J/MNRAS/510/1716 Hydra I cluster study with H I emission (Reynolds+, 2022)
WALLABY pilot survey H I gas disc truncation and star formation of galaxies
falling into the Hydra I cluster.
Reynolds T.N., Catinella B., Cortese L., Westmeier T., Meurer G.R.,
Shao L., Obreschkow D., Roman J., Verdes-Montenegro L., Deg N., Denes H.,
For B.-Q., Kleiner D., Koribalski B.S., Lee-Waddell K., Murugeshan C.,
Oh S.-H., Rhee J., Spekkens K., Staveley-Smith L., Stevens A.R.H.,
Van der Hulst J.M., Wang J., Wong O.I., Holwerda B.W., Bosma A.,
Madrid J.P., Bekki K.
<Mon. Not. R. Astron. Soc. 510, 1716-1732 (2022)>
=2022MNRAS.510.1716R 2022MNRAS.510.1716R (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, group ; Galaxies, nearby ;
Intergalactic medium ; Photometry, hydrogen-line ; H I data ;
Radio sources ; Ultraviolet ; Infrared ; Optical ;
Star Forming Region ; Positional data ; Velocity dispersion ;
Galaxies, radius ; Stars, masses
Keywords: galaxies: clusters: individual: Abell 1060 - radio lines: galaxies
Abstract:
We present results from our analysis of the Hydra I cluster observed
in neutral atomic hydrogen (H I) as part of the Widefield ASKAP L-band
Legacy All-sky Blind Survey (WALLABY). These WALLABY observations
cover a 60-square-degree field of view with uniform sensitivity and a
spatial resolution of 30 arcsec. We use these wide-field observations
to investigate the effect of galaxy environment on H I gas removal and
star formation quenching by comparing the properties of cluster,
infall, and field galaxies extending up to ∼5R200 from the cluster
centre. We find a sharp decrease in the H I-detected fraction of
infalling galaxies at a projected distance of ∼1.5*R200 from the
cluster centre from ∼85 per cent to ∼35 per cent. We see evidence for
the environment removing gas from the outskirts of H I-detected
cluster and infall galaxies through the decrease in the H I to r-band
optical disc diameter ratio. These galaxies lie on the star-forming
main sequence, indicating that gas removal is not yet affecting the
inner star-forming discs and is limited to the galaxy outskirts.
Although we do not detect galaxies undergoing galaxy-wide quenching,
we do observe a reduction in recent star formation in the outer disc
of cluster galaxies, which is likely due to the smaller gas reservoirs
present beyond the optical radius in these galaxies. Stacking of H I
non-detections with H I masses below MHI ≲ 108.4{M}☉ will
be required to probe the H I of galaxies undergoing quenching at
distances ~> 60 Mpc with WALLABY.
Description:
The environment in which a galaxy resides has a large effect on its
observed properties. This is clearly demonstrated by the
morphology-density relation (e.g. Oemler 1974ApJ...194....1O 1974ApJ...194....1O ;
Dressler 1980ApJ...236..351D 1980ApJ...236..351D), in which the fraction of late-type
galaxies decreases (and early-type galaxies increase) with increasing
galaxy number density (i.e. moving from galaxies located in the field
to the centre of clusters). The environments with the highest galaxy
number and intergalactic medium (IGM) densities are galaxy clusters,
containing hundreds to thousands of galaxies. Here we investigate the
star formation connected to the neutral atomic hydrogen (H I) gas
content of galaxies, as H I provides a potential reservoir for
future star formation through its conversion to molecular gas, H2
(e.g. Leroy et al. 2008AJ....136.2782L 2008AJ....136.2782L).
In this study, we use the Widefield ASKAP L-band (radio around 21
cm H I for our case) Legacy All-sky Blind Survey (WALLABY, Koribalski
et al. 2020Ap&SS.365..118K 2020Ap&SS.365..118K) on ASKAP aiming to cover three-quarters of
the sky up to δ = +30 deg and detect H I emission in 500000
galaxies in which ∼ 5000 will be spatially resolved. ASKAP provide 30
deg2 instantaneous field-of-view footprint on the sky with high flux
sensitivity. Thanks to it, we are focusing on gas removal and star
formation in the Hydra I cluster using wide-field, high spatial
resolution WALLABY observations that cover 60 deg2, going out
to ∼5*Rvir from the cluster centre, by comparing the H I to optical
disc diameter ratio and star formation rate (SFR) of cluster and
infall galaxies with a control sample of field galaxies. We adopt
optical velocities (cz) in the heliocentric reference frame, the AB
magnitude convention and we assume a flat Γ cold dark matter
cosmology with H0 = 67.7 km/s/Mpc (i.e see Introduction section).
