Building the red sequence through gas-rich major mergers

AbstractUnderstanding the details of how the red sequence is built is a key question in galaxy evolution. What are the relative roles of gas-rich vs. dry mergers, major vs. minor mergers or galaxy mergers vs. gas accretion? In a recent paper (Wild et al. 2009), we compare hydrodynamic simulations with observations to show how gas-rich major mergers result in galaxies with strong post-starburst spectral features, a population of galaxies easily identified in the real Universe using optical spectra. Using spectra from the VVDS deep survey with <z> = 0.7, and a principal component analysis technique to provide indices with high enough SNR, we find that 40% of the mass flux onto the red-sequence could enter through a strong post-starburst phase, and thus through gas-rich major mergers. The deeper samples provided by next generation galaxy redshift surveys will allow us to observe the primary physical processes responsible for the shut-down in starformation and build-up of the red sequence.

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Galaxy Dynamics: Secular Evolution and Accretion

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311017522 ◽

2010 ◽

Vol 6 (S271) ◽

pp. 119-126 ◽

Cited By ~ 1

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.

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Lyα Forest Tomography of the z > 2 Cosmic Web

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316010164 ◽

2014 ◽

Vol 11 (S308) ◽

pp. 360-363

Author(s):

Khee-Gan Lee

Keyword(s):

Galaxy Evolution ◽

Large Scale ◽

High Redshift ◽

Large Scale Structure ◽

Area Density ◽

Star Forming ◽

Redshift Surveys ◽

High Area ◽

Galaxy Redshift ◽

Large Telescopes

AbstractThe hydrogen Lyα forest is an important probe of the z > 2 Universe that is otherwise challenging to observe with galaxy redshift surveys, but this technique has traditionally been limited to 1D studies in front of bright quasars. However, by pushing to faint magnitudes (g > 23) with 8-10m large telescopes it becomes possible to exploit the high area density of high-redshift star-forming galaxies to create 3D tomographic maps of large-scale structure in the foreground. I describe the first pilot observations using this technique, as well discuss future surveys and the resulting science possibilities for galaxy evolution and cosmology.

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The most massive, passive, and oldest galaxies at 0.5 < z < 2.1: Downsizing signature from galaxies selected from MgUV index

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935813 ◽

2019 ◽

Vol 630 ◽

pp. A145 ◽

Cited By ~ 3

Author(s):

R. Thomas ◽

O. Le Fèvre ◽

G. Zamorani ◽

B. C. Lemaux ◽

P. Hibon ◽

...

Keyword(s):

Photometric Data ◽

Early Type ◽

Massive Galaxies ◽

Spectral Fitting ◽

Redshift Surveys ◽

Deep Survey ◽

Galaxy Redshift ◽

Using Data ◽

Stellar Masses ◽

Best Fit

Aims. We seek is to identify old and massive galaxies at 0.5 < z < 2.1 on the basis of the magnesium index MgUV and then study their physical properties. Methods. We computed the MgUV index based on the best spectral fitting template of ∼3700 galaxies using data from the VLT VIMOS Deep Survey (VVDS) and VIMOS Ultra Deep Survey (VUDS) galaxy redshift surveys. Based on galaxies with the largest signal to noise and the best fit spectra we selected 103 objects with the highest spectral MgUV signature. We performed an independent fit of the photometric data of these galaxies and computed their stellar masses, star formation rates, extinction by dust and age, and we related these quantities to the MgUV index. Results. We find that the MgUV index is a suitable tracer of early-type galaxies at an advanced stage of evolution. Selecting galaxies with the highest MgUV index allows us to choose the most massive, passive, and oldest galaxies at any epoch. The formation epoch tf computed from the fitted age as a function of the total mass in stars supports the downsizing formation paradigm in which galaxies with the highest mass formed most of their stars at an earlier epoch.

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Constraints on Galaxy Evolution from Faint Redshift Surveys, Keck, and HST

Symposium - International Astronomical Union ◽

10.1017/s0074180900233032 ◽

1996 ◽

Vol 171 ◽

pp. 384-384

Author(s):

Caryl Gronwall

Keyword(s):

Galaxy Evolution ◽

Luminosity Function ◽

Current Model ◽

Angular Size ◽

Small Sample ◽

Redshift Surveys ◽

Luminosity Functions ◽

The Galaxy ◽

Deep Survey ◽

Galaxy Luminosity Function

The nature of faint field galaxy evolution remains controversial. While many workers advocate exotic theories, such as rapid merging or disappearing populations, we have found that it is possible to explain the published counts and redshift data with traditional luminosity evolution models which derive an optimal set of local luminosity functions for different galaxy types (Gronwall & Koo 1995). Recently, there has been a tremendous amount of new data addressing this question, including 1) the measurement of the galaxy luminosity function vs. redshift from faint redshift surveys down to B = 24 and I = 22 (Colless 1995; Lilly et al. 1995), 2) morphological and angular size data from the HST Medium Deep Survey (Driver et al. 1995; Phillips et al. 1995), and 3) redshift measurements with Keck for a small sample of galaxies with I > 22 (Koo 1995). We have explored these new data and have found that while our model continues to provide an excellent match to the faintest observed redshift and angular size distributions, it underpredicts the faint counts and luminosity function evolution for very blue late-type galaxies. Since our current model includes only minimal evolution of these galaxies, the new observations suggest a need for additional evolution, perhaps through a starbursting or mild merging component.

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An ANN Approach to Classification of Galaxy Spectra for the 2DF Galaxy Redshift Survey

Symposium - International Astronomical Union ◽

10.1017/s0074180900132346 ◽

1999 ◽

Vol 183 ◽

pp. 154-154

Author(s):

S.R. Folkes ◽

O. Lahav ◽

S.J. Maddox

Keyword(s):

Principal Component ◽

Automated Classification ◽

Signal To Noise ◽

Normal Galaxies ◽

Redshift Surveys ◽

Redshift Survey ◽

Galaxy Redshift ◽

Spectral Simulations ◽

Artificial Neural Network Ann

We present a method for automated classification of galaxies with low signal-to-noise (S/N) spectra typical of redshift surveys. We develop spectral simulations based on the parameters for the 2dF Galaxy Redshift Survey and investigate the technique of Principal Component Analysis when applied to spectra of low S/N. It is found that the projection onto the first 8 Principal Components hold most of the real spectral information, with later projections only adding noise. Using these components as input, we train an Artificial Neural Network (ANN) to classify the noisy simulated spectra into morphological classes. We find that more than 90% of our sample of normal galaxies are correctly classified into one of five morphological classes for simulations at bJ=19.7.

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