smooth Hα morphology of the emission at the Smith Cloud velocity suggests photoionization by the Galactic ionizing radiation field as the dominant ionization mechanism, while the filamentary morphology and high (≈1 Rayleigh) Hα intensity of the lower-velocity magnetized ionized gas suggests an ionization process associated with shocks due to interaction with the Galactic interstellar medium. The presence of the magnetic field may contribute to the survival of high velocity clouds like the Smith Cloud as they move from the Galactic halo to the disk. We expect these data to provide a test for magnetohydrodynamic simulations of infalling gas.« less

Spectrophotometric Study of the Region of the Sky Around the Galaxies Markarian 261 and 262

NASA Astrophysics Data System (ADS)

Khachikian, E. Ye.; Sargsyan, L. A.

2005-10-01

Results are presented from a detailed spectrophotometric study of a unique system of physically coupled galaxies whose spectra contain identical emission lines. This system consists of four galaxies, three of which have a double or multiple structure in their central portions and are, by definition, galaxies with two or multiple nuclei. Two of these objects are the galaxies with an ultraviolet excess (UVE), Mark 261 and Mark 262, while one is a galaxy made up of two identical starlike nuclei that are referred to as the “twin objects.” In the DSS2 charts, the latter show up as two adjacent stars without any surroundings. However, there are two condensations between these starlike nuclei. The fourth object has a triplet structure. It is shown here that all these objects have the same emission (line) spectra and red shifts. All the physical characteristics that can be determined from the spectra are determined: red shifts, relative intensities of emission lines, their equivalent widths, distances to the galaxies, etc. It is concluded that the members of this system have a common origin, more or less consistent with Ambartsumyan's idea of the fragmentation of an isolated, high density body.

Rotational velocities of newly discovered, low-mass members of the Alpha Persei cluster

NASA Technical Reports Server (NTRS)

Stauffer, John R.; Hartmann, Lee W.; Jones, Burton F.

1989-01-01

About 30 new, low-mass members of the young open cluster Alpha Persei are identified via a proper-motion study and subsequent photometric and spectroscopic observations. Membership in the cluster is confirmed for a number of the fainter proper-motion candidates from Heckman, Dieckvoss, and Kox (1956). Coordinates, finding charts, BVRI photometry, and rotational velocities are provided for most of the stars. At least two of the stars show peculiar H-alpha emission profiles, with weak but very broad emission wings, and relatively narrow absorption reversals. The rotational velocity distribution for low-mass stars in the Alpha Per cluster are compared with recently derived rotational velocity distributions for T Tauri stars, placing strong constraints on the mechanisms for angular momentum loss during pre-main-sequence evolution.

Young stellar objects & photoevaporating protoplanetary disks in the Orion's sibling NGC 1977.

NASA Astrophysics Data System (ADS)

Kim, J. S.; Fang, M.; Clarke, C. J.; Facchini, S.; Pascucci, I.; Apai, D.; Bally, J.

We present young stellar population in NGC 1977, Orion Nebula's sibling, and the discovery of new photoevaporating protoplanetary disks (proplyds) around a B star, 42 Ori. NGC 1977 (age≲2 Myr) is located at ˜30arcmin north of the Orion Nebula at a distance of ˜400 pc, but it lacks high mass O stars unlike in Orion Nebula Cluster (ONC). Nevertheless, we have identified seven proplyds in vicinity of its most massive star, 42 Ori (B1V). The proplyds show cometary Halpha emission in HST images, with clear ionization front and tails evaporating away from 42 Ori. These are the first proplyds to be found around a B star, while previously known proplyds were found near O stars. The FUV radiation impinging on these proplyds is 10-30 times weaker than that on the proplyds in ONC. We find that observed proplyd sizes are consistent with a model for photoevaporation in weak FUV radiation field. We briefly discuss one of the interesting YSOs found in this lesser-known star forming region in Orion, NGC 1977.

Ellerman bombs and UV bursts: reconnection at different atmospheric layers?

NASA Astrophysics Data System (ADS)

Hansteen, V. H.; Ortiz-Carbonell, A. N.; Rouppe van der Voort, L.

2017-12-01

The emergence of magnetic flux through the photosphere and into the outer solar atmosphere produces, amongst many other phenomena, the appearance of Ellerman bombs (EBs) in the photosphere. EBs are observed in the wings of H(alpha) and are highly likely to be due to reconnection in the photosphere, below the chromospheric canopy. However, signs of the reconnection process are also observed in several other spectral lines, typical of the chromosphere or transition region. An example are the UV bursts observed in the transition region lines of Si IV. In this work we analyze high cadence coordinated observations between the 1-m Swedish Solar Telescope and the IRIS spacecraft in order to study the possible relationship between reconnection events at different layers in the atmosphere, and in particular, the timing history between them. High cadence, high resolution H-alpha images from the SST provide us with the positions, timings and trajectories of Ellerman bombs in an emerging flux region. Simultaneous co-aligned IRIS slit-jaw images at 1400 and 1330 A and detailed Si IV spectra from the fast spectrograph raster allow us to study the transition region counterparts of those photospheric Ellerman bombs. Our main goal is to study whether there is a temporal relationship between the appearance of an EB and the appearance of a UV burst. Eventually we would like to investigate whether reconnection happens at discrete heights, or as a reconnection sheet spanning several layers at the same time.

CAUGHT IN THE ACT: STRONG, ACTIVE RAM PRESSURE STRIPPING IN VIRGO CLUSTER SPIRAL NGC 4330

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abramson, Anne; Kenney, Jeffrey D. P.; Crowl, Hugh H.

We present a multi-wavelength study of NGC 4330, a highly inclined spiral galaxy in the Virgo Cluster which is a clear example of strong, ongoing intracluster medium-interstellar medium (ICM-ISM) ram pressure stripping. The H I has been removed from well within the undisturbed old stellar disk, to 50%-65% of R{sub 25}. Multi-wavelength data (WIYN BVR-H{alpha}, Very Large Array 21 cm H I and radio continuum, and Galaxy Evolution Explorer NUV and FUV) reveal several one-sided extraplanar features likely caused by ram pressure at an intermediate disk-wind angle. At the leading edge of the interaction, the H{alpha} and dust extinction curvemore » sharply out of the disk in a remarkable and distinctive 'upturn' feature that may be generally useful as a diagnostic indicator of active ram pressure. On the trailing side, the ISM is stretched out in a long tail which contains 10% of the galaxy's total H I emission, 6%-9% of its NUV-FUV emission, but only 2% of the H{alpha}. The centroid of the H I tail is downwind of the UV/H{alpha} tail, suggesting that the ICM wind has shifted most of the ISM downwind over the course of the past 10-300 Myr. Along the major axis, the disk is highly asymmetric in the UV, but more symmetric in H{alpha} and H I, also implying recent changes in the distributions of gas and star formation. The UV-optical colors indicate very different star formation histories for the leading and trailing sides of the galaxy. On the leading side, a strong gradient in the UV-optical colors of the gas-stripped disk suggests that it has taken 200-400 Myr to strip the gas from a radius of >8 to 5 kpc, but on the trailing side there is no age gradient. All our data suggest a scenario in which NGC 4330 is falling into the cluster center for the first time and has experienced a significant increase in ram pressure over the last 200-400 Myr. Many of the UV-bright stars that form outside the thin disk due to ram pressure will ultimately produce stellar thick disk and halo components with characteristic morphologies and age distributions distinct from those produced by gravitational interactions.« less

A RADIAL VELOCITY TEST FOR SUPERMASSIVE BLACK HOLE BINARIES AS AN EXPLANATION FOR BROAD, DOUBLE-PEAKED EMISSION LINES IN ACTIVE GALACTIC NUCLEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jia; Halpern, Jules P.; Eracleous, Michael

2016-01-20

One of the proposed explanations for the broad, double-peaked Balmer emission lines observed in the spectra of some active galactic nuclei (AGNs) is that they are associated with sub-parsec supermassive black hole (SMBH) binaries. Here, we test the binary broad-line region hypothesis through several decades of monitoring of the velocity structure of double-peaked Hα emission lines in 13 low-redshift, mostly radio-loud AGNs. This is a much larger set of objects compared to an earlier test by Eracleous et al. and we use much longer time series for the three objects studied in that paper. Although systematic changes in radial velocitymore » can be traced in many of their lines, they are demonstrably not like those of a spectroscopic binary in a circular orbit. Any spectroscopic binary period must therefore be much longer than the span of the monitoring (assuming a circular orbit), which in turn would require black hole masses that exceed by 1–2 orders of magnitude the values obtained for these objects using techniques such as reverberation mapping and stellar velocity dispersion. Moreover, the response of the double-peaked Balmer line profiles to fluctuations of the ionizing continuum and the shape of the Lyα profiles are incompatible with an SMBH binary. The binary broad-line region hypothesis is therefore disfavored. Other processes evidently shape these line profiles and cause the long-term velocity variations of the double peaks.« less

Multispectral Observations and Analysis of the Rosette Nebula

NASA Astrophysics Data System (ADS)

Huber, Jeremy

The Rosette nebula is a large, ring-shaped emission nebula with a distinctive central cavity excavated by its central cluster of OB stars. Toward understanding the three dimensional structure and fundamental physical processes of this object, we have acquired ux-calibrated, 4-degree field, deep exposures of the Rosette region through 3 nm bandwidth Halpha (656.3 nm) as well as Hbeta (486.1nm), [OIII] (500.7 nm) and [SII] (671.6 nm) filters with 4.5 nm bandwidth. The 4 arcsec/pixel images are supplemented with 4 degree field slit spectra and combined with archival data from the Galactic Evolution Explorer satellite (GALEX), Akari, the Infrared Astronomical Satellite (IRAS), the Midcourse Space Experiment (MSX), the Wide-field Infrared Survey Explorer (WISE), the Wilkinson Microwave Anisotropy Probe (WMAP) and the Planck mission, along with published single dish radio data of the hydrogen continuum at 1410, 2700, and 4750 MHz. These disparate sources have been converted to the same flux and spatial scale as our own wide field data to create a multispectral data cube which allows comparative analysis across the electromagnetic spectrum. Using ratios of data cube slices, spatial maps of extinction and ionization have been constructed to explore the spatial variation of these parameters across the nebula. Comparison of emission in different wavelengths across the data cube allows generation of a spectral energy distribution (SED) to probe dust temperature and geometry. A radial profile analysis of emission from the Rosette in each band supports a spherical shell model of three dimensional structure, and visual representations of this model have been generated in both Python and Javascript/GLSL. An investigation of anomalous dust emission in the center of the nebula via supplemental spectroscopy, conducted on the Anglo-Australian Telescope, is also presented.

Orbital Stability Results for Soliton Solutions to Nonlinear Schrodinger Equations with External Potentials

NASA Astrophysics Data System (ADS)

Lindgren, Joseph B.

The Rosette nebula is a large, ring-shaped emission nebula with a distinctive central cavity excavated by its central cluster of OB stars. Toward understanding the three dimensional structure and fundamental physical processes of this object, we have acquired ux-calibrated, 4-degree field, deep exposures of the Rosette region through 3 nm bandwidth Halpha (656.3 nm) as well as Hbeta (486.1nm), [OIII] (500.7 nm) and [SII] (671.6 nm) filters with 4.5 nm bandwidth. The 4 arcsec/pixel images are supplemented with 4 degree field slit spectra and combined with archival data from the Galactic Evolution Explorer satellite (GALEX), Akari, the Infrared Astronomical Satellite (IRAS), the Midcourse Space Experiment (MSX), the Wide-field Infrared Survey Explorer (WISE), the Wilkinson Microwave Anisotropy Probe (WMAP) and the Planck mission, along with published single dish radio data of the hydrogen continuum at 1410, 2700, and 4750 MHz. These disparate sources have been converted to the same flux and spatial scale as our own wide field data to create a multispectral data cube which allows comparative analysis across the electromagnetic spectrum. Using ratios of data cube slices, spatial maps of extinction and ionization have been constructed to explore the spatial variation of these parameters across the nebula. Comparison of emission in different wavelengths across the data cube allows generation of a spectral energy distribution (SED) to probe dust temperature and geometry. A radial profile analysis of emission from the Rosette in each band supports a spherical shell model of three dimensional structure, and visual representations of this model have been generated in both Python and Javascript/GLSL. An investigation of anomalous dust emission in the center of the nebula via supplemental spectroscopy, conducted on the Anglo-Australian Telescope, is also presented.

A Study on Atomically Thin Ultra Short Conducting Channels, Breakdown, and Environmental Effects

NASA Astrophysics Data System (ADS)

Sundararajan, Abhishek

The Rosette nebula is a large, ring-shaped emission nebula with a distinctive central cavity excavated by its central cluster of OB stars. Toward understanding the three dimensional structure and fundamental physical processes of this object, we have acquired ux-calibrated, 4-degree field, deep exposures of the Rosette region through 3 nm bandwidth Halpha (656.3 nm) as well as Hbeta (486.1nm), [OIII] (500.7 nm) and [SII] (671.6 nm) filters with 4.5 nm bandwidth. The 4 arcsec/pixel images are supplemented with 4 degree field slit spectra and combined with archival data from the Galactic Evolution Explorer satellite (GALEX), Akari, the Infrared Astronomical Satellite (IRAS), the Midcourse Space Experiment (MSX), the Wide-field Infrared Survey Explorer (WISE), the Wilkinson Microwave Anisotropy Probe (WMAP) and the Planck mission, along with published single dish radio data of the hydrogen continuum at 1410, 2700, and 4750 MHz. These disparate sources have been converted to the same flux and spatial scale as our own wide field data to create a multispectral data cube which allows comparative analysis across the electromagnetic spectrum. Using ratios of data cube slices, spatial maps of extinction and ionization have been constructed to explore the spatial variation of these parameters across the nebula. Comparison of emission in different wavelengths across the data cube allows generation of a spectral energy distribution (SED) to probe dust temperature and geometry. A radial profile analysis of emission from the Rosette in each band supports a spherical shell model of three dimensional structure, and visual representations of this model have been generated in both Python and Javascript/GLSL. An investigation of anomalous dust emission in the center of the nebula via supplemental spectroscopy, conducted on the Anglo-Australian Telescope, is also presented.

A revised and updated catalog of quasi-stellar objects

NASA Technical Reports Server (NTRS)

Hewitt, A.; Burbidge, G.

1993-01-01

The paper contains a catalog of all known quasi-stellar objects (QSOs) with measured emission redshifts, and BL Lac objects, complete to 1992 December 31. The catalog contains 7315 objects, nearly all QSOs including about 90 BL Lac objects. The catalog and references contain extensive information on names, positions, magnitudes, colors, emission-line redshifts, absorption, variability, polarization, and X-ray, radio, and infrared data. A key in the form of subsidiary tables enables the reader to relate the name of a given object to its coordinate name, which is used throughout the compilation. Plots of the Hubble diagram, the apparent magnitude distribution, the emission redshift distribution, and the distribution of the QSOs on the sky are also given.

First measurements of Dα spectrum produced by anisotropic fast ions in the gas dynamic trap

NASA Astrophysics Data System (ADS)

Lizunov, A.; Anikeev, A.

2014-11-01

Angled injection of eight deuterium beams in gas dynamic trap (GDT) plasmas builds up the population of fast ions with the distribution function, which conserves a high degree of initial anisotropy in space, energy, and pitch angle. Unlike the Maxwellian distribution case, the fast ion plasma component in GDT cannot be exhaustively characterized by the temperature and density. The instrumentation complex to study of fast ions is comprised of motional Stark effect diagnostic, analyzers of charge exchange atoms, and others. The set of numerical codes using for equilibrium modeling is also an important tool of analysis. In the recent campaign of summer 2014, we recorded first signals from the new fast ion D-alpha diagnostic on GDT. This paper presents the diagnostic description and results of pilot measurements. The diagnostic has four lines of sight, distributed across the radius of an axially symmetric plasma column in GDT. In the present setup, a line-integrated optical signal is measured in each channel. In the transverse direction, the spatial resolution is 18 mm. Collected light comes to the grating spectrometer with the low-noise detector based on a charge-coupled device matrix. In the regime of four spectra stacked vertically on the sensor, the effective spectral resolution of measurements is approximately 0.015 nm. Exposure timing is provided by the fast optical ferroelectric crystal shutter, allowing frames of duration down to 70 μs. This number represents the time resolution of measurements. A large dynamic range of the camera permits for a measurement of relatively small light signals produced by fast ions on top of the bright background emission from the bulk plasma. The fast ion emission has a non-Gaussian spectrum featuring the characteristic width of approximately 4 nm, which can be separated from relatively narrow Gaussian lines of D-alpha and H-alpha coming from the plasma periphery, and diagnostic beam emission. The signal to noise ratio varies from approximately ten for the central channel to approximately five for the outermost channel. We used the special set of Monte Carlo codes to fit the measured spectra. The shape of model fit shows a good agreement with the experimental fast ion D-alpha spectrum.