Throughout these observations (Reynolds et al. 2021MNRAS.505.1891R 2021MNRAS.505.1891R)
and data reductions (ASKAP/WALLABY process) (i.e section 2 Data), we
produce H I spectral line cube with spectral resolution of 4 km/s.
Further, we apply the Source Finding Application 2 (SoFiA 2, Serra et
al. 2015MNRAS.448.1922S 2015MNRAS.448.1922S; Westmeier et al. 2021MNRAS.506.3962W 2021MNRAS.506.3962W) to
detect sources of H I emission across a redshift range of cz
∼500-25000 km/s. As Hydra I has a systemic velocity of cz ∼3780 km/s,
we select a subsample of the H I detections below cz < 7000 km/s
detections for which the H I mass sensitivity will be similar to
cluster members. After several quality cuts (i.e section 2.1 WALLABY
observations and sample selection), our sample contains 129 individual
galaxies with detected H I emission and systemic velocities cz < 7000 km/s.
While for galaxies with not considered H I emission, we use the 6dF
Galaxy Survey (6dFGS, Jones et al. 2009MNRAS.399..683J 2009MNRAS.399..683J, Cat. VII/259)
to identify galaxies within the Hydra field footprint and with
systemic velocities cz < 7000 km/s leading us to a second galaxy group
of 142 galaxies.
Next, out of this two galaxy samples, we classify galaxies within the
Hydra field footprint as cluster, infall, or field galaxies based on
their location on a phase space diagram of the Hydra I cluster (i.e
see figure 2 of the section 2.1 WALLABY observations and sample
selection). Finally, we compute physical properties such gas/stellar
masses, angular light diameters and total SFR with the help of optical
photometric images from PanSTARRS g/r bands, UV and IR photometric
images from GALEX and WISE (see its dedicated subsections in the
section 2 Data). Our results are synthesized in the tablea1.dat for H
I WALLABY detections and in the tablea2.dat for H I not WALLABY
detections cases respectively.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 188 129 Measured and derived properties for galaxies
detected in H I with WALLABY
tablea2.dat 174 142 Measured and derived properties for galaxies
in the 6dFGS catalogue that are not detected
in H I with WALLABY
--------------------------------------------------------------------------------
See also:
VII/259 : 6dF galaxy survey final redshift release (Jones+, 2009)
J/MNRAS/460/2143 : HI size-mass relation of galaxies
II/335 : Revised catalog of GALEX UV sources (GUVcat_AIS GR6+7)
(Bianchi+ 2017)
https://doi.org/10.25919/5f7bde37c20b5 : ASKAP Science data archive
https://ps1images.stsci.edu/cgi-bin/ps1cutouts : PanSTARRS image access server
http://galex.stsci.edu/data : GALEX DR6+7 NUV band imaging
http://unwise.me/data/neo6/unwise-coadds/fulldepth : W1 imaging data
http://unwise.me/data/allwise/unwise-coadds/fulldepth : W3/W4 imaging data
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- WALLABY WALLABY identifier (JHHMMSS+DDMMSS)
(WALLABY_ID)
16- 22 A7 --- Group Environment group (Environment) (G1)
24- 39 F16.13 Mpc DL Distance luminosity (DL) (G2)
41- 57 F17.15 --- r/R200 Ratio of the projected distance r to Hydra I
virial radius R200 (r/R200) (G3)
59- 75 F17.15 --- dv/sigma Ratio of the galaxy relative velocity Δv
to Hydra I velocity dispersion
σdisp = 676 ± 35 km/s
(Δv/σdisp)
77- 93 F17.14 [Msun] log(M*) ?=- Logarithm of the galaxy stellar mass
in M☉ unit (logM*/M☉) (G4)
95-111 F17.14 [Msun] log(MHI) Logarithm of the H I mass in M☉ unit
(logMHI/M☉) (G5)
113-129 F17.13 arcsec dHI Diameter of the H I disc (dHI) (G6)
131-148 F18.14 arcsec dopt Optical r-band diameter as the size of
the galaxy (DIAMETER_R) (G7)
150-167 F18.14 arcsec dNUV ?=- NUV GALEX band diameter as the size of
the galaxy (DIAMETER_NUV) (G8)
169-186 F18.15 arcsec SFR ?=- The total NUV + MIR star formation
rate (SFR_NUV+MIR ) (G9)
188 I1 --- f_SFR [0/1] Flag indicates when the SFR is computed
with magnitudes upper limit value (SFR_UPLIM)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- 6dFGS 6dFGS identifier (gHHMMSSs+DDMMSS)
