scholarly journals Resolution and evolution of the core of the giant HII region NGC 3603

1995 ◽  
Vol 163 ◽  
pp. 43-47
Author(s):  
K.-H. Hofmann ◽  
G. Weigelt ◽  
W. Seggewiss
Keyword(s):  
Star Cluster ◽  
Emission Lines ◽  
Hii Region ◽  
The Core ◽  
Star Evolution ◽  
Magnitude Diagram ◽  
Hα Emission ◽  
Cluster Age ◽  
Rayet Star ◽  
Selection Of

We present diffraction-limited speckle-masking observations of the central object HD 97950 in the giant HII region and star cluster NGC 3603. Twenty-eight stellar components have been detected in the 6.″3 x 6.″3 field from our reconstructed images. Four different filter combinations were used for the selection of distinct spectral regions comprising Hα emission, the main Wolf-Rayet and Of-type emission lines, and two continuum bands. Stellar components having WN-type characteristics have been found. A color-magnitude diagram has been constructed. Isochrone fits yield a cluster age of about 3.2 Myr, which is in accordance with the time-scale of Wolf-Rayet star evolution.

scholarly journals Similarities of the intermediate-age SMC star cluster NGC 152 with inner disk clusters in the Milky Way

1991 ◽  
Vol 148 ◽  
pp. 198-199
Author(s):  
T. Richtler ◽  
Klaas S. De Boer ◽  
A. Vallenari ◽  
W. Seggewiss
Keyword(s):  
Globular Cluster ◽  
Milky Way ◽  
Star Clusters ◽  
Star Cluster ◽  
Horizontal Branch ◽  
Vertical Extension ◽  
Magnitude Diagram ◽  
The Mean ◽  
Normal Feature ◽  
Selection Of

A colour-magnitude diagram (CMD) of the region containing the intermediate-age SMC globular cluster NGC 152 was published recently (Melcher & Richtler 1989). A particularly interesting feature of this CMD is the “clump” of He-core burning stars, which are predominantly field stars. A selection of stars near the cluster centre leads to the CMD shown in Figure 1. The vertical extension of the clump (explainable by the evolution of stars younger than 1 Gyr) is replaced by a “tilted horizontal branch” (we use this expression for lack of a better one). The age of NGC 152 is about 1.3 Gyr and the reddening is small; the metallicity is unknown but less than −0.6 dex, which is the mean metallicity of the young SMC population. The tilted HB can be reproduced in CMD simulations using the method developed by Vallenari et al. (1990), and thus can be considered as a normal feature of star clusters like NGC 152. It is evident also in other intermediate-age MC clusters like Kron 3 (Rich et al. 1984).

scholarly journals New Massive Contacting Twin Binary in a Radio-quiet HII Region Associated with the M17 Complex

2022 ◽  
Author(s):  
Jia Yin ◽  
Zhiwei Chen ◽  
Yong-Qiang Yao ◽  
Jian Chen ◽  
Bin Li ◽  
...  
Keyword(s):  
Binary Systems ◽  
Massive Stars ◽  
Physical Parameters ◽  
Main Sequence Stars ◽  
Eclipsing Binary ◽  
Hii Region ◽  
B Stars ◽  
Short Period ◽  
Magnitude Diagram ◽  
Hα Emission

Abstract Early-B stars, much less energetic than O stars, may create an HII region that appears as radio-quiet. We report the identification of new early-B stars associated with the radio-quiet HII region G014.645--00.606 in the M17 complex. The ratio-quiet HII region G014.645--00.606 is adjacent to three radio-quiet WISE HII region candidates \citep{2014ApJS..212....1A}. The ionizing sources of the radio-quiet HII regions are expected to later than B1V, given the sensitivity about 1-2 mJy of the MAGPIS 20 cm survey. The stars were first selected if their parallaxes of GAIA EDR3 match that of the 22 GHz H2O maser source within the same region. We used the color-magnitude diagram made from the ZTF photometric catalog to select the candidates for massive stars because the intrinsic g-r colors of massive stars change little from B-type to O-type stars. Five stars lie in the areas of the color-magnitude diagram where either reddened massive stars or evolved post-main sequence stars of lower masses are commonly found. Three of the five stars, sources 1, 2, and 3, are located at the cavities of the three IR bubbles, and extended Hα emission is detected around the three IR bubbles. We suggest that sources 1, 2, and 3 are candidates for early-B stars associated with the radio-quiet region G014.645--00.606. Particularly, source 1 is an EW type eclipsing binary with a short period of 0.825 day, while source 2 is an EA type eclipsing binary with a short period of 0.919 day. The physical parameters of the two binary systems have been derived through the PHOEBE model. Source 1 is a twin binary of two stars with Teff ≈ 23,500 K, and source 2 contains a hotter component (Teff≈20,100 K) and a cooler one (Teff≈15,500 K). The O-C values of source 1 show a trend of decline, implying that the period of source is deceasing. Source 1 is likely a contacting early-B twin binary, for which mass transfer might cause its orbit to shrink.

