scholarly journals Disk and spheroidal components of external galaxies: an overview

1979 ◽  
Vol 84 ◽  
pp. 9-26
Author(s):  
S. E. Strom ◽  
K. M. Strom
Keyword(s):  
Surface Brightness ◽  
Large Scale ◽  
Disk Surface ◽  
Optical Observations ◽  
Galactic Halos ◽  
Star Forming ◽  
Isolated Galaxies ◽  
Disk Size ◽  
History Of ◽  
External Galaxies

A brief review of current theoretical views on how disk and spheroidal galaxies form and evolve provides the background for a summary of recent optical observations of external galaxies. Primary emphasis is placed on a discussion of the large-scale distribution and chemical composition of the stellar and gaseous constituents of relatively isolated galaxies. New studies of halo and disk surface-brightness distributions in spiral and SO galaxies are summarized. The “missing mass” in galactic halos, the relationship between disk size and luminosity, the nonexponential character of disk light distributions and very low-surface-brightness disk systems are highlighted in this section. Next discussed are observations which may provide insight into the factors which regulate the star-forming history of galactic disks and the post-astration appearance of spiral galaxies. Finally, the observed properties of relatively isolated disk galaxies are compared with those located in dense groups. It appears from this comparison that environment plays a significant role in governing the evolutionary history of a galaxy.

scholarly journals Recent Star Formation History of the Magellanic Clouds

1999 ◽  
Vol 190 ◽  
pp. 470-472
Author(s):  
Eva K. Grebel ◽  
Wolfgang Brandner
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
New Age ◽  
Magellanic Clouds ◽  
Star Formation History ◽  
Star Forming ◽  
Formation History ◽  
History Of

A new age calibration of Cepheids and supergiants is used to study the large-scale recent star formation history of the LMC and the SMC. We find evidence for migration of star formation along the LMC bar as well as for the existence of long-lived (≈ 200 Myr) extended star-forming features.

scholarly journals Distribution of star-forming complexes and the structure of our Galaxy

2003 ◽  
Vol 212 ◽  
pp. 431-440 ◽  
Author(s):  
Delphine Russeil
Keyword(s):  
Large Scale ◽  
Stellar Population ◽  
Line Of Sight ◽  
H Ii Regions ◽  
Spiral Arms ◽  
Ob Stars ◽  
Star Forming ◽  
Optical Images ◽  
External Galaxies

The determination of the external galaxies morphology is generally based on their appearance on optical images. At these wavelengths young stellar population and their associated H ii regions, which can be grouped into star-forming complexes, appear preferentially located along spiral arms. Hence, it is naturally to use the same tracers to delineate the arms of our own Galaxy. But, where for external galaxies the distribution of star-forming complexes along the spiral arms is generally evident from direct imaging, for our Galaxy the spiral arms are strung out along the line of sight, leading to the superposition and mixing of information from the different complexes in the spiral arms making it difficult to distinguish them. Thus to access to the spatial distribution of young objects, hence to the large scale structure of our Galaxy, it is required first to identify and collect star-forming complexes (molecular clouds – H ii regions – OB stars) and then to determine their distance. In this framework I review the observational results and difficulties concerning the distribution of star-forming complexes and the determination of the structure of our Galaxy.

scholarly journals Optical Observations of Ionized Gas in External Galaxies

1974 ◽  
Vol 60 ◽  
pp. 249-256
Author(s):  
G. Monnet
Keyword(s):  
Large Scale ◽  
Spiral Galaxies ◽  
Optical Observations ◽  
Diffuse Emission ◽  
Ionized Gas ◽  
External Galaxies

This paper reviews recent optical results on the large scale distribution of ionized gas in spiral galaxies, including our own. There is a diffuse, inhomogeneous emission in the arm region in spirals, including our Galaxy, and in gas-rich galaxies a fainter diffuse emission between the arms.

scholarly journals The Universe Behind the Southern Milky Way

2005 ◽  
Vol 216 ◽  
pp. 203-210 ◽  
Author(s):  
Renée C. Kraan-Korteweg ◽  
Lister Staveley-Smith ◽  
Jennifer Donley ◽  
Bärbel Koribalski ◽  
Patricia A. Henning
Keyword(s):  
Surface Brightness ◽  
Large Scale ◽  
High Surface ◽  
Star Forming ◽  
Large Scale Structures ◽  
The North ◽  
Low Surface Brightness ◽  
Scale Structures ◽  
Zone Of Avoidance ◽  
The Universe

