scholarly journals 1.10. The effects of the disk field on the bulge surface brightness

1998 ◽  
Vol 184 ◽  
pp. 35-36
Author(s):  
Y.C. Andredakis ◽  
R.H. Sanders
Keyword(s):  
Surface Brightness ◽  
Morphological Type ◽  
Intermediate Type ◽  
Classical Description ◽  
The Galaxy ◽  
Image Position

After the classical description of bulges by a de Vaucouleurs profile was found to be inadequate, a generalized profile, Sersic's law, was used successfully to describe the surface brightness: (Andredakis et al. 1994 (APB95)). The exponent n was found to vary systematically with the morphological type of the galaxy, from n = 4 for the bulges of S0s to n = 2 for intermediate type spirals and n = 1 (pure exponential) for the late types. (APB95, de Jong 1996). This has been confirmed also by the kinematics (Heraudeau et al 1996). This variation of n has been interpreted in two ways: (i) As the effect of the disk forming around an already developed bulge (APB95) and (ii) as evidence that the bulge originated from secular processes in the galaxy, after the disk was formed (Courteau et al. 1996). This needs to be resolved.

scholarly journals Opaque Spiral Disks: Some Empirical Facts and Consequences

1991 ◽  
Vol 144 ◽  
pp. 245-256
Author(s):  
Edwin A. Valentijn
Keyword(s):  
Surface Brightness ◽  
Axial Ratio ◽  
Recent Analysis ◽  
Line Of Sight ◽  
Selection Effects ◽  
Complete Sample ◽  
Large Samples ◽  
The Galaxy ◽  
Absorbing Material ◽  
Image Position

A recent analysis of the surface brightness profiles of a complete sample of 9381 spiral galaxies extracted from ESO-LV (Lauberts and Valentijn, 1989) showed that many galaxy disks of especially Sb–Sc galaxies are opaque (Valentijn, 1990). This paper studied how the observed surface brightness μobs varies as a function of the observed axial ratio a/b, by fitting the data of samples of spirals with (1) assuming the a/b to give the inclination angle of the disks to the line of sight. A sample of galaxies that were fully transparent at the particular radius used for the test would have C ≃ 1, while C <~ 0.25 signifies opaque conditions, the transition value being heavily dependent on the spatial distribution of the absorbing material and the effect of multiple scatterings (Bruzual et al. 1988). The most frequently-used C values range from 0.5–0.9 (Holmberg 1975, de Vaucouleurs et al. 1976, Sandage and Tammann 1981). However, Valentijn (1990) derived C values well below 0.25 for large samples of spirals throughout the galaxy disks; this result is not significantly affected by selection effects in either magnitude, angular diameter or axial ratio, nor by the presence of bulges (at least for types Sb and later).

scholarly journals The Shape of the Luminosity Profiles of Bulges

1996 ◽  
Vol 157 ◽  
pp. 86-87 ◽  
Author(s):  
Y. Andredakis ◽  
R. Peletier ◽  
M. Balcells
Keyword(s):  
Density Distribution ◽  
Decomposition Method ◽  
Surface Brightness ◽  
A Priori ◽  
Morphological Type ◽  
Early Type ◽  
Late Type ◽  
Dimensional Decomposition ◽  
The Galaxy ◽  
Light Profiles

AbstractWe extract the bulge light profiles of a sample of early type spirals, using K-band photometry and a new 2-dimensional decomposition method that does not assume a priori any surface brightness laws. We find that the shape of the light profile shows a good correlation with the morphological type of the galaxy, in the sense that the profiles tend to fall off more steeply at large radii for the later types. This trend shows that the formation of or interaction with the disk has probably affected the density distribution of the bulge. The fact that the transition in shape is continuous might also imply that most of the bulges of late type spirals were not formed by different mechanisms than the ones of early types.

scholarly journals Low Luminosity Galaxies in Large Surveys

1999 ◽  
Vol 171 ◽  
pp. 45-51
Author(s):  
John P. Huchra
Keyword(s):  
Surface Brightness ◽  
Luminosity Function ◽  
Morphological Type ◽  
Large Excess ◽  
Redshift Surveys ◽  
Low Surface Brightness ◽  
The Galaxy ◽  
Emission Line Galaxies ◽  
Low Surface Brightness Galaxies ◽  
Galaxy Luminosity Function

