Some Musings on Galaxy Morphology, Galactic Colors, and the Environments of Galaxies

Bergh, Sidney van den

doi:10.1086/521342

Cited by 16 publications

(9 citation statements)

References 26 publications

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“…7. The ATLAS 3D sample of ETGs indeed defines a narrow colour–magnitude sequence approximated, in SDSS magnitudes, by As found by previous authors there is little scatter in the relation at the high‐mass end, while at the lower mass end some galaxies appear to be still in transition between the blue and red sequence (Strateva et al 2001; Conselice 2006; van den Bergh 2007; Bernardi et al 2010). The 31 ETGs with SDSS colour and defined as slow rotators in Paper III all lie close to the red sequence with an rms scatter of 0.13 mag from the best‐fitting relation.…”

Section: The Atlas3d Samplesupporting

confidence: 67%

“…E and S0 galaxies invariably lie on the red sequence, while late‐type spirals are generally on the blue cloud. However large fractions of spirals populate the red sequence as well and overlap with ETGs (Strateva et al 2001; Conselice 2006; van den Bergh 2007; Bernardi et al 2010). An accurate morphology is easier to obtain for nearby galaxies and it is more robust than colour to dust and inclination effects.…”

Section: The Atlas3d Samplementioning

confidence: 99%

See 1 more Smart Citation

The ATLAS3D project - I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria

Cappellari¹,

Emsellem²,

Krajnović³

et al. 2011

Monthly Notices of the Royal Astronomical Society

1,024

737

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The ATLAS3D project is a multiwavelength survey combined with a theoretical modelling effort. The observations span from the radio to the millimetre and optical, and provide multicolour imaging, two‐dimensional kinematics of the atomic (H i), molecular (CO) and ionized gas (Hβ, [O iii] and [N i]), together with the kinematics and population of the stars (Hβ, Fe5015 and Mg b), for a carefully selected, volume‐limited (1.16 × 105 Mpc3) sample of 260 early‐type (elliptical E and lenticular S0) galaxies (ETGs). The models include semi‐analytic, N‐body binary mergers and cosmological simulations of galaxy formation. Here we present the science goals for the project and introduce the galaxy sample and the selection criteria. The sample consists of nearby (D < 42 Mpc, |δ− 29°| < 35°, |b| > 15°) morphologically selected ETGs extracted from a parent sample of 871 galaxies (8 per cent E, 22 per cent S0 and 70 per cent spirals) brighter than MK < −21.5 mag (stellar mass M★≳ 6 ×109 M⊙). We analyse possible selection biases and we conclude that the parent sample is essentially complete and statistically representative of the nearby galaxy population. We present the size–luminosity relation for the spirals and ETGs and show that the ETGs in the ATLAS3D sample define a tight red sequence in a colour–magnitude diagram, with few objects in the transition from the blue cloud. We describe the strategy of the SAURON integral field observations and the extraction of the stellar kinematics with the ppxf method. We find typical 1σ errors of ΔV≈ 6 km s−1, Δσ≈ 7 km s−1, Δh3≈Δh4≈ 0.03 in the mean velocity, the velocity dispersion and Gauss–Hermite (GH) moments for galaxies with effective dispersion σe≳ 120 km s−1. For galaxies with lower σe (≈40 per cent of the sample) the GH moments are gradually penalized by ppxf towards zero to suppress the noise produced by the spectral undersampling and only V and σ can be measured. We give an overview of the characteristics of the other main data sets already available for our sample and of the ongoing modelling projects.

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Section: The Atlas3d Samplesupporting

confidence: 67%

Section: The Atlas3d Samplementioning

confidence: 99%

The ATLAS3D project - I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria

Cappellari¹,

Emsellem²,

Krajnović³

et al. 2011

Monthly Notices of the Royal Astronomical Society

1,024

737

View full text Add to dashboard Cite

show abstract

“…Also in the MGC, Ellis et al (2005) study a well‐defined sample of 350 galaxies and find, using multivariate statistical analysis of the galaxy properties, that only two populations, corresponding to early and late types, are justified, and the late types (Sa–Irr) are smoothly spread within the late‐type region of parameter space. In a sample of 1 246 galaxies with Hubble types from the Revised Shapely–Ames catalogue, van den Bergh (2007) similarly find a continuum of Hubble types but a bimodality in colour.…”

