scholarly journals NIRS0S: Observations of early-type galaxy secular evolution spanning the Sa/S0/disky-E boundaries

2012 ◽  
Vol 10 (H16) ◽  
pp. 331-331
Author(s):  
Eija Laurikainen ◽  
Heikki Salo ◽  
Ronald Buta ◽  
Johan Knapen
Keyword(s):  
Galaxy Evolution ◽  
Critical Role ◽  
Early Type ◽  
Secular Evolution ◽  
Near Ir ◽  
Sky Survey ◽  
Merger Event ◽  
Structural Decompositions ◽  
Magnitude Difference ◽  
Inner Parts

AbstractNIRS0S (Near-IR S0 galaxy Survey), is a K-band survey of ~ 200 early-type disk galaxies, mainly S0s, 2-3 mag deeper than the 2Micron All Sky Survey. In depth morphological analysis was done, in which multi-component structural decompositions played an important role. Possible implications to internal dynamical galaxy evolution were discussed. S0s were suggested to be former spirals in which star formation has ceased, forming a parallel sequence with spirals (see Fig. 1). If that evolution is faster among the brighter galaxies, the observed magnitude difference between the barred and non-barred S0s could be understood. Bars are suggested to play a critical role in such evolution. For example, the inner lenses in the bright non-barred S0s can be explained as former barlenses (inner parts of bars), in which the elongated bar component has dissolved. We suggest that the last destructive merger event happened at a fairly large redshift.

scholarly journals Recent star formation in intermediate redshift (0.35< z <1.5) early–type galaxies

2012 ◽  
Vol 10 (H16) ◽  
pp. 132-132
Author(s):  
M. J. Rutkowski ◽  
H. Jeong ◽  
S. Yi ◽  
S. Kaviraj ◽  
S. H. Cohen ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Hubble Space Telescope ◽  
Spectral Energy ◽  
Observational Constraints ◽  
Wide Field ◽  
Early Type ◽  
Energy Distributions ◽  
Near Ir ◽  
Intermediate Redshift

AbstractWe measured the UV-optical-near-IR spectral energy distributions (SEDs) of redshift z ~ 0.3-1.5 early-type galaxies (ETGs) with the Hubble Space Telescope (HST) Wide Field Camera 3 (Rutkowski et al.2012). We searched for young stellar populations and morphological signatures of the mechanisms driving recent star formation (RSF) in these ETGs in order to provide observational constraints on models of galaxy evolution.

scholarly journals Is Centaurus A Special? A Neutral-Hydrogen Perspective

2010 ◽  
Vol 27 (4) ◽  
pp. 390-395 ◽  
Author(s):  
Christian Struve ◽  
Raffaella Morganti ◽  
Tom A. Oosterloo ◽  
Bjorn H. C. Emonts
Keyword(s):  
Galaxy Evolution ◽  
Radio Galaxy ◽  
Neutral Hydrogen ◽  
Radio Galaxies ◽  
Current Phase ◽  
Observational Result ◽  
Good Sensitivity ◽  
Early Type ◽  
Merger Event ◽  
Centaurus A

AbstractDue to its proximity, the neutral hydrogen belonging to Cen A can be observed at high resolution with good sensitivity. This allows us to study the morphology and kinematics in detail, in order to understand the evolution of this radio-loud source (e.g. merger history, AGN activity). At the same time, it is important to compare results to other sources of the same class (i.e. early-type galaxies in general and radio galaxies in particular) to see how Cen A fits into the global picture of early-type/radio galaxy evolution. The amount of Hi, the morphology of a warped disk with Hi clouds surrounding the disk and the regular kinematics of the inner part of the Hi disk are not unusual for early-type galaxies. The growing evidence that mergers are not necessarily responsible for AGN activity fits with the observational result that the recent merger event in Cen A is not directly connected to the current phase of activity. Based on these results, we conclude that Cen A has typical neutral hydrogen properties for an early-type and radio galaxy and it can therefore — from the perspective of Hi — be seen as a typical example of its class.

scholarly journals The Milky Way’s bulge star formation history as constrained from its bimodal chemical abundance distribution