(6dFGS_ID) (1)
17- 23 A7 --- Group Environment group (Environment) (G1)
25- 40 F16.13 Mpc DL Distance luminosity (DL) (G2)
42- 58 F17.15 --- r/R200 Ratio of the projected distance r to Hydra I
virial radius R200 (r/R200) (G3)
60- 76 F17.15 --- dv/sigma Ratio of the galaxy relative velocity Δv
to Hydra I velocity dispersion
σdisp = 676 ± 35 km/s
(Δv/σdisp)
78- 94 F17.14 [Msun] log(M*) ?=- Logarithm of the galaxy stellar mass
in M☉ unit (logM*/M☉) (G4)
96- 98 F3.1 [Msun] log(MHI) ?=- Logarithm of the H I mass in M☉ unit
(logMHI/M☉) (G5)
100-116 F17.14 arcsec dHI ?=- Diameter of the H I disc (dHI) (G6)
118-134 F17.13 arcsec dopt Optical r-band diameter as the size of
the galaxy (DIAMETER_R) (G7)
136-153 F18.14 arcsec dNUV ?=- NUV GALEX band diameter as the size of
the galaxy (DIAMETER_NUV) (G8)
155-172 F18.15 arcsec SFR ?=- The total NUV + MIR star formation
rate (SFR_NUV+MIR ) (G9)
174 I1 --- f_SFR [0/1] Flag indicates when the SFR is computed
with magnitudes upper limit value (SFR_UPLIM)
--------------------------------------------------------------------------------
Note (1): As a blind H I survey, WALLABY is most sensitive to gas-rich galaxies
and will detect few gas-poor galaxies (predominantly early-types),
which are the dominant type of galaxy found in clusters. Thus, H I
detections alone do not provide a complete galaxy sample for probing
the effect of the environment on H I content and star formation.
We use the 6dF Galaxy Survey (6dFGS, Jones et al. 2009MNRAS.399..683J 2009MNRAS.399..683J,
Cat. VII/259) to identify galaxies within the Hydra field footprint
and with systemic velocities cz < 7000 km/s without detected H I
emission. The 6dFGS survey is complete to near-infrared magnitudes
of 12.65, 12.95, and 13.75 in the K-, H-, and J- bands and at the
distance of Hydra I detects galaxies with stellar masses
M* => 109 M☉ (i.e 2.1 WALLABY observations and sample
selection).
--------------------------------------------------------------------------------
Global notes:
Note (G1): The environment group are organized as follows:
cluster = 44 WALLABY galaxies with H I detected emission
and 102 6dFGS galaxies with H I not detected emission
are part of Hydra field footprints
field = 43 WALLABY galaxies with H I detected emission
and 5 6dFGS galaxies with H I not detected emission
are considered as field galaxies opposed to infall
galaxies parameter criteria
infall = 42 WALLABY galaxies with H I detected emission
and 35 6dFGS galaxies with H I not detected emission
are classified as infall galaxies of Hydra I cluster
As described in the section 2 Data. We classify galaxies within
the Hydra field footprint as cluster, infall, or field galaxies based
on their location on a phase space diagram
(e.g. Rhee et al. 2017ApJ...843..128R 2017ApJ...843..128R) of the Hydra I cluster
(i.e see figure 2 of this section).
Cluster galaxies have projected distances from the
cluster centre of r < R200 and velocities relative to the cluster
systemic velocity Δv/σdisp < 3σesc, where
σesc is the uncertainty in the escape velocity. We calculate
the escape velocity and σesc following equations (1)-(4) from
Rhee et al. (2017ApJ...843..128R 2017ApJ...843..128R) using R200, M200, and
σdisp given in section 1.1 The Hydra I cluster. Infall
galaxies are defined by R200 < r < 2.5*R200 and
Δv/{simga}disp < 3σesc above the cluster escape
velocity curve. All other galaxies are classified as field galaxies.
Note (G2): As explained in section 1.1 The Hydra I cluster, this cluster has a
heliocentric recessional velocity of cz ∼ 3780 km/s so The systemic
velocity in the cosmic microwave background reference frame
is cz = 4120 km/s. This gives a luminosity distance of
DL = cz/H0 = 4120/67.7 ≃ 61 Mpc, which we adopt as the distance
of Hydra I throughout this work, and is in good agreement with the
redshift-independent distance of 59 Mpc
(Jorgensen et al. 1996MNRAS.280..167J 1996MNRAS.280..167J).
