A Spatially Resolved Spectroscopic Study of NGC 7009

Liu et al. (1995) and Luo, Liu & Barlow (2001) determined the CNONe abundances in NGC 7009 using optical recombination lines (ORLs) and found that they are all approximately a factor of five higher than the corresponding values derived from collisionally excited lines (CELs). We have obtained new deep high resolution long-slit spectra of NGC 7009. The data have been used to map the electron temperature, density and element abundances across the nebula, using both CELs and ORLs. While the electron temperature derived from the [O III] forbidden line ratio, Te([O III]), is found to be largely constant, that derived from Balmer jump of H I recombination spectrum, Te(BJ), shows large amplitude complicated variations. The ratios of the heavy element abundances derived from ORLs to those deduced from CELs are found to be correlated with the difference between the difference between Te([O III]) and Te(BJ) – a relation previously known to exist from analyses of the integration spectra of individual nebulae (Liu et al. 2001).

Download Full-text

Chemical Abundances from Planetary Nebulae in the Magellanic Clouds

Highlights of Astronomy ◽

10.1017/s1539299600011813 ◽

1995 ◽

Vol 10 ◽

pp. 476-479 ◽

Cited By ~ 1

Author(s):

M.J. Barlow

Keyword(s):

Electron Temperature ◽

Heavy Element ◽

Planetary Nebulae ◽

Density Fluctuations ◽

Magellanic Cloud ◽

Magellanic Clouds ◽

Chemical Abundances ◽

Element Abundances

AbstractHeavy element abundances, in particular those of oxygen, obtained from recent spectroscopic surveys of Magellanic Cloud planetary nebulae (PN), are reviewed and compared with those derived for H regions and objects in our own galaxy. These abundances have been based on collisionally excited lines and are very sensitive to the adopted electron temperature. There is increasing evidence that temperature or density fluctuations within nebulae lead to the electron temperatures being overestimated, with the corollary that the heavy element abundances have been underestimated.

Download Full-text

Absorption Line Systems at z > 3 in the QSO 2000-330

Symposium - International Astronomical Union ◽

10.1017/s0074180900159935 ◽

1987 ◽

Vol 124 ◽

pp. 799-802

Author(s):

R.W. Hunstead ◽

M. Pettini ◽

J.C. Blades ◽

H.S. Murdoch

Keyword(s):

High Resolution ◽

Absorption Line ◽

Heavy Element ◽

Absorption Lines ◽

List Type ◽

Type Number ◽

Element Abundances ◽

Preliminary Results ◽

Forest Region ◽

Velocity Dispersions

This paper presents some preliminary results from analysis of our high-resolution (30–35 km/s FWHM) spectra of the Lyman α forest region in the z = 3.78 QSO 2000-330. These spectra were obtained at the Anglo-Australian Telescope over several observing seasons and have been analysed by fitting multiple-cloud Voigt profiles to Lyman series and heavy-element absorption lines. Two specific issues are addressed here: (i)The distribution of column densities, N(H I), and velocity dispersions, b, for hydrogen clouds in the interval zabs = 3.43–3.78;(ii)Heavy-element abundances in a system at zabs = 3.1723.

Download Full-text

Temperature Variations from HST Imagery and Spectroscopy of NGC 7009

Symposium - International Astronomical Union ◽

10.1017/s0074180900209017 ◽

2003 ◽

Vol 209 ◽

pp. 361-362

Author(s):

R. H. Rubin ◽

N. J. Bhatt ◽

R. J. Dufour ◽

B. A. Buckalew ◽

M. J. Barlow ◽

...

Keyword(s):

Electron Temperature ◽

Spatial Resolution ◽

Planetary Nebula ◽

Heavy Element ◽

High Spatial Resolution ◽

Flux Ratio ◽

Mean Square ◽

Temperature Variations ◽

Element Abundances ◽

Intrinsic Flux

We obtained new HST/STIS long-slit spectra and WFPC2 imagery of the planetary nebula NGC 7009 in order to obtain high spatial resolution of the intrinsic flux ratio [O III] 4364/5008, which is a well-known diagnostic for electron temperature (Te). Our primary purpose was to quantify Te variations across the nebula. We address whether the observational data support the possibility that the [fractional] mean-square Te variation (t2) (Peimbert 1967) in NGC 7009 may be as large as ~0.1. Such large values are required to reconcile the “abundance dichotomy” by Te variations alone. The abundance dichotomy (discussed by Liu at greater length elsewhere in this volume) refers to the significantly higher heavy element abundances derived from optical recombination lines (e.g., a factor of ~5 for NGC 7009, Liu et al. 1995) compared with the corresponding values deduced from collisionally-excited lines.