2020 ◽  
Vol 497 (3) ◽  
pp. 3557-3570 ◽  
Author(s):  
Jianhui Lian ◽  
Gail Zasowski ◽  
Sten Hasselquist ◽  
David M Nataf ◽  
Daniel Thomas ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Critical Role ◽  
Bimodal Distribution ◽  
Distribution Functions ◽  
Star Formation History ◽  
Chemical Abundance ◽  
Secular Evolution ◽  
Formation History ◽  
Quenching Process

ABSTRACT We conduct a quantitative analysis of the star formation history (SFH) of the Milky Way’s (MW) bulge by exploiting the constraining power of its stellar [Fe/H] and [Mg/Fe] distribution functions. Using Apache Point Observatory Galactic Evolution Experiment survey data, we confirm the previously established bimodal [Mg/Fe]–[Fe/H] distribution within 3 kpc of the inner Galaxy. To fit the chemical bimodal distribution, we use a simple but flexible star formation framework, which assumes two distinct stages of gas accretion and star formation, and systematically evaluate a wide multidimensional parameter space. We find that the data favour a three-phase SFH that consists of an initial starburst, followed by a rapid star formation quenching episode, and a lengthy, quiescent secular evolution phase. The metal-poor, high-α bulge stars ([Fe/H] &lt; 0.0 and [Mg/Fe] &gt; 0.15) are formed rapidly (&lt;2 Gyr) during the early starburst. The density gap between the high- and low-α sequences is due to the quenching process. The metal-rich, low-α population ([Fe/H] &gt; 0.0 and [Mg/Fe] &lt; 0.15) then accumulates gradually through inefficient star formation during the secular phase. This is qualitatively consistent with the early SFH of the inner disc. Given this scenario, a notable fraction of young stars (age &lt;5 Gyr) is expected to persist in the bulge. Combined with extragalactic observations, these results suggest that a rapid star formation quenching process is responsible for bimodal distributions in both the MW’s stellar populations and in the general galaxy population and thus plays a critical role in galaxy evolution.

Detecting Gas Outflows in Type-2 AGNs Selected from the Sloan Digital Sky Survey

2012 ◽  
Vol 8 (S292) ◽  
pp. 372-372
Author(s):  
Hyun-Jin Bae ◽  
Jong-Hak Woo ◽  
Semyeong Oh
Keyword(s):  
Galaxy Evolution ◽  
Critical Role ◽  
Sloan Digital Sky Survey ◽  
Host Galaxies ◽  
Star Forming ◽  
Line Region ◽  
Systemic Velocity ◽  
Stellar Component ◽  
Sky Survey

AbstractEnergetic outflow from active galactic nuclei (AGNs) may play a critical role in galaxy evolution (e.g., Silk & Rees 1998). We present a velocity diagnostic for detecting gas outflow in the narrow-line region of Type-2 AGNs using line-of-sight velocity offsets of the [O iii] λ5007 and Hα emission lines with respect to the systemic velocity of stars in host galaxies (See Figure 1). We apply the diagnostics to nearby galaxies at 0.02 < z < 0.05, 3775 AGN-host and 907 star-forming galaxies as a comparison sample, which are selected from the Sloan Digital Sky Survey DR7. After obtaining a best-fit stellar population model for the continuum and a systemic velocity based on stellar lines, we subtract the stellar component to measure velocity offsets of each emission line. We find a sample of 169 AGN-host galaxies with outflow signatures, displaying a larger velocity shift of [O iii] than that of Hα, as expected in a decelerating outflow model (Komossa et al. 2008). We find that the offset velocity of [O iii] increases with Eddington ratio, suggesting that gas outflow depends on the energetics of AGN.

scholarly journals Galaxy Dynamics: Secular Evolution and Accretion

2010 ◽  
Vol 6 (S271) ◽  
pp. 119-126 ◽  
Author(s):  
Francoise Combes
Keyword(s):  
Angular Momentum ◽  
Galaxy Evolution ◽  
Resonant Scattering ◽  
Relative Role ◽  
Radial Migration ◽  
Galaxy Dynamics ◽  
Secular Evolution ◽  
Minor Mergers ◽  
Gas Accretion