Sensitivity Analysis and Selection of Check Index of Signal Intersection Simulation Model Based on VISSIM

2019 ◽  
Vol 2 (5) ◽  
Author(s):  
Mengda Zhang ◽  
Chenjing Zhou ◽  
Tian-tian Zhang ◽  
Yan Han
Keyword(s):  
Sensitivity Analysis ◽  
Simulation Model ◽  
Optimal Process ◽  
Parameter Calibration ◽  
Index Set ◽  
The Core ◽  
Core Module ◽  
Simulation Parameter ◽  
Simulation Parameters ◽  
Selection Of

Selecting check index quantitatively is the core of the calibration of micro traffic simulation parameters at signal intersection. Five indexes in the node (intersection) module of VISSIM were selected as the check index set. Twelve simulation parameters in the core module were selected as the simulation parameters set. Optimal process of parameter calibration was proposed and model of the intersection of Huangcun west street and Xinghua street in Beijing was built in VISSIM to verify it. The sensitivity analysis between each check index and simulation parameter in their own set was conducted respectively. Sensitive parameter sets of different check indices were obtained and compared. The results show that different indexes have different size of set, and average vehicle delay's is maximum, so it's necessary to select index quantitatively. The results can provide references for scientific selection of the check indexes and improve the study efficiency of parameter calibration.

Discovery of five new Galactic symbiotic stars in the VPHAS+ survey

2021 ◽  
Vol 502 (2) ◽  
pp. 2513-2517
Author(s):  
Stavros Akras ◽  
Denise R Gonçalves ◽  
Alvaro Alvarez-Candal ◽  
Claudio B Pereira
Keyword(s):  
Spectroscopic Data ◽  
Selection Criterion ◽  
Optical Spectra ◽  
Emission Lines ◽  
High Rate ◽  
Symbiotic Stars ◽  
Selection Of

ABSTRACT We report the validation of a recently proposed infrared (IR) selection criterion for symbiotic stars (SySts). Spectroscopic data were obtained for seven candidates, selected from the SySt candidates of Akras et al. by employing the new supplementary IR selection criterion for SySts in the VST/OmegaCAM Photometric H-Alpha Survey. Five of them turned out to be genuine SySts after the detection of H α, He ii, and [O iii] emission lines as well as TiO molecular bands. The characteristic O vi Raman-scattered line is also detected in one of these SySts. According to their IR colours and optical spectra, all five newly discovered SySts are classified as S-type. The high rate of true SySts detections of this work demonstrates that the combination of the H α emission and the new IR criterion improves the selection of target lists for follow-up observations by minimizing the number of contaminants and optimizing the observing time.

scholarly journals Deepening and Connecting Democratic Processes. The Opportunities and Pitfalls of Mini-Publics in Renewing Democracy

2018 ◽  
Vol 7 (11) ◽  
pp. 236
Author(s):  
Ank Michels ◽  
Harmen Binnema
Keyword(s):  
The Netherlands ◽  
Random Sampling ◽  
Policy Making ◽  
Specific Design ◽  
Fundamental Nature ◽  
The Core ◽  
Equal Chance ◽  
Political Impact ◽  
Selection Of

In recent decades, so-called “mini-publics” have been organized in many countries to renew policy making and democracy. One characteristic of mini-publics is that the selection of the participants is based on random sampling or sortition. This gives each member of the community an equal chance of being selected. Another feature is that deliberation forms the core of the process of how proposals are developed. In this paper, we investigate the possibilities and challenges of sortition and deliberation in the context of the call for a deepening of democracy and more citizen engagement in policy making. Based on extensive research on citizens’ forums (G1000) in The Netherlands, we show the potential of mini-publics, but a number of shortcomings as well. Some of these are related to the specific design of the G1000, while others are of a more fundamental nature and are due to the contradictory democratic values that deliberative mini-publics try to combine. One of these concerns the tension between the quality of deliberation and political impact. We conclude that combining institutional approaches could be a way out to deal with these tensions and a step forward to both deepen and connect democratic processes.

scholarly journals Limits to Ionization-parameter Mapping as a Diagnostic of Hii Region Optical Depth

2021 ◽  
Vol 923 (1) ◽  
pp. 78
Author(s):  
Amit N. Sawant ◽  
Eric W. Pellegrini ◽  
M. S. Oey ◽  
Jesús López-Hernández ◽  
Genoveva Micheva
Keyword(s):  
Optical Depth ◽  
Strong Dependence ◽  
Light Flux ◽  
Emission Lines ◽  
Ionization State ◽  
Hii Region ◽  
Parameter Mapping ◽  
Ionization Structure ◽  
The Galaxy ◽  
Ionization Parameter

