J/A+A/695/A79 Nancay HI observations in the ZoA (Schroeder+, 2025)
EZOA: Nancay HI follow-up observations in the Zone of Avoidance.
Schroeder A.C., van Driel W., Kraan-Korteweg R.C., Belleval C.
<Astron. Astrophys. 695, A79 (2025)>
=2025A&A...695A..79S 2025A&A...695A..79S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; Radial velocities ; Spectroscopy
Keywords: surveys - galaxies: distances and redshifts -
galaxies: fundamental parameters -
large-scale structure of the universe - radio lines: galaxies
Abstract:
We present follow-up 21cm HI line observations made with the Nanccay
Radio Telescope (NRT) of 99 weak or potential detections of galaxies
from the EZOA catalogue in the northern Zone of Avoidance (ZoA), which
were extracted from the shallow version of the EBHIS blind HI survey
performed with the Effelsberg radio telescope. The new NRT
observations are on average almost three times as sensitive as those
from EBHIS. Of the 99 observed sources, we confirmed 72, while three
yielded inconclusive results. We find that the quality assessment of
the EZOA catalogue entries correlates well with the NRT recovery rate;
for instance, only four of the 22 potential detections could be
confirmed. Due to the higher sensitivity as well as the large
north-south extent of the NRT beam, the NRT observations also yielded
five serendipitous detections, which we include here. We updated the
EZOA catalogue with the improved HI parameters and detections. To test
mitigation of Radio Frequency Interference signals, we also observed
selected sources using a dedicated receiver and data processing
system.
Description:
The observations described here were taken with the 100m class Nanccay
Radio Telescope (NRT) with a velocity resolution of 10km/s. The median
rms level of the detected sources is 3.6mJy/beam.
Table A.1 lists uncatalogued galaxies around those EZOA detections
that we have observed at the NRT (and being large enough to be
relevant for our discussion). These were found while examining
multi-wavelength images in the search for cross-matches (see
Schroeder et al., 2019MNRAS.489.2907S 2019MNRAS.489.2907S, Cat. J/MNRAS/489/2907). We
usually only list galaxies within the EZOA position uncertainty radius
of 3.5 arcmin, though in cases of suspected in-beam confusion also
galaxies further away are listed. Furthermore, we list previously
catalogued galaxies where we improved the position, since these are
important for our discussion. We note that all previously published
galaxies near EZOA detections that are not listed in this table can be
found in the CDS Simbad and NED databases.
Table B.1 lists all observations and compares them to the original
EBHIS HI detection (Schroeder et al., 2019MNRAS.489.2907S 2019MNRAS.489.2907S, Cat.
J/MNRAS/489/2907).
Table B.2 lists the NRT parameters for the adopted detection and gives
information on the stellar counterpart where one was identified.
The notes give details on individual cases where the HI line emission
shows a complex profile or its origin is ambiguous. When discussing
possible contamination of a profile by a source close to the target,
we often prefer to express angular distances in units of the NRT beam
radius b to better understand relative parameters like flux ratios.