AbstractThe debate about the slope and amplitude of the galaxy luminosity function at the faint end is discussed w.r.t. faint galaxies in large surveys, in particular the second CfA (CfA2) and the Las Campanas (LCRS) redshift surveys. Large surveys are necessary to determine the statistics of rare objects or objects that can only be seen out to limited volumes. Both surveys show excesses of faint galaxies over Schechter function fits, but the parent sample for the LCRS survey generally does not contain large or low surface brightness galaxies which do appear in the CfA2 survey. The objects that comprise the relatively large excess of faint galaxies in the CfA2 survey are shown to be primarily of low surface brightness and late morphological type and are generally emission line galaxies. Galaxy samples constructed like the LCRS will generally always be deficient in low luminosity galaxies and thus are not useful for constraining the faint end of the galaxy luminosity function.

scholarly journals Surface Photometry of Spiral Galaxy NGC 5005 and Elliptical Galaxy NGC 4278

2018 ◽  
Vol 15 (3) ◽  
pp. 314-323
Author(s):  
Baghdad Science Journal
Keyword(s):  
Spiral Galaxy ◽  
Surface Brightness ◽  
Elliptical Galaxy ◽  
Position Angle ◽  
Sloan Digital Sky Survey ◽  
Surface Photometry ◽  
Contour Maps ◽  
Sky Survey ◽  
Flat Field ◽  
The Galaxy

Two galaxies have been chosen, spiral galaxy NGC 5005 and elliptical galaxy NGC 4278 to study their photometric properties by using surface photometric techniques with griz-Filters. Observations are obtained from the Sloan Digital Sky Survey (SDSS). The data reduction of all images have done, like bias and flat field, by SDSS pipeline. The overall structure of the two galaxies (a bulge, a disk), together with isophotal contour maps, surface brightness profiles and a bulge/disk decomposition of the galaxy images were performed, although the disk position angle, ellipticity and inclination of the galaxies have been estimated.

scholarly journals Study of the Magnetic Field of the Galaxy using Correlation Functions of the Intensity of Synchrotron Background Radio Emission

1996 ◽  
Vol 169 ◽  
pp. 615-616
Author(s):  
V.R. Shoutenkov
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Correlation Functions ◽  
Theoretical Calculations ◽  
Angular Separation ◽  
Field Studies ◽  
Position Angle ◽  
The Galaxy ◽  
Image Position ◽  
The Magnetic Field

The possibility to study magnetic field of the Galaxy calculating correlation or structure functions of synchrotron background radio emission have been known long ago (Kaplan and Pikel'ner (1963); Getmantsev (1958)). But this method had not been as popular as other methods of magnetic field studies. However theoretical calculations made by Chibisov and Ptuskin (1981) showed that correlation functions of intensity of synchrotron background radio emission can give a lot of valuable information about galactic magnetic fields because of the intensity of synchrotron background radio emission depends on H⊥. According to this theory correlation C(θ, φ) and structure S(θ, φ) functions of intensity, as functions of angular separation θ between two lines of sight and position angle φ on the sky between this two lines of sight, can be presented as a sum of isotropic (not dependent from angle φ) and anisotropic parts:

scholarly journals Kinematics of Planetary Nebulae in M51's Tidal Tail

2003 ◽  
Vol 209 ◽  
pp. 633-634
Author(s):  
John J. Feldmeier ◽  
J. Christopher Mihos ◽  
Patrick R. Durrell ◽  
Robin Ciardullo ◽  
George H. Jacoby
Keyword(s):  
Surface Brightness ◽  
Numerical Models ◽  
Planetary Nebulae ◽  
Tidal Tail ◽  
Low Surface Brightness ◽  
Galaxy Interaction ◽  
Self Consistent ◽  
The Galaxy ◽  
Interacting Systems ◽  
Kinematic Properties

The galaxy pair NGC 5194/95 (M51) is one of the closest and best known interacting systems. Despite its notoriety, however, many of its features are not well studied. Extending westward from NGC 5195 is a low surface brightness tidal tail, which can only be seen in deep broadband exposures. Our previous [O III] λ5007 planetary nebulae (PN) survey of M51 recovered this tidal tail, and presented us with a opportunity to study the kinematics of a galaxy interaction in progress. We report the results of a spectroscopy survey of the PN, aimed at determining their kinematic properties. We then use these data to constrain new self-consistent numerical models of the system.

scholarly journals Kinematics, structure and environment of three dwarf spheroidal galaxies

