J/MNRAS/506/323 Kinematic study of KGES galaxies (Tiley+, 2021)
The KMOS galaxy evolution survey (KGES): the angular momentum of star-forming
galaxies over the last ≃ 10 Gyr.
Tiley A.L., Gillman S., Cortese L., Swinbank A.M., Dudzeviciute U.,
Harrison C.M., Smail I., Obreschkow D., Croom S.M., Sharples R.M.,
Puglisi A.
<Mon. Not. R. Astron. Soc., 506, 323-342 (2021)>
=2021MNRAS.506..323T 2021MNRAS.506..323T (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Active gal. nuclei ; Star Forming Region ;
H II regions ; Infrared ; Photometry, H-alpha ; Line Profiles ;
Spectroscopy ; Rotational velocities ; Velocity dispersion ;
Redshifts
Keywords: galaxies: evolution - galaxies: general -
galaxies: kinematics and dynamics - galaxies: star formation
Abstract:
We present the KMOS Galaxy Evolution Survey (KGES), a K-band
Multi-Object Spectrograph (KMOS) study of the Hα and [N II]
emission from 288 K-band- selected galaxies at 1.2 ≲ z ≲ 1.8, with
stellar masses in the range log10(M*/M☉) ∼ 9 - 11.5. In this
paper, we describe the survey design, present the sample, and discuss
the key properties of the KGES galaxies. We combine KGES with
appropriately matched samples at lower redshifts from the KMOS
Redshift One Spectroscopic Survey (KROSS) and the SAMI Galaxy Survey.
Accounting for the effects of sample selection, data quality, and
analysis techniques between surveys, we examine the kinematic
characteristics and angular momentum content of star-forming galaxies
at z ≃ 1.5, ≃ 1, and ≃ 0. We find that stellar mass, rather than
redshift, most strongly correlates with the disc fraction amongst
star-forming galaxies at z ≲ 1.5, observing only a modest increase in
the prevalence of discs between z ≃ 1.5 and z ≃ 0.04 at fixed
stellar mass. Furthermore, typical star-forming galaxies follow the
same median relation between specific angular momentum and stellar
mass, regardless of their redshift, with the normalization of the
relation depending more strongly on how disc-like a galaxy's
kinematics are. This suggests that massive star-forming discs form in
a very similar manner across the ≃10 Gyr encompassed by our study and
that the inferred link between the angular momentum of galaxies and
their haloes does not change significantly across the stellar mass and
redshift ranges probed in this work.
Description:
To address these outstanding issues, in this work we present the KMOS
Galaxy Evolution Survey (KGES). KGES aims to study the spatially
resolved gas properties and kinematics of a statistically large and
representative sample of 'normal' star-forming galaxies at z ≃ 1.5.
KGES is a Durham University guaranteed time survey with the ESO KMOS
on the Very Large Telescope, Paranal, Chile. With deep KMOS H-band
observations, it targets the Hα and [N II]6548,6583 nebular
line emission from 288 massive galaxies in well-known, deep
extragalactic fields (Scoville et al. 2007ASPC..375..166S 2007ASPC..375..166S),
(Giacconi et al. 2001ApJ...551..624G 2001ApJ...551..624G), (Lawrence et al.
2007MNRAS.379.1599L 2007MNRAS.379.1599L, Cat. II/314),
(Cirasuolo et al. 2007MNRAS.380..585C 2007MNRAS.380..585C),
(see section 2.1 Sample selection criteria).
We describe the KGES survey design and data reduction, and we present
measurements of the key properties of the KGES galaxies,
(for more details on procedures please see sections 2-5).