HI spectra in ps file format:
NRT 21cm HI line spectra of EZOA source observations. The velocity
resolution is 10km/s. The pointing ID (see Table B.1) is indicated
for each spectrum. To help the comparison with the EBHIS detections,
the dashed vertical lines in each spectrum indicate the velocity range
of the EBHIS detection, which was excluded in the EBHIS baseline fit.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 105 94 Uncatalogued galaxies around EZOA sources and
previously catalogued galaxies with
improved positions
tableb1.dat 182 154 HI observations of EZOA sources
tableb2a.dat 178 82 NRT detections of EZOA galaxies
tableb2b.dat 174 5 Serendipitious NRT detections
notes.dat 94 354 Individual notes
sp/* . 152 Individual HI spectra in ps format
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See also:
J/MNRAS/481/1262 : 2MASS bright galaxies HI ZoA survey (Kraan-Korteweg+, 2018)
J/MNRAS/489/2907 : The EZOA survey (Schroder+, 2019)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- EZOA ID of the EZOA source (JHHMM-DDA)
10- 33 A24 --- Galaxy Galaxy ID (1)
35- 36 I2 h RAh Right Ascension (J2000) (2)
38- 39 I2 min RAm Right Ascension (J2000) (2)
41- 44 F4.1 s RAs Right Ascension (J2000) (2)
46 A1 --- DE- Declination sign (J2000) (2)
47- 48 I2 deg DEd Declination (J2000) (2)
50- 51 I2 arcmin DEm Declination (J2000) (2)
53- 54 I2 arcsec DEs Declination (J2000) (2)
56 A1 --- upos [:] Coordinate uncertainty flag (2)
58- 60 F3.1 arcmin Sep Angular distance from the nominal EZOA
position (3)
62-105 A44 --- Comment Comment
--------------------------------------------------------------------------------
Note (1): Previously uncatalogued galaxies are given J2000.0-coordinate IDs
without a prefix.
Note (2): Coordinates may differ from the galaxy ID where we were able to
improve on the published coordinates. An uncertainty flag (:) is given if the
centre of the galaxy could not easily be determined.
Note (3): For comparison, the EZOA position uncertainty is 3.5arcmin.
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- EZOA ID of the EZOA source (JHHMM-DD)
9 A1 --- m_EZOA [B] Multiplicity index on EZOA
11- 18 A8 --- Class Classification of the HI detection (G1)
20 A1 --- Note [n] Indicates a note in notes.dat file
22- 23 I2 h RAh EBHIS Right Ascension (J2000)
25- 26 I2 min RAm EBHIS Right Ascension (J2000)
28- 31 F4.1 s RAs EBHIS Right Ascension (J2000)
33 A1 --- DE- EBHIS Declination sign (J2000)
34- 35 I2 deg DEd EBHIS Declination (J2000)
37- 38 I2 arcmin DEm EBHIS Declination (J2000)
40- 41 I2 arcsec DEs EBHIS Declination (J2000)
43- 47 I5 km/s HRV-E EBHIS heliocentric radial velocity
49- 50 I2 km/s e_HRV-E Uncertainty in HRV
52- 54 I3 km/s W50-E EBHIS line width at 50% peak flux density
56- 57 I2 km/s e_W50-E Uncertainty in W50
59- 62 F4.1 Jy.km/s FHI-E EBHIS HI flux integral
64- 66 F3.1 Jy.km/s e_FHI-E Uncertainty in FHI
68- 71 F4.1 --- SNR-E EBHIS Peak signal to noise ratio
73 A1 --- Ptg [ABCDE] NRT pointing ID
75 A1 --- n_Ptg Pointing footnote (G2)
77- 78 I2 h RAPh Ptg Right Ascension (J2000)
80- 81 I2 min RAPm Ptg Right Ascension (J2000)
83- 86 F4.1 s RAPs Ptg Right Ascension (J2000)
88 A1 --- DEP- Ptg Declination sign (J2000)
89- 90 I2 deg DEPd Ptg Declination (J2000)
92- 93 I2 arcmin DEPm Ptg Declination (J2000)
95- 96 I2 arcsec DEPs Ptg Declination (J2000)
98 A1 --- Tgt Pointing target classification (G3)
100-102 F3.1 beam d-E Angular distance between the NRT pointing
position and the EBHIS source position (G4)
