scholarly journals Evolution of Star-forming and Active Galaxies in Nearby Clusters

2002 ◽  
Vol 124 (5) ◽  
pp. 2453-2470 ◽  
Author(s):  
Neal A. Miller ◽  
Frazer N. Owen
Keyword(s):  
Active Galaxies ◽  
Star Forming

scholarly journals Quantifying correlations between galaxy emission lines and stellar continua using a PCA-based technique

2014 ◽  
Vol 10 (S306) ◽  
pp. 301-303
Author(s):  
Róbert Beck ◽  
László Dobos ◽  
István Csabai
Keyword(s):  
Emission Line ◽  
Stellar Population ◽  
Active Galaxies ◽  
Emission Lines ◽  
Theoretical Modelling ◽  
Support Vector ◽  
Population Synthesis ◽  
Star Forming ◽  
Stellar Population Synthesis ◽  
Empirical Curve

AbstractWe analyse the correlations between continuum properties and emission line equivalent widths of star-forming and narrow-line active galaxies from SDSS. We show that emission line strengths can be predicted reasonably well from PCA coefficients of the stellar continuum using local multiple linear regression. Since upcoming sky surveys will make broadband observations only, theoretical modelling of spectra will be essential to estimate physical properties of galaxies. Combined with stellar population synthesis models, our technique will help generate more accurate model spectra and mock catalogues of galaxies to be used to fit data from new surveys. We also show that, by combining PCA coefficients from the pure continuum and the emission lines, a plausible distinction can be made between weak AGNs and quiescent star-forming galaxies. Our method uses a support vector machine, and allows a more refined separation of active and star-forming galaxies than the empirical curve of Kauffmann et al. (2003).

scholarly journals Ambartsumian's Greatest Insight - The Origin of Galaxies

1999 ◽  
Vol 194 ◽  
pp. 473-477
Author(s):  
Halton Arp
Keyword(s):  
Big Bang ◽  
Young Star ◽  
Active Galaxies ◽  
Compact Objects ◽  
Particle Mass ◽  
Star Forming ◽  
Original Insight ◽  
The Big Bang

From simply looking at pictures of galaxies Ambartsumian realized that new galaxies were formed in ejections from old galaxies. In the ensuing 40 years, observations have supported in increasing detail his original insight. We can now empirically outline the development of compact objects emerging from the nuclei of active galaxies into young star forming galaxies and finally into aggregates of old stars.The observations actually require galaxies to continually originate in a low particle mass plasma which has remarkably similar properties to the “superfluid” which Ambartsumian foresaw. He had the courage to present these conclusions to influential astronomers who still today reject any origin of galaxies other than in the Big Bang. In this most important subject of science, the nature of our universe, Ambartsumian's revolutionary insights are now increasingly vindicated by observation.

scholarly journals Galactic Winds and the Missing Baryons

2004 ◽  
Vol 21 (4) ◽  
pp. 393-395 ◽  
Author(s):  
Sylvain Veilleux ◽  
David S. Rupke
Keyword(s):  
Active Galaxies ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Star Forming ◽  
Preliminary Results ◽  
Systematic Survey ◽  
Galactic Winds ◽  
Modern Cosmology ◽  
The Impact

AbstractGalaxy-scale winds are poised to solve a number of ailments in modern cosmology. However, we know little about trends of wind properties with host galaxy properties. In an attempt to quantify the impact of galactic winds on their host galaxies and the environment, we are conducting a systematic survey of star-forming and active galaxies at z = 0–0.5. Preliminary results on the star-forming galaxies are presented.

THE COSMIC RADIO BACKGROUND AND JET CONNECTION

2010 ◽  
Vol 19 (06) ◽  
pp. 965-969
Author(s):  
JACK SINGAL ◽  
LUKASZ STAWARZ ◽  
VAHE PETROSIAN ◽  
ANDREW LAWRENCE
Keyword(s):  
Radio Galaxies ◽  
Active Galaxies ◽  
Cosmological Evolution ◽  
Cosmic Radio ◽  
Star Forming ◽  
Radio Background

The recently characterized Cosmic Radio Background provides a unique perspective in which to study the nonthermal universe, including properties and cosmological evolution of active galaxies and their outflows. As much as 1/3 of the total intensity of the radio background can be due to emission resulting from classical jet processes in radio galaxies and radio quiet quasars. Furthermore, weak jet activity in Seyferts and ordinary star-forming galaxies may also be important.

