Color bimodality: Implications for galaxy evolution

Baldry, I. K.

doi:10.1063/1.1848322

Cited by 23 publications

(6 citation statements)

References 69 publications

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“…elliptical-like morphologies; on the other side, blue-cloud galaxies that are on the star-forming main sequence and with late-type i.e. disk-like morphologies (Strateva et al 2001;Kauffmann et al 2003;Baldry et al 2004;Balogh et al 2004). For example, Kauffmann et al (2004) and Wetzel et al (2012) have examined the number density distribution of SDSS galaxies in specific star-formation rate and found a break, a local minimum at sSFR = 10 −11 yr −1 at 0.04 < z < 0.06 whose value is independent of galaxy stellar mass and host halo mass (at least for stellar masses around 10 10 M and above).…”

Section: On the Bimodality: Color Vs Sfrmentioning

confidence: 99%

“…Broadly speaking, galaxies in the local Universe can be mainly divided into two categories: disk-like 'star-forming' galaxies that preferentially populate the low-density regions of the Universe, and 'passive' or 'quenched' galaxies, with older stellar populations and little-to-no star formation, which are mostly observed at high stellar masses and/or populating the high-density environments. The latter type is comprised mainly of spheroidal or elliptical galaxies (Kauffmann et al 2003;Baldry et al 2004).…”

Section: Introductionmentioning

confidence: 99%

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The star formation activity of IllustrisTNG galaxies: main sequence, UVJ diagram, quenched fractions, and systematics

Donnari

Pillepich

Nelson

et al. 2019

Monthly Notices of the Royal Astronomical Society

281

359

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We select galaxies from the IllustrisTNG hydrodynamical simulations (M stars > 10 9 M at 0 z 2) and characterize the shapes and evolutions of their UVJ and star-formation rate -stellar mass (SFR-M stars ) diagrams. We quantify the systematic uncertainties related to different criteria to classify star-forming vs. quiescent galaxies, different SFR estimates, and by accounting for the star formation measured within different physical apertures. The TNG model returns the observed features of the UVJ diagram at z 2, with a clear separation between two classes of galaxies. It also returns a tight star-forming main sequence (MS) for M stars < 10 10.5 (M ) with a ∼ 0.3 dex scatter at z ∼ 0 in our fiducial choices. If a UVJ-based cut is adopted, the TNG MS exhibits a downwardly bending at stellar masses of about 10 10.5−10.7 M . Moreover, the model predicts that ∼ 80 (50) per cent of 10 10.5−11 M galaxies at z = 0 (z = 2) are quiescent and the numbers of quenched galaxies at intermediate redshifts and high masses are in better agreement with observational estimates than previous models. However, shorter SFR-averaging timescales imply higher normalizations and scatter of the MS, while smaller apertures lead to underestimating the galaxy SFRs: overall we estimate the inspected systematic uncertainties to sum up to about 0.2−0.3 dex in the locus of the MS and to about 15 percentage points in the fraction of quenched galaxies. While TNG color distributions are clearly bimodal, this is not the case for the SFR logarithmic distributions in bins of stellar mass (SFR 10 −3 M yr −1 ). Finally, the slope and z = 0 normalization of the TNG MS are consistent with observational findings; however, the locus of the TNG MS remains lower by about 0.2 − 0.5 dex at 0.75 z < 2 than the available observational estimates taken at face value.

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Section: On the Bimodality: Color Vs Sfrmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The star formation activity of IllustrisTNG galaxies: main sequence, UVJ diagram, quenched fractions, and systematics

Donnari

Pillepich

Nelson

et al. 2019

Monthly Notices of the Royal Astronomical Society

281

359

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“…Over the last 10 years a large number of publications have addressed possible physical causes (Peng et al 2010(Peng et al , 2012Schawinski et al 2014a), such as AGN feedback (Salim et al 2007;Kauffmann et al 2007;Georgakakis et al 2008;Hickox et al 2009;Mancini et al 2015;Bongiorno et al 2016), major mergers (Sanders et al 1988;Mihos & Hernquist 1996;Hopkins et al 2006), environmental effects (Woo E-mail: baerr@phys.ethz.ch † Ambizione fellow Knobel et al 2015;Peng et al 2015) and secular processes (Kormendy & Kennicutt 2004;Masters et al 2011;Cheung et al 2013), for the quenching of star formation in galaxies. All these processes could explain the bi-modality in colour-mass and colour-magnitude space (Bell et al 2003;Baldry et al 2004;Faber et al 2007;Martin et al 2007;Schawinski et al 2014b;Taylor et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Active galactic nuclei from He ii: a more complete census of AGN in SDSS galaxies yields a new population of low-luminosity AGN in highly star-forming galaxies

Bär¹,

Weigel²,

Sartori³

et al. 2016

Mon. Not. R. Astron. Soc.