Download Full-text

Distribution of R- and S-Process Elements in the Galactic Halo

Symposium - International Astronomical Union ◽

10.1017/s0074180900035555 ◽

1988 ◽

Vol 132 ◽

pp. 501-506

Author(s):

C. Sneden ◽

C. A. Pilachowski ◽

K. K. Gilroy ◽

J. J. Cowan

Keyword(s):

Heavy Element ◽

Galactic Halo ◽

Low Noise ◽

Heavy Elements ◽

Process Synthesis ◽

Element Abundances ◽

Halo Stars ◽

Abundance Patterns ◽

R Process ◽

Process Elements

Current observational results for the abundances of the very heavy elements (Z>30) in Population II halo stars are reviewed. New high resolution, low noise spectra of many of these extremely metal-poor stars reveal general consistency in their overall abundance patterns. Below Galactic metallicities of [Fe/H] Ã −2, all of the very heavy elements were manufactured almost exclusively in r-process synthesis events. However, there is considerable star-to-star scatter in the overall level of very heavy element abundances, indicating the influence of local supernovas on element production in the very early, unmixed Galactic halo. The s-process appears to contribute substantially to stellar abundances only in stars more metal-rich than [Fe/H] Ã −2.

Download Full-text

Origin of the alternate bright/dark contrast in HREM images of hexagonal crystals, particularly 6H-SiC

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015040x ◽

1993 ◽

Vol 51 ◽

pp. 914-915

Author(s):

J.S. Bow ◽

R.W. Carpenter ◽

M.J. Kim

Keyword(s):

High Resolution ◽

Incident Beam ◽

Hexagonal Crystal ◽

Detailed Explanation ◽

Similar Character ◽

High Resolution Images ◽

The Difference ◽

Zigzag Shape ◽

Hexagonal Crystals ◽

Dark Contrast

A prominent characteristic of high-resolution images of 6H-SiC viewed from [110] is a zigzag shape with a period of 6 layers as shown in Fig.1. Sometimes the contrast is same through the 6 layers of (0006) planes (Fig.1a), but in most cases it appears as in Fig.1b -- alternate bright/dark contrast among every three (0006) planes. Alternate bright/dark contrast is most common for the thicker specimens. The SAD patterns of these two types of image are almost same, and there is no indication that the difference results from compositional ordering. O’Keefe et al. concluded this type of alternate contrast was due to crystal tilt in thick parts of the specimen. However, no detailed explanation was given. Images of similar character from Ti3Al, which is also a hexagonal crystal, were reported by Howe et al. Howe attributed the bright/dark contrast among alternate (0002) Ti3Al planes to phase shifts produced by incident beam tilt.

Download Full-text

The difference bands nu11-nu4 and nu10-nu18 of benzene at high resolution

Molecular Physics ◽

10.1080/00268979650027216 ◽

1996 ◽

Vol 87 (4) ◽

pp. 859-863

Author(s):

J. PLIVA

Keyword(s):

High Resolution ◽

The Difference

Download Full-text

Heavy‐Element Abundances in Blue Compact Galaxies

The Astrophysical Journal ◽

10.1086/306708 ◽

1999 ◽

Vol 511 (2) ◽

pp. 639-659 ◽

Cited By ~ 343

Author(s):

Yuri I. Izotov ◽

Trinh X. Thuan

Keyword(s):

Heavy Element ◽

Element Abundances ◽

Compact Galaxies

Download Full-text

High-resolution spectroscopic study of hot electron induced copper M-shell charge states emission from laser produced plasmas

High Energy Density Physics ◽

10.1016/j.hedp.2019.06.004 ◽

2019 ◽

Vol 32 ◽

pp. 89-95 ◽

Cited By ~ 2

Author(s):

F.P. Condamine ◽

E. Filippov ◽

P. Angelo ◽

S.A. Pikuz ◽

O. Renner ◽

...

Keyword(s):

High Resolution ◽

Spectroscopic Study ◽

Hot Electron ◽

Charge States

Download Full-text

Exploring the robustness of Keplerian signals to the removal of active and telluric features

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3180 ◽

2020 ◽

Vol 500 (1) ◽

pp. 548-557

Author(s):

M Lisogorskyi ◽

H R A Jones ◽

F Feng ◽

R P Butler ◽

S Vogt

Keyword(s):

Monte Carlo ◽

High Resolution ◽

Monte Carlo Simulations ◽

Large Amplitude ◽

Absorption Cell ◽

Stellar Rotation ◽

Long Period ◽

Active Line ◽

Low Amplitude ◽

Rotation Signal

ABSTRACT We examine the influence of activity- and telluric-induced radial velocity (RV) signals on high-resolution spectra taken with an iodine absorption cell. We exclude 2-$\mathring{\rm A}$ spectral chunks containing active and telluric lines based on the well-characterized K1V star α Centauri B and illustrate the method on Epsilon Eridani – an active K2V star with a long-period, low-amplitude planetary signal. After removal of the activity- and telluric-sensitive parts of the spectrum from the RV calculation, the significance of the planetary signal is increased and the stellar rotation signal disappears. In order to assess the robustness of the procedure, we perform Monte Carlo simulations based on removing random chunks of the spectrum. Simulations confirm that the removal of lines impacted by activity and tellurics provides a method for checking the robustness of a given Keplerian signal. We also test the approach on HD 40979, which is an active F8V star with a large-amplitude planetary signal. Our Monte Carlo simulations reveal that the significance of the Keplerian signal in the F star is much more sensitive to wavelength. Unlike the K star, the removal of active lines from the F star greatly reduces the RV precision. In this case, our removal of a K star active line from an F star does not a provide a simple useful diagnostic because it has far less RV information and heavily relies on the strong active lines.

Download Full-text