J/MNRAS/480/2292 Quantifying maximum discs in galaxies (Starkman+, 2018)
A new algorithm to quantify maximum discs in galaxies.
Starkman N., Lelli F., McGaugh S., Schombert J.
<Mon. Not. R. Astron. Soc., 480, 2292-2301 (2018)>
=2018MNRAS.480.2292S 2018MNRAS.480.2292S (SIMBAD/NED BibCode)
ADC_Keywords: Galactic center ; Galaxies, rotation ; Galaxies, photometry ;
Models
Keywords: galaxy: bulge - galaxy: disc - galaxy: structure -
galaxies: luminosity function, mass function -
galaxies: kinematics and dynamics
Abstract:
Maximum disc decompositions of rotation curves place a dynamical upper
limit to the mass attributable to stars in galaxies. The precise
definition of this term, however, can be vague and varies in usage. We
develop an algorithm to robustly quantify maximum-disc mass models and
apply it to 153 galaxies from the Spitzer Photometry and Accurate
Rotation Curve data base. Our automatic procedure recovers classic
results from manual decompositions. High-mass, high-surface-brightness
galaxies have mean maximum-disc mass-to-light ratios of
∼0.7M☉/L☉ in the Spitzer 3.6µm band, which are close to
the expectations from stellar population models, suggesting that these
galaxies are nearly maximal. Low-mass, low-surface-brightness galaxies
have very high maximum-disc mass-to-light ratios (up to
10M☉/L☉), which are unphysical for standard stellar
population models, confirming they are sub-maximal. The maximum-disc
mass-to-light ratios are more closely correlated with surface
brightness than luminosity. The mean ratio between baryonic and
observed velocity at the peak of the baryonic contribution is
Vbar/Vp∼0.88, but correlates with surface brightness, so it is unwise
to use this mean value to define the maximum disc concept. Our
algorithm requires no manual intervention and could be applied to
large galaxy samples from future HI surveys with Apertif, Askap, and
SKA.
Description:
A galaxy can be broadly decomposed into a few baryonic components: gas
disc, stellar disc, and bulge (if present). The conversion from 21cm
flux to atomic gas mass is specified by the physics of the spin-flip
transition, fixing the gas contribution. The conversion from stellar
light to stellar mass is less well determined. For bulge and stellar
disc, we need to introduce mass-to-light ratios, denoted as Ybul and
Ydisc, respectively. The values of Ybul and Ydisc can be fixed
using stellar population synthesis models (Bell & de Jong
2001ApJ...550..212B 2001ApJ...550..212B; McGaugh & Schombert 2014AJ....148...77M 2014AJ....148...77M;
Schombert & McGaugh 2014PASA...31...36S 2014PASA...31...36S; Lelli et al.
2016AJ....152..157L 2016AJ....152..157L, 2016ApJ...827L..19L 2016ApJ...827L..19L), but in this work we will
use them as free parameters to determine their maximum allowed values
from a dynamical perspective.
