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J/A+A/610/A5    Stellar structure models of edge-on galaxies    (Comeron+, 2018)

The reports of thick discs' death are greatly exaggerated. Thick discs are NOT artefacts caused by diffuse scattered light. Comeron S., Salo H., Knapen J.H. <Astron. Astrophys. 610, A5 (2018)> =2018A&A...610A...5C (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, IR ; Galaxies, nearby ; Galaxies, photometry Keywords: methods: data analysis - methods: observational - galaxies: spiral - galaxies: structure Abstract: Recent studies have made the community aware of the importance of accounting for scattered light when examining low-surface-brightness galaxy features such as thick discs. In our past studies of the thick discs of edge-on galaxies in the Spitzer Survey of Stellar Structure in Galaxies - the S4G - we modelled the point spread function as a Gaussian. In this paper we re- examine our results using a revised point spread function model that accounts for extended wings out to more than 2.5arcmin. We study the 3.6micron images of 141 edge-on galaxies from the S4G and its early-type galaxy extension. Thus, we more than double the samples examined in our past studies. We decompose the surface-brightness profiles of the galaxies perpendicular to their mid-planes assuming that discs are made of two stellar discs in hydrostatic equilibrium. We decompose the axial surface- brightness profiles of galaxies to model the central mass concentration - described by a Sersic function - and the disc - described by a broken exponential disc seen edge-on. Our improved treatment fully confirms the ubiquitous occurrence of thick discs. The main difference between our current fits and those presented in our previous papers is that now the scattered light from the thin disc dominates the surface brightness at levels below ∼26mag/arcsec2. We stress that those extended thin disc tails are not physical, but pure scattered light. This change, however, does not drastically affect any of our previously presented results: 1) Thick discs are nearly ubiquitous. They are not an artefact caused by scattered light as has been suggested elsewhere. 2) Thick discs have masses comparable to those of thin discs in low-mass galaxies - with circular velocities vc<120km/s - whereas they are typically less massive than the thin discs in high-mass galaxies. 3) Thick discs and central mass concentrations seem to have formed at the same epoch from a common material reservoir. 4) Approximately 50% of the up-bending breaks in face-on galaxies are caused by the superposition of a thin and a thick disc where the scale-length of the latter is the largest. Description: Appendice B and C. Information on the studied edge-on galaxies and their decompositions. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file tableb.dat 286 124 Galaxies with at least two distinct discs tablec.dat 286 17 Galaxies that do not have at least two distinct discs
See also: J/A+AS/93/255 : Axial ratios of edge-on spirals (Guthrie 1992) J/PAZh/27/250 : Rotation curves for 135 edge-on galaxies (Makarov+, 2001) J/A+A/389/795 : Vertical structure of edge-on galaxies (Bizyaev+, 2002) J/A+A/435/459 : HI data of edge-on spiral galaxies (Huchtmeier+, 2005) J/A+A/445/765 : A Catalog of Edge-on Disk Galaxies (Kautsch+, 2006) J/ApJ/702/1567 : Structure of 2MASS edge-on galaxies (Bizyaev+, 2009) J/ApJ/787/24 : Structural parameters of true edge-on galaxies (Bizyaev+ 2014) Byte-by-byte Description of file: table?.dat
Bytes Format Units Label Explanations
1- 9 A9 --- ID Galaxy name 11- 15 F5.1 arcsec r25 Isophotal 25mag/arcsec2 radius in the B-band from HyperLeda 17- 21 F5.1 deg PA Majot axis position angle 23- 29 F7.3 mag M3.6 Absolute 3.6um magnitude in the AB system (1) 31- 35 F5.2 Mpc Dist Galaxy distance 37 I1 --- r_Dist [1/5] Source of the galaxy distance (2) 39- 41 I3 km/s vc Galaxy maximum circular velocity 43- 44 I2 --- r_vc [1/19] Source of the galaxy maximum circular velocity (3) 46- 49 F4.1 arcsec zc1 ?=- Lower limit of the region where most of the light is emitted by the thick disc 51- 55 F5.1 arcsec zc2 ?=- Higher limit of the region where most of the light is emitted by the thick disc 57- 61 F5.1 arcsec zu Height where the surface brightness is 26mag/arcsec2 63- 66 F4.2 arcsec rCMC ?