J/MNRAS/446/2144 Galaxy And Mass Assembly: red & blue galaxies (Taylor+, 2015) ================================================================================ Galaxy And Mass Assembly (GAMA): deconstructing bimodality - I. Red ones and blue ones. Taylor E.N., Hopkins A.M., Baldry I.K., Bland-Hawthorn J., Brown M.J.I., Colless M., Driver S., Norberg P., Robotham A.S.G., Alpaslan M., Brough S., Cluver M.E., Gunawardhana M., Kelvin L.S., Liske J., Conselice C.J., Croom S., Foster C., Jarrett T.H., Lara-Lopez M., Loveday J. =2015MNRAS.446.2144T (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Galaxies ; Blue objects ; Stars, masses ; Colors ; Surveys ; Models Keywords: galaxies: evolution - galaxies: formation - galaxies: fundamental parameters - galaxies: luminosity function, mass function - galaxies: statistics - galaxies: stellar content Abstract: We measure the mass functions for generically red and blue galaxies, using a z<0.12 sample of logM_*_>8.7 field galaxies from the Galaxy And Mass Assembly (GAMA) survey. Our motivation is that, as we show, the dominant uncertainty in existing measurements stems from how "red" and "blue" galaxies have been selected/defined. Accordingly, we model our data as two naturally overlapping populations, each with their own mass function and colour-mass relation, which enables us characterize the two populations without having to specify a priori which galaxies are "red" and "blue". Our results then provide the means to derive objective operational definitions for the terms "red" and "blue", which are based on the phenomenology of the colour-mass diagrams. Informed by this descriptive modelling, we show that (1) after accounting for dust, the stellar colours of "blue" galaxies do not depend strongly on mass; (2) the tight, flat "dead sequence" does not extend much below logM_*_~10.5; instead, (3) the stellar colours of "red" galaxies vary rather strongly with mass, such that lower mass "red" galaxies have bluer stellar populations; (4) below logM_*_~9.3, the "red" population dissolves into obscurity, and it becomes problematic to talk about two distinct populations; as a consequence, (5) it is hard to meaningfully constrain the shape, including the existence of an upturn, of the "red" galaxy mass function below logM_*_~9.3. Points 1-4 provide meaningful targets for models of galaxy formation and evolution to aim for. Description: As an optical spectroscopic survey, the Galaxy and Mass Assembly (GAMA; Driver et al. 2009A&G....50e..12D, 2011, J/MNRAS/413/971) survey has now completed its observations of three separate equatorial fields of 60 deg^2^ each. The spectroscopic target selection is described by Baldry et al. (2010MNRAS.404...86B). Targets have been selected on the basis of dust-corrected PETROr-band magnitudes from the SDSS DR7 (Abazajian et al. 2009, Cat. II/294). For GAMA-II, all three fields have been surveyed to a depth of r_petro_<19.8 mag. In GAMA-II nomenclature, these define the SURVEY_CLASS>=4 sample selection limits. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file fig8.dat 97 70 Results of our fits for the (g-i) colour-mass relations (CMRs) fig9.dat 97 70 Results of our fits for the (g*-i*) CMRs fig10.dat 107 26368 Results of our fits to the (g-i) colour-mass diagrams (CMDs) fig11.dat 107 26368 Results of our fits to the (g*-i*) CMDs fig12.dat 318 70 The mass functions (MFs) for the B and R galaxy populations, as derived from our fits to the rest-frame (g-i) CMD fig13.dat 318 70 The MFs for B and R galaxy populations, as derived from our fits to the intrinsic (g*-i*) CMD -------------------------------------------------------------------------------- See also: II/294 : The SDSS Photometric Catalog, Release 7 J/MNRAS/413/971 : Galaxy And Mass Assembly (GAMA) DR1 (Driver+, 2011) J/MNRAS/452/2087 : Galaxy And Mass Assembly (GAMA): DR2 (Liske+, 2015) J/MNRAS/456/2221 : Optically red galaxies in H-ATLAS/GAMA (Dariush+, 2016) J/MNRAS/474/3875 : Galaxy And Mass Assembly (GAMA): DR3 (Baldry+, 2018) Byte-by-byte Description of file: fig8.dat fig9.