We develop a fitting scheme that matches the baryonic rotation curve
to the observed one at small radii, specifically near the 'turning
radius' where the rotation curves start to approach a flat part. The
algorithm produces good results in disc-dominated cases. However, for
galaxies with bulges, the mass-to-light ratios of bulge and disc can
be degenerated. In these cases, we break the degeneracy by imposing
Ybul>Ydisc. This choice is motivated by stellar population
synthesis models. To confirm the algorithm's efficacy and estimate the
uncertainties, a Markov Chain Monte Carlo (MCMC) routine was also run
on all galaxies, giving consistent results.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1a.dat 192 175 SPARC: Mass Models for 175 Disk Galaxies with
Spitzer Photometry and Accurate Rotation Curves
(Galaxy Sample Supplement)
table1b.dat 103 3391 SPARC: Mass Models for 175 Disk Galaxies with
Spitzer Photometry and Accurate Rotation Curves
(Mass Models Supplement)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1a.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- ID Galaxy Name
13- 17 F5.2 Msun/Lsun M/L Mass-to-Light Ratio
19- 23 F5.3 Msun/Lsun e_M/L Unvertainty in M/L
25- 29 F5.3 Msun/Lsun M/Lb Bulge Mass-to-Light Ratio
31- 32 I2 --- Type Hubble Type (1)
34- 39 F6.2 Mpc Dist Distance
41- 45 F5.2 Mpc e_Dist Mean error on Dist
47- 50 F4.1 deg Inc Inclination
52- 55 F4.1 deg e_Inc Mean error on Inc
57- 63 F7.3 10+9Lsun L3.6 Total Luminosity at 3.6µm
65- 69 F5.3 10+9Lsun e_L3.6 Mean error on L3.6
71- 77 F7.3 10+9Lsun Lbulge Bulge Luminosity at 3.6µm
79- 83 F5.2 kpc Reff Effective Radius at 3.6µm
85- 89 F5.2 kpc Rp Radius of peak Vbar
91- 98 F8.3 Lsun/pc2 SBeff Effective Surface Brightness at 3.6µm
100-106 F7.3 Lsun/pc2 e_SBeff Uncertainty in SBeff
108-112 F5.2 kpc Rdisk Disk Scale Length at 3.6µm
114-121 F8.3 Lsun/pc2 SB0 Disk Central Surface Brightness at
3.6µm
123-129 F7.3 Lsun/pc2 e_SB0 Uncertainty in SBdisk
131-136 F6.2 10+9Msun/pc2 Mbar Baryonic mass (2)
138-143 F6.3 10+9Msun/pc2 e_Mbar Uncertainty in Mbar (2)
145-154 F10.3 Lsun/pc2 SBbar Baryonic Surface Brightness at
3.6µm (2)
156-164 F9.3 Lsun/pc2 e_SBbar Uncertainty in SBbar (2)
166-171 F6.2 km/s Vobsp Observed circular velocity at Rp (2)
173-177 F5.2 km/s e_Vobsp Uncertainty in Vobsp (2)
179-185 F7.3 km/s Vbarp Total baryonic velocity at Rp (2)
187-192 F6.3 km/s e_Vbarp Uncertainty in Vbarp (2)
--------------------------------------------------------------------------------
Note (1): Hubble type as follows:
0 = S0
1 = Sa
2 = Sab
3 = Sb
4 = Sbc
5 = Sc
6 = Scd
7 = Sd
8 = Sdm
9 = Sm
10 = Im
11 = BCD
Note (2): Values given in Mass Models Supplement table
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1b.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- ID Galaxy identifier
13- 18 F6.2 kpc R Galactocentric radius
20- 25 F6.2 km/s Vobs Observed circular velocity
27- 31 F5.2 km/s e_Vobs Uncertainty in Vobs (1)
33- 38 F6.2 km/s Vgas Gas velocity contribution (2)
40- 46 F7.3 km/s Vdisk Disk velocity contribution (3)
48- 53 F6.3 km/s e_Vdisk Uncertainty in Vdisk
55- 62 F8.3 Lsun/pc2 SBdisk Disk surface brightness
64- 70 F7.3 Lsun/pc2 e_SBdisk Disk surface brightness
72- 78 F7.3 km/s Vbul Bulge velocity contribution (3)
80- 88 F9.3 Lsun/pc2 SBbul Bulge surface brightness
90- 96 F7.3 km/s Vbar Total baryonic velocity (3)
98-103 F6.3 km/s e_Vbar Total baryonic velocity
--------------------------------------------------------------------------------
Note (1): Random error due to non-circular motions and/or kinematic asymmetries.
It does not include systematic uncertainties due to inclination
corrections.
Note (2): Vgas includes a factor 1.33 to account for cosmological helium
Note (3): Vdisk and Vbul are given for their maximized M/L at 3.6µm in
Galaxy Sample Supplement table
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 23-May-2022