Abstract We employ ionization-parameter mapping (IPM) to infer the optical depth of H ii regions in the northern half of M33. We construct [O iii]λ5007/[O ii]λ3727 and [O iii]λ5007/[S ii]λ6724 ratio maps from narrowband images continuum-subtracted in this way, from which we classify the H ii regions by optical depth to ionizing radiation, based on their ionization structure. This method works relatively well in the low-metallicity regime, 12 + log ( O / H ) ≤ 8.4 , where [O iii]λ λ4959, 5007 is strong. However, at higher metallicities, the method breaks down due to the strong dependence of the [O iii]λ λ4959, 5007 emission lines on the nebular temperature. Thus, although O++ may be present in metal-rich H ii regions, these commonly used emission lines do not serve as a useful indicator of its presence, and hence the O ionization state. In addition, IPM as a diagnostic of optical depth is limited by spatial resolution. We also report a region of highly excited [O iii] extending over an area ∼1 kpc across and [O iii]λ5007 luminosity of 4.9 ± 1.5 × 1038 erg s−1, which is several times higher than the ionizing budget of any potential sources in this portion of the galaxy. Finally, this work introduces a new method for continuum subtraction of narrowband images based on the dispersion of pixels around the mode of the diffuse-light flux distribution. In addition to M33, we demonstrate the method on C iii]λ1909 imaging of Haro 11, ESO 338-IG004, and Mrk 71.

scholarly journals Massive Star Cluster Formation and Destruction in Luminous Infrared Galaxies in GOALS. II. An ACS/WFC3 Survey of Nearby LIRGs

2021 ◽  
Vol 923 (2) ◽  
pp. 278
Author(s):  
S. T. Linden ◽  
A. S. Evans ◽  
K. Larson ◽  
G. C. Privon ◽  
L. Armus ◽  
...  
Keyword(s):  
Hubble Space Telescope ◽  
Early Stage ◽  
Cluster Formation ◽  
Age Distribution ◽  
Star Clusters ◽  
Star Cluster ◽  
Wide Field ◽  
Infrared Galaxies ◽  
Luminous Infrared Galaxies ◽  
Cluster Age

Abstract We present the results of a Hubble Space Telescope WFC3 near-UV and Advanced Camera for Surveys Wide Field Channel optical study into the star cluster populations of a sample of 10 luminous infrared galaxies (LIRGs) in the Great Observatories All-Sky LIRG Survey. Through integrated broadband photometry we have derived ages, masses, and extinctions for a total of 1027 star clusters in galaxies with d L < 110 Mpc in order to avoid issues related to cluster bending. The measured cluster age distribution slope of dN / d τ ∝ τ − 0.5 + / − 0.12 is steeper than what has been observed in lower-luminosity star-forming galaxies. Further, differences in the slope of the observed cluster age distribution between inner- ( dN / d τ ∝ τ − 1.07 + / − 0.12 ) and outer-disk ( dN / d τ ∝ τ − 0.37 + / − 0.09 ) star clusters provide evidence of mass-dependent cluster destruction in the central regions of LIRGs driven primarily by the combined effect of strong tidal shocks and encounters with massive giant molecular clouds. Excluding the nuclear ring surrounding the Seyfert 1 nucleus in NGC 7469, the derived cluster mass function (CMF; dN / dM ∝ M α ) offers marginal evidence for a truncation in the power law at M t ∼ 2×106 M ⊙ for our three most cluster-rich sources, which are all classified as early stage mergers. Finally, we find evidence of a flattening of the CMF slope of dN / dM ∝ M − 1.42 ± 0.1 for clusters in late-stage mergers relative to early stage (α = −1.65 ± 0.02), which we attribute to an increase in the formation of massive clusters over the course of the interaction.

scholarly journals Infrared helium emission lines from Cygnus X-3 suggesting a Wolf-Rayet star companion

Nature ◽  
1992 ◽  
Vol 355 (6362) ◽  
pp. 703-705 ◽  
Author(s):  
M. H. van Kerkwijk ◽  
P. A. Charles ◽  
T. R. Geballe ◽  
D. L. King ◽  
G. K. Miley ◽  
...  
Keyword(s):  
Emission Lines ◽  
Rayet Star ◽  
Helium Emission

The problem of selecting capabilities: Nussbaum’s philosophical road to democracy

2021 ◽  
Author(s):  
Hugo Rajão
Keyword(s):  
Human Dignity ◽  
Capability Approach ◽  
The Core ◽  
New Interpretation ◽  
Selection Of

Abstract: Capability Approach theorists have placed the recognition of capabilities and functionings at the core of their theories. However, they disagree about the selection of relevant capabilities. In this article, I argue that contrary to what the author claims, it is not philosophically possible to derive a list of central capabilities in this way, from the concept of human dignity underlying Martha Nussbaum’s theory. From that concept it is only possible to derive a process of democratic decision, in which everybody is represented fairly and equally. It should be noted that the proposal presented in this article is not in opposition to Nussbaum’s theory, but rather an attempt to offer a new interpretation of it, based on the normative groundings of theory, in order to address some of its theoretical problems. This thesis occupies forth section. In the second and third sections, I summarize the debate around the problem of selecting capabilities.

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