J/A+A/690/A264 Dissecting the planetary nebula NGC 4361 with MUSE (Walsh+, 2024)
Dissecting the planetary nebula NGC 4361 with MUSE.
Walsh J.R., Monreal Ibero A., Laging J., Romeijnders M.
<Astron. Astrophys. 690, A264 (2024)>
=2024A&A...690A.264W 2024A&A...690A.264W (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, optical ; Planetary nebulae ; Spectroscopy
Keywords: atomic processes - planetary nebulae: general -
planetary nebulae: individual: NGC 4361
Abstract:
The optical line and continuum emission in the very-high-ionisation
Galactic PN, NGC 4361, were mapped to study the distribution of
ionisation, extinction, electron temperature, and density.
Based on commissioning data, MUSE Wide Field (60x60 arcsec)
normal-mode (4750-9300Å) observations of NGC 4361 were reduced. The
PN is larger than a single MUSE field and only the central 1 arcmin
square of the PN was observed in good conditions. Emission images in
recombination and collisionally excited lines were extracted and the
line ratios provided the dust extinction, electron density and
temperature, and ionic abundances using standard techniques. A family
of compact low-ionisation knots (dubbed 'freckles') was discovered
and techniques developed to measure their spectra, independently of
the extended high-ionisation medium.
The nebula is confirmed as optically thin in the H-ionising continuum,
based on its very low HeI emission, even to the edges of the field.
The electron temperature, Te, is shown to have a large-scale
spatially coherent structure, as indicated by a previous long-slit
spectrum. Prior to this study, no low-ionisation emission had been
positively detected, although MUSE revealed both weak extended [NII]
and [OII] and >100 spatially unresolved knots. There are several
linear associations of these knots, but none of them point
convincingly back to the central star. They have low-to-moderate
ionisation with Te∼11000K, Ne∼1500cm-3 and generally exhibit a
higher extinction than the extended high-ionisation nebula.
Within the MUSE field, a low-redshift emission-line galaxy was
serendipitously found to be hiding behind NGC 4361. The spectrum of
this dwarf galaxy was carefully extracted from the bright foreground
nebular emission and the galaxy's line and continuum properties were
then determined.
NGC 4361 is not completely optically thin, as indicated by several
extended regions and many compact features of lower ionisation
emission. The low-ionisation 'freckles' identified here do not clearly
appear to differ in (He, N, O, S) abundance with respect to the
extended high-ionisation gas. The spatial distribution and radial
velocities of these features suggest that they belong to a thick disk
oriented perpendicular to the large-scale nebular gas, which may
perhaps be remnants of an earlier structure. The low-luminosity disk
galaxy at ∼87Mpc has bright H II regions with metallicity 12+log(O/H)
∼8.4 and is suggested as a Magellanic irregular or low-mass spiral.
Description:
Table 1 presents the observation log of the 55 MUSE exposures of
NGC 4361.
Table 2 lists wavelengths and fluxes of the 149 emission lines
detected in the integrated spectrum of the full MUSE field
(60x60 arcsec) from 4750-9300Å.
Table 6 presents the positions (relative to the position of the
central star) of the 102 compact low ionisation knots ('freckles'),
their area, [NII] 6583Å flux and radial velocities, both
heliocentric and with respect to the emission of the local high
ionisation gas.
In Table 7, the extracted emission line spectra of the freckles are
listed, with observed H-alpha flux and the relative flux with respect
to H-alpha for the detectable lines. The final column of this table
lists the quality assessment of the freckle spectrum.
Table 9 then lists the [N II]6583/H-alpha ratio, the extinction,
[SII] Ne, [NII] Te and [SIII] Te for those freckles with quality
bands A and B (from Table 7).
Table 12 presents the observed properties of the 39 HII regions in the
galaxy detected behind NGC 4361 (NGC4361-BgGalJ1224290-184707): their
positions (with respect to the optical centre of the galaxy),
projected size, H-alpha luminosity and velocity in the galaxy rest
frame.
Table 14 lists the observed line ratios and errors of [OIII], [NII]
and [SII] for the 39 HII regions of NGC4361-BgGalJ1224290-184707 with
respect to the flux of H-alpha. Where both [OIII] and [NII] lines
were detected, the derived metallicity Z(O3/N2) and error is also
given.