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In order to perform a more complete census of active galactic nuclei (AGN) in the local Universe, we investigate the use of the He II λ4685 emission line diagnostic diagram by Shirazi & Brinchmann (2012) in addition to the standard methods based on other optical emission lines. The He II based diagnostics is more sensitive to AGN ionization in the presence of strong star formation than conventional line diagnostics. We survey a magnitude-limited sample of 63,915 galaxies from the Sloan Digital Sky Survey Data Release 7 at 0.02 < z < 0.05 and use both the conventional BPT emission line diagnostic diagrams, as well as the He II diagram to identify AGN. In this sample, 1,075 galaxies are selected as AGN using the BPT diagram, while an additional 234 galaxies are identified as AGN using the He II diagnostic diagram, representing a 22% increase of AGN in the parent galaxy sample. We explore the host galaxy properties of these new He II selected AGN candidates and find that they are most common in star-forming galaxies on the blue cloud and on the main sequence where ionization from starformation is most likely to mask AGN emission in the BPT lines. We note in particular a high He II AGN fraction in galaxies above the high-mass end of the main sequence where quenching is expected to occur. We use archival Chandra observations to confirm the AGN nature of candidates selected through He II based diagnostic.Finally, we discuss how this technique can help inform galaxy/black hole co-evolution scenarios.

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“…The red sequence is tight, and typically home to early-type galaxies with little star formation activity. The blue cloud is comparatively more dispersed, and is normally home to late-type galaxies with higher star formation rates (Baldry et al 2004;Driver et al 2006;Schiminovich et al 2007). Between these two populations is a region denoted the green valley, which appears in observations to be sparsely populated (Martin et al 2007;Salim 2014) (though work by Eales et al (2018) demonstrates that observational biases could be responsible for the under-density).…”

Section: Introductionmentioning

confidence: 99%

Quenching time-scales of galaxies in the eagle simulations

Wright

Lagos

Davies

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We use the eagle simulations to study the connection between the quenching timescale, τ Q , and the physical mechanisms that transform star-forming galaxies into passive galaxies. By quantifying τ Q in two complementary ways -as the time over which (i) galaxies traverse the green valley on the colour-mass diagram, or (ii) leave the main sequence of star formation and subsequently arrive on the passive cloud in specific star formation rate (SSFR)-mass space -we find that the τ Q distribution of high-mass centrals, low-mass centrals and satellites are divergent. In the low stellar mass regime where M < 10 9.6 M , centrals exhibit systematically longer quenching timescales than satellites (≈ 4 Gyr compared to ≈ 2 Gyr). Satellites with low stellar mass relative to their halo mass cause this disparity, with ram pressure stripping quenching these galaxies rapidly. Low mass centrals are quenched as a result of stellar feedback, associated with long τ Q 3 Gyr. At intermediate stellar masses where 10 9.7 M < M < 10 10.3 M , τ Q are the longest for both centrals and satellites, particularly for galaxies with higher gas fractions. At M 10 10.3 M , galaxy merger counts and black hole activity increase steeply for all galaxies. Quenching timescales for centrals and satellites decrease with stellar mass in this regime to τ Q 2 Gyr. In anticipation of new intermediate redshift observational galaxy surveys, we analyse the passive and star-forming fractions of galaxies across redshift, and find that the τ Q peak at intermediate stellar masses is responsible for a peak (inflection point) in the fraction of green valley central (satellite) galaxies at z ≈ 0.5 − 0.7.

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Color bimodality: Implications for galaxy evolution

Cited by 23 publications

References 69 publications

The star formation activity of IllustrisTNG galaxies: main sequence, UVJ diagram, quenched fractions, and systematics

The star formation activity of IllustrisTNG galaxies: main sequence, UVJ diagram, quenched fractions, and systematics

Active galactic nuclei from He ii: a more complete census of AGN in SDSS galaxies yields a new population of low-luminosity AGN in highly star-forming galaxies

Quenching time-scales of galaxies in the eagle simulations

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