J/ApJ/893/4 KiDS ultracompact massive galaxies sp. obs. (Scognamiglio+, 2020)
Building the largest spectroscopic sample of ultracompact massive galaxies with
the Kilo Degree Survey.
Scognamiglio D., Tortora C., Spavone M., Spiniello C., Napolitano N.R.,
D'Ago G., La Barbera F., Getman F., Roy N., Raj M.A., Radovich M.,
Brescia M., Cavuoti S., Koopmans L.V.E., Kuijken K.H., Longo G.,
Petrillo C.E.
<Astrophys. J., 893, 4 (2020)>
=2020ApJ...893....4S 2020ApJ...893....4S
ADC_Keywords: Galaxies, spectra; Photometry, ugriz; Redshifts;
Velocity dispersion; Morphology; Surveys
Keywords: Early-type galaxies; Galaxy formation; Galaxy mergers; Spectroscopy;
Galaxy counts; Galaxy kinematics
Abstract:
Ultracompact massive galaxies (UCMGs), i.e., galaxies with stellar
masses M*>8x1010M☉ and effective radii Re<1.5kpc, are very
rare systems, in particular at low and intermediate redshifts. Their
origin as well as their number density across cosmic time are still
under scrutiny, especially because of the paucity of spectroscopically
confirmed samples. We have started a systematic census of UCMG
candidates within the ESO Kilo Degree Survey, together with a large
spectroscopic follow-up campaign to build the largest possible sample
of confirmed UCMGs. This is the third paper of the series and the
second based on the spectroscopic follow-up program. Here, we present
photometrical and structural parameters of 33 new candidates at
redshifts 0.15≲z≲0.5 and confirm 19 of them as UCMGs, based on their
nominal spectroscopically inferred M* and Re. This corresponds to
a success rate of ∼58% , nicely consistent with our previous findings.
The addition of these 19 newly confirmed objects allows us to fully
assess the systematics on the system selection-and to finally reduce
the number density uncertainties. Moreover, putting together the
results from our current and past observational campaigns and some
literature data, we build the largest sample of ucmgs ever collected,
comprising 92 spectroscopically confirmed objects at 0.1≲z≲0.5. This
number raises to 116, allowing for a 3σ tolerance on the M*
and Re thresholds for the ucmg definition. For all these galaxies,
we have estimated the velocity dispersion values at the effective
radii, which have been used to derive a preliminary mass-velocity
dispersion correlation.
Description:
The ESO Kilo Degree Survey (KiDS) is one of the ESO public wide-area
surveys (1350deg2 in total) being carried out with the VLT Survey
Telescope. It provides imaging data with unique image quality (pixel
scale of 0.21/pixel and a median r-band seeing of 0.65") and baseline.
As baseline sample of our search, we use the data included in the
third Data Release of KiDS (KiDS-DR3) presented in de Jong+ 2017 (II/347).
Spectroscopic follow-up data have been collected in the years 2017 and
2018 during three separate runs, two carried out with the 3.6m
Telescopio Nazionale Galileo (TNG) and one using the 2.54m Isaac
Newton Telescope (INT), both located at Roque de los Muchachos
Observatory (Canary Islands).
Data on 13 luminous UCMG candidates have been obtained with the IDS
spectrograph during six nights in March 2017 at the INT telescope
(wavelength range 4000-8000Å and R=560), in visitor mode
(PI: C. Tortora, ID: 17AN005). See Section 3.1.
20 spectra of UCMG candidates have been collected using the Device
Optimized for the Low RESolution (DOLORES) spectrograph mounted on the
3.5m TNG, during six nights in March 2017 and 2018 (PI: N.R. Napolitano,
ID: A34TAC_22 and A36TAC_20; resolution R=585 and wavelength range
4000-8000Å). See Section 3.2.