Most Massive Spiral Galaxy Known in the Universe

NASA Astrophysics Data System (ADS)

2000-12-01

The VLT Observes Rapid Motion in Distant Object Summary The most massive spiral galaxy known so far in the Universe has been discovered by a team of astronomers from Garching, Padova, Leiden, ESO and London [1]. They base their conclusion on recent observations with ISAAC , an infrared-sensitive, multi-mode instrument on ESO's Very Large Telescope at the Paranal Observatory. This galaxy has been designated ISOHDFS 27 and is located at a distance of approx. 6 billion light-years (the redshift is 0.58). Its measured mass is more than 1000 billion times that of the Sun [2]. It is thus about four times more massive than our own galaxy, the Milky Way, and twice as heavy as the heaviest spiral galaxy known so far. The determination of the mass of ISOHDFS 27 is based on a unique measurement of the motions of its stars and nebulae around the center. The faster the motion is, the greater is the mass. It is, in essence, the same method that allows determining the mass of the Earth from the orbital speed and distance of the Moon. This is the first time a "rotation curve" has been observed in such a distant galaxy by means of infrared observations, allowing a very detailed dynamical study. Other observations by the team concern a pair of distant, interacting galaxies that were also found to possess comparably high masses. They also have observations of a third galaxy at a distance of about 10 billion light-years, with a mass that approaches that of ISOHDFS 27 . The new result has important cosmological implications, as it demonstrates that very heavy structures had already been formed in the Universe at a comparatively early epoch . PR Photo 33a/00 : ISOHDFS 27 , the heaviest spiral galaxy known. PR Photo 33b/00 : The "raw" ISAAC spectrum of ISOHDFS 27 . PR Photo 33c/00 : H-alpha profile of ISOHDFS 27 . Star formation in young galaxies It is of fundamental importance to current cosmological studies to understand how stars evolve within galaxies and how the galaxies themselves evolve into the various shapes we observe. Some are elliptical, others have the form of single or multiple spirals. Quite a few, especially smaller ones, appear to have no particular structure at all and are referred to as "irregular". With the advent of large optical/infrared telescopes like the ESO VLT, astronomers are now able to observe extremely distant objects and hence to "look back" to the time when galaxies were being formed in the young Universe. They have found it particularly useful to observe in the infrared part of the spectrum during the present search for "young galaxies". Such observations minimize the effects of dust obscuration and serve to trace the active phases of galaxy evolution , i.e. those specific periods of time when there is particularly intense star-formation in a galaxy. It is still not well known what triggers such phases of enhanced star-forming activity, but it is suspected that galaxy collisions and mergers may play an important role. The formation of stars usually takes place deep inside thick dust clouds that absorb the optical and UV light from the young stars and re-emit it in the infrared region of the spectrum. The imprints of this type of activity are thus best observed in that spectral band. Indeed, the infrared spectra of such objects have been found to undergo huge variations that relate to the related, complex processes. Infrared observations are therefore crucial for the study of these most violent episodes in the Universe. By means of detailed observations of distant galaxies, we may hope to learn how they occurred at earlier times and, in particular, how the major structures (e.g., spirals, bulges) that we now see in most galaxies were formed. Dusty Infrared-Luminous Galaxies In 1995-98, the infrared camera ISOCAM onboard the ESA Infrared Space Observatory (ISO) , with its unique imaging capabilities, provided astronomers with the first deep, overall "infrared view" of the Universe. Through various deep surveys with ISO, a new class of objects was discovered: luminous, distant galaxies detected during transient phases of enhanced infrared emission and undergoing rapid evolution with cosmic time. One of the sky areas surveyed by ISO was the Hubble Deep Field South (HDF-S) , that has also been observed with various ESO telescopes including the VLT, cf. ESO PR 20/98. The present team of astronomers decided to investigate some of the luminous galaxies that were detected by ISOCAM in the HDF-S area. Their goal was to better understand the enigmatic nature of these unsual objects and to try to learn which processes are really behind those huge amounts of energy that are emitted by these galaxies in the infrared region of the spectrum. However, all of the galaxies in HDF-S are at very large distances - several billion light-years away (i.e. with redshifts between 0.6 and 1.5) and they are rather faint. They refer to these objects as ISOHDFS galaxies and their colours are quite red. The astronomers therefore decided to use one of the most efficient astronomical infrared instruments now available, the multi-mode ISAAC on the 8.2-m VLT ANTU telescope. VLT Observations of ISOHDFS galaxies In September 1999, the team began to obtain low-resolution spectra of about one dozen of these galaxies. This initial observing run at Paranal was very successful and it provided a first clue towards the true nature of these systems. It was found, in particular, that ISOHDFS galaxies emit strongly in the H-alpha spectral line from hydrogen atoms and that this emission originates in dusty regions with intense star formation activity in these galaxies. The astronomers determined accurate redshifts (and hence, distances to the individual galaxies) by measuring the Doppler shifts of the H-alpha lines in their infrared spectra (an example of an early observation of this type is shown in ESO PR 19/98 ). Inspired by the excellent quality of these first VLT observations, they were ready to take the next, challenging step in August 2000. They now attempted to get a deeper insight into the nature and dynamical stage of the ISOHDFS galaxies, by means of measurements of the stellar masses in the nuclear regions of these objects. The spectrum of ISOHDFS 27 ESO PR Photo 33a/00 ESO PR Photo 33a/00 [Preview - JPEG: 400 x 358 pix - 74k] [Normal - JPEG: 800 x 715 pix - 240ak] [Hi-Res - JPEG: 3000 x 2683 pix - 1.8Mb] Caption : PR Photo 33a/00 is reproduced from an optical image of the distant galaxy ISOHDFS 27 , obtained with the Hubble Space Telescope (HST). The angular size of this galaxy is about 7 arcsec, corresponding to about 130,000 light-years (40 kpc) at the distance of the galaxy, approx. 6,000 million light-years. The inclination of the galaxy's main plane to the line-of-sight is about 50°. Technical information about this photo is available below. The first target for this new study was a large spiral galaxy, designated ISOHDFS 27 and of which an HST image is shown in Photo 33a/00 . The superb observing conditions at Paranal - the seeing improved to the near-record value of only 0.2 arcsec during the acquisition of these data! - made it possible to obtain the first spatially resolved, infrared H-alpha spectra of some of the ISOHDFS galaxies, allowing for the first time a probe into the dynamical stage of these distant objects. ESO PR Photo 33b/00 ESO PR Photo 33b/00 [Preview - JPEG: 400 x 322 pix - 69k] [Normal - JPEG: 800 x 643 pix - 728k] [Hi-Res - JPEG: 3000 x 2413 pix - 944k] ESO PR Photo 33c/00 ESO PR Photo 33c/00 [Preview - JPEG: 400 x 344 pix - 19k] [Normal - JPEG: 800 x 687 pix - 76k] Caption : PR Photo 33b/00 shows the "raw" spectrum of the distant galaxy ISOHDFS 27 , obtained with the ISAAC infrared instrument at the 8.2-m VLT ANTU telescope. Light from hydrogen atoms emitted in the red spectral region (the H-alpha emission line) is visible as two prominent "blobs" on either side of the central, featureless spectrum (the galaxy "continuum"). A weaker emission line from singly ionized nitrogen ([N II]) is seen to the right; it shows exactly the same behaviour. Technical information about this photo is available below. Caption : PR Photo 33c/00 shows the extracted H-alpha profile in ISOHDFS 27 , following extensive image processing of the spectrum shown in Photo 33b/00. When corrected for the inclination of the galaxy (50°), the peak-to-peak velocity difference is about 830 km/sec, corresponding to a rotational velocity of about 415 km/sec. This is about three times more than what is typical for normal spiral galaxies and hence indicates a very large mass. Photo 33b/00 shows the "raw" ISAAC spectrum, i.e. the image of the spectrum as seen in the read-out from the detector. The derived spectral profile of the H-alpha line is shown in Photo 33c/00 . The shape is very unusual and implies that the emitting region is probably not concentrated at the centre of the galaxy, but most likely has a disk-like structure. Taking into account the inclination of the galaxy (50°), the difference in velocity between the two peaks is 830 km/sec, i.e. the rotational velocity is half of that, 415 km/sec, or significantly more than what is measured in normal spiral galaxies. This was an interesting start for an ambitious project. But the astronomers got really excited when they made the first estimate of the total mass of that galaxy. "I can't believe it, this spiral galaxy is really massive!" , said Dimitra Rigopoulou from the Garching team. And she added: "With an estimated mass of 10 12 times that of our Sun and 4 times the mass of our own Galaxy, it seems to be the most massive spiral galaxy found so far in the Universe!" Indeed, careful calculations later showed that a total mass of 1.04 10 12 solar masses is present within 4 arcsec of the central region of (an area of 8 arcsec across), corresponding to 100,000 light-years (40 kpc) in ISOHDFS 27 . This is enormous by all standards [3]. The baryonic mass which corresponds to the mass in the older stars and is estimated from the infrared spectrum, is found to be 6 x10 11 solar masses, about half the dynamical mass. During the same observing run, two other ISO-detected infrared sources were observed. One turned out to be a system of two counter-rotating galaxies with masses of about 2 x 10 11 solar masses and the other an even more distant galaxy (about 12 billion light-years) with comparably high mass. Implications and Future Plans The present programme is a fine illustration of the importance of "collaboration" between space- and ground-based telescopes. While the galaxies were first found with ISO and HST, it took the enormous light-gathering capability of the VLT to obtain a detailed spectrum and measure their masses. Clearly, these exciting results have important implications for future studies of formation and evolution of galaxies, as well as the origin of the IR background. The discovery of such massive spiral galaxies at very large distances implies that enormous structures were in place in the Universe, already some 6 billion years ago. Galaxies like ISOHDFS 27 which are strongly emitting in the infrared region of the spectrum are presumed to contribute significantly to the observed infrared background radiation. Consequently, these new observations imply that the infrared background is largely made up of massive galaxies with recent star formation activity. The team now plans to continue its work on the determination of the dynamical status of other high-redshift galaxies. These studies are indeed very timely since a plethora of future space- and ground-based missions such as NGST, SIRTF, FIRST and ALMA will be able to perform even more detailed follow-up observations of these objects. The present observations open a new and exciting era in the study of the formation of galaxies in the young Universe. Notes [1]: The project on exploring the dynamical stage of ISO-detected galaxies in the Hubble Deep Field South is being carried out by a large international collaboration led by astronomers from the Max-Planck-Institut für Extraterrestrische Physik (MPE) in Garching (Germany) and the Padova University (Italy). Besides Dimitra Rigopoulou and Alberto Franceschini , the team includes Herve Aussel (Padova), Catherine Cesarsky (ESO), Reinhard Genzel (MPE), David Elbaz (Saclay, France), Michael Rowan-Robinson (IC, UK), Niranjan Thatte (MPE), and Paul van der Werf (Leiden, The Netherlands). [2]: 1 billion = 1,000 million = 10 9. [3]: Some other distant spiral galaxies have been found with masses in the range of 1 - 5 x 10 11 solar masses. The heaviest spiral galaxy known until now is UGC 12591 , with a measured mass of 6 x10 11 solar masses. Technical information about the photos PR Photo 33a/00 covers an area of approx. 7 x 8 arcsec 2 ; North is up, East is to the left. The present results, including the spectrum shown in PR Photo 33b/00 , are based on observations that were collected in visitor mode during August 18-20, 2000. For these observations, ISAAC was used in medium resolution mode (R ~ 5000) with a slit of 0.6 arcsec x 2 arcmin. The pixel scale is 0.146 arcsec/pix. The wavelength for the H-alpha is 1.0370 µm and the SZ band was used for the observations. The seeing was very good throughout the run (from 0.2 - 0.9 arcsec). The spectrum shown in PR Photo 33b/00 was acquired under 0.2 arcsec seeing.

Laboratory simulation of photoionized plasma among astronomical compact objects

NASA Astrophysics Data System (ADS)

Fujioka, Shinsuke; Yamamoto, Norimasa; Wang, Feilu; Salzmann, David; Li, Yutong; Rhee, Yong-Joo; Nishimura, Hiroaki; Takabe, Hideaki; Mima, Kunioki

2008-11-01

X-ray line emission with several-keV of photon energy was observed from photoionized accreting clouds, for example CYGNUS X-3 and VELA X-1, those are exposed by hard x-ray continuum from the compact objects, such as neutron stars, black holes, or white dwarfs, although accreting clouds are thermally cold. The x-ray continuum-induced line emission gives a good insight to the accreting clouds. We will present a novel laboratory simulation of the photoionized plasma under well-characterized conditions by using high-power laser facility. Blackbody radiator with 500-eV of temperature, as a miniature of a hot compact object, was created.Silicon (Si) plasma with 30-eV of electron temperature was produced in the vicinity of the 0.5-keV blackbody radiator. Line emissions of lithium- and helium-like Si ions was clearly observed around 2-keV of photon-energy from the thermally cold Si plasma, this result is hardly interpreted without consideration of the photoionization. Atomic kinetics code reveals importance of inner-shell ionization directly caused by incoming hard x-rays.

Megamasers: Molecular Diagnostics of the Nuclear ISM

NASA Astrophysics Data System (ADS)

Baan, Willem A.; Klöckner, Hans-R.

Molecular emissions are powerful tracers of intense heating and star-formation processes in galactic nuclei. In this paper we consider the characteristics of molecular Megamaser emission among the population of (Ultra-) Luminous Infrared Galaxies that are powered by intense star-formation or accretion onto a massive compact object. In addition, we consider the systematic behavior of the line emission of high-density tracer molecules. An evolutionary scenario is presented for ULIRGs that may explain the molecular line ratios observed in the population of FIR galaxies.

Megamasers: Molecular Diagnostics of the Nuclear Ism

NASA Astrophysics Data System (ADS)

Baan, Willem A.; Klöckner, Hans-R.

2005-01-01

Molecular emissions are powerful tracers of intense heating and star-formation processes in galactic nuclei. In this paper we consider the characteristics of molecular Megamaser emission among the population of (Ultra-) Luminous Infrared Galaxies that are powered by intense star-formation or accretion onto a massive compact object. In addition, we consider the systematic behavior of the line emission of high-density tracer molecules. An evolutionary scenario is presented for ULIRGs that may explain the molecular line ratios observed in the population of FIR galaxies.

Redshifts for Superliminal Candidates.II.

NASA Astrophysics Data System (ADS)

Vermeulen, R. C.; Taylor, G. B.; Readhead, A. C. S.; Browne, I. W. A.

1996-03-01

Spectra are presented for 24 compact extragalactic radio sources from complete samples being studied with VLBI. New emission line redshifts are given for 21 of the objects; in 7 of these we have also identified associated or intervening absorption line systems. In 1 other source there are absorption lines which provide a lower limit to the redshift. The remaining 2 objects have strong featureless spectra and are likely to be blazars.

ORFEUS spectroscopy of the O BT VI lines in symbiotic stars and the Raman scattering process

NASA Astrophysics Data System (ADS)

Schmid, H. M.; Krautter, J.; Appenzeller, I.; Barnstedt, J.; Dumm, T.; Fromm, A.; Gölz, M.; Grewing, M.; Gringel, W.; Haas, C.; Hopfensitz, W.; Kappelmann, N.; Krämer, G.; Lindenberger, A.; Mandel, H.; Mürset, U.; Schild, H.; Schmutz, W.; Widmann, H.

1999-08-01

We present orfeus spectra of the O vi lambda lambda 1032,1038 emission lines in the symbiotic stars AG Dra, V1016 Cyg, RR Tel, CD-43(deg) 14304, AG Peg and Z And. The O vi emission lines can convert into broad and highly polarized emission lines at lambda 6825 and lambda 7082 in a Raman scattering process by neutral hydrogen. From a comparison of direct and Raman scattered radiation we extract new information on the scattering geometry in symbiotic systems. The nebular O vi emission lines are in all objects redshifted by about +40 km s(-1) . This can be explained as a radiative line transfer effect in a slowly expanding emission region. A comparable redshift is measured in the Raman scattered O vi lines. In AG Peg the O vi emissions show beside a narrow nebular line a broad component from a fast stellar wind outflow. Many interstellar absorption lines of molecular hydrogen are detected, particularly near the O vi lambda 1038 component. With model calculations we investigate their impact on the O vi lines. From the dereddened line fluxes of the direct and Raman scattered O vi lines we derive the scattering efficiency, which is defined as photon flux ratio N_Raman/N_O VI. The efficiencies derived for RR Tel, V1016 Cyg and Z And indicate that about 30% of the released O vi lambda 1032 photons interact with the neutral scattering region. The efficiencies for AG Dra and CD-43(deg14304) are much higher, which may suggest that the O vi nebulosity is embedded in a H(0) -region. The D-type system RR Tel shows strong line profile differences between the direct O vi emission, which is single-peaked, and the Raman scattered emission, which is double-peaked. This indicates that the neutral scattering region in RR Tel ``sees'' different O vi line profiles, implying that the O vi nebulosity is far from spherically symmetric. In a tentative model we suggest for RR Tel an O vi flow pattern where material streams from the cool giant towards the hot component, which further accelerates the gas radially. For the S-type systems AG Dra, CD-43(deg14304) and Z And the line profile differences between the direct and the Raman scattered O vi emissions are less pronounced. This may suggest that the O vi profiles depend less on the emission direction than in the D-type system RR Tel. For AG Peg we detect for the first time the Raman scattered emission at lambda 6825. The Raman line shows a narrow, nebular component as the O vi line, but no equivalent emission to the broad O vi wind component. The higher conversion efficiency for the narrow component indicates that the nebular O vi emission is significantly closer to the cool giant than the hot, mass losing component, and strongly supports previous colliding wind models for this object. Based on observations taken during the orfeus-spas i and orfeus-spas ii space shuttle missions, and ground based data collected at the ESO 2.2m and 3.6m telescopes at La Silla, Chile, and the 4.2m William Herschel Telescope at La Palma, Canary Islands. ESO observations were granted for the programs 52.7-040 and 58.D-0866.

Results of Detailed Modeling of the Narrow-Line Region of Seyfert Galaxies

NASA Technical Reports Server (NTRS)

Moore, David; Cohen, Ross D.

1996-01-01

We present model line profiles of [O II] lambda3727, [Ne III] lambda3869, [O I] lambda5007, [Fe VII] lambda6087, [Fe X] lambda6374, [O I] lambda6300, H(alpha) lambda6563, and [S 2] lambda6731. The profiles presented here illustrate explicitly the pronounced effects that collisional de-excitation, and that spatial variations in both the ionization parameter and cloud column density, have on Narrow-Line Region (NLR) model profiles. The above effects were included only qualitatively in a previous analytical treatment by Moore and Cohen. By making a direct correspondence between these model profiles and the analytical model profiles of Moore and Cohen, and by comparing with the observed profiles presented in a companion paper and also with those presented elsewhere in the literature, we strengthen some of the conclusions of Moore and Cohen. Most notably, we argue for constant ionization parameter, uniformly accelerated outflow of clouds that are individually stratified in ionization, and the interpretation of emission-line width correlations with ionization potential as a column density effect. For comparison with previous observational studies, such as our own in a companion paper, we also calculate profile parameters for some of the models, and we present and discuss the resulting line width correlations with critical density (n(sub cr)) and Ionization Potential (IP). Because the models we favor are those that produce extended profile wings as observed in high spectral resolution studies, the line width correlations of our favoured models are of particular interest. Line width correlations with n(sub cr) and/or IP result only if the width parameter is more sensitive to extended profile wings than is the Full Width at Half-Maximum (FWHM). Correlations between FWHM and n(sub cr) and/or IP result only after convolving the model profiles with a broad instrumental profile that simulates the lower spectral resolution used in early observational studies. The model in agreement with the greatest number of observational considerations has electron density decreasing outward from n(sub e) approx. equals 10(exp 6)/cu cm to n(sub e) approx. equals 10(exp 2)/cu cm and, due to collisional de-excitation effects in the lowest velocity clouds, it generates broad flat-topped profile peaks in the lines of lowest critical density (e.g., [O II] lambda3727 and [S II] lambda(lambda)6716, 6731). Because the observed profile peaks of both low and high critical density lines are often very similar, our favored model requires a contribution to NLR emission-line spectra from low-velocity, low-density, and low-ionization gas not included in the model NLR.

VizieR Online Data Catalog: M33 molecular clouds and young stellar clusters (Corbelli+, 2017)

NASA Astrophysics Data System (ADS)

Corbelli, E.; Braine, J.; Bandiera, R.; Brouillet, N.; Combes, F.; Druard, C.; Gratier, P.; Mata, J.; Schuster, K.; Xilouris, M.; Palla, F.