A first analysis of a deep blind HI survey covering the southern Zone of Avoidance plus an extension towards the north (196† ≤ ℓ ≤ 52†) obtained with the Multibeam receiver at the 64-m Parkes telescope reveals slightly over a thousand galaxies within the latitude completeness limit of |b| ≤ 5†. The characteristics and the uncovered large-scale structures of this survey are described, in particular the prominence of the Norma Supercluster, the possible cluster around PKS 1343–601 (both in the Great Attractor region), as well as the Local Void and the clustering in the Puppis region. In this blind HI survey HIZOA J0836–43 was discovered, one of the most massive spiral galaxies known to date (MHI = 7.3 × 1010 M⊙, MT = 1.1 × 1012 M⊙; H0 = 75 km/s/Mpc). Although of similar mass to Malin 1-like objects, this galaxy does not share their typical low-surface brightness properties, but seems an exceptionally massive but normal, high surface brightness, star-forming galaxy.

scholarly journals Unveiling the environment and faint features of the isolated galaxy CIG 96 with deep optical and HI observations

2018 ◽  
Vol 619 ◽  
pp. A163 ◽  
Author(s):  
P. Ramírez-Moreta ◽  
L. Verdes-Montenegro ◽  
J. Blasco-Herrera ◽  
S. Leon ◽  
A. Venhola ◽  
...  
Keyword(s):  
Data Cube ◽  
Optical Observations ◽  
Wide Field ◽  
Main Hypothesis ◽  
Star Forming ◽  
Secular Evolution ◽  
Star Forming Regions ◽  
Isolated Galaxies ◽  
Gas Accretion ◽  
Ideal Framework

Context. Asymmetries in atomic hydrogen (HI) in galaxies are often caused by the interaction with close companions, making isolated galaxies an ideal framework to study secular evolution. The AMIGA project has demonstrated that isolated galaxies show the lowest level of asymmetry in their HI integrated profiles compared to even field galaxies, yet some present significant asymmetries. CIG 96 (NGC 864) is a representative case reaching a 16% level. Aims. Our aim is to investigate the HI asymmetries of the spiral galaxy CIG 96 and what processes have triggered the star-forming regions observed in the XUV pseudo-ring. Methods. We performed deep optical observations at CAHA1.23m, CAHA2.2m and VST (OmegaCAM wide-field camera) telescopes. We reach surface brightness (SB) limits of μCAHA2.2m = 27.5 mag arcsec−2 (Cousins R) and μVST = 28.7 mag arcsec−2 (SDSS r) that show the XUV pseudo-ring of the galaxy in detail. Additionally, a wavelet filtering of the HI data cube from our deep observations with VLA/EVLA telescope allowed us to reach a column density of NHI = 8.9 × 1018 cm−2 (5σ) (28″ × 28″ beam), lower than in any isolated galaxy. Results. We confirm that the HI of CIG 96 extends farther than 4 × r25 in all directions. Furthermore, we detect for the first time two gaseous structures (∼106 M⊙) in the outskirts. The SDSS g - r colour index image from CAHA1.23m shows extremely blue colours in certain regions of the pseudo-ring where NHI > 8.5 × 1020 cm−2, whereas the rest show red colours. Galactic cirrus contaminate the field, setting an unavoidable detection limit at 28.5 mag arcsec−2 (SDSS r). Conclusions. At the current SB and NHI levels, we detect no stellar link within 1° × 1° or gaseous link within 40′ × 40′ between CIG 96 and any companion. The isolation criteria rule out interactions with other similar-sized galaxies for at least ∼2.7 Gyr. Using existing stellar evolution models, the age of the pseudo-ring is estimated at 1 Gyr or older. Undetected previously accreted companions and cold gas accretion remain as the main hypothesis to explain the optical pseudo-ring and HI features of CIG 96.

scholarly journals Inner-Truncated Disks – Are They Tied to Bars?