In addition to the 33 new UCMG candidates presented in this paper, we
also apply the same kinematics procedure to the 28 UCMG candidates
from Tortora+ 2018MNRAS.481.4728T 2018MNRAS.481.4728T
6 observed with TNG and 22 with the New Technology Telescope (NTT),
which we refer to as the ucmgtngt18 and ucmgnttt18 samples,
respectively. See Sections 1 and 3.4.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 106 33 Integrated photometry for the 33 UCMG candidates
observed within our spectroscopic program
table2.dat 105 33 Structural parameters derived running
2Dphot on g-, r-, and i-bands
table3.dat 58 33 Results of the fitting procedure on the spectra
belonging to the three observational runs
table4.dat 79 28 *Results of the fitting procedure on the spectra
for samples ucmgtngt18 and ucmgnttt18
table5.dat 36 33 Photometric and spectroscopic parameters for the
validation of the new UCMG candidates
table6.dat 36 28 Photometric and spectroscopic parameters for the
validation of ucmgtngt18 and ucmgnttt18 samples
tablea1.dat 94 55 *Integrated photometry for the 55 systems in
the ucmg_spec sample
tablea2.dat 112 55 Structural parameters derived running 2Dphot on
g-, r-, and i-bands for the ucmg_spec sample
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Note on table4.dat: In addition to the 33 new UCMG candidates presented in
this paper, we also apply the same kinematics procedure to the 28 UCMG
candidates from Tortora+ 2018MNRAS.481.4728T 2018MNRAS.481.4728T
6 observed with TNG and 22 with the New Technology Telescope (NTT),
which we refer to as the ucmgtngt18 and ucmgnttt18 samples,
respectively (see Sections 1 and 3.4).
Note on tablea1.dat: In order to quantify the impact of the systematics on the
UCMG selection, we have created (in Section 4.2) the ucmg_spec sample:
a sample of 55 UCMGs with spectroscopic redshifts from the literature,
similar to the sample used in Tortora+ 2018MNRAS.481.4728T 2018MNRAS.481.4728T, but
selected with the new mass setup. We have gathered these spectroscopic
redshifts from SDSS (see DR9, V/139 and DR10, 2014ApJS..211...17A 2014ApJS..211...17A),
GAMA (Driver+ 2011, J/MNRAS/413/971), which overlap the KiDS fields in
the Northern cap, and 2dFLenS (Blake+ 2016MNRAS.462.4240B 2016MNRAS.462.4240B), observed
in the Southern hemisphere.
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See also:
B/eso : ESO Science Archive Catalog (ESO, 1991-2021)
II/347 : KiDS-ESO-DR3 multi-band source catalog (de Jong+, 2017)
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
J/ApJ/720/723 : Compact galaxies in the local universe (Taylor+, 2010)
J/MNRAS/404/1639 : MILES base models & new line index system (Vazdekis+, 2010)
J/ApJ/739/L44 : Structural data for gal. between 0.2<z<2.7 (Damjanov+, 2011)
J/MNRAS/413/971 : Galaxy And Mass Assembly (GAMA) DR1 (Driver+, 2011)
J/ApJ/762/77 : PM2GC mass-limited sample surface phot. (Poggianti+, 2013)
J/ApJ/793/39 : Sp. properties of BOSS compact galaxies (Damjanov+, 2014)
J/MNRAS/452/2087 : Galaxy And Mass Assembly (GAMA): DR2 (Liske+, 2015)
J/A+A/578/A134 : Compact early-type galaxies in SDSS (Saulder+, 2015)
J/ApJS/218/10 : HET Massive Galaxy Survey (HETMGS) (van den Bosch+, 2015)
J/A+A/632/A34 : KiDS+VIKING-450 opt+NIR dataset (Wright+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 "Y/M" Date Date of observation (UT)
9- 19 A11 --- Inst Instrument (1)
21- 22 I2 --- Seq [1/33] Running sequence number
24- 27 A4 --- --- [KIDS]
29- 48 A20 --- KIDS Name (JHHMMSS.ss+DDMMSS.ss)
50- 54 F5.2 --- rmagA [18.56/19.96] r-band KiDS MAG_AUTO
56- 60 F5.2 mag umag [20.4/24.6] KiDS 6" aperture u-band magnitude (G1)
62- 65 F4.2 mag e_umag [0.02/1.76] Uncertainty on the umag