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 6 F6.3 [-] logM [8.725/12.175] Log mass (in dex) (logM) 8- 15 F8.6 mag (g-i)R [0.509614/1.19776] Rest-frame (g-i) colour for the "red" (R) population (cmrR_locus) (1) 17- 24 F8.6 mag e_(g-i)R [0.001645/0.048823] Uncertainty in (g-i)R (cmrR_locus_unc) 26- 33 F8.6 mag CMRR-scat [0/0.13605] Scatter around the R CMR (cmrR_scatter) 35- 42 F8.6 mag e_CMRR-scat [0/0.019473] Uncertainty in CMRR-scat (cmrR_scatter_unc) 44- 52 F9.6 --- CorrR [-0.865219/0.207213]? Correlation coefficient for the R population (cmrR_locus_scat_corrcoef) 54- 61 F8.6 mag (g-i)B [0.32972/1.15571] Rest-frame (g-i) colour for the "blue" (B) population (cmrB_locus) (1) 63- 70 F8.6 mag e_(g-i)B [0.001943/0.285534] Uncertainty in (g-i)B (cmrB_locus_unc) 72- 79 F8.6 mag CMRB-scat [2e-05/0.273328] Scatter around the B CMR (cmrB_scatter) 81- 88 F8.6 mag e_CMRB-scat [0.000446/0.048309] Uncertainty in CMRB-scat (cmrB_scatter_unc) 90- 97 F8.6 --- CorrB [0.031897/0.818761] Correlation coefficient for the B population (cmrB_locus_scat_corrcoef) -------------------------------------------------------------------------------- Note (1): In fig9.dat, it is the rest-frame (g*-i*) colour: the dust-corrected, intrinsic stellar colour. This parameter is a very good proxy for luminosity-weighted mean stellar age, . Quantitatively, at fixed (g*-i*), the range in s is everywhere ~<0.1 dex, and ~<0.05 dex for (g*-i*)>~0.5. The values of (g*-i*) have also been derived in the course of the stellar population synthesis (SPS) fits, but can be derived to within ~<0.01 mag from the values of (g-i) and A_V_ directly: (g*-i*~(g-i)-6.0A_V_). -------------------------------------------------------------------------------- Byte-by-byte Description of file: fig10.dat fig11.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 F8.5 [-] logM* [8.70003/12.406] Log stellar mass (in dex) (logmstar) 10- 17 F8.6 [-] e_logM* [0.018282/0.515653] Uncertainty in logM* (in dex) (dellogmstar) 19- 27 F9.6 mag (g-i) [-0.375918/2.99356]? Rest-frame (g-i) colour (only in Fig 10) (gminusi) 29- 36 F8.6 mag e_(g-i) [0.02154/0.532467]? Uncertainty in (g-i) (only in Fig 10) (delgminusi) 38- 46 F9.6 mag (g*-i*) [-0.382121/1.4821]? Intrinsic (g*-i*) stellar colour (only in Fig 11) (gminusi_stars) 48- 55 F8.6 mag e_(g*-i*) [0.001227/0.098258]? Uncertainty in (g*-i*) (only in Fig 11) (delgminusi_stars) 57- 65 F9.6 --- rhoxy [-0.496506/0.989224] Pearson correlation coefficient {rho}_xy_ (xycorrcoef) (1) 67- 78 E12.6 Mpc3 Vmax [76036.1/2.28108e+06] Maximum volume (Vmax) 80- 87 F8.6 --- Wred [0/0.986884] Red classification (Wred) (2) 89- 96 F8.6 --- Wblue [0/0.986845] Blue classification (Wblue) (2) 98-107 F10.6 --- lnLi [-42.9734/4.5752] Log scalar likelihood (lnLi) (3) -------------------------------------------------------------------------------- Note (1): When we come to fitting the galaxy distributions in colour-mass space in Section 5, we will want to account for the fact that the measurement errors/uncertainties in M_*_ and (g-i) are correlated. The strength of this correlation is characterized by the (Pearson) correlation coefficient: {rho}_xy_=<((x-)(y-))/{sigma}_x_{sigma}_y_>. Here, x and y can be taken to be logM_*_ and either (g-i) or (g*-i*); {sigma}_x_ and {sigma}_y_ are the uncertainties in these values. Note (2): "Red"/"blue" classification scheme, based on the likelihood that a given data point has been drawn from one or the other population. Note (3): L_i_ describes the likelihood of observing the data point x_i_ with formal observational uncertainties {sigma}_i_, given or assuming a specific set of values for P. To reflect this fact, the likelihood function is represented as L_i_(x_i_,{sigma}_i_|P). -------------------------------------------------------------------------------- Byte-by-byte Description of file: fig12.dat fig13.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 6 F6.3 [-] logM [8.725/12.175] Log mass (in dex) (logM) 8- 19 E12.6 Mpc-3 MF [0/0.0134463] Mass function (mf) 21- 32 E12.6 Mpc-3 MFB [0/0.011534] Mass function for the B population (mfB) 34- 45 E12.6 Mpc-3 MFR [0/0.00353686] Mass function for the R population (mfR) 47- 58 E12.6 Mpc-3 fitMFB [9.80701e-19/0.0124547] Fit mass function for the B population (fitmfB) 60- 71 E12.6 Mpc-3 fitMFR [6.78082e-14/0.0030983] Fit mass function for the R population (fitmfR) 73- 84 E12.6 Mpc-3 fitMF [1.57981e-13/0.0146083] Fit mass function (fitmf) 86- 97 E12.6 Mpc-3 e_MF [1e-10/0.012716] Mass function 68% confidence interval, lower value (mf_m1sig) 99-110 E12.6 Mpc-3 E_MF [1e-10/0.0142113] Mass function 68% confidence interval, upper value (mf_p1sig) 112-123 E12.6 Mpc-3 e_MFB [1e-10/0.0109082] Mass function for the B population 68% confidence interval, lower value (mfB_m1sig) 125-136 E12.6 Mpc-3 E_MFB [1e-10/0.0121684] Mass function for the B population 68% confidence interval, upper value (mfB_p1sig) 138-149 E12.6 Mpc-3 e_MFR [1e-10/0.00305143] Mass function for the R population 68% confidence interval, lower value (mfR_m1sig) 151-162 E12.6 Mpc-3 E_MFR [1e-10/0.00415728] Mass function for the R population 68% confidence interval, upper value (mfR_p1sig) 164-175 E12.6 Mpc-3 e_fitMFB-m1 [7.5207e-29/0.0120975] Fit mass function for the B population 68% confidence interval, lower value (fitmfB_m1sig) 177-188 E12.6 Mpc-3 E_fitMFB-p1 [3.3722e-13/0.012779] Fit mass function for the B population 68% confidence interval, upper value (fitmfB_p1sig) 190-201 E12.6 Mpc-3 e_fitMFR-m1 [1.83859e-14/0.00270516] Fit mass function for the R population 68% confidence interval, lower value (fitmfR_m1sig) 203-214 E12.6 Mpc-3 E_fitMFR-p1 [2.27661e-13/0.00354406] Fit mass function for the R population 68% confidence interval, upper value (fitmfR_p1sig) 216-227 E12.6 Mpc-3 e_fitMF-m1 [4.42432e-14/0.0143785] Fit mass function 68% confidence interval, lower value (fitmf_m1sig) 229-240 E12.6 Mpc-3 E_fitMF-p1 [5.94442e-13/0.0148499] Fit mass function 68% confidence interval, upper value (fitmf_p1sig) 242-253 E12.6 Mpc-3 e_fitMFB-m3 [0/0.0108847] Fit mass function for the B population 99% confidence interval, lower value (fitmfB_m3sig) 255-266 E12.6 Mpc-3 E_fitMFB-p3 [2.0761e-10/0.013448] Fit mass function for the B population 99% confidence interval, upper value (fitmfB_p3sig) 268-279 E12.6 Mpc-3 e_fitMFR-m3 [7.46471e-16/0.0023102] Fit mass function for the R population 99% confidence interval, lower value (fitmfR_m3sig) 281-292 E12.6 Mpc-3 E_fitMFR-p3 [2.30511e-12/0.00443756] Fit mass function for the R population 99% confidence interval, upper value (fitmfR_p3sig) 294-305 E12.6 Mpc-3 e_fitMF-m3 [3.91104e-15/0.0140094] Fit mass function 99% confidence interval, lower value (fitmf_m3sig) 307-318 E12.6 Mpc-3 E_fitMF-p3 [2.07611e-10/0.0153574] Fit mass function 99% confidence interval, upper value (fitmf_p3sig) -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Tiphaine Pouvreau [CDS] 17-Sep-2019