2014 ◽  
Vol 11 (S308) ◽  
pp. 473-474
Author(s):  
M. E. Sharina ◽  
I. D. Karachentsev ◽  
V. E. Karachentseva
Keyword(s):  
Surface Brightness ◽  
Morphological Type ◽  
Virgo Cluster ◽  
Sloan Digital Sky Survey ◽  
Dwarf Spheroidal Galaxies ◽  
Isolated Galaxies ◽  
Environmental Status ◽  
The Moment ◽  
Academy Of Sciences ◽  
Spheroidal Galaxies

AbstractWe explore the environmental status of three low surface brightness dwarf spheroidal galaxies (dSphs) KKH65, KK180 and KK227 using the results of our long slit spectroscopic observations at the 6m telescope of the Russian Academy of Sciences and surface photometry on the Sloan Digital Sky Survey (SDSS) images. The objects were selected by Karachentseva in 2010 as presumably isolated galaxies. The obtained surface brightness profiles demonstrate that our sample dSphs are less centrally concentrated than the objects of the same morphological type in the Virgo cluster (VC). Using the derived kinematic data we searched for possible neighbours of the dSphs within the projected distances from them Rproj > 500 kpc and with the differences in radial velocities |Δ V| > 500 kms−1. We applied the group finding algorithm by Makarov and Karachentsev to the selected sample. Our analysis shows that the dwarf galaxies of our study are not isolated. KKH65 and KK227 belong to the groups NGC3414 and NGC5371, respectively. KK180 is in the VC infall region. We conclude that it is not possible at the moment to justify the existence of isolated dSphs outside the Local Volume. The searches are complicated due to the lack of the accurate distances to the galaxies farther than 10 Mpc.

The Hi Neighborhoods Around STARBIRDS

2018 ◽  
Vol 14 (S344) ◽  
pp. 280-282
Author(s):  
Megan C. Johnson ◽  
Kristen B. W. McQuinn ◽  
John Cannon ◽  
Charlotte Martinkus ◽  
Evan Skillman ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Spiral Galaxies ◽  
Dwarf Galaxies ◽  
Neutral Hydrogen ◽  
Tidal Interactions ◽  
Low Surface Brightness ◽  
The Galaxy ◽  
Green Bank Telescope ◽  
Intense Star Formation

AbstractStarbursts are finite periods of intense star formation (SF) that can dramatically impact the evolutionary state of a galaxy. Recent results suggest that starbursts in dwarf galaxies last longer and are distributed over more of the galaxy than previously thought, with star formation efficiencies (SFEs) comparable to spiral galaxies, much higher than those typical of non-bursting dwarfs. This difference might be explainable if the starburst mode is externally triggered by gravitational interactions with other nearby systems. We present new, sensitive neutral hydrogen observations of 18 starburst dwarf galaxies, which are part of the STARburst IRregular Dwarf Survey (STARBIRDS) and each were mapped with the Green Bank Telescope (GBT) and/or Parkes Telescope in order to study the low surface brightness gas distributions, a common tracer for tidal interactions.

scholarly journals Galactic and extra-galactic radio frequency radiation due to sources other than the thermal and 21-cm emission of the interstellar gas

1958 ◽  
Vol 5 ◽  
pp. 37-43
Author(s):  
R. Hanbury Brown
Keyword(s):  
Thermal Emission ◽  
Wave Length ◽  
Black Body ◽  
Interstellar Gas ◽  
Ionized Gas ◽  
Radio Frequency Radiation ◽  
The Galaxy ◽  
Image Position ◽  
Galactic Radio ◽  
Frequency Radiation

At wave-lengths greater than about one metre the majority of the radio emission which is observed from the Galaxy cannot be explained in terms of thermal emission from ionized interstellar gas. This conclusion is widely accepted and is based on observations of the equivalent temperature of the sky and the spectrum of the radiation. The spectrum at metre wave-lengths is of the general form: where TA is the equivalent black-body temperature of a region of sky and A is the wave-length. The exponent n varies with direction but lies between about 2·5 and 2·8, and is thus significantly greater than the value of 2·0 which is the maximum to be expected for thermal emission from an ionized gas. Furthermore the value of TA is about 1050 K at 15 m and thus greatly exceeds the electron temperature expected in H 11 regions.At centimetre wave-lengths it is likely that the majority of the radiation observed originates in thermal emission from ionized gas; however, the present discussion is limited to a range of wave-lengths from about 1 m to 10 m where the ionized gas in the Galaxy is believed to be substantially transparent and where the origin of most of the radiation is believed to be non-thermal.

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