67- 71 F5.2 mag gmag [19.9/21.5] KiDS 6" aperture g-band magnitude (G1)
73- 77 F5.3 mag e_gmag [0.006/0.2] Uncertainty on the gmag
79- 83 F5.2 mag rmag [18.58/20] KiDS 6" aperture r-band magnitude (G1)
85- 89 F5.3 mag e_rmag [0.002/0.04] Uncertainty on the rmag
91- 95 F5.2 mag imag [18.1/19.5] KiDS 6" aperture i-band magnitude (G1)
97- 101 F5.3 mag e_imag [0.005/0.08] Uncertainty on the imag
103- 106 F4.2 --- zphot [0.22/0.45] Photometric redshift
from machine learning
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Note (1): Instrument as follows:
INT/IDS = the 2.54m Isaac Newton Telescope (13 occurrences)
TNG/DOLORES = the 3.6m Telescopio Nazionale Galileo (20 occurrences)
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [1/33] Running sequence number
4- 7 F4.2 arcsec Radg [0.06/0.7] g-band circularized effective radius,
θe
9- 12 F4.2 kpc Reffg [0.3/3.1] g-band circularized effective radius
14- 18 F5.2 --- ng [1.5/10.1] g-band Sersic index
20- 23 F4.2 --- qg [0.1/0.99] g-band axis ratio
25- 28 F4.2 --- Chi2g [0.99/1.1] χ2 of the surface photometry
fit in g-band
30- 33 F4.2 --- Chir2g [0.9/1.4] χ2 of the surface photometry
fit including only central pixels in g-band
35- 37 I3 --- SNRg [36/161] signal-to-noise ratio S/N of the
photometric g-band images (G2)
39- 42 F4.2 arcsec Radr [0.06/0.4] r-band circularized effective radius,
θe
44- 47 F4.2 kpc Reffr [0.35/1.55] r-band circularized effective radius
49- 52 F4.2 --- nr [2.15/9.54] r-band Sersic index
54- 57 F4.2 --- qr [0.2/0.9] r-band axis ratio
59- 62 F4.2 --- Chi2r [0.98/1.15] χ2 of the surface photometry
fit in r-band
64- 67 F4.2 --- Chir2r [0.9/2.8] χ2 of the surface photometry
fit including only central pixels in r-band
69- 71 I3 --- SNRr [36/421] signal-to-noise ratio S/N of the
photometric r-band images (G2)
73- 76 F4.2 arcsec Radi [0.1/0.7] i-band circularized effective radius,
θe
78- 81 F4.2 kpc Reffi [0.45/2.6] i-band circularized effective radius
83- 86 F4.2 --- ni [2.1/9.16] i-band Sersic index
88- 91 F4.2 --- qi [0.04/0.87] i-band axis ratio
93- 96 F4.2 --- Chi2i [0.97/1.1] χ2 of the surface photometry
fit in i-band
98- 101 F4.2 --- Chir2i [0.87/1.1] χ2 of the surface photometry
fit including only central pixels in i-band
103- 105 I3 --- SNRi [62/244] signal-to-noise ratio S/N of the
photometric i-band images (G2)
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Byte-by-byte Description of file: table[34].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [1/61] Running sequence number
4- 7 F4.2 --- zphot [0.2/0.45] Photometric redshift
9- 14 F6.4 --- zspec [0.15/0.47] Measured spectroscopic redshift
16- 21 F6.4 --- e_zspec [0.0001/0.006] zspec uncertainty
23- 25 I3 km/s sigma [142/432] Velocity dispersion
27- 29 I3 km/s e_sigma [22/113] sigma uncertainty
31- 33 I3 --- sige [149/464] The corrected velocity dispersion to
the effective radius, σe
35- 38 F4.2 arcsec Ap [0.69/1.6] The circular aperture
40- 43 F4.2 --- SR [0.02/1] The success rate (ratio between the
number of accepted fits over the total 257
attempts)
45- 49 F5.2 --- SNRsp [1.39/15.1] The signal-to-noise ratio per pixel
calculated in the range 3600-4600Å
51- 55 F5.2 --- SNRk [2/24.6] The signal-to-noise ratio per pixel
calculated over the region used for the fit by
OMEGA-K
57- 58 A2 --- Qual The quality level of the velocity dispersion
estimates (2)
60- 79 A20 --- KIDS KiDS identifier (JHHMMSS.ss+DDMMSS.ss)
for Tortora+ 2018MNRAS.481.4728T 2018MNRAS.481.4728T sample;
column added by CDS
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Note (2): Quality level of the velocity dispersion as follows:
HQ = high-quality if SR≥0.3, SNRsp≥3.5, and SNRk≥6.5/px;
LQ = low-quality
See Section 3.4.