2017-04-01

Table 5 : Physical parameters for the 566 molecular clouds identified through the IRAM 30m CO J=2-1 survey of the star forming disk of M33. For each cloud the cloud type and the following properties are listed: celestial coordinates, galactocentric radius, cloud deconvolved effective radius and its uncertainty, CO(2-1) line velocity dispersion from CPROPS and its uncertainty, line velocity dispersion from a Gaussian fit, CO luminous mass and its uncertainty, and virial mass from a Gaussian fit. In the last column the identification number of the young stellar cluster candidates associated with the molecular cloud are listed. Notes: We identify up to four young stellar cluster candidates (YSCCs) associated with each molecular cloud and we list them according to the identification number of Sharma et al. (2011, Cat. J/A+A/545/A96) given also in Table 6. Table 6 : Physical parameters for the 630 young stellar cluster candidates identified via their mid-infrared emission in the star forming disk of M33. For each YSCC we list the type of source, the identified number of the molecular clouds associated with it (if any) and the corresponding cloud classes. In addition, for each YSCC we give the celestial coordinates, the bolometric, total infrared, FUV and Halpha luminosities, the estimated mass and age, the visual extinction, the galactocentric radius, the source size, and its flux at 24μm. (2 data files).

Superwind Outflows in Seyfert Galaxies? : Large-Scale Radio Maps of an Edge-On Sample

NASA Astrophysics Data System (ADS)

Colbert, E.; Gallimore, J.; Baum, S.; O'Dea, C.

1995-03-01

Large-scale galactic winds (superwinds) are commonly found flowing out of the nuclear region of ultraluminous infrared and powerful starburst galaxies. Stellar winds and supernovae from the nuclear starburst provide the energy to drive these superwinds. The outflowing gas escapes along the rotation axis, sweeping up and shock-heating clouds in the halo, which produces optical line emission, radio synchrotron emission, and X-rays. These features can most easily be studied in edge-on systems, so that the wind emission is not confused by that from the disk. We have begun a systematic search for superwind outflows in Seyfert galaxies. In an earlier optical emission-line survey, we found extended minor axis emission and/or double-peaked emission line profiles in >~30% of the sample objects. We present here large-scale (6cm VLA C-config) radio maps of 11 edge-on Seyfert galaxies, selected (without bias) from a distance-limited sample of 23 edge-on Seyferts. These data have been used to estimate the frequency of occurrence of superwinds. Preliminary results indicate that four (36%) of the 11 objects observed and six (26%) of the 23 objects in the distance-limited sample have extended radio emission oriented perpendicular to the galaxy disk. This emission may be produced by a galactic wind blowing out of the disk. Two (NGC 2992 and NGC 5506) of the nine objects for which we have both radio and optical data show good evidence for a galactic wind in both datasets. We suggest that galactic winds occur in >~30% of all Seyferts. A goal of this work is to find a diagnostic that can be used to distinguish between large-scale outflows that are driven by starbursts and those that are driven by an AGN. The presence of starburst-driven superwinds in Seyferts, if established, would have important implications for the connection between starburst galaxies and AGN.

The Quasar Fraction in Low-Frequency Selected Complete Samples and Implications for Unified Schemes

NASA Technical Reports Server (NTRS)

Willott, Chris J.; Rawlings, Steve; Blundell, Katherine M.; Lacy, Mark

2000-01-01

Low-frequency radio surveys are ideal for selecting orientation-independent samples of extragalactic sources because the sample members are selected by virtue of their isotropic steep-spectrum extended emission. We use the new 7C Redshift Survey along with the brighter 3CRR and 6C samples to investigate the fraction of objects with observed broad emission lines - the 'quasar fraction' - as a function of redshift and of radio and narrow emission line luminosity. We find that the quasar fraction is more strongly dependent upon luminosity (both narrow line and radio) than it is on redshift. Above a narrow [OII] emission line luminosity of log(base 10) (L(sub [OII])/W) approximately > 35 [or radio luminosity log(base 10) (L(sub 151)/ W/Hz.sr) approximately > 26.5], the quasar fraction is virtually independent of redshift and luminosity; this is consistent with a simple unified scheme with an obscuring torus with a half-opening angle theta(sub trans) approximately equal 53 deg. For objects with less luminous narrow lines, the quasar fraction is lower. We show that this is not due to the difficulty of detecting lower-luminosity broad emission lines in a less luminous, but otherwise similar, quasar population. We discuss evidence which supports at least two probable physical causes for the drop in quasar fraction at low luminosity: (i) a gradual decrease in theta(sub trans) and/or a gradual increase in the fraction of lightly-reddened (0 approximately < A(sub V) approximately < 5) lines-of-sight with decreasing quasar luminosity; and (ii) the emergence of a distinct second population of low luminosity radio sources which, like M8T, lack a well-fed quasar nucleus and may well lack a thick obscuring torus.

"Untangling the centimetre-wavelength sky"

NASA Astrophysics Data System (ADS)

Leahy, J. Patrick

2015-08-01

The global SED of the Milky Way reaches a minimum at about 80 GHz. In the decade below this, three emission processes predominate: synchrotron, from cosmic ray leptons spiralling in the Galactic magnetic field; free-free, from ionized gas in nebulae and the diffuse warm ionized medium; and anomalous microwaves (AME), believed to be dipole emission from spinning very small dust grains. Each component provides unique diagnostics: synchroton traces the lepton energy spectrum near 20 GeV and reveals the local and global structure of the Galactic magnetic field, free-free probes ionized gas where the usual H-alpha tracer is obscured, and AME traces a new interstellar component, whose relation to the general dust population can now be explored. In total intensity, accurate separation of these components is a hard problem not yet completely solved, mainly due to the spatial variability of the AME spectrum, which in the Planck 2015 analysis dominates the SED between 20 and 60 GHz. New large-area surveys in the frequency decade below the satellite microwave will, in combination with Planck and WMAP, will provide a far more robust determination of each component.In contrast to the confused situation in total intensity, only synchrotron contributes significant polarization in our band, and WMAP and Planck give a clear view of the polarized synchrotron sky, for the first time effectively free of Faraday rotation and depolarization. New ground-based microwave polarization surveys such as GMIMS, S-PASS, C-BASS, and QUIJOTE, will add much higher sensitivity and also have the high frequency resolution needed to trace the line-of-sight component of the magnetic field via Faraday synthesis. The polarization along the Galactic plane constrains models of the global Galactic magnetic field. Away from the plane, polarization probes the tangling of the field in the Galactic halo and clarifies the structure of the Galactic loops and spurs, which impose a large-scale coherence on the synchrotron sky. These loops are the largest objects in the sky, but their nature and distance is still controversial, and will be clarified by on-going studies of the ISM structure within 1-2 kpc of the Sun.

STAR FORMATION ACTIVITY IN THE GALACTIC H II REGION Sh2-297

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mallick, K. K.; Ojha, D. K.; Dewangan, L. K.

We present a multiwavelength study of the Galactic H II region Sh2-297, located in the Canis Major OB1 complex. Optical spectroscopic observations are used to constrain the spectral type of ionizing star HD 53623 as B0V. The classical nature of this H II region is affirmed by the low values of electron density and emission measure, which are calculated to be 756 cm{sup -3} and 9.15 Multiplication-Sign 10{sup 5} cm{sup -6} pc using the radio continuum observations at 610 and 1280 MHz, and Very Large Array archival data at 1420 MHz. To understand local star formation, we identified the youngmore » stellar object (YSO) candidates in a region of area {approx}7.'5 Multiplication-Sign 7.'5 centered on Sh2-297 using grism slitless spectroscopy (to identify the H{alpha} emission line stars), and near infrared (NIR) observations. NIR YSO candidates are further classified into various evolutionary stages using color-color and color-magnitude (CM) diagrams, giving 50 red sources (H - K > 0.6) and 26 Class II-like sources. The mass and age range of the YSOs are estimated to be {approx}0.1-2 M {sub Sun} and 0.5-2 Myr using optical (V/V-I) and NIR (J/J-H) CM diagrams. The mean age of the YSOs is found to be {approx}1 Myr, which is of the order of dynamical age of 1.07 Myr of the H II region. Using the estimated range of visual extinction (1.1-25 mag) from literature and NIR data for the region, spectral energy distribution models have been implemented for selected YSOs which show masses and ages to be consistent with estimated values. The spatial distribution of YSOs shows an evolutionary sequence, suggesting triggered star formation in the region. The star formation seems to have propagated from the ionizing star toward the cold dark cloud LDN1657A located west of Sh2-297.« less

The open cluster IC 4665

NASA Technical Reports Server (NTRS)

Prosser, Charles F.

1993-01-01

The results of a combined astrometric, photometric, and spectroscopic program to identify members of the open cluster IC 4665 are presented. Numerous new proper motion/photometric candidate members and at least 23 M dwarfs with H-alpha emission have been identified. A reanalysis of IC 4665 age using different methods yields conflicting results ranging from about 3 X 10 exp 7 yr to the age of the Pleiades. This study provides a list of candidate cluster members in the intermediate and low-mass regime of this cluster. Future spectroscopic observations of these candidates should eventually identify true cluster members.

Luminous Herbig-Haro objects from a massive protostar: The unique case of HH 80/81

NASA Astrophysics Data System (ADS)

Reipurth, Bo

2017-08-01

Herbig-Haro (HH) objects are the optical manifestations of shock waves excited by outflows from young stars. They represent one of the few classes of spatially extended astronomical objects where both structural changes and proper motions can be measured on time scales of years to decades. HH 80/81 is a pair of HH objects in Sagittarius which are the intrinsically most luminous HH objects known. The driving source of HH 80/81 is the embedded star IRAS 18162-2048, which has a luminosity of 20,000 Lsun and excites a compact HII region, suggesting that it is a newborn massive star. HH objects associated with massive young stars are very rare, only a handful of cases are known, but what makes the HH 80/81 source unique among massive protostars is that it produces a finely collimated bipolar radio jet with extremely high velocity and pointing straight to HH 80/81. We propose to observe the HH 80/81 complex with WFC3 and the following four filters: Halpha 6563, Hbeta 4861, [SII] 6717/31, and [OIII] 5007. First epoch HST images were obtained 22 years ago, which now allows a very precise determination of proper motions. Groundbased optical and radio proper motions are not only uncertain, but actually contradict each other, a controversy that will be resolved by HST. The fine resolution of WFC3 allows a study of both fine structural details and structural changes of the shocks. Finally we will use a sophisticated adaptive grid code to interpret the (de-reddened) line ratios across the shocks.

Role of tolerogen conformation in induction of oral tolerance in experimental autoimmune myasthenia gravis.

PubMed

Im, S H; Barchan, D; Souroujon, M C; Fuchs, S

2000-10-01

We recently demonstrated that oral or nasal administration of recombinant fragments of the acetylcholine receptor (AChR) prevents the induction of experimental autoimmune myasthenia gravis (EAMG) and suppresses ongoing EAMG in rats. We have now studied the role of spatial conformation of these recombinant fragments in determining their tolerogenicity. Two fragments corresponding to the extracellular domain of the human AChR alpha-subunit and differing in conformation were tested: Halpha1-205 expressed with no fusion partner and Halpha1-210 fused to thioredoxin (Trx), and designated Trx-Halpha1-210. The conformational similarity of the fragments to intact AChR was assessed by their reactivity with alpha-bungarotoxin and with anti-AChR mAbs, specific for conformation-dependent epitopes. Oral administration of the more native fragment, Trx-Halpha1-210, at the acute phase of disease led to exacerbation of EAMG, accompanied by an elevation of AChR-specific humoral and cellular reactivity, increased levels of Th1-type cytokines (IL-2, IL-12), decreased levels of Th2 (IL-10)- or Th3 (TGF-beta)-type cytokines, and higher expression of costimulatory factors (CD28, CTLA4, B7-1, B7-2, CD40L, and CD40). On the other hand, oral administration of the less native fragments Halpha1-205 or denatured Trx-Halpha1-210 suppressed ongoing EAMG and led to opposite changes in the immunological parameters. It thus seems that native conformation of AChR-derived fragments renders them immunogenic and immunopathogenic and therefore not suitable for treatment of myasthenia gravis. Conformation of tolerogens should therefore be given careful attention when considering oral tolerance for treatment of autoimmune diseases.

Extremely red quasars from SDSS, BOSS and WISE: classification of optical spectra

NASA Astrophysics Data System (ADS)

Ross, Nicholas P.; Hamann, Fred; Zakamska, Nadia L.; Richards, Gordon T.; Villforth, Carolin; Strauss, Michael A.; Greene, Jenny E.; Alexandroff, Rachael; Brandt, W. Niel; Liu, Guilin; Myers, Adam D.; Pâris, Isabelle; Schneider, Donald P.

2015-11-01

Quasars with extremely red infrared-to-optical colours are an interesting population that can test ideas about quasar evolution as well as orientation, obscuration and geometric effects in the so-called AGN unified model. To identify such a population, we match the quasar catalogues of the Sloan Digital Sky Survey (SDSS), the Baryon Oscillation Spectroscopic Survey (BOSS) to the Wide-Field Infrared Survey Explorer (WISE) to identify quasars with extremely high infrared-to-optical ratios. We identify 65 objects with rAB - W4Vega > 14 mag (i.e. Fν(22 μm)/Fν(r) ≳ 1000). This sample spans a redshift range of 0.28 < z < 4.36 and has a bimodal distribution, with peaks at z ˜ 0.8 and z ˜ 2.5. It includes three z > 2.6 objects that are detected in the W4 band but not W1 or W2 (i.e. `W1W2 dropouts'). The SDSS/BOSS spectra show that the majority of the objects are reddened type 1 quasars, type 2 quasars (both at low and high redshift) or objects with deep low-ionization broad absorption lines (BALs) that suppress the observed r-band flux. In addition, we identify a class of type 1 permitted broad emission-line objects at z ≃ 2-3 which are characterized by emission line rest-frame equivalent widths (REWs) of ≳150 Å, much larger than those of typical quasars. In particular, 55 per cent (45 per cent) of the non-BAL type 1s with measurable C IV in our sample have REW(C IV) > 100 (150) Å, compared to only 5.8 per cent (1.3 per cent) for non-BAL quasars in BOSS. These objects often also have unusual line ratios, such as very high N V/Ly α ratios. These large REWs might be caused by suppressed continuum emission analogous to type 2 quasars; however, there is no obvious mechanism in standard unified models to suppress the continuum without also obscuring the broad emission lines.

Some properties of the filamentary nebula at 1723 - 46

NASA Technical Reports Server (NTRS)

Bedford, D. K.; Elliott, K. H.; Ramsey, B.; Meaburn, J.

1984-01-01

High resolution spectra of the interstellar NaI D2 absorption line have been obtained for seven B-type stars aligned with an extensive filamentary nebula. Very fine filaments have now been found on a high contrast print of a deep H-alpha and forbidden N II plate, making identification as a fossilized remnant probable but uncertain. The inferred age is about 20,000 yr, the distance less than 200 pc, the diameter less than 17.5 pec, but the initial energy is only about 2 x 10 to the 47th erg.

Spectroscopic identification of SNe 2004ds and SN 2004dt

NASA Astrophysics Data System (ADS)

Gal-Yam, Avishay

2004-08-01

A. Gal-Yam, D. Fox and S. Kulkarni, California Institute of Technology, report on red spectra (range 550-780 nm) obtained by Kulkarni and Fox on Aug. 13.5 UT at the 10-m Keck I telescope (+ LRIS). The spectrum of of SN 2004ds (IAUC #8386), shows a broad, well-developed P-Cyg H_alpha line and suggests that this is a type II supernova. The spectrum of SN 2004dt (IAUC #8386), shows the distinctive Si II 6100 absorption trough around 6100 Angstrom, indicating this is a young SN Ia.

Low-redshift quasars in the SDSS Stripe 82: associated companion galaxies and signature of star formation

NASA Astrophysics Data System (ADS)

Bettoni, D.; Falomo, R.; Kotilainen, J. K.; Karhunen, K.

2017-04-01

We obtained optical spectroscopy of close (<80 kpc) companion objects of a sample of 12 low-redshift quasars (z < 0.3) selected from the SDSS Stripe82 area and that are in the subsample of 52 QSOs for which both multicolour host galaxies properties and galaxy environment were recently investigated in detail. We found that for 8 out of 12 sources the companion galaxy is associated with the QSO having a difference of radial velocity that is less than 400 km s-1. Many of these associated companions exhibit [OII] λ3727 Å emission lines suggestive of episodes of (recent) star formation possibly induced by past interactions. The star formation rate of the companion galaxies as derived from [O II] line luminosity is, however, modest, with a median value of 1.0 ± 0.8 M⊙ yr-1, and the emission lines are barely consistent with expectation from gas ionization by the QSO. The role of the QSO for inducing star formation in close companion galaxies appears meager. For three objects we also detect the starlight spectrum of the QSO host galaxy, which is characterized by absorption lines of old stellar population and [O II] emission line.

Optical observational programs at the Indian Institute of Astrophysics

NASA Astrophysics Data System (ADS)

Singh, Jagdev; Ravindra, B.

The Indian Institute of Astrophysics has been making optical observations of the sun for more than a century by taking images of the sun in continuum to study the photosphere, Ca-K line and H-alpha line in order to study the chromosphere by using the same instruments which are used to study the long term variations of the magnetic fields on the sun. The digitizers have been developed using uniform light sources, imaging optics without any vignetting in the required FOV and large format 4K×4K CCD cameras to digitize the data for scientific studies. At the Solar Tower Telescope we have performed very high resolution spectroscopic observations around Ca-K line to investigate the variations and delineate the contribution of various features to the solar cycle variations. Solar coronal studies have been done during the occurrence of total solar eclipses and with a coronagraph to study the coronal heating. Here we discuss the systematic temporal variations observed in the green and red emission profiles using high spectral and temporal observations during the 2006, 2009 and 2010 total solar eclipses. The TWIN telescope a new facility has been fabricated and installed at Kodaikanal observatory to continue the synoptic observations of the sun and a space-based coronagraph is also being designed and fabricated in collaboration with various laboratories of ISRO (LEOS, ISAC and SAC) and USO. In this article we present the summary of results of optical observational programs carried out at Kodaikanal Observatory and during the eclipse expeditions where authors have played a leading role. Furthermore, this review is not complete in all respects of all the observational programs carried out at the Kodaikanal observatory.

METALLICITY AND TEMPERATURE INDICATORS IN M DWARF K-BAND SPECTRA: TESTING NEW AND UPDATED CALIBRATIONS WITH OBSERVATIONS OF 133 SOLAR NEIGHBORHOOD M DWARFS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rojas-Ayala, Barbara; Covey, Kevin R.; Lloyd, James P.