AbstractRecent results are reviewed on galaxy dynamics, bar evolution, destruction and re-formation, cold gas accretion, gas radial flows and AGN fueling, minor mergers. Some problems of galaxy evolution are discussed in particular, exchange of angular momentum, radial migration through resonant scattering, and consequences on abundance gradients, the frequency of bulgeless galaxies, and the relative role of secular evolution and hierarchical formation.

scholarly journals The Optical/Near-IR Colours of Red Quasars

2000 ◽  
Vol 17 (1) ◽  
pp. 56-71 ◽  
Author(s):  
Paul J. Francis ◽  
Matthew T. Whiting ◽  
Rachel L. Webster
Keyword(s):  
Power Law ◽  
High Redshift ◽  
Sloan Digital Sky Survey ◽  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Red Power ◽  
Near Ir ◽  
Sky Survey ◽  
Ir Photometry

AbstractWe present quasi-simultaneous multi-colour optical/near-IR photometry for 157 radio selected quasars, forming an unbiassed sub-sample of the Parkes Flat-Spectrum Sample. Data are also presented for 12 optically selected QSOs, drawn from the Large Bright QSO Survey. The spectral energy distributions of the radio- and optically-selected sources are quite different. The optically selected QSOs are all very similar: they have blue spectral energy distributions curving downwards at shorter wavelengths. Roughly 90% of the radio-selected quasars have roughly power-law spectral energy distributions, with slopes ranging from Fv∝v0 to Fv∝v−2. The remaining 10% have spectral energy distributions showing sharp peaks: these are radio galaxies and highly reddened quasars. Four radio sources were not detected down to magnitude limits of H ∼ 19·6. These are probably high redshift (z > 3) galaxies or quasars. We show that the colours of our red quasars lie close to the stellar locus in the optical: they will be hard to identify in surveys such as the Sloan Digital Sky Survey. If near-IR photometry is added, however, the red power-law sources can be clearly separated from the stellar locus: IR surveys such as 2MASS should be capable of finding these sources on the basis of their excess flux in the K-band.

scholarly journals Stellar populations in the highest redshift galaxies

2015 ◽  
Vol 11 (A29B) ◽  
pp. 197-198
Author(s):  
Andrew J. Bunker
Keyword(s):  
Galaxy Evolution ◽  
High Redshift ◽  
Stellar Populations ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Forming ◽  
Near Ir ◽  
James Webb Space Telescope ◽  
Large Telescopes ◽  
The Universe

AbstractI discuss stellar populations in galaxies at high redshift (z > 6), in particular the blue rest-frame UV colours which have been detected in recent years through near-IR imaging with HST. These spectral slopes of β < −2 are much more blue than star-forming galaxies at lower redshift, and may suggest less dust obscuration, lower metallicity or perhaps a different initial mass function. I describe current work on the luminosity function of high redshift star- forming galaxies, the evolution of the fraction of strong Lyman-α emitters in this population, and the contribution of the ionizing photon budget from such galaxies towards the reionization of the Universe. I also describe constraints placed by Spitzer/IRAC on stellar populations in galaxies within the first billion years, and look towards future developments in spectroscopy with Extremely Large Telescopes and the James Webb Space Telescope, including the JWST/NIRSpec GTO programme on galaxy evolution at high redshift.

scholarly journals Galaxy Scaling Relations as a Result of Secular Evolution

2004 ◽  
Vol 220 ◽  
pp. 417-418
Author(s):  
Xiaolei Zhang
Keyword(s):  
Galaxy Evolution ◽  
Morphological Evolution ◽  
Evolution Process ◽  
Scaling Relations ◽  
Secular Evolution ◽  
The Past

The secular evolution process which slowly transforms the morphology of a given galaxy over its lifetime through mostly internal dynamical mechanisms could naturally account for most of the observed properties of physical galaxies (Zhang 2003a). As an emerging paradigm for galaxy evolution, its dynamical foundations had been established in the past few years (Zhang 1996, 1998, 1999). in this paper, we explore further implications of the secular morphological evolution process in reproducing the well-known scaling relations of galaxies.

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