=- Scale size of the central mass concentration (CMC) 68- 71 F4.2 arcsec nCMC ?=- Sersic index of the central mass concentration (CMC) 73- 86 A14 --- Ttot Axial surface brightness profile type of the whole disc 88- 98 F11.1 arcsec h1tot Scale-length of the first exponential section of the whole disc 100-108 F9.1 arcsec h2tot ?=- Scale-length of the second exponential section of the whole disc 110-114 F5.1 arcsec h3tot ?=- Scale-length of the third exponential section of the whole disc 116-120 F5.1 arcsec h4tot ?=- Scale-length of the fourth exponential section of the whole disc 122-126 F5.1 arcsec r12tot ?=- Radius of the break between the first and the second exponential sections of the whole disc 128-132 F5.1 arcsec r23tot ?=- Radius of the break between the second and the third exponential sections of the whole disc 134-138 F5.1 arcsec r34tot ?=- Radius of the break between the third and the fourth exponential sections of the whole disc 140-153 A14 --- Tthin Axial surface brightness profile type of the thin disc 155-164 F10.1 arcsec h1thin ?=- Scale-length of the first exponential section of the thin disc 166-175 F10.1 arcsec h2thin ?=- Scale-length of the second exponential section of the thin disc 177-181 F5.1 arcsec h3thin ?=- Scale-length of the third exponential section of the thin disc 183-187 F5.1 arcsec h4thin ?=- Scale-length of the fourth exponential section of the thin disc 189-193 F5.1 arcsec r12thin ?=- Radius of the break between the first and the second exponential sections of the thin disc 195-199 F5.1 arcsec r23thin ?=- Radius of the break between the second and the third exponential sections of the thin disc 201-205 F5.1 arcsec r34thin ?=- Radius of the break between the third and the fourth exponential sections of the thin disc 207-216 A10 --- Tthick Axial surface brightness profile type of the thick disc 218-227 F10.1 arcsec h1thick ?=- Scale-length of the first exponential section of the thick disc 229-235 F7.1 arcsec h2thick ?=- Scale-length of the second exponential section of the thick disc 237-240 F4.1 arcsec h3thick ?=- Scale-length of the third exponential section of the thick disc 242-246 F5.1 arcsec r12thick ?=- Radius of the break between the first and the second exponential sections of the thick disc 248-252 F5.1 arcsec r23thick ?=- Radius of the break between the second and the third exponential sections of the thick disc 254-258 F5.2 10+9Msun GasM Gas disc mass 260-264 F5.2 10+9Msun ThinM Thin disc mass 266-270 F5.2 10+9Msun ThickM Thick disc mass 272-276 F5.2 10+9Msun CMCM Central mass concentration (CMC) mass 278-281 F4.1 arcsec sc-thin Thin disc scale-height 283-286 F4.1 arcsec sc-thick Thick disc scale-height
Note (1): From Munoz-Mateos et al. (2015ApJS..219....3M) and this paper. Note (2): Distance references as follows: 1 = CF1 (Tully et al., 2008, Cat. J/ApJ/676/184) 2 = CF3 Tully et al. (2016, Cat. J/AJ/152/50) 3 = SFI++ Springob et al. (2007, Cat. J/ApJS/172/599) 4 = Theureau et al. (2007, Cat. J/A+A/465/71) 5 = Hubble-Lemaitre flow distances with respect to the cosmic microwave background assuming a Hubble-Lemaitre constant of H0=75km/s. Note (3): Circular velocity references as follows: 1 = Springob et al. (2005ApJS..160..149S, Cat VIII/77) 2 = Theureau et al. (2006, ASPCS, 351, 429) 3 = Courtois et al. (2009, Cat. J/AJ/138/1938) 4 = pre-digital measurements compiled in the EDD 5 = Krumm & Salpeter (1976ApJ...208L...7K) 6 = Balkowski & Chamaraux (1981A&A....97..223B) 7 = Richter & Huchtmeier (1987A&AS...68..427R) 8 = Haynes et al. (1990AJ.....99.1740H) 9 = D'Onofrio et al. (1995, Cat. J/A+A/296/319) 10 = Mathewson & Ford (1996, Cat J/ApJS/107/97) 11 = Simien & Prugniel (1997, Cat J/A+AS/126/15, Cat. J/A+AS/126/519) 12 = Simien & Prugniel (1998, Cat J/A+AS/131/287) 13 = Rubin et al. (1999AJ....118..236R) 14 = Simien & Prugniel (2000, Cat J/A+AS/145/263) 15 = Karachentsev et al. (2004, Cat. J/AJ/127/2031) 16 = Chung & Bureau (2004AJ....127.3192C) 17 = Meyer et al. (2004MNRAS.350.1195M, Cat. VIII/73) 18 = Bedregal et al. (2006MNRAS.371.1912B) 19 = ATLAS3D (Cappellari et al. 2011, Cat J/MNRAS/413/813; Krajnovic et al. 2011MNRAS.414.2923K) The recession velocities are taken from the NED.
Acknowledgements: Sebastien Comeron, seb.comeron(at)gmail.com
(End) S. Comeron [Univ. Oulu, Finland], P. Vannier [CDS] 29-Nov-2017
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