2012-04-01

We present K-band spectra for 133 nearby (d < 33 ps) M dwarfs, including 18 M dwarfs with reliable metallicity estimates (as inferred from an FGK type companion), 11 M dwarf planet hosts, more than 2/3 of the M dwarfs in the northern 8 pc sample, and several M dwarfs from the LSPM catalog. From these spectra, we measure equivalent widths of the Ca and Na lines, and a spectral index quantifying the absorption due to H{sub 2}O opacity (the H{sub 2}O-K2 index). Using empirical spectral type standards and synthetic models, we calibrate the H{sub 2}O-K2 index as an indicatormore » of an M dwarf's spectral type and effective temperature. We also present a revised relationship that estimates the [Fe/H] and [M/H] metallicities of M dwarfs from their Na I, Ca I, and H{sub 2}O-K2 measurements. Comparisons to model atmosphere provide a qualitative validation of our approach, but also reveal an overall offset between the atomic line strengths predicted by models as compared to actual observations. Our metallicity estimates also reproduce expected correlations with Galactic space motions and H{alpha} emission line strengths, and return statistically identical metallicities for M dwarfs within a common multiple system. Finally, we find systematic residuals between our H{sub 2}O-based spectral types and those derived from optical spectral features with previously known sensitivity to stellar metallicity, such as TiO, and identify the CaH1 index as a promising optical index for diagnosing the metallicities of near-solar M dwarfs.« less

HR Del REMNANT ANATOMY USING TWO-DIMENSIONAL SPECTRAL DATA AND THREE-DIMENSIONAL PHOTOIONIZATION SHELL MODELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moraes, Manoel; Diaz, Marcos

2009-12-15

The HR Del nova remnant was observed with the IFU-GMOS at Gemini North. The spatially resolved spectral data cube was used in the kinematic, morphological, and abundance analysis of the ejecta. The line maps show a very clumpy shell with two main symmetric structures. The first one is the outer part of the shell seen in H{alpha}, which forms two rings projected in the sky plane. These ring structures correspond to a closed hourglass shape, first proposed by Harman and O'Brien. The equatorial emission enhancement is caused by the superimposed hourglass structures in the line of sight. The second structuremore » seen only in the [O III] and [N II] maps is located along the polar directions inside the hourglass structure. Abundance gradients between the polar caps and equatorial region were not found. However, the outer part of the shell seems to be less abundant in oxygen and nitrogen than the inner regions. Detailed 2.5-dimensional photoionization modeling of the three-dimensional shell was performed using the mass distribution inferred from the observations and the presence of mass clumps. The resulting model grids are used to constrain the physical properties of the shell as well as the central ionizing source. A sequence of three-dimensional clumpy models including a disk-shaped ionization source is able to reproduce the ionization gradients between polar and equatorial regions of the shell. Differences between shell axial ratios in different lines can also be explained by aspherical illumination. A total shell mass of 9 x 10{sup -4} M {sub sun} is derived from these models. We estimate that 50%-70% of the shell mass is contained in neutral clumps with density contrast up to a factor of 30.« less

Winds from T Tauri stars. II - Balmer line profiles for inner disk winds

NASA Technical Reports Server (NTRS)

Calvet, Nuria; Hartmann, Lee; Hewett, Robert

1992-01-01

Results are presented of calculations of Balmer emission line profiles using escape probability methods for T Tauri wind models with nonspherically symmetric geometry. The wind is assumed to originate in the inner regions of an accretion disk surrounding the T Tauri star, and flows outward in a 'cone' geometry. Two types of wind models are considered, both with monotonically increasing expansion velocities as a function of radial distance. For flows with large turbulent velocities, such as the HF Alfven wave-driven wind models, the effect of cone geometry is to increase the blue wing emission, and to move the absorption reversal close to line center. Line profiles for a wind model rotating with the same angular velocity as the inner disk are also calculated. The Balmer lines of this model are significantly broader than observed in most objects, suggesting that the observed emission lines do not arise in a region rotating at Keplerian velocity.

The Kinematics of Multiple-peaked Lyα Emission in Star-forming Galaxies at z ~ 2-3

NASA Astrophysics Data System (ADS)

Kulas, Kristin R.; Shapley, Alice E.; Kollmeier, Juna A.; Zheng, Zheng; Steidel, Charles C.; Hainline, Kevin N.

2012-01-01

We present new results on the Lyα emission-line kinematics of 18 z ~ 2-3 star-forming galaxies with multiple-peaked Lyα profiles. With our large spectroscopic database of UV-selected star-forming galaxies at these redshifts, we have determined that ~30% of such objects with detectable Lyα emission display multiple-peaked emission profiles. These profiles provide additional constraints on the escape of Lyα photons due to the rich velocity structure in the emergent line. Despite recent advances in modeling the escape of Lyα from star-forming galaxies at high redshifts, comparisons between models and data are often missing crucial observational information. Using Keck II NIRSPEC spectra of Hα (z ~ 2) and [O III]λ5007 (z ~ 3), we have measured accurate systemic redshifts, rest-frame optical nebular velocity dispersions, and emission-line fluxes for the objects in the sample. In addition, rest-frame UV luminosities and colors provide estimates of star formation rates and the degree of dust extinction. In concert with the profile sub-structure, these measurements provide critical constraints on the geometry and kinematics of interstellar gas in high-redshift galaxies. Accurate systemic redshifts allow us to translate the multiple-peaked Lyα profiles into velocity space, revealing that the majority (11/18) display double-peaked emission straddling the velocity-field zero point with stronger red-side emission. Interstellar absorption-line kinematics suggest the presence of large-scale outflows for the majority of objects in our sample, with an average measured interstellar absorption velocity offset of langΔv absrang = -230 km s-1. A comparison of the interstellar absorption kinematics for objects with multiple- and single-peaked Lyα profiles indicate that the multiple-peaked objects are characterized by significantly narrower absorption line widths. We compare our data with the predictions of simple models for outflowing and infalling gas distributions around high-redshift galaxies. While popular "shell" models provide a qualitative match with many of the observations of Lyα emission, we find that in detail there are important discrepancies between the models and data, as well as problems with applying the framework of an expanding thin shell of gas to explain high-redshift galaxy spectra. Our data highlight these inconsistencies, as well as illuminating critical elements for success in future models of outflow and infall in high-redshift galaxies. Based, in part, on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

ALMA WILL DETERMINE THE SPECTROSCOPIC REDSHIFT z > 8 WITH FIR [O III] EMISSION LINES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Inoue, A. K.; Shimizu, I.; Tamura, Y.

We investigate the potential use of nebular emission lines in the rest-frame far-infrared (FIR) for determining spectroscopic redshift of z > 8 galaxies with the Atacama Large Millimeter/submillimeter Array (ALMA). After making a line emissivity model as a function of metallicity, especially for the [O III] 88 μm line which is likely to be the strongest FIR line from H II regions, we predict the line fluxes from high-z galaxies based on a cosmological hydrodynamics simulation of galaxy formation. Since the metallicity of galaxies reaches at ∼0.2 Z {sub ☉} even at z > 8 in our simulation, we expectmore » the [O III] 88 μm line as strong as 1.3 mJy for 27 AB objects, which is detectable at a high significance by <1 hr integration with ALMA. Therefore, the [O III] 88 μm line would be the best tool to confirm the spectroscopic redshifts beyond z = 8.« less

The Radio-optical Spectra of BL Lacs and Possible Relatives

NASA Astrophysics Data System (ADS)

Dennett-Thorpe, J.

I consider the suggestion that, in a complete sample of flat-spectrum radio sources with available optical spectra (Marcha et al 1996), the strong emission line objects, or those with passive elliptical spectra are close relatives of the BL Lacs. New observations at four frequencies from 8 to 43GHz are presented, together with evidence for radio variability. Combined with other radio and optical data from the literature, we are able to construct the non-thermal SEDs and use these to address the questions: are the optically passive objects potentially `unrecognised' BL Lacs (either intrinsically weak and/or hidden by starlight)? What is the relationship between the surprising number of strong emission-line objects and the BL Lacs?

Relation of large-scale coronal X-ray structure and cosmic rays. I - Sources of solar wind streams as defined by X-ray emission and H-alpha absorption features

NASA Technical Reports Server (NTRS)

Krieger, A. S.; Nolte, J. T.; Sullivan, J. D.; Lazarus, A. J.; Mcintosh, P. S.; Gold, R. E.; Roelof, E. C.

1975-01-01

The large-scale structure of the corona and the interplanetary medium during Carrington rotations 1601-1607 is discussed relative to recurrent high-speed solar wind streams and their coronal sources. Only streams A, C, D, and F recur on more than one rotation. Streams A and D are associated with coronal holes, while C and F originate in the high corona (20-50 solar radii) over faint X-ray emissions. The association of the streams with holes is confirmed by earlier findings that there are no large equatorial holes without an associated high-speed stream and that the area of the equatorial region of coronal holes is highly correlated with the maximum velocity observed in the associated stream near 1 AU.

Identification of two hard X-ray emitting Be stars using the HEAO 1 scanning modulation collimator

NASA Technical Reports Server (NTRS)

Steiner, J. E.; Ferrara, A.; Garcia, M.; Patterson, J.; Schwartz, D. A.; Warwick, R. S.; Watson, M. G.; Mcclintock, J. E.

1984-01-01

Using precise positions from the HEAO 1 Scanning Modulation Collimator experiment, two hard X-ray sources, 4U 0728 - 25 = 3A 0726 - 260 and 4U 2206 + 54 = 3A 2206 + 543, are identified with early-type stars. In both cases broad (10 A FWHM) H-alpha emission is detected. The UBV colors suggest that the optical counterparts are main-sequence B0-B2 stars at 2-6 kpc, implying a mean X-ray luminosity of order 10 to the 35th ergs/sq cm s (2-10 keV). The X-ray emission in both cases is highly variable, and it is suggested that they belong to the class of X-ray emitting Be stars, containing a neutron star in a widely separated binary system.

Chemi-luminescence measurements of hyperthermal Xe{sup +}/Xe{sup 2+}+ NH{sub 3} reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prince, Benjamin D.; Steiner, Colby P.; Chiu, Yu-Hui

2012-04-14

Luminescence spectra are recorded for the reactions of Xe{sup +}+ NH{sub 3} and Xe{sup 2+}+ NH{sub 3} at energies ranging from 11.5 to 206 eV in the center-of-mass (E{sub cm}) frame. Intense features of the luminescence spectra are attributed to the NH (A {sup 3}{Pi}{sub i}-X {sup 3}{Sigma}{sup -}), hydrogen Balmer series, and Xe I emission observable for both primary ions. Evidence for charge transfer products is only found through Xe I emission for both primary ions and NH{sup +} emission for Xe{sup 2+} primary ions. For both primary ions, the absolute NH (A-X) cross section increases with collision energymore » before leveling off at a constant value, approximately 9 x 10{sup -18} cm{sup 2}, at about 50 eV while H-{alpha} emission increases linearly with collision energy. The nascent NH (A) populations derived from the spectral analysis are found to be independent of collision energy and have a constant rotational temperature of 4200 K.« less

THE VIRUS-P EXPLORATION OF NEARBY GALAXIES (VENGA): THE X {sub CO} GRADIENT IN NGC 628

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blanc, Guillermo A.; Schruba, Andreas; Evans, Neal J. II

2013-02-20

We measure the radial profile of the {sup 12}CO(1-0) to H{sub 2} conversion factor (X {sub CO}) in NGC 628. The H{alpha} emission from the VENGA integral field spectroscopy is used to map the star formation rate (SFR) surface density ({Sigma}{sub SFR}). We estimate the molecular gas surface density ({Sigma}{sub H2}) from {Sigma}{sub SFR} by inverting the molecular star formation law (SFL), and compare it to the CO intensity to measure X {sub CO}. We study the impact of systematic uncertainties by changing the slope of the SFL, using different SFR tracers (H{alpha} versus far-UV plus 24 {mu}m), and COmore » maps from different telescopes (single-dish and interferometers). The observed X {sub CO} profile is robust against these systematics, drops by a factor of two from R {approx} 7 kpc to the center of the galaxy, and is well fit by a gradient {Delta}log(X {sub CO}) = 0.06 {+-} 0.02 dex kpc{sup -1}. We study how changes in X {sub CO} follow changes in metallicity, gas density, and ionization parameter. Theoretical models show that the gradient in X {sub CO} can be explained by a combination of decreasing metallicity, and decreasing {Sigma}{sub H2} with radius. Photoelectric heating from the local UV radiation field appears to contribute to the decrease of X {sub CO} in higher density regions. Our results show that galactic environment plays an important role at setting the physical conditions in star-forming regions, in particular the chemistry of carbon in molecular complexes, and the radiative transfer of CO emission. We caution against adopting a single X {sub CO} value when large changes in gas surface density or metallicity are present.« less

Probing circumplanetary disks with MagAO and ALMA

NASA Astrophysics Data System (ADS)

Wu, Ya-Lin

2018-01-01

The dedication of the Magellan Adaptive Optics (MagAO) on the 6.5 m Clay Telescope has opened a new era in high-contrast imaging. Its unique diffraction-limited wavelengths of 0.6 to 1 micron helps to probe circumplanetary disks by measuring the amount of dust reddening as well as by searching for the strongest gas accretion indicator H-alpha (0.65 micron). Using MagAO, I found that two wide-orbit planetary-mass companions CT Cha B and 1RXS 1609 B have a significant dust extinction of Av ~ 3 to 5 mag likely from their disks. For GQ Lup B, I found that it is actively accreting material from its disk and emitting strong H-alpha emission. My research with MagAO demonstrates that circumplanetary disks could be ubiquitous among young giant planets. I later carried out a survey using ALMA to image accretion disks around several wide planet-mass companions at 1.3 mm continuum and CO (2-1). This is the first systematic study aiming to measure the size, mass, and structure of planetary disks. However, except for FW Tau C (which was shown to actually be a low-mass star from the dynamical mass measurement) no disks around the companions were found in my ALMA survey. This surprising null result implies that circumplanetary disks are much more compact and denser than expected, so they are faint and optically thick in the radio wavelengths. Therefore, mid- to far-infrared may be more favorable to characterize disk properties. The MIRI camera on the JWST can test this compact optically-thick disk hypothesis by probing disk thermal emission between 10 and 25 micron.

Unusual Emissions at Various Energies and Coronal Mass Ejection Prior to the November 4, 2003 Large Solar Flare

NASA Astrophysics Data System (ADS)

Kaufmann, Pierre; Holman, G. D.; Su, Y.; Gimenez de Castro, C.; Correia, E.; de Souza, R. V.; Marun, A.; Pereyra, P.

2010-05-01

The November 4, 2003 GOES X28 flare was the largest ever recorded in its class. It produced the first evidence of the two spectrally separated radio/far-infrared emission components, one at microwaves and another in the THz range of frequencies (Kaufmann et al. 2004). We analyzed the 20 minutes before the impulsive onset of this event and found unusual activity at X-rays (RHESSI), at sub-THz frequencies (SST), at H-alpha (BBSO) and at microwaves (Itapetinga 7 GHz polarimeter, RSTN and OVSA). SOHO LASCO images have shown a large CME launched well before the large burst onset. The unusual activity began at about 19 27 UT with a slow rise at 6-10 keV and the start of a precursor at 7 GHz. Pulsations at sub-THz became pronounced, exhibiting correlations with RHESSI 25-50 keV pulsations and similar pulsations at 7 GHz. Impulsive bursts were detected with peaks at 19 34 UT at 100-300 keV and 7 GHz. LASCO movie show a large CME which linear extrapolation to the solar surface correspond to the first H-alpha BBSO brightening, suggesting an approximate launch time at about 1934 UT, close to the hard X-ray and microwave impulsive bursts and nearly 8 minutes before the onset of the large flare. These events had different locations within the AR that included the major flare location at the solar west limb, as indicated by SST pulses positions and images obtained by RHESSI and BBSO. The pulsations phenomena and superimposed impulsive events might represent the complex energy buildup mechanisms leading to the CME launch, quite distinct in time and space from the major flare that exploded afterwards.

On the origins of part-time radio pulsars

NASA Astrophysics Data System (ADS)

Zhang, Bing; Gil, Janusz; Dyks, Jaroslaw

2007-01-01

Growing evidence suggests that some radio pulsars only act sporadically. These `part-time' pulsars include long-term nulls, quasi-periodic radio flares in PSR B1931+24, as well as the so-called Rotating Radio Transients (RRATs). Based on the assumption that these objects are isolated neutron stars similar to conventional radio pulsars, we discuss two possible interpretations to the phenomenon. The first interpretation suggests that these objects are pulsars slightly below the radio emission `death line', which become occasionally active only when the conditions for pair production and coherent emission are satisfied. The second interpretation invokes a radio emission direction reversal in conventional pulsars, as has been introduced to interpret the peculiar mode changing phenomenon in PSR B1822-09. In this picture, our line of sight misses the main radio emission beam of the pulsar but happens to sweep the emission beam when the radio emission direction is reversed. These part-time pulsars are therefore the other half of `nulling' pulsars. We suggest that X-ray observations may provide clues to differentiate between these two possibilities.

Exploring the Structure of the Distant Universe with MUSE Data Cubes

NASA Astrophysics Data System (ADS)

MacDougall, Mason; Christensen, Lise

2018-01-01

The mass distribution in intergalactic and circumgalactic space is not well known since it is difficult to characterize objects in the distant universe. An ideal tool for studying such distant structure is the Multi-Unit Spectroscopic Explorer (MUSE) of the Very Large Telescope array, which employs a wide field-of-view and a large spectral range to produce high spatial resolution datasets. Here we exploit the 2 spatial dimensions and 1 spectral dimension of a particular MUSE “data cube” to identify and characterize emission line sources near the line-of-sight to quasar PKS1937-101, which lies at a redshift of z=3.787. In particular, we search for galaxy companions to a z=3.572 Lyman-limit system measured in the quasar spectrum and find an associated Lyman-alpha emitter at z=3.556 with a projected distance of 30.2 kpc from the quasar line-of-sight. Through a combination of automated source extraction and manual investigation, we also identify 25 emission line galaxies and 1 other Lyman-alpha emitter in our field. The proximity of several of these objects to the quasar line-of-sight allows us to reliably identify absorption lines in the quasar spectrum that can be associated with observed emission lines with resolved fluxes. This will help characterize the metallicities and kinematics of galaxy halos and circumgalactic media in the early universe.

Wisconsin H-Alpha Mapper | UW-Madison Astronomy

Science.gov Websites

Department of Astronomy Wisconsin H-Alpha Mapper Overview Description About WHAM Fabry-Perot Spectroscopy National Science Foundation Astronomy and... 02.20.2012 | Continue Reading » WHAM featured at Natural Astronomy Galactic Structure GALFA GLIMPSE GLIMPSE360 WHAM Extragalactic Astronomy & Cosmology Local

X Persei - correlation between H-alpha and X-ray variability

NASA Astrophysics Data System (ADS)

Zamanov, R.; Stoyanov, K. A.; Petrov, N.; Nikolov, Y.; Marchev, D.; Wolter, U.