We then combine the KGES sample with large and representative samples
of star-forming galaxies typical for their epoch. (KGES galaxies at
z ≃ 1.5, KROSS galaxies at z≃ 0.9, SAMI galaxies at z ≃ 0.04), (for
more details on kinematic subsamples construction please see the
section 6.2 Kinematics subsample selection). We finally provide a broad
overview of the KGES sample presenting the integrated properties of
KGES galaxies, their resolved properties and kinematics as the tablea1.dat
shoes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 148 288 *Key properties of the KGES sample galaxies
discussed in this study
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Note on tablea1.dat: A Nine-Year Wilkinson Microwave Anisotropy Probe
(WMAP9; Hinshaw et al. 2013ApJS..208...19H 2013ApJS..208...19H) cosmology is used throughout this
work (Hubble constant at z = 0, H0 = 69.3 km/s/Mpc; non-relativistic matter
density at z = 0, Ω0 = 0.287; dark energy density at z = 0,
Ω_Λ = 0.713). All magnitudes are quoted in the AB system.
All stellar masses assume a Chabrier (Chabrier 2003PASP..115..763C 2003PASP..115..763C) initial
mass function.
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See also:
J/MNRAS/413/813 : ATLAS3D project. I. (Cappellari+, 2011)
J/MNRAS/467/1965 : KMOS Redshift One Spectroscopic Survey (Harrison+, 2017)
J/ApJ/886/124 : Completed KMOS3D survey NIR obs. (Wisnioski+, 2019)
J/ApJ/706/1364 : SINS survey of high-redshift galaxies
(Forster Schreiber+, 2009)
J/MNRAS/482/2166 : Tully-Fisher relation across 8Gyr since z∼1 (Tiley+,2019)
II/314 : UKIDSS-DR8 LAS, GCS and DXS Surveys (Lawrence+ 2012)
J/MNRAS/494/3828 : ALMA survey of the SCUBA-2 CLS UDS field
(Dudzeviciute+, 2020)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- ID KGES identifier number (KGESSURVEYID)
10- 19 F10.6 deg RAdeg Right ascension in ICRS (RA) (J2000)
21- 31 F11.7 deg DEdeg Declination in ICRS (Dec) (J2000)
33- 45 F13.11 --- z Redshift (Redshift)
47 I1 --- Ha [0/1] Indicates if the galaxy is detected
in Hα (Hαdetected) (1)
49 I1 --- HaRes [0/1] Indicates if the galaxy is spatially
resolved in Hα (Halpha_resolved) (2)
51 I1 --- AGN [0/1] Indicates if the galaxy
is a candidate AGN host (AGN) (3)
53 I1 --- Kin [0/1] Indicates if the galaxy
is in the kinematics subsample
at z ≃ 1.5 (kinematics) (4)
55- 62 E8.6 Msun M* ?=- Stellar mass of the galaxy (M*) (5)
64- 76 F13.11 kpc R50 Stellar ligth effective radius containing
half the members (R50) (6)
78- 94 F17.13 Msun/yr HaSFR ?=- Star-formation rate based on its Hα
flux and redshifts (SFRHα) (7)
96-112 F17.13 km/s v2.2c ?=- Corrected rotation velocity calculated
at 1.31*R50 (v22C) (8)
114-130 F17.13 km/s sigma0c ?=- Corrected observed velocity dispersion
calculated at 1.31*R50 (Sigma0C) (9)
132-148 F17.12 kpc.km/s j2.2c ?=- Corrected total stellar specific angular
momentum calculated at 1.31*R50 (j22C) (10)
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Note (1): We classify a galaxy as detected (Halpha_detected = 1) in Hα
emission if its signal-to-noise S/NHα_ ≥ 5 in at least
one of the integrated spectra extracted from the two aperture sizes,
(see section 3.1 Integrated fluxes and spectroscopic redshifts).
We detect Hα emission in the integrated spectrum of
243 (≃ 84 per cent) of these.
Note (2): We classify a galaxy as spatially resolved (HaRes = 1)
in Hα emission if its IHα_ map, after masking any
bad pixels, contains at least one contiguous emission region with
an area larger than 1.1 times the area of one resolution element
(defined by the FWHM contour of the KMOS PSF).