Note (G3): Hydra I has a velocity dispersion of σdisp = 676 ± 35 km/s
(Richter et al. 1982A&A...111..193R 1982A&A...111..193R). We adopt the cluster virial
radius of R200 ∼ 1.44 ± 0.08 Mpc from Reiprich & Bohringer
(2002ApJ...567..716R 2002ApJ...567..716R) (∼1.35 deg projected on the sky at 61 Mpc),
(i.e see section 1.1 The Hydra I cluster).
As detailed in the section 2.1.1 H I mass, we estimate r (the length
of the semimajor axis as a galaxy radius taken from Hydra I center)
from a linear best fit to the H I detections radius versus stellar
mass over the range M* = 107 - 1010 M_☉ as writen in the
equation 3 of this section.
Note (G4): As seen in the section 2.2.1 Stellar mass and r-band diameter, we use
the empirical relation from Taylor et al. (2011MNRAS.418.1587T 2011MNRAS.418.1587T) and
total PanSTARRS g- and r-band magnitudes (i.e section 2.2 PanSTARRS)
to calculate stellar masses as presented in the equation 6 of this
section.
Note (G5): In this work (i.e section 2.1.1 H I mass), we use two H I properties,
the total H I mass and the size of the H I disc. We use the
integrated fluxes and integrated intensity (moment 0) WALLABY maps to
measure these quantities for the H I detections and derive upper
limits for the H I non-detections cases.
For galaxies detected in H I, we calculate the H I mass, MHI,
using equation (48) from Meyer et al. (2017PASA...34...52M 2017PASA...34...52M) as
presented in the equation 1 of this section. We can place an upper
limit on MHI for those galaxies not detected with WALLABY using the
minimum SNR of our H I detections (SNR = 5) and flux density
sensitivity. We derive the theoretical H I mass sensitivity of
WALLABY at the distance of the Hydra I cluster (61 Mpc) using
equation (157) for the SNR for a given set of observational
parameters from Meyer et al. (2017PASA...34...52M 2017PASA...34...52M) as presented in
the equation 2 of this section.
Note (G6): Hereafter (i.e section 2.1.2 H I diameter), for H I-detected
galaxies, we measure the diameter of the H I disc from the moment 0
(integrated intensity) map at a H I surface density
of 1 M☉ pc-2 which mainly lead us to dHI expressed as the
equation 4 of this section. For galaxies not detected in H I, we
estimate the maximum H I disc these galaxies may have based on the
H I size-mass relation. We use the H I size-mass relation from
Wang et al. (2016MNRAS.460.2143W 2016MNRAS.460.2143W, Cat. J/MNRAS/460/2143) and
the H I mass limit defined previously (i.e equation 2 of the
section 2.1.1 H I mass) to estimate upper limit H I disc diameters
for the galaxies not detected in H I.
Note (G7): We define a galaxy's optical diameter as the size of the galaxy at
which the r-band surface brightness reaches 23.5 mag arcsec-2 (to
ensure that we are well above the noise level of the images
compared to the common B-band 25 mag arcsec-2 surface
brightness). We measure this by interpolating between the two
isophotes bridging this surface brightness. Similar to the H I
diameter, we correct the r-band diameter for the size of the point
spread function (PSF) using equation 4 of the section 2.1.2 H I
diameter and the PanSTARRS PSF FWHM, (i.e section 2.2.1 Stellar mass
and r-band diameter).
Note (G8): As explicited in the section 2.3 GALEX and WISE, we use UV imaging
comes from GALEX near-UV (NUV) band to construst NUV magnitudes
(see section 2.3.1 GALEX). Similarly to the r-band, we measure
NUV-band disc diameters at an isophotal surface brightness
of 28 mag.arcsec-2. We also correct the NUV disc diameter for the
PSF using equation 4 of the section 2.1.2 H I diameter adopting the
NUV PSF FWHM (refer to section 2.3.3 Star formation rate).
Note (G9): Following the procedure explained in the section 2.3.3 Star formation
rate, we calculate total SFRs for our galaxies by combining the
contributions derived from GALEX NUV and WISE mid-infrared (MIR)
magnitudes according to Janowiecki et al. (2017MNRAS.466.4795J 2017MNRAS.466.4795J).
The equation 12 of this section shows an expression of the total
SFR_NUV+MIR. We set SFR upper limits flag to indicate when NUV
and/or WISE magnitudes stand to SNR < 5.
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 18-Oct-2024