2018-03-01

We performed H-alpha spectroscopic observations of the Be/X-ray binary X Per, optical counterpart of the slow X-ray pulsar 4U 0352+30, using the 2.0m telescope of the Rozhen National Astronomical Observatory, Bulgaria and the 1.2m TIGRE telescope located in Mexico.

Segmentation and Classification of Nepal Earthquake Induced Landslides Using SENTINEL-1 Product

NASA Astrophysics Data System (ADS)

Kunwar, Saket

2016-06-01

On April 26, 2015, an earthquake of magnitude 7.8 on the Richter scale occurred, with epicentre at Barpak (28°12'20''N,84°44'19''E), Nepal. Landslides induced due to the earthquake and its aftershock added to the natural disaster claiming more than 9000 lives. Landslides represented as lines that extend from the head scarp to the toe of the deposit were mapped by the staff of the British Geological Survey and is available freely under Open Data Commons Open Database License(ODC-ODbL) license at the Humanitarian Data Exchange Program. This collection of 5578 landslides is used as preliminary ground truth in this study with the aim of producing polygonal delineation of the landslides from the polylines via object oriented segmentation. Texture measures from Sentinel-1a Ground Range Detected (GRD) Amplitude data and eigenvalue-decomposed Single Look Complex (SLC) polarimetry product are stacked for this purpose. This has also enabled the investigation of landslide properties in the H-Alpha plane, while developing a classification mechanism for identifying the occurrence of landslides.

Relationships of a growing magnetic flux region to flares

NASA Technical Reports Server (NTRS)

Martin, S. F.; Bentley, R. D.; Schadee, A.; Antalova, A.; Kucera, A.; Dezso, L.; Gesztelyi, L.; Harvey, K. L.; Jones, H.; Livi, S. H. B.

1984-01-01

The evolution of flare sites at the boundaries of major new and growing magnetic flux regions within complexes of active regions has been analyzed using H-alpha images. A spectrum of possible relationships of growing flux regions to flares is described. An 'intimate' interaction between old and new flux and flare sites occurs at the boundaries of their regions. Forced or 'intimidated' interaction involves new flux pushing older, lower flux density fields toward a neighboring old polarity inversion line, followed by the occurrence of a flare. In 'influential' interaction, magnetic lines of force over an old polarity inversion line reconnect to new emerging flux, and a flare occurs when the magnetic field overlying the filament becomes too weak to prevent its eruption. 'Inconsequential' interaction occurs when a new flux region is too small or has the wrong orientation for creating flare conditions. 'Incidental' interaction involves a flare occurring without any significant relationship to new flux regions.

An Interferometric 270--355 GHz Spectral Line Survey of the Red Supergiant VY CMa

NASA Astrophysics Data System (ADS)

Menten, K. M.; Young, K. H.; Patel, N. A.; Gottlieb, C. A.; Thaddeus, P.; McCarthy, M. C.; Gurwell, M. A.; Belloche, A.; Kaminski, T.; Verheyen, L.; Decin, L.; Brunken, S.; Holger, S. P. M.

2011-05-01

We have used the Submillimeter Array to image the molecular line emission in the circumstellar envelope of the peculiar red supergiant star VY Canis Majoris over the whole 870 μm atmospheric window. Employing adaptive calibration using the object's continuum emission we achieve high quality one arcsecond resolution imaging of the whole 280--355 GHz range within which we find 211 distinct spectral lines from 33 molecules (including isotopologues) plus 40 unidentified lines. From the distribution of molecules we are obtaining their abundances and isotopologic abundance ratios. Using data for multiple transitions in a number of molecules we are deriving the physical conditions in the circumstellar envelope to reach a picture of the star's chemistry that can be compared with models. Our legacy survey is accompanied by a strong laboratory effort that helps with the identification of possibly newly found molecules traced by unidentified lines. We shall create a publicly accessible database of spectral-line channel-maps of the emission from all the lines detected in the survey.

X-shooter spectroscopy of young stellar objects. III. Photospheric and chromospheric properties of Class III objects

NASA Astrophysics Data System (ADS)

Stelzer, B.; Frasca, A.; Alcalá, J. M.; Manara, C. F.; Biazzo, K.; Covino, E.; Rigliaco, E.; Testi, L.; Covino, S.; D'Elia, V.

2013-10-01

Context. Traditionally, the chromospheres of late-type stars are studied through their strongest emission lines, Hα and Ca ii HK emission. Our knowledge on the whole emission line spectrum is more elusive as a result of the limited spectral range and sensitivity of most available spectrographs. Aims: We intend to reduce this gap with a comprehensive spectroscopic study of the chromospheric emission line spectrum of a sample of non-accreting pre-main sequence stars (Class III sources). Methods: We analyzed X-shooter/VLT spectra of 24 Class III sources from three nearby star-forming regions (σ Orionis, Lupus III, and TW Hya). We determined the effective temperature, surface gravity, rotational velocity, and radial velocity by comparing the observed spectra with synthetic BT-Settl model spectra. We investigated in detail the emission lines emerging from the stellar chromospheres and combined these data with archival X-ray data to allow for a comparison between chromospheric and coronal emissions. Results: For some objects in the sample the atmospheric and kinematic parameters are presented here for the first time. The effective temperatures are consistent with those derived for the same stars from an empirical calibration with spectral types. Small differences in the surface gravity found between the stars can be attributed to differences in the average age of the three star-forming regions. The strength of lithium absorption and radial velocities confirm the young age of all but one object in the sample (Sz 94). Both X-ray and Hα luminosity as measured in terms of the bolometric luminosity are independent of the effective temperature for early-M stars but decline toward the end of the spectral M sequence. For the saturated early-M stars the average emission level is almost one dex higher for X-rays than for Hα: log (Lx/Lbol) = -2.85 ± 0.36 vs. log (LHα/Lbol) = -3.72 ± 0.21. When all chromospheric emission lines (including the Balmer series up to H11, Ca ii HK, the Ca ii infrared triplet, and several He i lines) are summed up the coronal flux still dominates that of the chromosphere, typically by a factor 2-5. Flux-flux relations between activity diagnostics that probe different atmospheric layers (from the lower chromosphere to the corona) separate our sample of active pre-main sequence stars from the bulk of field M dwarfs studied in the literature. Flux ratios between individual optical emission lines show a smooth dependence on the effective temperature. The Balmer decrements can roughly be reproduced by an NLTE radiative transfer model devised for another young star of similar age. Future, more complete chromospheric model grids can be tested against this data set. Based on observations collected at the Very Large Telescope of the European Southern Observatory under programs 084.C-0269, 085.C-0238, 086.C-0173, 087.C-0244, and 089.C-0143.Tables 2-4 are available in electronic form at http://www.aanda.org

Discovery of a narrow line quasar

NASA Technical Reports Server (NTRS)

Stocke, J.; Liebert, J.; Maccacaro, T.; Griffiths, R. E.; Steiner, J. E.

1982-01-01

A stellar object is reported which, while having X-ray and optical luminosities typical of quasars, has narrow permitted and forbidden emission lines over the observed spectral range. The narrow-line spectrum is high-excitation, the Balmer lines seem to be recombinational, and a redder optical spectrum than that of most quasars is exhibited, despite detection as a weak radio source. The object does not conform to the relationships between H-beta parameters and X-ray flux previously claimed for a large sample of the active galactic nuclei. Because reddish quasars with narrow lines, such as the object identified, may not be found by the standard techniques for the discovery of quasars, the object may be a prototype of a new class of quasars analogous to high-luminosity Seyfert type 2 galaxies. It is suggested that these objects cannot comprise more than 10% of all quasars.

Optical/Infrared properties of Be stars in X-ray Binary systems

NASA Astrophysics Data System (ADS)

Naik, Sachindra

2018-04-01

Be/X-ray binaries, consisting of a Be star and a compact object (neutron star), form the largest subclass of High Mass X-ray Binaries. The orbit of the compact object around the Be star is wide and highly eccentric. Neutron stars in the Be/X-ray binaries are generally quiescent in X-ray emission. Transient X-ray outbursts seen in these objects are thought to be due to the interaction between the compact object and the circumstellar disk of the Be star at the periastron passage. Optical/infrared observations of the companion Be star during these outbursts show that the increase in the X-ray intensity of the neutron star is coupled with the decrease in the optical/infrared flux of the companion star. Apart from the change in optical/infrared flux, dramatic changes in the Be star emission line profiles are also seen during X-ray outbursts. Observational evidences of changes in the emission line profiles and optical/infrared continuum flux along with associated X-ray outbursts from the neutron stars in several Be/X-ray binaries are presented in this paper.

Resolving the Optical Emission Lines of Lyα Blob "B1" at z = 2.38: Another Hidden Quasar

NASA Astrophysics Data System (ADS)

Overzier, R. A.; Nesvadba, N. P. H.; Dijkstra, M.; Hatch, N. A.; Lehnert, M. D.; Villar-Martín, M.; Wilman, R. J.; Zirm, A. W.

2013-07-01

We have used the SINFONI near-infrared integral field unit on the Very Large Telescope to resolve the optical emission line structure of one of the brightest (L Lyα ≈ 1044 erg s-1) and nearest (z ≈ 2.38) of all Lyα blobs (LABs). The target, known in the literature as object "B1", lies at a redshift where the main optical emission lines are accessible in the observed near-infrared. We detect luminous [O III] λλ4959, 5007 and Hα emission with a spatial extent of at least 32 × 40 kpc (4'' × 5''). The dominant optical emission line component shows relatively broad lines (600-800 km s-1, FWHM) and line ratios consistent with active galactic nucleus (AGN) photoionization. The new evidence for AGN photoionization, combined with previously detected C IV and luminous, warm infrared emission, suggest that B1 is the site of a hidden quasar. This is confirmed by the fact that [O II] is relatively weak compared with [O III] (extinction-corrected [O III]/[O II] of about 3.8), which is indicative of a high, Seyfert-like ionization parameter. From the extinction-corrected [O III] luminosity we infer a bolometric AGN luminosity of ~3 × 1046 erg s-1, and further conclude that the obscured AGN may be Compton-thick given existing X-ray limits. The large line widths observed are consistent with clouds moving within the narrow-line region of a luminous QSO. The AGN scenario is capable of producing sufficient ionizing photons to power the Lyα, even in the presence of dust. By performing a census of similar objects in the literature, we find that virtually all luminous LABs harbor obscured quasars. Based on simple duty-cycle arguments, we conclude that AGNs are the main drivers of the Lyα in LABs rather than the gravitational heating and subsequent cooling suggested by cold stream models. We also conclude that the empirical relation between LABs and overdense environments at high redshift must be due to a more fundamental correlation between AGNs (or massive galaxies) and environment.

Faint Object Camera imaging and spectroscopy of NGC 4151

NASA Technical Reports Server (NTRS)

Boksenberg, A.; Catchpole, R. M.; Macchetto, F.; Albrecht, R.; Barbieri, C.; Blades, J. C.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen, P.

1995-01-01

We describe ultraviolet and optical imaging and spectroscopy within the central few arcseconds of the Seyfert galaxy NGC 4151, obtained with the Faint Object Camera on the Hubble Space Telescope. A narrowband image including (O III) lambda(5007) shows a bright nucleus centered on a complex biconical structure having apparent opening angle approximately 65 deg and axis at a position angle along 65 deg-245 deg; images in bands including Lyman-alpha and C IV lambda(1550) and in the optical continuum near 5500 A, show only the bright nucleus. In an off-nuclear optical long-slit spectrum we find a high and a low radial velocity component within the narrow emission lines. We identify the low-velocity component with the bright, extended, knotty structure within the cones, and the high-velocity component with more confined diffuse emission. Also present are strong continuum emission and broad Balmer emission line components, which we attribute to the extended point spread function arising from the intense nuclear emission. Adopting the geometry pointed out by Pedlar et al. (1993) to explain the observed misalignment of the radio jets and the main optical structure we model an ionizing radiation bicone, originating within a galactic disk, with apex at the active nucleus and axis centered on the extended radio jets. We confirm that through density bounding the gross spatial structure of the emission line region can be reproduced with a wide opening angle that includes the line of sight, consistent with the presence of a simple opaque torus allowing direct view of the nucleus. In particular, our modelling reproduces the observed decrease in position angle with distance from the nucleus, progressing initially from the direction of the extended radio jet, through our optical structure, and on to the extended narrow-line region. We explore the kinematics of the narrow-line low- and high-velocity components on the basis of our spectroscopy and adopted model structure.

KPNO 0.9m H(alpha) Imaging Survey of ``Transforming Galaxies" in Local Galaxy Groups

NASA Astrophysics Data System (ADS)

Haines, Christopher; O'Sullivan, Ewan; Raychaudhury, Somak; Gargiulo, Adriana; Campusano, Luis

2012-02-01

We propose to use the KPNO 0.9-m telescope to obtain panoramic H(alpha) imaging of ~200 galaxies in two nearby (32, 35 Mpc) galaxy groups NGC 4261 and NGC 5353 from the CLoGS local group survey. In rich clusters ram-pressure stripping has been shown to be very effective at removing the gas contents and quenching star formation in infalling spiral galaxies. It is much less clear how galaxies are affected by the much lower ram pressures found in galaxy groups, or if other environmental processes begin to dominate. Given that >50% of galaxies in the local volume reside in groups, it is vital we gain new insights into which mechanisms drive the SFR-density relation in groups. The proposed H(alpha) imaging will allow us to resolve where star-formation is occuring in each galaxy. This can effectively discriminate between ram-pressure stripping characterized by truncated H(alpha) disks, the much gentler starvation mechanism which produces anemic spirals, and nuclear star-bursts triggered by low-velocity encounters which should be most frequent in groups.

KPNO 0.9m H(alpha) Imaging Survey of ``Transforming Galaxies'' in Local Galaxy Groups

NASA Astrophysics Data System (ADS)

Haines, Christopher; O'Sullivan, Ewan; Raychaudhury, Somak; Egami, Eiichi; Campusano, Luis

2012-08-01

We propose to use the KPNO 0.9-m telescope to obtain panoramic H(alpha) imaging of ~135 galaxies in ten nearby galaxy groups (60- 80 Mpc) from the Complete Local-Volume Groups Sample (CLoGS). In rich clusters ram-pressure stripping has been shown to be very effective at removing the gas contents and quenching star formation in infalling spiral galaxies. It is much less clear how galaxies are affected by the much lower ram pressures found in galaxy groups, or if other environmental processes begin to dominate. Given that >50% of galaxies in the local volume reside in groups, it is vital that we gain new insights into which mechanisms drive the SFR-density relation in groups. The proposed H(alpha) imaging will allow us to resolve where star-formation is occurring in each galaxy. This can effectively discriminate between ram-pressure stripping characterized by truncated H(alpha) disks, the much gentler starvation mechanism which produces anemic spirals, and nuclear starbursts triggered by low-velocity encounters and mergers which should be most frequent in groups.

The Influence Of Environment On The Star Formation Properties Of Galaxies

NASA Astrophysics Data System (ADS)

Rodriguez Del Pino, Bruno

2015-10-01

This thesis explores the properties of galaxies that reside in regions of high density and the influence of the environment in their evolution. n particular, it aims to shed more light on the understanding of how galaxies stop forming stars, becoming passive objects, and the role played by environment in this process. The work presented here includes the study of the properties of galaxies in clusters at two different stages of their evolution: we first look at cluster galaxies that have recently stopped forming stars, and then we investigate the influence of environment on galaxies while they are still forming stars. The first study is based on Integral Field Spectroscopic (IFS) observations of a sample of disk `k+a' galaxies in a cluster at z 0.3. The `k+a' spectral feature imply a recent suppression of star formation in the galaxies, and therefore the study of their properties is crucial to understanding how the suppression happened. We study the kinematics and spatial distributions of the different stellar populations inhabiting these galaxies. We found that the last stars that were formed (i.e., younger stars) are rotationally-supported and behave similar to the older stars. Moreover, the spatial distribution of the young stars also resembles that of the older stellar populations, although the young stars tend to be more concentrated towards the central regions of the galaxies. These findings indicate that the process responsible for the suppression of the star formation in the cluster disk galaxies had to be gentle, withouth perturbing significantly the old stellar disks. However, a significant number of galaxies with centrally-concentrated young populations were found to have close companions, therefore implying that galaxy-galaxy interactions might also contribute to the cessation of the star formation. These results provide very valuable information on the putative transformation of star-forming galaxies into passive S0s. We then move to the study of the star formation properties and nuclear activity in galaxies in a multi-cluster system at z 0.165. We employ Tuneable Filter observations to map the Halpha and N[II] emission lines. We show the feasibility and advantages of using these type of observations to map emission lines in a large number of objects at a single redshift, and developed a procedure for the reduction and analysis of the data. We find a large number of optical AGN that were not previously detected as X-ray point sources. The probability that a galaxy hosts an AGN is not found to correlate with environment. From the analysis of the integrated star formation properties of the galaxies in the multi-cluster system we observe a significant number of galaxies with suppressed star formation with respect to the field. Although stellar mass is the main driver of the suppression of star formation, once its effect is removed, we find that galaxies in the core regions have reduced specific star formation rates (SSFRs) with respect to the infall regions. Moreover, the environment influences galaxies differently depending on their stellar mass. Galaxies with low masses experience a change in morphology (from irregulars and spirals to early-types) and colour (blue to red) as they fall into regions of higher density. However, many massive spiral galaxies retain their disk morphologies and the visibility of their spiral arms all the way to the core regions. Before becoming passive, these galaxies experience a phase exhibiting red colours and relatively high SSFRs. A significant fraction of the spiral galaxies with relatively high masses go through this phase, which could represent the transition towards becoming S0s. We finish by presenting some interesting results on the spatial distribution of the emission-line regions in the cluster galaxies. We develop a method to create emission-line images, which successfully preserves the flux within the emission lines. Our analysis on the concentrations and sizes of the star-forming regions shows that the star-forming regions of cluster galaxies are generally more concentrated than the underlying stellar populations. However, we find no differences in the spatial distribution of the star formation between galaxies in the infall and in the core regions, but the star formation is more concentrated than in the field galaxies studied in previous works. These results imply that the process responsible for the concentration or truncation of the star formation in the galaxies took place before entering the multi-cluster system of our study.

The connection between the peaks in velocity dispersion and star-forming clumps of turbulent galaxies

NASA Astrophysics Data System (ADS)

Oliva-Altamirano, P.; Fisher, D. B.; Glazebrook, K.; Wisnioski, E.; Bekiaris, G.; Bassett, R.; Obreschkow, D.; Abraham, R.