We spatially resolve the Hα emission from 235 out of the 288
targeted KGES galaxies, corresponding to ≃ 82 per cent of the total
sample, and ≃ 97 per cent of those from which we detect Hα,
(see section 5.2 Resolved Hα emission).
Note (3): Take an conservative approach, identifying candidate AGN hosts amongst
the KGES galaxies by examining their integrated Hα linewidths
and [N II]/Hα flux ratios. We also make use of ancillary
Spitzer and WISE near-infrared data available for KGES galaxies,
and various X-ray catalogues. In total we identify 41 unique
candidate AGN hosts in the KGES sample (AGN = 1),
(see section 3.3 Identifying candidate AGN hosts).
Note (4): As explained in the 6.2 Kinematics subsample selection, we select
galaxies that are main sequence star-forming systems spatially
resolved in Hα emission, with associated M*, R50, v2.2c,
sigma0c (i.e robust kinematic measurements, Kin = 1).
The 126 KGES galaxies that remain after application of all the
selection criteria listed make up our kinematics subsample
at z ≃ 1.5.
Note (5): The derivation of stellar masses for the KGES sample is described
in detail in Gillman et al. (2020MNRAS.492.1492G 2020MNRAS.492.1492G). In summary,
a stellar mass estimate for each KGES galaxy was obtained via
the application, in Dudzeviciute et al. (2020MNRAS.494.3828D 2020MNRAS.494.3828D,
Cat. J/MNRAS/494/3828), of the Multi-wavelength Analysis of
Galaxy Physical Properties SED fitting routine to model its SED,
(magphys; Da Cunha et al. 2008MNRAS.388.1595D 2008MNRAS.388.1595D),
(see section 4.1 Stellar masses).
Note (6): Defined and derived in the section 4.3 Stellar structural parameters,
R50 is used in section 5 Resolved galaxy properties and kinematic
to resolved KMOS maps and Hα emissions, to derive kinematic
position angles, observed rotation velocities and velocity dispersions
v2.2,obs, sigma0,obs and finally the specific angular momentum
measurements.
Note (7): As the section 4.2 Hα luminosities and star-formation rates
explains, The star-formation rate for each galaxy is converted from
its LHα according to the prescription of Kennicutt
(1998ARA&A..36..189K 1998ARA&A..36..189K) as written in the equation 4.
Note (8): We construct maps of observed line-of-sight velocity (vobs) from
the KMOS data cubes. Herafter, we measure the observed rotation
velocities v2.2,obs for each KGES galaxy (spatially resolved in
Hα emission) from the best fit, centred
(i.e. voff = 0 and roff = 0) exponential disc model
(i.e equation 5 gaussian fit) at 1.31*R50 which
corresponds to 2.2 times the disc scale radius and also to the peak
of the rotation curve for a pure disc,
(see section 5.4.1 Observed rotation velocities).
Secondly, we apply a correction (i.e see equation 6
in the section 5.4.3 Corrected rotation velocities) to v2.2,obs
in order to v2.2c.
Note (9): We construct maps ofobserved line-of-sight velocity dispersion
(σobs) from the KMOS data cubes. We define the observed
velocity dispersion for each KGES galaxy in one of two ways.
We adopt 1.31*R50 radii for these measurements.
(see section 5.5.1 Observed velocity dispersions).
Then we apply a correction (as explained in the section
5.5.2 Corrected velocity dispersions, equation 7), to obtain
the corrected velocity dispersions (σoc).
Note (10): Assuming that the rotation velocity of the gas is equivalent to
that of the stars, we calculate the total specific stellar angular
momentum (j*2.2c) based on the approximation devised by
Romanowsky & Fall (2012ApJS..203...17R 2012ApJS..203...17R) as shown in the equation 8,
(see section 5.6 Specific angular momentum).
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 19-Jun-2024