104-111 A8 --- Cand Classification of the cross-match
candidate (G5)
113 I1 --- cFlux ?=- Class of the NRT/EBHIS flux ratio (G6)
115-117 F3.1 --- Rflux ? Ratio of NRT and EBHIS integrated fluxes
119-120 A2 --- ffinal Final NRT flag (G7)
122-125 F4.2 mJy RMS-N ? NRT spectrum rms noise level
127-130 I4 km/s HRV-N ? NRT heliocentric radial velocity
132-133 I2 km/s e_HRV-N ? Uncertainty in HRV
135-137 I3 km/s W50-N ? NRT line width at 50% peak flux density
139-140 I2 km/s e_W50-N ? Uncertainty in W50
142-144 I3 km/s W20-N ? NRT line width at 20% peak flux density
146-147 I2 km/s e_W20-N ? Uncertainty in W20
149-152 F4.1 Jy.km/s FHI-N ? NRT HI flux integral
154-156 F3.1 Jy.km/s e_FHI-N ? Uncertainty in FHI
158-161 F4.1 --- SNR-N ? NRT Peak signal to noise ratio
163-182 A20 --- FileName Name of the spectrum file in subdirectory sp
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Byte-by-byte Description of file: tableb2a.dat tableb2b.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- EZOA ID of the EZOA source (JHHMM-DD)
9 A1 --- m_EZOA [B] Multiplicity index on EZOA
11- 12 A2 --- Class Classification of the HI NRT detection (G1)
14 A1 --- Note [n] Indicates a note in notes.dat file
16 A1 --- Ptg NRT pointing ID
18 A1 --- f_Ptg Pointing footnote (G2)
20- 23 I4 km/s HRV-N ?=- NRT heliocentric radial velocity
25- 26 I2 km/s e_HRV-N ?=- Uncertainty in HRV
28- 30 I3 km/s W50-N ?=- NRT line width at 50% peak flux density
32- 33 I2 km/s e_W50-N ?=- Uncertainty in W50
35- 37 I3 km/s W20-N ?=- NRT line width at 20% peak flux density
39- 40 I2 km/s e_W20-N ?=- Uncertainty in W20
42- 45 F4.1 Jy.km/s FHI-N ?=- NRT HI flux integral
47- 49 F3.1 Jy.km/s e_FHI-N ?=- Uncertainty in FHI
51 A1 --- u_FHI-N Uncertainty flag on flux (G8)
53- 56 F4.1 --- SNR-N NRT Peak signal to noise ratio
58- 61 I4 km/s vLG ?=- Galaxy velocity vLG (G9)
63- 68 F6.2 Mpc Dist ?=- Distance to the galaxy (based on vLG and
H0=75km/s/Mpc)
69- 73 F5.2 [Msun] logMHI ?=- Log HI mass
74 A1 --- u_logMHI Uncertainty flag on HI mass (G8)
76- 77 A2 --- ffinal Final NRT flag (G7)
79 A1 --- Cand Final Classification of the cross-match
candidate (G5)
81- 83 F3.1 beam dbeam Distance between the NRT pointing
position and the crossmatch (G10)
85- 86 I2 h RACh Right Ascension of counterpart (J2000) (G11)
88- 89 I2 min RACm Right Ascension of counterpart (J2000) (G11)
91- 94 F4.1 s RACs Right Ascension of counterpart (J2000) (G11)
96 A1 --- DEC- Declination sign of counterpart (J2000) (G11)
97- 98 I2 deg DECd Declination of counterpart (J2000) (G11)
100-101 I2 arcmin DECm Declination of counterpart (J2000) (G11)
103-104 I2 arcsec DECs Declination of counterpart (J2000) (G11)
106-114 A9 --- ePos Positional uncertainty (G12)
115-121 F7.3 deg GLON Galactic longitude of counterpart
position (G11)
123-128 F6.3 deg GLAT Galactic latitude of of counterpart
position (G11)
130-133 F4.2 mag AK The K band extinction (G13)
135-157 A23 --- IDc ID of counterpart (G14)
159-178 A20 --- FileName Name of the spectrum file in subdirectory sp
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Byte-by-byte Description of file: notes.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [EZOA]
6- 13 A8 --- EZOA ID of the EZOA source (JHHMM-DD)
14 A1 --- m_EZOA [B] Multiplicity index on EZOA
16- 94 A79 --- Note Text of the note
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Global notes:
Note (G1): The EBHIS classification is given to the left of the arrow and the
new, NRT, classification to the right.