2018-02-01

We present Keck/OSIRIS adaptive optics observations with 150-400 pc spatial sampling of 7 turbulent, clumpy disc galaxies from the DYNAMO sample ($0.07

Hibernating black holes revealed by photometric mass functions

NASA Astrophysics Data System (ADS)

Casares, Jorge

2018-02-01

We present a novel strategy to uncover the Galactic population of quiescent black holes (BHs). This is based on a new concept, the photometric mass function (PMF), which opens up the possibility of an efficient identification of dynamical BHs in large fields-of-view. This exploits the width of the disc H α emission line, combined with orbital period information. We here show that H α widths can be recovered using a combination of customized H α filters. By setting a width cut-off at 2200 km s-1 we are able to cleanly remove other Galactic populations of H α emitters, including ∼99.9 per cent of cataclysmic variables (CVs). Only short-period (Porb <2.1 h) eclipsing CVs and AGNs will contaminate the sample but these can be easily flagged through photometric variability and, in the latter case, also mid-IR colours. We also describe the strategy of a deep (r = 22) Galactic plane survey based on the concept of PMFs: HAWKs, the HAlpha-Width Kilo-deg Survey. We estimate that ∼800 deg2 are required to unveil ∼50 new dynamical BHs, a three-fold improvement over the known population. For comparison, a century would be needed to produce an enlarged sample of 50 dynamical BHs from X-ray transients at the current discovery rate.

Far-Infrared and Nebular Star-Formation Rate of Dusty Star Forming Galaxies from Herschel, CANDELS and 3D-HST at z~1

NASA Astrophysics Data System (ADS)

Hasan, Farhanul; Nayyeri, Hooshang; Cooray, Asantha R.; Herschel Group: University of California Irvine. Dept. of Physics & Astronomy. Led by professor Asantha Cooray, Reed College Undergraduate Research Committee

2017-06-01

We present a combined Herschel/PACS and SPIRE and HST/WFC3 observations of the five CANDELS fields, EGS, GOODS-N, GOODS-S, COSMOS and UDS, to study star-formation activity in dusty star-forming galaxies (DSFGs) at z~1. We use 3D-HST photometry and Grism spectroscopic redshifts to construct the Spectral Energy Distributions (SED) of galaxies in the near UV, optical and near infrared, along with IRAC measurements at 3.6-8 μm in the mid-infrared, and Herschel data at 250-500 μm in the far-infrared. The 3D-HST grism line measurements are used to estimate the star-formation rate from nebular emission. In particular, we compare the H-alpha measured SFRs (corrected for attenuation) to that of direct observations of the far-infrared from Herschel. We further look at the infrared excess in this sample of dusty star-forming galaxies (denoted by LIR/LUV) as a function of the UV slope. We find that the population of high-z DSFGs sit above the trend expected for normal star-forming galaxies. Additionally, we study the dependence of SFR on total dust attenuation and confirm a strong correlation between SFR(Ha) and the balmer decrement (Hα/Hβ).

A UV spectroscopic snapshot survey of low-mass stars in the Hyades

NASA Astrophysics Data System (ADS)

Agueros, Marcel

2017-08-01

Because of its proximity, the 650-Myr-old Hyades open cluster is a unique resource for exploring the relationship between magnetic activity, rotation, and age in low-mass stars. While the cluster has been largely ignored in UV studies of the dependence of activity on rotation, we now have an extensive and growing set of complementary rotation period, Halpha, and X-ray measurements with which to examine in detail the rotation-activity relation at 650 Myr and to constrain theories of magnetic heating. We propose to measure Mg II line emission, the strongest NUV activity tracer, in COS spectra of 86 Hyads ranging in spectral type from G to M with known rotation periods or currently being observed by K2. These stars form a representative sample of low-mass Hyads with known periods and are a significant addition to, and expansion of, the sample of 20 mainly solar-mass rotators with existing (mostly low-resolution) IUE NUV spectra. The Mg II measurements will contribute significantly to our goal of mapping out the rotation-activity relation star-by-star in this benchmark open cluster. This, in turn, will move us toward an improved understanding of the radiation environment and habitability of the exoplanets we continue to find around low-mass stars.

Approaching reionization from two directions: high-redshift Lyman-alpha emitters and local analogs

NASA Astrophysics Data System (ADS)

Bagley, Micaela

2018-01-01

The dark ages that followed the recombination of the universe ended with the appearance of metal-free stars and the subsequent formation of numerous low-mass, metal-poor galaxies. The collective ionizing background from these newly-forming galaxies is thought to be responsible for the reionization of the diffuse hydrogen in the intergalactic medium between redshifts 10 and 6.5. The progression of the reionization history depends on the nature of these first sources -- their number densities, luminosities, clustering, and production rates of ionizing photons -- which is currently the subject of considerable observational and theoretical efforts.I will present results of a two-pronged approach to studying the Epoch of Reionization: a systematic search for Lyman-alpha emitting galaxies at redshifts greater than 6, and an analysis of high S/N spectra of a sample of local galaxies that are potential analogs to those responsible for the reionization. Selected for their large [OIII]/[OII] ratios and high H-alpha equivalent widths, the local galaxies have very low masses and are consistent with photoionization by stars with effective temperatures of 10^5 K. Both the emission lines and continua of the spectra are spatially extended, allowing for an analysis of galaxy properties such as gas temperature, elemental abundance, and ionizing power at different radii.

Direct photography of the Gum Nebula

NASA Technical Reports Server (NTRS)

Brandt, J. C.; Roosen, R. G.; Thompson, J.; Ludden, D. J.

1976-01-01

The paper discusses a series of wide-angle photographs taken of the Gum Nebula in the traditional region including H-alpha with the aid of a 40-cm and an 80-cm lens in both the red and the green. The photographs support the large dimensions (75 deg in galactic longitude by 40 deg in galactic latitude) of the Gum Nebula suggested earlier, and the appearance is consistent with an origin due to photons from a supernova outburst. The relatively high-density gas has cooled and is visible on the red plates. The low-density gas has remained at a high temperature and may be visible as diffuse emission on the green plates.

Optical and infrared spectrophotometry of the symbiotic system V1016 Cygni

NASA Technical Reports Server (NTRS)

Rudy, Richard J.; Rossano, George S.; Cohen, Ross D.; Puetter, R. C.

1990-01-01

Spectrophotometry from 0.46 to 1.3 micron of the peculiar emission-line object V1016 Cyg is presented. The optical region displays a weak continuum underlying the rich emission-line spectrum detailed in past studies. The infrared spectrum consists of prominent emission lines of H I, He I, He II, forbidden Ni, O I, and forbidden S III overlying a strong stellar continuum. The latter displays bands at 0.94 micron and 1.13 micron characteristic of a late-type, oxygen-rich giant as well as an absorption at 1.05 micron which is due to VO. The presence of these molecular features indicates a spectral class of M6 or later for the cool secondary. The reddening of the secondary does not appear to be much different from that of the emission lines. Among the infrared emission features is the rarely seen permitted transition of neutral oxygen at 1.1287 micron. Its presence at a strength comparable to O I 8446 A, together with the absence of O I 13164 A, confirms the result of Strafella that the strong O I lines arise primarily from fluorescent excitation by Ly-beta.

The Nature of Active Galactic Nuclei with Velocity Offset Emission Lines

NASA Astrophysics Data System (ADS)

Müller-Sánchez, F.; Comerford, J.; Stern, D.; Harrison, F. A.

2016-10-01

We obtained Keck/OSIRIS near-IR adaptive optics-assisted integral-field spectroscopy to probe the morphology and kinematics of the ionized gas in four velocity-offset active galactic nuclei (AGNs) from the Sloan Digital Sky Survey. These objects possess optical emission lines that are offset in velocity from systemic as measured from stellar absorption features. At a resolution of ˜0.″18, OSIRIS allows us to distinguish which velocity offset emission lines are produced by the motion of an AGN in a dual supermassive black hole system, and which are produced by outflows or other kinematic structures. In three galaxies, J1018+2941, J1055+1520, and J1346+5228, the spectral offset of the emission lines is caused by AGN-driven outflows. In the remaining galaxy, J1117+6140, a counterrotating nuclear disk is observed that contains the peak of Paα emission 0.″2 from the center of the galaxy. The most plausible explanation for the origin of this spatially and kinematically offset peak is that it is a region of enhanced Paα emission located at the intersection zone between the nuclear disk and the bar of the galaxy. In all four objects, the peak of ionized gas emission is not spatially coincident with the center of the galaxy as traced by the peak of the near-IR continuum emission. The peaks of ionized gas emission are spatially offset from the galaxy centers by 0.″1-0.″4 (0.1-0.7 kpc). We find that the velocity offset originates at the location of this peak of emission, and the value of the offset can be directly measured in the velocity maps. The emission-line ratios of these four velocity-offset AGNs can be reproduced only with a mixture of shocks and AGN photoionization. Shocks provide a natural explanation for the origin of the spatially and spectrally offset peaks of ionized gas emission in these galaxies. Based on observations at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Broad Hβ Emission-line Variability in a Sample of 102 Local Active Galaxies

NASA Astrophysics Data System (ADS)

Runco, Jordan N.; Cosens, Maren; Bennert, Vardha N.; Scott, Bryan; Komossa, S.; Malkan, Matthew A.; Lazarova, Mariana S.; Auger, Matthew W.; Treu, Tommaso; Park, Daeseong

2016-04-01

A sample of 102 local (0.02 ≤ z ≤ 0.1) Seyfert galaxies with black hole masses MBH > 107M⊙ was selected from the Sloan Digital Sky Survey (SDSS) and observed using the Keck 10 m telescope to study the scaling relations between MBH and host galaxy properties. We study profile changes of the broad Hβ emission line within the three to nine year time frame between the two sets of spectra. The variability of the broad Hβ emission line is of particular interest, not only because it is used to estimate MBH, but also because its strength and width are used to classify Seyfert galaxies into different types. At least some form of broad-line variability (in either width or flux) is observed in the majority (∼66%) of the objects, resulting in a Seyfert-type change for ∼38% of the objects, likely driven by variable accretion and/or obscuration. The broad Hβ line virtually disappears in 3/102 (∼3%) extreme cases. We discuss potential causes for these changing look active galactic nuclei. While similar dramatic transitions have previously been reported in the literature, either on a case-by-case basis or in larger samples focusing on quasars at higher redshifts, our study provides statistical information on the frequency of Hβ line variability in a sample of low-redshift Seyfert galaxies.

Retrieval of haze properties and HCN concentrations from the three-micron spectrum of Titan

NASA Astrophysics Data System (ADS)

Kim, Sang J.; Lee, D. W.; Sim, C. K.; Seon, K. I.; Courtin, R.; Geballe, T. R.

2018-05-01

The 3 μm spectrum of Titan contains line emission and absorption as well as a significant haze continuum. The line emission has been previously analyzed in the literature, but that analysis has not properly included the influence of haze on the line emission. We report a new analysis of the 3 μm HCN emission spectrum using radiative transfer equations that include scattering and absorption by molecules and haze particles at altitudes lower than 500 km, where the influence of haze on the emergent spectrum becomes significant. Taking advantage of the dominance of resonant single scattering in the HCN ν3 fundamental and of the moderate haze optical thickness of the atmosphere around 3 μm, we adopt single dust and molecular scattering and present a formulation for the radiative transfer process. We evaluate the quantitative influence of haze scattering on the emission line intensities, and derive vertically-resolved single scattering albedos of the haze from model fits. We also present the resulting concentrations of HCN for altitudes below 500 km, where we find that the haze scattering significantly influences the retrieval of the concentrations of HCN. We conclude that the formulation we present is useful for the analysis of the HCN line emission from Titan and other similar hazy planetary or celestial objects.

IUE observations of extragalactic objects

NASA Technical Reports Server (NTRS)

Boksenberg, A.; Snijders, M. A. J.; Wilson, R.; Benvenuti, P.; Clavell, J.; Macchetto, F.; Penston, M.; Boggess, A.; Gull, T. R.; Gondhalekar, P.

1978-01-01

During the commissioning phase of IUE several extragalactic objects were observed spectrally at low dispersion in the UV range lambda lambda 1150-3200: the Seyfert galaxies NGC4151 and NGC1068, the QSO 3C273, the BL Lacertae object B2 1101+38, the giant elliptical galaxy M87 and the spiral galaxy M81. The results obtained are presented and a preliminary analysis given for all six objects, discussing the continuous spectrum, extinction, emission line spectrum and absorption line spectrum, where possible for each case. Several new or confirmatory astrophysical results are obtained.

Spectroscopic follow-up of variability-selected active galactic nuclei in the Chandra Deep Field South

NASA Astrophysics Data System (ADS)

Boutsia, K.; Leibundgut, B.; Trevese, D.; Vagnetti, F.

2009-04-01

Context: Supermassive black holes with masses of 10^5-109 M⊙ are believed to inhabit most, if not all, nuclear regions of galaxies, and both observational evidence and theoretical models suggest a scenario where galaxy and black hole evolution are tightly related. Luminous AGNs are usually selected by their non-stellar colours or their X-ray emission. Colour selection cannot be used to select low-luminosity AGNs, since their emission is dominated by the host galaxy. Objects with low X-ray to optical ratio escape even the deepest X-ray surveys performed so far. In a previous study we presented a sample of candidates selected through optical variability in the Chandra Deep Field South, where repeated optical observations were performed in the framework of the STRESS supernova survey. Aims: The analysis is devoted to breaking down the sample in AGNs, starburst galaxies, and low-ionisation narrow-emission line objects, to providing new information about the possible dependence of the emission mechanisms on nuclear luminosity and black-hole mass, and eventually studying the evolution in cosmic time of the different populations. Methods: We obtained new optical spectroscopy for a sample of variability selected candidates with the ESO NTT telescope. We analysed the new spectra, together with those existing in the literature and studied the distribution of the objects in U-B and B-V colours, optical and X-ray luminosity, and variability amplitude. Results: A large fraction (17/27) of the observed candidates are broad-line luminous AGNs, confirming the efficiency of variability in detecting quasars. We detect: i) extended objects which would have escaped the colour selection and ii) objects of very low X-ray to optical ratio, in a few cases without any X-ray detection at all. Several objects resulted to be narrow-emission line galaxies where variability indicates nuclear activity, while no emission lines were detected in others. Some of these galaxies have variability and X-ray to optical ratio close to active galactic nuclei, while others have much lower variability and X-ray to optical ratio. This result can be explained by the dilution of the nuclear light due to the host galaxy. Conclusions: Our results demonstrate the effectiveness of supernova search programmes to detect large samples of low-luminosity AGNs. A sizable fraction of the AGN in our variability sample had escaped X-ray detection (5/47) and/or colour selection (9/48). Spectroscopic follow-up to fainter flux limits is strongly encouraged. Based on observations collected at the European Southern Observatory, Chile, 080.B-0187(A).

Uv Spectroscopy of Low-Redshift Active Galaxies -- Cyc 4

NASA Astrophysics Data System (ADS)

Boggess, Albert

1994-01-01

FOS will be used to measure the ultraviolet spectrum of active galaxies. Complementary and simultaneous visual and infrared data will also be obtained. The profile of the emission lines will provide information on the broadening mechanism and dynamics of the emitting regions. Comparison of the profile and radial velocity of the emission lines produced by species of different ioni- zation potential will allow the study of the thermal and density stratification of the emitting regions. The degree of asymmetry of lines at different wave- lengths will allow the absorbing material be identified and located. The ratio of the UV to visible lines, such as those for O I and He II will be used to estimate the reddening along the line of sight. Ratio of emission line fluxes will be compared with models in order to derive the ionization mechanism, elec- tron temperature and density, and chemical composition of the emitting gas. The emission line properties of low luminosity will be compared with those of high luminosity objects in order to investigate the covering factor and evolutionary effects. The continumm spectrum from the UV to the IR will be used to establish the emission mechanism and the nature and luminosity of the energy source. The weak absorption lines will be used to establish the physical conditions and the chemical composition of the gas in: our Galaxy, intergalactic medium and the parent galaxy. Absorption produced by broad line clouds will give information on cloud motion and covering factor.

Infrared heterodyne spectroscopy. [for observation of thermal emission from astrophysical objects

NASA Technical Reports Server (NTRS)

Mumma, M. J.; Kostiuk, T.; Buhl, D.; Chin, G.; Zipoy, D.

1982-01-01

Infrared heterodyne spectroscopy is an extremely useful tool for Doppler-limited studies of atomic and molecular lines in diverse astrophysical regions. The current state of the art is reviewed, and the analysis of CO2 lines in the atmosphere of Mars is outlined. Doppler-limited observations have enabled the discovery of natural laser emission in the mesosphere of Mars and the discovery of failure of local thermodynamic equilibrium near the surface of Mars.

A survey of IRAS data on 41 classical novae

NASA Astrophysics Data System (ADS)

Harrison, T. E.; Gehrz, R. D.

1988-09-01

The IRAS database has been searched for detections of 41 classical novae using coadditions of survey scans; 15 were detected. IRAS temporal observations of novae in outburst are discussed. The observed long-wavelength infrared distributions of DQ Her, and possibly HR Del, can be explained by emission from small (a of about 0.1 microns) dust grains heated by the central object. An alternative explanation for the energy distributions of DQ Her and HR Del is emission from fine-structure lines. FH Ser and LW Ser display energy distributions that have color temperatures much too hot to be due to heating of dust by the central source in any plausible scenario. Line emission is probably the best explanation of their observed energy distributions. The novae NQ Vul and LV Vul have energy distributions that may be contaminated by emission from galactic cirrus. The unusual object PL 1547.3-5612 exhibits an energy distribution that does not resemble those of planetary nebulae or other novae detected in this sample. An IRAS low-resolution spectrum of RR Tel shows the 10-micron silicate emission feature.

Spectra of galaxies in the Case Low-Dispersion Sky Survey in the direction of the Bootes void

NASA Technical Reports Server (NTRS)

Weistrop, Donna; Downes, Ronald A.

1988-01-01

A sample of 34 galaxies selected from the Case Low-Dispersion Northern Sky Survey in the direction of the Bootes void. Emission-line redshifts were obtained for 33 objects; the spectrum of the thirty-fourth galaxy contains no obvious features. Three of the emission-line galaxies are lcoated within the boundaries of the Bootes void, including one not previously reported. To date, all the galaxies discovered in the void have emission-line spectra. Although more than half the galaxies in the sample are fainter than M(B) = -21.0 mag, all five of the galaxies that were detected by IRAS are brighter than M(B) = 21.5 mag. The relative strengths of the emission lines in most of the galaxies, including those in the void, indicate the lines are excited by photoionization due to young, hot O and B stars. Possible causes for the star formation occurring in these galaxies include interaction with nearby galaxies, star formation induced by nuclear activity, and/or recent development of physical conditions required for star formation.

A spectroscopic search for colliding stellar winds in O-type close binary systems. I - AO Cassiopeiae

NASA Technical Reports Server (NTRS)

Gies, Douglas R.; Wiggs, Michael S.