Objects:
------------------------------------------------------
RA (2000) DE Designation(s)
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12 24 30.75 -18 47 05.5 NGC 4361 = PN G294.1+43.6
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 74 55 Observation log of 55 MUSE exposures
table2.dat 54 149 Wavelengths and fluxes of emission lines
detected in full MUSE field
table6.dat 35 102 Position, area, [NII] 6583Å flux, and radial
velocities of freckles
table7.dat 125 100 Emission line spectra of the freckles
table9.dat 32 41 Derived parameters for freckles with quality
bands A and B
table12.dat 28 39 Observed properties of HII regions in the
galaxy NGC4361-BgGalJ1224290-184707
table14.dat 55 39 Observed line ratios and metallicities for HII
regions of NGC4361-BgGalJ1224290-184707
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Target Target pointing name
13- 14 I2 h RAh Right ascension (J2000.0)
16- 17 I2 min RAm Right ascension (J2000.0)
19- 23 F5.2 s RAs Right ascension (J2000.0)
25 A1 --- DE- Declination sign (J2000.0)
26- 27 I2 deg DEd Declination (J2000.0)
29- 30 I2 arcmin DEm Declination (J2000.0)
32- 35 F4.1 arcsec DEs Declination (J2000.0)
37- 39 I3 deg PA Position angle of MUSE
41- 50 A10 "date" obs.Date Date of observation
52- 63 A12 "h:m:s" obs.Time Dataset time stamp
65- 69 F5.3 --- Airmass Airmass
71- 74 F4.2 arcsec DIMM ? DIMM seeing
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 F6.1 0.1nm lambda Line wavelength (Angstroem)
8- 25 A18 --- ID Line species (1)
27- 33 F7.3 --- ObsFl Observed flux (H-beta=100) (2)
35- 39 F5.3 --- e_ObsFl Observed flux error
41- 47 F7.3 --- DerFl Dereddened flux (H-beta=100) (2)
49- 54 F6.3 --- e_DerFl Dereddened flux error
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Note (1): Line identifications were primarily from the Atomic Line List
(van Hoof, 2018Galax...6...63V 2018Galax...6...63V), supplemented by the extensive line lists
for NGC 7009 (Fang & Liu, 2011MNRAS.415..181F 2011MNRAS.415..181F, Cat. J/MNRAS/416/181) and
NGC 7027 (Zhang et al., 2005A&A...442..249Z 2005A&A...442..249Z, Cat. J/A+A/442/249, erratum
in 2007A&A...472..555Z 2007A&A...472..555Z ). If a line is identified, then the rest wavelength
is listed; if no identification was found, the wavelength is the observed
value, corrected for the systemic heliocentric radial velocity (+10km/s).
Note (2):
Observed H-beta normalising flux: 1.66x10-11±6.88x10-16erg/cm2/s
Dereddened H-beta normalising flux: 2.09x10-11±4.82x10-13erg/cm2/s
Extinction c=0.10±0.01 calculated with Te= 18000 K; Ne=1000.0cm-3
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- No Identification index
5- 9 F5.1 arcsec oRA Right Ascension offset position (1)
11- 15 F5.1 arcsec oDE Declination offset position (1)
17- 20 F4.2 arcsec2 Area Surface area
22- 27 I6 10-23W/m2 N2Fl Observed flux in [NII] 6583Å
(in 10-20erg/cm2/s)
29- 31 I3 km/s Vel Heliocentric radial velocity
33- 35 I3 km/s DelVel Radial velocity - local radial velocity
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Note (1): Delta right ascension and delta declination relative to the
position of the central star of NGC 4361 (12:24:39.75 -18:47:05.73)
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- No Identification index (1)
5- 12 E8.2 mW/m2 FHa Observed H-alpha flux (erg/cm2/s)
14- 18 F5.1 --- FHb Observed flux H-beta 4861Å (H-alpha=100)