scholarly journals The Starburst – AGN Connection: a Critical Review

2011 ◽  
Vol 20 (3) ◽  
Author(s):  
P. Rafanelli ◽  
G. La Mura ◽  
D. Bindoni ◽  
S. Ciroi ◽  
V. Cracco ◽  
...  
Keyword(s):  
Star Formation ◽  
Active Galaxies ◽  
Host Galaxy ◽  
Nuclear Activity ◽  
Massive Black Holes ◽  
Star Forming ◽  
Spectral Signatures ◽  
Star Formation Activity ◽  
Nuclear Regions

AbstractNuclear activity and star formation processes represent two key elements in the evolution of galaxies across the cosmic ages. In spite of very different physical backgrounds, several arguments suggest that they should be closely connected. On the basis of simple theoretical considerations, the transport of appreciable amounts of fuel to the AGN scale is very likely to trigger star formation in the gas. Young stellar populations, in their turn, are expected to affect the properties of the interstellar medium, leading to a complex balance of interactions among nuclear activity and star formation. This scenario is also supported by the observation of super-massive black holes and host galaxy properties, which strongly suggest a common evolutionary track. However, despite several years of extensive investigation, the relationship among the two processes still has to be properly explained. Here we provide a review of some of the most important observations, which are relevant to the issue of the connection among AGN and starburst events. Based on a wide sample of observations, we present an analysis of the spectral signatures connected with AGN and star formation activity. Expanding the concept of the distinction among star forming galaxies and the true active nuclei, we provide systematic evidence for a role of recent starburst events in the circum-nuclear regions of active galaxies and discuss the possibility of its influence onto the AGN environment. We also analyze the age, mass and metallicity properties of star-forming and active galaxies, illustrating that they are arranged in a sequence that is consistent with the identified relation.

scholarly journals 5.14. NMA survey of HCN and CO emission from nearby active galaxies

1998 ◽  
Vol 184 ◽  
pp. 239-240
Author(s):  
Kohno Kotaro ◽  
Kawabe Ryohei ◽  
Sakamoto Kazushi ◽  
Ishizuki Sumio ◽  
Baltasar Vila-Vilaro
Keyword(s):  
Massive Star ◽  
Gravitational Instability ◽  
Active Galaxies ◽  
Molecular Gas ◽  
Star Forming ◽  
Twin Peaks ◽  
Integrated Intensity ◽  
Seyfert Nucleus ◽  
Tight Correlation ◽  
Co Emission

In order to study the spatial variation of molecular gas properties and their relation to the nuclear activities of galaxies, we have conducted an imaging survey of HCN(1-0) and CO(1-0) emission from nearby active galaxies with the Nobeyama Millimeter Array. Here we present the results of three galaxies, NGC 3504 (Starburst nucleus), NGC 4736 (Post-Starburst nucleus), and NGC 6951 (Seyfert nucleus with a circumnuclear star-forming ring).In the observations of these three galaxies, we find that (1) the HCN distribution is significantly different from that of CO, and that (2) the HCN emission spatially correlates better with the massive star-forming region than CO emission (Figure 1, 2(a), and 2(b)). For instance, in the Post-Starburst nucleus of NGC 4736, we find a remarkable decrease of the HCN emission, despite of strong CO nuclear concentration. The upper limit (2σ) of the integrated intensity ratio I(HCN)/I(CO) within the central r < 150 pc region is 0.04, which is surprisingly low compared with the value in other galactic nucleus (cf. ratio = 0.08 within r < 300 pc in Milky Way, Jackson et al. 1996, ApJ, 456, 91). Presumably the dense molecular gas must have been consumed by a past starburst event in the nucleus. These results suggest a tight correlation between the gas density measured by the I(HCN)/I(CO) ratio and the star-forming activities in the central region of galaxies.It seems that there exist a spatial anti-correlation between the I(HCN)/ I(CO) ratio and the gas velocity dispersion in NGC 6951 (Figure 2(c)). The ratio is not enhanced in the CO twin peaks which are interpreted as shock regions due to gas orbit crowding. These imply the importance of gravitational instability on the formation of dense molecular gas and successive massive starformation in this region.

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