1991-01-01

AO Cas, a short-period, double-lined spectroscopic binary, is studied as part of a search for spectroscopic evidence of colliding stellar winds in binary systems of O-type stars. High S/N ratio spectra of the H-alpha and He I 6678-A line profiles are presented, and their orbital-phase-related variations are examined in order to derive the location and motions of high-density circumstellar gas in the system. These profile variations are compared with those observed in the UV stellar wind lines in IUE archival spectra. IUE spectra are also used to derive a system mass ratio by constructing cross-correlation functions of a single-lined phase spectrum with each of the other spectra. The resulting mass ratio is consistent with the rotational line broadening of the primary star, if the primary is rotating synchronously with the binary system. The best-fit models were found to have an inclination of 61.1 deg + or - 3.0 deg and have a primary which is close to filling its critical Roche lobe.

Ti-44 Gamma-Ray Emission Lines from SN1987A Reveal an Asymmetric Explosion

NASA Technical Reports Server (NTRS)

Boggs, S. E.; Harrison, F. A.; Miyasaka, H.; Grefenstette, B. W.; Zoglauer, A.; Fryer, C. L.; Reynolds, S. P.; Alexander, D. M.; An, H.; Barret, D.;

Characterizing Quasar Outflows I: Sample, Spectral Measurements

NASA Astrophysics Data System (ADS)

Ganguly, Rajib; Christenson, D. H.; Richmond, J. M.; Derseweh, J. A.; Robbins, J. M.; Townsend, S. L.; Stark, M. A.

2012-05-01

Galaxy evolution models have shown that quasars are a crucial ingredient in the evolution of massive galaxies. Outflows play a key role in the story of quasars and their host galaxies, by helping regulate the accretion process, the star-formation rate and mass of the host galaxy (i.e., feedback). The prescription for modeling outflows as a contributor to feedback requires knowledge of the outflow velocity, geometry, and column density. In particular, we need to understand how these depend on physical parameters and how much is determined stochastically (and with what distribution). For this purpose, we are examining a sample of 11000 z=1.7-2.0 quasars from the Sloan Digital Sky Survey. This redshift range permits the following from the SDSS spectra: (1) separation of objects that do and do not exhibit outflows; (2) classification/measurement of outflow properties (ionization, velocity, velocity width); and (3) measurements of UV emission line and continuum parameters. In this poster, we subjectively divide these quasars into four categories: broad absorption-line quasars (2700 objects), associated absorption-line quasars (1700 objects), reddened quasars (160 objects), and unabsorbed/unreddened quasars (6300 objects). We present measurements of the absorption (velocities, velocity widths, equivalent widths), composite spectral profiles of outflows as a function of velocity, as well as measurements of the continuum and CIV, MgII, and FeII emission-line properties. In accompanying posters, we add photometry from the rest-frame X-ray (ROSAT and Chandra), EUV (GALEX), optical (2MASS), and infrared (WISE) bands to complete the SED. The continuum and emission-line measurements from the SDSS spectra and accompanying photometry provides estimates on the black hole masses, bolometric luminsosities, and SED. We consider empirically how these affect the outflow properties. This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. 09-ADP09-0016 issued through the Astrophysics Data Analysis Program.

The ionization mechanism of NGC 185: how to fake a Seyfert galaxy?

NASA Astrophysics Data System (ADS)

Martins, L. P.; Lanfranchi, G.; Gonçalves, D. R.; Magrini, L.; Teodorescu, A. M.; Quireza, C.

2012-02-01

NGC 185 is a dwarf spheroidal satellite of the Andromeda galaxy. From mid-1990s onwards it was revealed that dwarf spheroidals often display a varied and in some cases complex star formation history. In an optical survey of bright nearby galaxies, NGC 185 was classified as a Seyfert galaxy based on its emission line ratios. However, although the emission lines in this object formally place it in the category of Seyferts, it is probable that this galaxy does not contain a genuine active nucleus. NGC 185 was not detected in radio surveys either in 6 or 20 cm, or X-ray observations, which means that the Seyfert-like line ratios may be produced by stellar processes. In this work, we try to identify the possible ionization mechanisms for this galaxy. We discussed the possibility of the line emissions being produced by planetary nebulae (PNe), using deep spectroscopy observations obtained with the Gemini Multi-Object Spectrograph - North (GMOS-N), at Gemini. Although the fluxes of the PNe are high enough to explain the integrated spectrum, the line ratios are very far from the values for the Seyfert classification. We then proposed that a mixture of supernova remnants and PNe could be the source of the ionization, and we show that a composition of these two objects do mimic Seyfert-like line ratios. We used chemical evolution models to predict the supernova rates and to support the idea that these supernova remnants should be present in the galaxy. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership.

Solar Spicules near and at The Limb, Observed from Hinode

NASA Technical Reports Server (NTRS)

Sterling, Alphonse C.

2009-01-01

Solar spicules appear as narrow jets emanating from the chromosphere and extending into the corona. They have been observed for over a hundred years,mainly in chromospheric spectral lines such as H-alpha. Because they are at the limit of visibility of ground-based instruments, their nature has long been a puzzle. In recent years however, vast progress has been made in understanding them both theoretically and observationally. Most recently, spicule studies have undergone revolution because of the superior resolution, time cadence, and atmosphere-free observations from the Solar Optical Telescope (SOT) instrument on the Hinode spacecraft. Here we present observations of spicules from {\\sl Hinode} SOT, and consider how the observations from Hinode compare with historical observations. We include data taken in the blue and red wings of Halpha, where the spicules have widths of a few approx.100 kms, and the longest ones reach about 10(exp 4) km in extent,similar to sizes long reported from ground-based instruments. Their dynamics are not easy to generalize, with many showing the upward movement followed by falling or fading, as traditionally reported, but with others showing more dynamic or even ejective aspects. There is a strong transverse component to their motion, as extensively reported previously from the Hinode data as evidence for Alfven waves.

Imaging of High Redshift Starburst galaxies in the light of Lyman alpha

NASA Astrophysics Data System (ADS)

Beckwith, Steven

1997-07-01

The PI is the designated director for STScI but has no experience with HST. The purpose of this proposal is to gain experience with the facility by carrying out a modest observational program that is unique and will not conflict with any community programs. The proposed science is divided into priority 1 and priority 2, for 6 + 4 orbits. This division will allow allocation in parts, if the pressure on DDT is large and the total of 10 orbits unusually difficult to schedule. The priority 1 science is rather predictable and, hence, conservative, consisting of the brightest of the objects under study. The priority 2 science is somewhat riskier, because it is more difficult to estimate object brightnesses in the filters to be used on HST. Both priority 1 and priority 2 observations allow for a large degree of serendipity, because the fields are likely to have more starburst galaxies at the observed redshifts that may show up in Lyman alpha. Exploration of the high redshift u niverse and discovery of the most distant objects is still in its infancy. Only recently have the tools been available to detect normal galaxies at redshifts larger than one when the first galaxies were created {Pescarelle et al. 1996; Hu & McMahon 1996; Cowie & Hu 1998; Steidel et al. 1996}. It seems likely that young galaxies will have a variety of different signatures {Franceschini et al. 1998; Guideroni et al. 1997}, so that it will be necessary to use several diverse techniques to uncover all of them: searches at optical, infrared, x-ray, and radio wavelengths, for example. It is already known that many of the optically selected galaxies using the "dropout" technique are reddened by dust {Pettini et al. 1997}. We carried out two surveys for infrared emission-line galaxies by imaging through narrow {Resolving power 100} and broad band filters between 1 and 2.5 microns and identifying objects that appeared brighter in the narrow filters. Our first survey was designed to uncover emission lines at th e redshifts of quasars within each survey field, in case there is substantial clustering marked by quasars {Thompson et al. 1996}. In an area of 276 square minutes of arc, only one emission-line galaxy was discovered {Beckwith et al. 1998}. The surface density of such objects implied by these results is similar to that inferred from other surveys {Cowie et al. 1994; Graham & Dey 1996; Malkan et al. 1996; Bechtold et al. 1997} and suggests that the infrared emission-line galaxies constitute at most a modest population of young galaxies at high redshift. Using the same instruments, we undertook a second infrared survey for emission-line galaxies targeted at the redshifts of damped Lyman alpha absorption lines or metal absorption line in the spectra of quasars. Damped Lyman alpha absorbers are thought to contain as much baryonic matter as seen in all spiral galaxies today {Wolfe et al. 1986} and may, therefore, mark sites of vigorous star formation. Metal lines are usually associated with damped Lyman alph a systems, and they give us access to lower redshifts than Lyman alpha alone. Several other groups {Lowenthal et al. 1991; Macchetto et al. 1993; Wolfe et al. 1992; Moller & Warren 1993; Djorgovski et al. 1996; Francis et al. 1998} carried out similar surveys at optical wavelengths looking for Lyman alpha emission-line galaxies in these regions. They discovered only five such emission-line galaxies, but Wolfe {1993} showed that the implied volume density was significantly higher than in the general field. Eighteen candidates for emission line galaxies were discovered in this second survey in an area of only 150 square minutes of arc {Mannucci et al. 1998}. The emission-lines correspond to H alpha at redshifts of 0.89 {6 objects} and 2.4 {10 objects}, and [OII] at a redshift of 2.3 {2 objects}. The presence of emission lines is inferred from the photometric magnitudes in narrow and broad band interference filters. A spectrum of one candidate confirms the emission line. Most of the objects are a few seco nds of arc in extent suggesting th a t they are galaxies at the redshifts of the damped Lyman alpha absorbers. Two of these objects, Q1623+268A & Q1623+268B, were serendipitously observed by HST in an independent program to study quasars with absorption lines {by Steidel; we retrieved these images from the HST archive}. The HST images resolve the objects showing they are spiral galaxies. It is only with the HST images that a morphological identification can be made. {nB: I can make these images available as TIFF or GIF files, but I do not know how to do this via the web page for DDT}. Because our first survey targeted at the redshifts of quasars themselves uncovered only one emission- line galaxy in a larger volume, the results imply substantial clustering of young galaxies or formation within filaments or sheets whose locations are indicated by the redshifts of strong Lyman alpha line absorption along the lines of sight to more distant quasars. Our eighteen emission-line objects are unique in highlighti ng these sheets from an infrared-s elected sample. The proposed HST observations have two goals. The first is to resolve the objects that have not been observed with HST to determine the types of underlying galaxies. Our ground-based observations in the infrared and R band {WIYN telescope} are sufficient to show that most of these objects are between 1 and 3 seconds of arc across, large enough to be galaxies at high redshifts but too small to study the distribution of light from the ground. The two extent HST images of Q1623+268 A & B show clearly how HST uncovers the nature of these galaxies. The second goal is to measure the amount of Lyman alpha emission to compare the morphology of the regions producing Lyman alpha to the continuum. Such a comparison is important to understand what fraction of a young galaxy's light is produced in the starburst population, what fraction in the old population, and what fraction might be associated with an active nucleus. We can get this information by imaging each ga laxy through two filters centered o n or near Lyman alpha with different widths. The technique is similar to the infrared technique used to discover these objects. Although the HST filters were not specifically designed for this task, there is sufficient choice to make it possible with various wide and medium width filters. In the event that Lyman alpha is weak or absent, we can average the data to create a higher signal to noise ratio image. The integration times have been chosen to give S/N ratios of between 10 and 50, depending on the {unknown} brightness of the galaxies in the selected bands. The infrared and R band magnitudes suggest AB magnitudes of order 24 to 25 for each object. Bechtold, J., Yee, H. K. C., Elston, R., & Ellingson, E. 1997, { it Ap. J. Letters}, { bf 477}, L29 Beckwith, S. V. W., Thompson, D. J., Mannucci, F., & Djorgovski, S. G. 1998, { it Ap. J.}, in press Cowie, L. L., & Hu, E. M., 1998, { it A. J.}, in press {astro- ph/9801003} Cowie, L. L., Songaila, A., Hu, E. M., Egam i, , Huang, J.-S., Pickles, A. J., Ridgway, S. E., & Wainscoat, R. J. 1994, { it Ap. J. Letters}, { bf 432}, L83 Djorgovski, S. G., Pahre, M. A., Bechtold J., & Elston, R., 1996, { it Nature}, { bf 382}, 234 Franceschini, A., Silva, L., Granato, G. L., Bressan, A., Danese, L., 1998, { it Ap. J. Lett}, in press Francis, P. J., Woodgate, B. E., and Danks, A. C. 1998, {astroph/9801300} Graham, J. R., & Dey, A. 1996, { it Ap. J.}, { bf 471}, 720 Guideroni, B., Bouchet, F. R., Puget, J.-L., Lagache, G., & Hivon, E., 1997, { it Nature}, { bf 390}, 257 Hu, E. M., McMahon, R. G., 1996, { it Nature}, { bf 382}, 231 Lowenthal, J. D., Hogan, C. J., Green, R. F., Caulet, A., Woodgate, B. E., Brown, L., and Foltz, C. B. 1991, { it Ap. J. Letters}, { bf 377}, L73 Macchetto, F., Lipari, S., Giavalisco, M., Turshek, D. A., & Sparks, W. B. 1993, { it Ap. J.} { bf 404}, 511 Malkan, M. A., Teplitz, H., & McLean, I. S. 1996, { it Ap. J. Letters}, { bf 468}, L9 Mannucci, F., Thompson, D. J., Beckwith, S.V.W., & Wil liger 1998, { it Ap. J. Letters}, i n press. Moller, P., & Warren, S. J., 1993, { it A. & A.}, { bf 270}, 43 Pascarelle, S. M., Windhorst, R. A., & Odewahn, S. C. 1996, { it Nature}, { bf 383}, 45 Pettini, M., Steidel, C. C., Adelberger, K. L, Kellogg, M., Dickinson, M., & Giavalisco, M. 1998, astro-ph/9708117 Steidel, C. C., Giavalisco, M., Pettini, M., Dickinson, M., & Adelberger, K. L. 1996, { it Ap. J.}, { bf 462}, 17 Thompson, D. J, Mannucci, F., & Beckwith, S. V. W. 1996, { it A. J.}, { bf 112}, 1794 Wolfe, A. M. 1993, { it Ap. J.}, { bf 402}, 411 Wolfe, A. M., Turnshek, D. A., Lanzetta, K. M., & Oke, J. B. 1992, { it Ap. J.}, { bf 385}, 151 Wolfe, A. M., Turnshek, D. A., Smith, H. E., & Cohen, R. E. 1986, { it Ap. J. Supp.}, { bf 61}, 249

Determination of physical parameters of magnetic active regions in stars with different evolutionary stages

NASA Astrophysics Data System (ADS)

Biazzo, K.

2006-11-01

Understanding stellar magnetic activity phenomena is of paramount importance for stellar evolution and for planetary systems formation and their atmosphere and climate. The dynamo process that generates magnetic fields in stars is well understood and there is still no comprehensive model of solar and stellar magnetic activity. Stellar activity is characterized by tracers such as spots, plages, flares and winds. These features are the fingerprints of magnetic field lines and their detailed analysis provides constraints for theoretical models. Our knowledge can only advance if the active stars besides the Sun are included in our study. Therefore, it is essential to accomplish comprehensive studies of active stars with a wide range of stellar parameters and a variety of activity phenomena. In this thesis, I concentrate on emergence of active regions at photospheric and chromospheric levels, namely spots and plages, in stars with different evolutionary stages. Spots are cool areas on the surface of the stars and are supposed to be the result of the blocking effect on convection caused by magnetic flux-tube emersion. Plages are bright areas linked to emersion of magnetic flux tubes from the sub-photospheric convective level. Starspot temperature represents an important parameter for the investigation of stellar magnetic activity, but its precise determination, relying only on light curve inversion techniques, is strongly hampered by the lack of solution uniqueness. Therefore, a method based on line-depth ratios as temperature discriminant has been developed. This technique is capable of resolving temperature differences less than 10 K. Moreover, combining temperature and light curve solutions, I am able to determine in a univocal way starspot temperature and area. Using the net Halpha emission as indicator of plage presence, I have also studied the spot and plage association. As a matter of fact, the residual Halpha profiles, obtained as the difference between the observed spectra and non-active templates, allows to study the chromospheric structures simultaneously to the photospheric ones. In addition, I have also detected the intensity of the HeI-D3 line to analyse the presence of surface features in the high chromosphere. The observations of both standard and target stars have been performed with different instruments. In particular, the spectra have been acquired at Catania Astrophysical Observatory (Italy), Observatoire de Haute-Provence (France) and Nordic Optical Observatory (Canarian Islands). The photometric observations have been obtained at Catania Astrophysical Observatory, Fairnborn Observatory (USA) and Ege University Observatory (Turkey). Finally, starspot and plage physical parameters have been obtained for sixteen stars of different effective temperature and gravity and different evolutionary stages. The main results can be summarized as follows: - starspot temperatures are more similar to solar penumbrae; - dwarf stars tend to have smaller spots compared to giant stars; - stars with higher gravity seem to have cooler (relative to their photosphere) spots compared to stars with lower gravity; - spatial association exists between surface inhomogeneities at different atmospheric levels.

The metallicities of the broad emission line regions in the nitrogen-loudest quasars

NASA Astrophysics Data System (ADS)

Batra, Neelam Dhanda; Baldwin, Jack A.

2014-03-01

We measured the metallicity Z in the broad emission-line regions (BELRs) of 43 Sloan Digital Sky Survey (SDSS) quasars with the strongest N IV] and N III] emission lines. These N-loud quasi-stellar objects (QSOs) have unusually low-black-hole masses. We used the intensity ratio of N lines to collisionally excited emission lines of other heavy elements to find metallicities in their BELR regions. We found that seven of the eight line-intensity ratios that we employed give roughly consistent metallicities as measured, but that for each individual QSO their differences from the mean of all metallicity measurements depend on the ionization potential of the ions that form the emission lines. After correcting for this effect, the different line-intensity ratios give metallicities that generally agree to within the 0.24 dex uncertainty in the measurements of the line-intensity ratios. The metallicities are very high, with mean log Z for the whole sample of 5.5 Z⊙ and a maximum of 18 Z⊙. Our results argue against the possibility that the strong N lines represent an overabundance only of N but not of all heavy elements. They are compatible with either that (1) the BELR gas has been chemically enriched by the general stellar population in the central bulge of the host galaxy, but the locally optimally emitting cloud model used in the analysis needs some fine tuning or (2) that instead this gas has been enriched by intense star formation on the very local scale of the active nucleus that has resulted in an abundance gradient within the BELR.

A high-redshift IRAS galaxy with huge luminosity - Hidden quasar or protogalaxy?

NASA Technical Reports Server (NTRS)

Rowan-Robinson, M.; Broadhurst, T.; Oliver, S. J.; Taylor, A. N.; Lawrence, A.; Mcmahon, R. G.; Lonsdale, C. J.; Hacking, P. B.; Conrow, T.