1996 ◽  
Vol 157 ◽  
pp. 91-93 ◽  
Author(s):  
W. E. Baggett ◽  
S. M. Baggett ◽  
K. S. J. Anderson
Keyword(s):  
Surface Brightness ◽  
Disk Surface ◽  
Type Ii ◽  
Early Type ◽  
Barred Galaxies ◽  
Outer Disk ◽  
The Galaxy ◽  
External Galaxies ◽  
Galaxy Center ◽  
Bar Formation

An inner-truncated disk (ITD) brightness profile is one in which the inward extrapolation of the outer disk surface brightness significantly exceeds the observed surface brightness in a region near the galaxy center. Freeman (1970) identified these profiles as Type II profiles. Fourteen of Freeman’s (1970) sample of 36 external galaxies are designated as Type II (ITD); seven of the ITD’s are classified as barred galaxies and ITD’s are found at all morphological types.Ohta, Hamabe, & Wakamatsu (1990) report that luminosity profiles perpendicular to the bars of six early-type galaxies all exhibit the Freeman Type II shape, while the feature is lost when azimuthally averaged profiles of the same galaxies are studied. They postulate that the bar formation resulted in an azimuthal redistribution of the stars, but no net radial redistribution.

Materials for the history of the gospel-Baptist movement in Ukraine

1996 ◽  
pp. 4-15
Author(s):  
S. Golovaschenko ◽  
Petro Kosuha
Keyword(s):  
Large Scale ◽  
Religious Studies ◽  
Theological Seminary ◽  
National Academy Of Sciences ◽  
Evangelical Christians ◽  
Evangelical Christian ◽  
First Results ◽  
History Of ◽  
Fruitful Cooperation ◽  
Academy Of Sciences

The report is based on the first results of the study "The History of the Evangelical Christians-Baptists in Ukraine", carried out in 1994-1996 by the joint efforts of the Department of Religious Studies at the Institute of Philosophy of the National Academy of Sciences of Ukraine and the Odessa Theological Seminary of Evangelical Christian Baptists. A large-scale description and research of archival sources on the history of evangelical movements in our country gave the first experience of fruitful cooperation between secular and church researchers.

Integration of Ecological and Engineering Aspects in Planning Large Scale Tidal Power Development in the Bay of Fundy, Canada

1984 ◽  
Vol 16 (1-2) ◽  
pp. 281-295 ◽  
Author(s):  
Donald C Gordon
Keyword(s):  
Large Scale ◽  
Feasibility Studies ◽  
Bay Of Fundy ◽  
Final Decision ◽  
Power Development ◽  
Tidal Power ◽  
History Of ◽  
Scientists And Engineers ◽  
The Many ◽  
University Scientists

Large-scale tidal power development in the Bay of Fundy has been given serious consideration for over 60 years. There has been a long history of productive interaction between environmental scientists and engineers durinn the many feasibility studies undertaken. Up until recently, tidal power proposals were dropped on economic grounds. However, large-scale development in the upper reaches of the Bay of Fundy now appears to be economically viable and a pre-commitment design program is highly likely in the near future. A large number of basic scientific research studies have been and are being conducted by government and university scientists. Likely environmental impacts have been examined by scientists and engineers together in a preliminary fashion on several occasions. A full environmental assessment will be conducted before a final decision is made and the results will definately influence the outcome.

scholarly journals Properties of galaxies with an offset between the position angles of the major kinematic and photometric axes

2020 ◽  
Vol 634 ◽  
pp. A26 ◽  
Author(s):  
L. S. Pilyugin ◽  
E. K. Grebel ◽  
I. A. Zinchenko ◽  
J. M. Vílchez ◽  
F. Sakhibov ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Velocity Fields ◽  
Oxygen Abundance ◽  
Star Forming ◽  
Measured Position ◽  
Central Oxygen ◽  
Straight Lines

We derive the photometric, kinematic, and abundance characteristics of 18 star-forming MaNGA galaxies with fairly regular velocity fields and surface brightness distributions and with a large offset between the measured position angles of the major kinematic and photometric axes, ΔPA ≳ 20°. The aim is to examine if there is any other distinctive characteristic common to these galaxies. We found morphological signs of interaction in some (in 11 out of 18) but not in all galaxies. The observed velocity fields show a large variety; the maps of the isovelocities vary from an hourglass-like appearance to a set of straight lines. The position angles of the major kinematic axes of the stellar and gas rotations are close to each other. The values of the central oxygen abundance, radial abundance gradient, and star formation rate are distributed within the intervals defined by galaxies with small (no) ΔPA of similar mass. Thus, we do not find any specific characteristic common to all galaxies with large ΔPA. Instead, the properties of these galaxies are similar to those of galaxies with small (no) ΔPA. This suggests that either the reason responsible for the large ΔPA does not influence other characteristics or the galaxies with large ΔPA do not share a common origin, they can, instead, originate through different channels.

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