Class 1 indicates a clear detection;
3+, 3, and 3- are detections with varying degree of confidence,
with 3- denoting a possible detection (not listed in the EZOA catalogue);
4 marks a non-detection;
5 indicates an inconclusive result.
Note (G2): Note as follows:
a = Data from Paturel et al., 2003A&A...412...57P 2003A&A...412...57P, Cat. VII/238
b = Data from Courtois et al. 2009AJ....138.1938C 2009AJ....138.1938C, Cat. J/AJ/138/1938
c = Data from Kraan-Korteweg et al. 2018MNRAS.481.1262K 2018MNRAS.481.1262K, Cat. J/MNRAS/481/1262
d = Data from Springob et al. 2005ApJS..160..149S 2005ApJS..160..149S, Cat. VIII/77
n = not observed
r = RFI mitigation test observation.
Note (G3): NRT pointing target classification as follows:
c = cross-match candidate
e = EBHIS position
s = NRT search position
Note (G4): For convenience, we introduce the angular distance parameter b,
which is expressed in units of the radius of the elliptically-shaped NRT
beam. The beam radius is defined as the angular distance from the pointing
centre at which the telescope gain has diminished to a level of 50% of its
peak level (i.e. 0.5 HPBW).
Note (G5): Classification of the cross-match candidate (that is,
for pointing target 'c', see Tgt):
d = definite
p = probable
a = ambiguous
c = contributor to a confused profile
u = uncertain galaxy
n = not a candidate
Where the classification has changed, the former EBHIS classification is
given on the left and the new (final) classification on the right, linked by
an arrow. TableB.2 gives only the latter.
Note (G6): Class of the NRT/EBHIS integrated flux ratio, (see R_flux):
While c_Flux = 2 stands for comparable fluxes (that is, 0.9 ≤ R_Flux ≤ 1.0),
classes 1 and 3 indicate a higher and lower NRT flux, respectively;
4 means no NRT detection, and 5 indicates that the flux ratio is not usable,
mainly when the profiles are not comparable (especially when the line width
is significantly different, e.g. due to confusion, or when RFI affects the
profile).
Note (G7): Final NRT flag as follows:
0 = observed candidate is the stellar counterpart
1 = pointing with the best detection (no cross-match candidate)
2 = candidate contributes to the EZOA detection (a plus denotes a major
contributor, a minus a minor contribution)
3 = low-level detection, not the best pointing
4 = not detected
5 = inconclusive (e.g. due to RFI)
Note (G8): A colon (:) means insufficient RFI subtraction on the profile,
flux and HI mass are uncertain.
Note (G9): Corrected to the Local Group frame of reference via:
vLG=(HRV-N)+300*sin(GLON)*cos(GLAT).
Note (G10): Angular distance between NRT pointing and position of the
optical/NIR cross-match (where they differ), in NRT beam radius units, b
(see Note (G4)). Uncertainties in integrated flux and other HI parameters
increase correspondingly. No corrections have been applied to the given
parameters.
Note (G11): Equatorial (J2000.0) coordinates of the cross-match (where
available) or of the best NRT pointing position.
Note (G12): Positional uncertainty: where the visible galaxy appears diffuse,
without a clear centre, we added a colon (:) to indicate a larger positional
uncertainty than implied by the precision of the coordinates. Where no
candidate is found, we give an improved positional uncertainty ellipse
(with minor and major semi-axes in arcminutes).
Note (G13): Galactic extinction in the K band, derived from the extinction
maps published by Planck Collaboration et al. 2016A&A...596A.109P 2016A&A...596A.109P
using the conversion AK=0.36*E(B-V) and a correction factor f=0.86
(Schroeder et al. 2021MNRAS.503.5351S 2021MNRAS.503.5351S).
Note (G14): ID of the cross-match (see TableA.1 for all previously
uncatalogued galaxies around the EZOA sources in our sample).
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Acknowledgements:
Anja Schroeder, anja(at)mpe.mpg.de
(End) Patricia Vannier [CDS] 31-Jan-2025