1991-01-01

An emission line galaxy with the enormous far-IR luminosity of 3 x 10 to the 14th solar has been found at z = 2.286. The spectrum is very unusual, showing lines of high excitation but with very weak Lyman-alpha emission. A self-absorbed synchrotron model for the IR energy distribution cannot be ruled out, but a thermal origin seems more plausible. A radio-quiet quasar embedded in a very dusty galaxy could account for the IR emission, as might a starburst embedded in 1-10 billion solar masses of dust. The latter case demands so much dust that the object would probably be a massive galaxy in the process of formation. The presence of a large amount of dust in an object of such high redshift implies the generation of heavy elements at an early cosmological epoch.

First results from the CALYPSO IRAM-PdBI survey. II. Resolving the hot corino in the Class 0 protostar NGC 1333-IRAS2A

NASA Astrophysics Data System (ADS)

Maury, A. J.; Belloche, A.; André, Ph.; Maret, S.; Gueth, F.; Codella, C.; Cabrit, S.; Testi, L.; Bontemps, S.

2014-03-01

Aims: We investigate the origin of complex organic molecules (COMs) in the gas phase around the low-mass Class 0 protostar NGC 1333-IRAS2A, to determine if the COM emission lines trace an embedded disk, shocks from the protostellar jet, or the warm inner parts of the protostellar envelope. Methods: In the framework of the CALYPSO IRAM Plateau de Bure survey, we obtained large bandwidth spectra at sub-arcsecond resolution towards NGC 1333-IRAS2A. We identify the emission lines towards the central protostar and perform Gaussian fits to constrain the size of the emitting region for each of these lines, tracing various physical conditions and scales. Results: The emission of numerous COMs such as methanol, ethylene glycol, and methyl formate is spatially resolved by our observations. This allows us to measure, for the first time, the size of the COM emission inside the protostellar envelope, finding that it originates from a region of radius 40-100 AU, centered on the NGC 1333-IRAS2A protostellar object. Our analysis shows no preferential elongation of the COM emission along the jet axis, and therefore does not support the hypothesis that COM emission arises from shocked envelope material at the base of the jet. Down to similar sizes, the dust continuum emission is well reproduced with a single power-law envelope model, and therefore does not favor the hypothesis that COM emission arises from the thermal sublimation of grains embedded in a circumstellar disk. Finally, the typical scale ~60 AU observed for COM emission is consistent with the size of the inner envelope where Tdust > 100 K is expected. Our data therefore strongly suggest that the COM emission traces the hot corino in IRAS2A, i.e., the warm inner envelope material where the icy mantles of dust grains evaporate because they are passively heated by the central protostellar object. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).CALYPSO stands for Continuum And Lines in Young ProtoStellar Objects.Appendix A, Tables 1, 2, and Figs. 3, 4 are available in electronic form at http://www.aanda.orgThe integrated emission maps shown in Fig. 3 are available in electronic form at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/563/L2

Ring nebulae around Wolf-Rayet stars in M33

NASA Technical Reports Server (NTRS)

Drissen, Laurent; Shara, Michael M.; Moffat, Anthony F. J.

1991-01-01

Results of a systematic search for H II ring nebulae surrounding Wolf-Rayet (WR) stars in M33 are presented. Eleven objects are found to be good candidates, while eight others are classified as possible WR ring nebulae. The WR rings in M33 are larger on average than their Galactic counterparts, but the H-alpha luminosity of most of them is comparable to the bright Galactic wind-blown bubbles. The rings are associated with WC as well as with WN stars.

Discovery of a Wolf-Rayet Star through Detection of Its Photometric Variability

NASA Astrophysics Data System (ADS)

Littlefield, Colin; Garnavich, Peter; Marion, G. H. Howie; Vinkó, József; McClelland, Colin; Rettig, Terrence; Wheeler, J. Craig

2012-06-01

We report the serendipitous discovery of a heavily reddened Wolf-Rayet star that we name WR 142b. While photometrically monitoring a cataclysmic variable, we detected weak variability in a nearby field star. Low-resolution spectroscopy revealed a strong emission line at 7100 Å, suggesting an unusual object and prompting further study. A spectrum taken with the Hobby-Eberly Telescope confirms strong He II emission and an N IV 7112 Å line consistent with a nitrogen-rich Wolf-Rayet star of spectral class WN6. Analysis of the He II line strengths reveals no detectable hydrogen in WR 142b. A blue-sensitive spectrum obtained with the Large Binocular Telescope shows no evidence for a hot companion star. The continuum shape and emission line ratios imply a reddening of E(B - V) = 2.2-2.6 mag. We estimate that the distance to WR 142b is 1.4 ± 0.3 kpc.

Probing Reionization at z >~ 7 with HST's Near-Infrared Grisms

NASA Astrophysics Data System (ADS)

Schmidt, Kasper B.

The epoch of reionization, i.e. the phase transition of the inter-galactic medium from neutral to fully ionized, is essential for our understanding of the evolution of the Universe and the formation of the first stars and galaxies. The Grism Lens-Amplified Survey from Space (GLASS) has obtained spectra of ten thousands of objects in and behind 10 massive galaxy clusters, including the six Hubble Frontier Fields. The grism spectroscopy from GLASS results in hundreds of spectra of z >~ 7 galaxy candidates. Taking advantage of the lensing magnification from the foreground clusters, the GLASS spectra reaches unprecedented depths in the near-infrared with observed flux limits of ~ 5 × 10-18erg/s/cm2 before correcting for the lens magnification. This has resulted in several Lyα detections at z ~ 7 and tight limits on the emission line fluxes for non-detections. From an ensemble of different photometric selections, we have assembled more than 150 z >~ 7 galaxy candidates from six of the ten GLASS clusters. Among these more than 20 objects show emission lines consistent with being Lyα at z >~ 7. The spatial extent of Lyα estimated from a stack of the most promising Lyα emitters at = 7.2 is consistent with the spatial extent of the UV continuum emission. From the stack we obtain upper limits on the emission line ratios between prominent rest-frame UV emission lines, finding that f CIV/f Lyα <~ 0.32 and f CIII]/f Lyα <~ 0.23 in good agreement with values published in the literature.

Ionized Absorbers in Active Galactic Nuclei and Very Steap Soft X-Ray Quasars

NASA Technical Reports Server (NTRS)

Fiore, Fabrizio; White, Nicholas (Technical Monitor)

2000-01-01

Steep soft X-ray (0.1-2 keV) quasars share several unusual properties: narrow Balmer lines, strong Fe II emission, large and fast X-ray variability, and a rather steep 2-10 keV spectrum. These intriguing objects have been suggested to be the analogues of Galactic black hole candidates in the high, soft state. We present here results from ASCA observations for two of these quasars: NAB 0205 + 024 and PG 1244 + 026. Both objects show similar variations (factor of approximately 2 in 10 ks), despite a factor of approximately 10 difference in the 0.5-10 keV luminosity (7.3 x 10(exp 43) erg/s for PG 1244 + 026 and 6.4 x 10(exp 44) erg/s for NAB 0205 + 024, assuming isotropic emission, H(sub 0) = 50.0 and q(sub 0) = 0.0). The X-ray continuum of the two quasars flattens by 0.5-1 going from the 0.1-2 keV band towards higher energies, strengthening recent results on another half-dozen steep soft X-ray active galactic nuclei. PG 1244 + 026 shows a significant feature in the '1-keV' region, which can be described either as a broad emission line centered at 0.95 keV (quasar frame) or as edge or line absorption at 1.17 (1.22) keV. The line emission could be a result of reflection from a highly ionized accretion disc, in line with the view that steep soft X-ray quasars are emitting close to the Eddington luminosity. Photoelectric edge absorption or resonant line absorption could be produced by gas outflowing at a large velocity (0.3-0.6 c).

The nature of extreme emission line galaxies at z = 1-2: kinematics and metallicities from near-infrared spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maseda, Michael V.; Van der Wel, Arjen; Rix, Hans-Walter

2014-08-10

We present near-infrared spectroscopy of a sample of 22 Extreme Emission Line Galaxies at redshifts 1.3 < z < 2.3, confirming that these are low-mass (M{sub *} = 10{sup 8}-10{sup 9} M{sub ☉}) galaxies undergoing intense starburst episodes (M{sub *}/SFR ∼ 10-100 Myr). The sample is selected by [O III] or Hα emission line flux and equivalent width using near-infrared grism spectroscopy from the 3D-HST survey. High-resolution NIR spectroscopy is obtained with LBT/LUCI and VLT/X-SHOOTER. The [O III]/Hβ line ratio is high (≳ 5) and [N II]/Hα is always significantly below unity, which suggests a low gas-phase metallicity. We aremore » able to determine gas-phase metallicities for seven of our objects using various strong-line methods, with values in the range 0.05-0.30 Z{sub ☉} and with a median of 0.15 Z{sub ☉}; for three of these objects we detect [O III] λ4363, which allows for a direct constraint on the metallicity. The velocity dispersion, as measured from the nebular emission lines, is typically ∼50 km s{sup –1}. Combined with the observed star-forming activity, the Jeans and Toomre stability criteria imply that the gas fraction must be large (f{sub gas} ≳ 2/3), consistent with the difference between our dynamical and stellar mass estimates. The implied gas depletion timescale (several hundred Myr) is substantially longer than the inferred mass-weighted ages (∼50 Myr), which further supports the emerging picture that most stars in low-mass galaxies form in short, intense bursts of star formation.« less

Physical properties of z ~ 4 LBGs: differences between galaxies with and without Lyα emission

NASA Astrophysics Data System (ADS)

Pentericci, L.; Grazian, A.; Fontana, A.; Salimbeni, S.; Santini, P.; de Santis, C.; Gallozzi, S.; Giallongo, E.

2007-08-01

Aims:We analysed the physical properties of z ˜4 Lyman Break Galaxies observed in the GOODS-S survey, in order to investigate possible differences between galaxies where the Lyα is present in emission, and those where the line is absent or in absorption. Methods: The objects were selected from their optical color and then spectroscopically confirmed by Vanzella et al. (2005). From the public spectra we assessed the nature of the Lyα emission and divided the sample into galaxies with Lyα in emission and objects without a Lyα line (i.e. either absent or in absorption). We then used complete photometry, from U band to mid-infrared from the GOODS-MUSIC database, to study the observational properties of the galaxies, such as UV spectral slopes and optical to mid-infrared colors, and the possible differences between the two samples. Lastly, we used standard spectral fitting techniques to determine the physical properties of the galaxies, such as total stellar mass, stellar ages and so on, and again we looked at the possible differences between the two samples. Results: Our results indicate that LBG with Lyα in emission are on average a much younger and less massive population than the LBGs without Lyα emission. Both populations are forming stars very actively and are relatively dust free, although those with line emission seem to be even less dusty on average. We briefly discuss these results in the context of recent models for the evolution of Lyman break galaxies and Lyα emitters.

Early Results from Star Date: M83 - A Citizen Science Project to Age Date Star Clusters in the Southern Pinwheel Galaxy

NASA Astrophysics Data System (ADS)

Heartley, Jeremy; Whitmore, B. C.; Blair, W. P.; Christian, C. A.; Donaldson, T.; Hammer, D.; Smith, S.; Viana, A.

2014-01-01

The M83 Citizen Science Project is a collaborative effort currently in development between the Space Telescope Science Institute (STScI) and Zooniverse under the guidance of Dr. Brad Whitmore as part of Cy 19 proposal 12513 (PI - Dr. William Blair). This unique citizen science project will allow users to analyze individual star clusters within The Southern Pinwheel Galaxy, M83. The project will show users color-composite images taken with Wide Field Camera 3 (WFC3) aboard the Hubble Space Telescope (HST) and ask them to estimate the age of the star cluster. Through a multistage process, the project will educate and familiarize the user with the appearance of each age category based on the presence and shape of H-alpha emission, degree of resolution of the individual stars, and color of the cluster. (Whitmore et al. 2011). Additionally, the project will involve the actual measurement of the star cluster and H-alpha cloud radii to be used for further assessment and reinforcement of age. The data from this project and the statistics it yields will quantify these ages which can then be used to inform the debate between universal and environmental models of star cluster formation and destruction in galaxies. The tentative launch date is December 2013, therefore early results should be available at the time of the conference.

A study of ten quasars with redshifts greater than four

NASA Technical Reports Server (NTRS)

Schneider, Donald P.; Schmidt, Maarten; Gunn, James E.

1989-01-01

Four quasars with redshifts greater than four were detected in a low-resolution CCD grism survey. CCD photometry and high S/N, moderate resolution spectra are presented for these quasars and the six other known quasars with redshifts above 4. The M sub B values of nine of the objects are between -27.5 and -25, with the tenth quasar having an M sub B value of -29. The emission lines and shapes of the continua of these ten quasars are similar to those of lower-redshift quasars. The results suggest that the C IV emission lines in high-redshift quasars may be weaker than those in lower-redshift quasars. The continua of all of the high-redshift quasars display strong depressions blueward of the Ly-alpha emission line.

Cutting the Composite Gordian Knot: Untangling the AGN-Starburst Threads in Single Aperture Spectra

NASA Astrophysics Data System (ADS)

Flury, Sophia; Moran, Edward C.

2018-01-01

Standard emission line diagnostics are able to segregate star-forming galaxies and Seyfert nuclei, and it is often assumed that ambiguous emission-line galaxies falling between these two populations are “composite” objects exhibiting both types of photoionization. We have developed a method that predicts the most probable H II and AGN components that could plausibly explain the “composite” classed objects solely on the basis of their SDSS spectra. The majority of our analysis is driven by empirical relationships revealed by SDSS data rather than theoretical models founded in assumptions. To verify our method, we have compared the predictions of our model with publicly released IFU data from the S7 survey and find that composite objects are not in fact a simple linear combination of the two types of emission. The data reveal a key component in the mixing sequence: geometric dilution of the ionizing radiation which powers the NLR of the active nucleus. When accounting for this effect, our model is successful when applied to several composite-class galaxies. Some objects, however, appear to be at variance with the predicted results, suggesting they may not be powered by black hole accretion.

An Automated Scheme for the Large-Scale Survey of Herbig-Haro Objects

NASA Astrophysics Data System (ADS)

Deng, Licai; Yang, Ji; Zheng, Zhongyuan; Jiang, Zhaoji

2001-04-01

Owing to their spectral properties, Herbig-Haro (HH) objects can be discovered using photometric methods through a combination of filters, sampling the characteristic spectral lines and the nearby continuum. The data are commonly processed through direct visual inspection of the images. To make data reduction more efficient and the results more uniform and complete, an automated searching scheme for HH objects is developed to manipulate the images using IRAF. This approach helps to extract images with only intrinsic HH emissions. By using this scheme, the pointlike stellar sources and extended nebulous sources with continuum emission can be eliminated from the original images. The objects with only characteristic HH emission become prominent and can be easily picked up. In this paper our scheme is illustrated by a sample field and has been applied to our surveys for HH objects.

QSO Broad Emission Line Asymmetries: Evidence of Gravitational Redshift?

NASA Astrophysics Data System (ADS)

Corbin, Michael R.

1995-07-01

The broad optical and ultraviolet emission lines of QSOs and active galactic nuclei (AGNs) display both redward and blueward asymmetries. This result is particularly well established for Hβ and C IV λ1549, and it has been found that Hβ becomes increasingly redward asymmetric with increasing soft X-ray luminosity. Two models for the origin of these asymmetries are investigated: (1) Anisotropic line emission from an ensemble of radially moving clouds, and (2) Two-component profiles consisting of a core of intermediate (˜1000-4000 km s-1) velocity width and a very broad (˜5000-20,000 km s-1) base, in which the asymmetries arise due to a velocity difference between the centroids of the components. The second model is motivated by the evidence that the traditional broad-line region is actually composed of an intermediate-line region (ILR) of optically thick clouds and a very broad line region (VBLR) of optically thin clouds lying closer to the central continuum source. Line profiles produced by model (1) are found to be inconsistent with those observed, being asymmetric mainly in their cores, whereas the asymmetries of actual profiles arise mainly from excess emission in their wings. By contrast, numerical fitting to actual Hβ and C IV λ1549 line profiles reveals that the majority can be accurately modeled by two components, either two Gaussians or the combination of a Gaussian base and a logarithmic core. The profile asymmetries in Hβ can be interpreted as arising from a shift of the base component over a range ˜6300 km s-1 relative to systemic velocity as defined by the position of the [O III] λ5007 line. A similar model appears to apply to C IV λ1549. The correlation between Hβ asymmetry and X-ray luminosity may thus be interpreted as a progressive red- shift of the VBLR velocity centroid relative to systemic velocity with increasing X-ray luminosity. This in turn suggests that the underlying effect is gravitational red shift, as soft X-ray emission arises from a region ˜ light-minutes in size and arguably traces the mass of the putative supermassive black hole. Depending on the size of the VBLR and the exact amount of its profile centroid shift, central masses in the range 109-10 Msun are implied for the objects displaying the strongest redward profile asymmetries, consistent with other estimates. The largest VBLR velocity dispersions measured from the two-component modeling are ˜20,000 km s-1, which also yields a virial mass ˜109 Msun for a VBLR size 0.1 pc. The gravitational redshift model does not explain the origin of the blueshift of the VBLR emission among low X-ray luminosity sources, however. This must be interpreted as arising from a competing effect such as electron scattering of line photons in the vicinity of the VBLR. On average, radio-loud objects have redward asymmetric broad-line profiles and stronger intermediate- and narrow-line emission than radio-quiet objects of comparable optical luminosity. Under the gravitational redshift model these differences may be interpreted as the result of black hole and host galaxy masses that are larger on average among the former class, consistent with the evidence that they are merger products.

BROAD Hβ EMISSION-LINE VARIABILITY IN A SAMPLE OF 102 LOCAL ACTIVE GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Runco, Jordan N.; Cosens, Maren; Bennert, Vardha N.

2016-04-10

A sample of 102 local (0.02 ≤ z ≤ 0.1) Seyfert galaxies with black hole masses M{sub BH} > 10{sup 7}M{sub ⊙} was selected from the Sloan Digital Sky Survey (SDSS) and observed using the Keck 10 m telescope to study the scaling relations between M{sub BH} and host galaxy properties. We study profile changes of the broad Hβ emission line within the three to nine year time frame between the two sets of spectra. The variability of the broad Hβ emission line is of particular interest, not only because it is used to estimate M{sub BH}, but also because its strengthmore » and width are used to classify Seyfert galaxies into different types. At least some form of broad-line variability (in either width or flux) is observed in the majority (∼66%) of the objects, resulting in a Seyfert-type change for ∼38% of the objects, likely driven by variable accretion and/or obscuration. The broad Hβ line virtually disappears in 3/102 (∼3%) extreme cases. We discuss potential causes for these changing look active galactic nuclei. While similar dramatic transitions have previously been reported in the literature, either on a case-by-case basis or in larger samples focusing on quasars at higher redshifts, our study provides statistical information on the frequency of Hβ line variability in a sample of low-redshift Seyfert galaxies.« less