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Byte-by-byte Description of file: table[56].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [1/61] Running sequence number
4- 7 F4.2 --- zphot [0.2/0.45] Photometric redshift
9- 12 F4.2 --- zspec [0.16/0.47] Spectroscopic redshift
14- 17 F4.2 kpc Reffp [0.35/1.5] Median effective radius, photometric
19- 22 F4.2 kpc Reffsp [0.28/1.81] Median effective radius,
spectroscopic
24- 28 F5.2 [Msun] Massp [10.7/11.4] Stellar mass, photometric
30- 34 F5.2 [Msun] Masssp [10.46/11.5] Stellar mass, spectroscopic
36 A1 --- Valid Spectral validation (3)
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Note (3): Spectral validation as follows:
Y = confirmed UCMG (i.e., log10(M*/M☉)>10.9 and Re<1.5kpc)
N = candidate is not a confirmed UCMG
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Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- ID Identifier
5- 8 A4 --- --- [KIDS]
10- 29 A20 --- KIDS Name (JHHMMSS.ss+DDMMSS.ss)
31- 35 F5.2 mag rmagA [17/20.94] r-band KiDS MAG_AUTO
37- 41 F5.2 mag umag [19.2/24.9] KiDS 6" aperture u-band magnitude (G1)
43- 46 F4.2 mag e_umag [0.01/1.76] Uncertainty on the umag
48- 52 F5.2 mag gmag [17.9/22.6] KiDS 6" aperture g-band magnitude (G1)
54- 58 F5.3 mag e_gmag [0.002/0.06] Uncertainty on the gmag
60- 64 F5.2 mag rmag [17/20.91] KiDS 6" aperture r-band magnitude (G1)
66- 71 F6.4 mag e_rmag [0.0008/0.01] Uncertainty on the rmag
73- 77 F5.2 mag imag [16.7/20.2] KiDS 6" aperture i-band magnitude (G1)
79- 83 F5.3 mag e_imag [0.001/0.04] Uncertainty on the imag
85- 88 F4.2 --- zphot [0.11/0.48] Photometric redshift
90- 94 F5.2 [Msun] Mass [10.58/11.3] Stellar mass
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Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- ID Identifier
5- 8 F4.2 arcsec Radg [0.05/0.81] g-band circularized effective radius,
θe
10- 13 F4.2 kpc Reffg [0.24/4.9] g-band circularized effective radius
15- 19 F5.2 --- ng [0.69/10.6] g-band Sersic index
21- 24 F4.2 --- qg [0.12/0.92] g-band axis ratio
26- 29 F4.2 --- Chi2g [0.83/1.2] χ2 of the surface photometry
fit in g-band
31- 35 F5.2 --- Chir2g [0.86/11.6] χ2 of the surface photometry
fit including only central pixels in g-band
37- 39 I3 --- SNRg [16/602] Signal-to-noise ratio S/N of the
photometric g-band images (G2)
41- 44 F4.2 arcsec Radr [0.09/0.64] r-band circularized effective radius,
θe
46- 49 F4.2 kpc Reffr [0.48/2] r-band circularized effective radius
51- 55 F5.2 --- nr [1.99/10.64] r-band Sersic index
57- 60 F4.2 --- qr [0.17/0.89] r-band axis ratio
62- 65 F4.2 --- Chi2r [0.98/1.5] χ2 of the surface photometry
fit in r-band
67- 71 F5.2 --- Chir2r [0.98/25.8] χ2 of the surface photometry
fit including only central pixels in r-band
73- 76 I4 --- SNRr [74/1109] signal-to-noise ratio S/N of the
photometric r-band images (G2)
78- 81 F4.2 arcsec Radi [0.1/1.3] i-band circularized effective radius,
θe
83- 86 F4.2 kpc Reffi [0.4/6] i-band circularized effective radius
88- 92 F5.2 --- ni [1/10.1] i-band Sersic index
94- 97 F4.2 --- qi [0.17/0.9] i-band axis ratio
99-102 F4.2 --- Chi2i [0.98/1.1] χ2 of the surface photometry
fit in i-band
104-108 F5.2 --- Chir2i [0.86/11.1] χ2 of the surface photometry
fit including only central pixels in i-band
110-112 I3 --- SNRi [32/641] signal-to-noise ratio S/N of the
photometric i-band images (G2)
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Globale notes:
Note (G1): All the magnitudes have been corrected for Galactic extinction
using Schlafly & Finkbeiner (2011ApJ...737..103S 2011ApJ...737..103S) maps.
Note (G2): The signal-to-noise ratio S/N of the photometric images, defined
as the inverse of the error on MAG_AUTO.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 04-Oct-2021