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.
<Mon. Not. R. Astron. Soc., 446, 2144-2185 (2015)>
=2015MNRAS.446.2144T 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 2009A&G....50e..12D, 2011, J/MNRAS/413/971) survey has
now completed its observations of three separate equatorial fields of
60 deg2 each. The spectroscopic target selection is described by
Baldry et al. (2010MNRAS.404...86B 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 rpetro<19.8 mag. In GAMA-II nomenclature,
these define the SURVEY_CLASS≥4 sample selection limits.
File Summary:
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FileName Lrecl Records Explanations
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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
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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
(cmrRlocusunc)
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
(cmrRscatterunc)
44- 52 F9.6 --- CorrR [-0.865219/0.207213]? Correlation coefficient
for the R population
(cmrRlocusscat_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
(cmrBlocusunc)
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
(cmrBscatterunc)
90- 97 F8.6 --- CorrB [0.031897/0.818761] Correlation coefficient
for the B population
(cmrBlocusscat_corrcoef)
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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, <t*>. Quantitatively, at fixed (g*-i*),
the range in <t*>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 AV directly: (g*-i*~(g-i)-6.0AV).
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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 ρxy (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)
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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:
ρxy=<((x-)(y-))/σxσy>.
Here, x and y can be taken to be logM* and either (g-i) or (g*-i*);
σx and σy 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): Li describes the likelihood of observing the data point xi with
formal observational uncertainties σi, given or assuming a specific
set of values for P. To reflect this fact, the likelihood function is
represented as Li(xi,σi|P).
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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)
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History:
From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 17-Sep-2019