Section: Discussionmentioning

confidence: 78%

Galaxy colour, morphology and environment in the Sloan Digital Sky Survey

Ball¹,

Loveday²,

Brunner³

2007

Monthly Notices of the Royal Astronomical Society

106

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We use the Fourth Data Release of the Sloan Digital Sky Survey to investigate the relation between galaxy rest‐frame u−r colour, morphology, as described by the concentration and Sérsic indices, and environmental density, for a sample of 79 553 galaxies at z≲ 0.1. We split the samples according to density and luminosity, and recover the expected bimodal distribution in the colour–morphology plane, shown especially clearly by this subsampling. We quantify the bimodality by a sum of two Gaussians on the colour and morphology axes, and show that, for the red‐/early‐type population both colour and morphology do not change significantly as a function of density. For the blue‐/late‐type population, with increasing density the colour becomes redder but the morphology again does not change significantly. Both populations become monotonically redder and of earlier type with increasing luminosity. There is no significant qualitative difference between the behaviour of the two morphological measures. Motivated by their long‐standing use in astronomy and their ability to utilize information not necessarily used by the concentration and Sérsic indices, we supplement the morphological sample with 13 655 galaxies assigned Hubble types by an artificial neural network. We find, however, that the resulting distribution is less well described by two Gaussians. Therefore, there are either more than two significant morphological populations, physical processes not seen in colour space, or the Hubble type, particularly the different subtypes of spirals Sa–Sd, has an irreducible fuzziness when related to environmental density. For each of the three measures of morphology, on removing the density relation due to it, we recover a strong residual relation in colour. However, on similarly removing the colour–density relation there is no evidence for a residual relation due to morphology. Therefore, either the morphology is not directly affected by the environmental density beyond the correlation to colour, or a single galaxy ‘type’ does not capture sufficient information.

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“…The effect of applying dust corrections is shown in Fig. 1 where the large increase in SFRs after applying dust corrections (to the Hα emission in this case) is a consequence of high star formation rate galaxies having much higher dust obscuration levels (Calzetti 2001; Hopkins et al 2001, 2003; Afonso et al 2003; van den Bergh 2007). The same figure illustrates the lack of dust in low star‐forming systems as galaxies at the very low SFR end maintain similar SFRs after dust corrections.…”

Section: Discussionmentioning

confidence: 98%

Galaxy and mass assembly (GAMA): dust obscuration in galaxies and their recent star formation histories

Wijesinghe¹,

Hopkins²,

Sharp³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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We present self‐consistent star formation rates derived through pan‐spectral analysis of galaxies drawn from the Galaxy and Mass Assembly (GAMA) survey. We determine the most appropriate form of dust obscuration correction via application of a range of extinction laws drawn from the literature as applied to Hα, [O ii] and UV luminosities. These corrections are applied to a sample of 31 508 galaxies from the GAMA survey at z < 0.35. We consider several different obscuration curves, including those of Milky Way, Calzetti and Fischera & Dopita curves and their effects on the observed luminosities. At the core of this technique is the observed Balmer decrement, and we provide a prescription to apply optimal obscuration corrections using the Balmer decrement. We carry out an analysis of the star formation history (SFH) using stellar population synthesis tools to investigate the evolutionary history of our sample of galaxies as well as to understand the effects of variation in the initial mass function (IMF) and the effects this has on the evolutionary history of galaxies. We find that the Fischera & Dopita obscuration curve with an Rv value of 4.5 gives the best agreement between the different SFR indicators. The 2200 Å feature needed to be removed from this curve to obtain complete consistency between all SFR indicators suggesting that this feature may not be common in the average integrated attenuation of galaxy emission. We also find that the UV dust obscuration is strongly dependent on the SFR.

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Some Musings on Galaxy Morphology, Galactic Colors, and the Environments of Galaxies

Cited by 16 publications

References 26 publications

The ATLAS3D project - I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria

The ATLAS3D project - I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria

Galaxy colour, morphology and environment in the Sloan Digital Sky Survey

Galaxy and mass assembly (GAMA): dust obscuration in galaxies and their recent star formation histories

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