20- 24 F5.1 --- FO3-4959 Observed flux [OIII] 4959Å (H-alpha=100)
26- 31 F6.1 --- FO3-5007 Observed flux [OIII] 5007Å (H-alpha=100)
33- 37 F5.1 --- FHe2-5412 Observed flux HeII 5412Å (H-alpha=100)
39- 42 F4.1 --- FN2-5755 Observed flux [NII] 5755Å (H-alpha=100)
44- 48 F5.1 --- FHe1-5876 Observed flux HeI 5876Å (H-alpha=100)
50- 55 F6.1 --- FO1-6300 Observed flux [OI] 6300Å (H-alpha=100)
57- 60 F4.1 --- FS3-6312 Observed flux [SIII] 6312Å (H-alpha=100)
62- 66 F5.1 --- FO1-6364 Observed flux [OI] 6364Å (H-alpha=100)
68- 72 F5.1 --- FN2-6583 Observed flux [NII] 6583Å (H-alpha=100)
74- 77 F4.1 --- FS2-6716 Observed flux [SII] 6716Å (H-alpha=100)
79- 83 F5.1 --- FS2-6731 Observed flux [SII] 6731Å (H-alpha=100)
85- 88 F4.1 --- FHe1-7065 Observed flux HeI 7065Å (H-alpha=100)
90- 94 F5.1 --- FAr3-7136 Observed flux [ArIII] 7136Å (H-alpha=100)
96- 99 F4.1 --- FO2-7319 Observed flux [OII] 7319Å (H-alpha=100)
101-105 F5.1 --- FO2-7330 Observed flux [OII] 7330Å (H-alpha=100)
107-111 F5.1 --- FAr5-7751 Observed flux [ArV] 7751Å (H-alpha=100)
113-117 F5.1 --- FS3-9069 Observed flux [SIII] 9069Å (H-alpha=100)
119-123 F5.1 --- FP9-9229 Observed flux H P09 9229Å (H-alpha=100)
125 A1 --- Qual Quality flag (A, B or C) (2)
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Note (1): Spectra are tabulated for all freckles with detectable H-alpha flux.
Note (2): Quality assessment flag (QuFl) of each spectrum is designated by A
(highest), B or C (lowest). See paper for details of the quality
assignment
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Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- No Identification index
5- 8 F4.2 --- N2/Ha Observed flux ratio [NII]6583/H-alpha
10- 14 F5.2 --- c Logarithmic extinction at H-beta
16- 20 I5 cm-3 S2Ne ? Electron density from [SII] 6716/6731Å
22- 26 I5 K N2Te ? Electron temperature from [NII] 5755/6583Å
28- 32 I5 K S3Te ? Electron temperature from [SIII] 6312/9069Å
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Byte-by-byte Description of file: table12.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- No [1/39] HII region identification index
4- 7 F4.1 arcsec oRA Right Ascension offset position (1)
9- 12 F4.1 arcsec oDE Declination offset position (1)
14- 17 F4.2 arcsec Radius Radius of HII region
19- 23 F5.1 Lsun LHa H-alpha luminosity (2)
25- 28 I4 km/s Vel ? Radial velocity (3)
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Note (1): Offset coordinates with respect to the V band centre of the galaxy
12:24:29.0 -18:47:07
Note (2): The H-alpha luminosity is based on a Hubble distance of 87.3Mpc.
Note (3): The radial velocity is given in the frame of the systemic velocity
of the galaxy, 6416km/s.
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Byte-by-byte Description of file: table14.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- No [1/39] HII region identification index
4- 8 E5.1 10-20W/m2 FHa HII region observed H-alpha flux (1)
10- 13 F4.1 10-20W/m2 e_FHa HII region observed H-alpha flux error
15- 19 F5.1 --- F5007 ? Observed [OIII] 5007A flux (H-alpha=100) (2)
21- 25 F5.1 --- e_F5007 ? Observed [OIII] 5007A flux error
(H-alpha=100)
27- 30 F4.1 --- F6583 ? Observed [NII] 6583A flux (H-alpha=100) (2)
32- 35 F4.1 --- e_F6583 ? Observed [N II] 6583A flux error
(H-alpha=100)
37- 40 F4.1 --- F6716 ? Observed [SII] 6716A flux (H-alpha=100) (2)
42- 45 F4.1 --- e_F6716 ? Observed [SII] 6716A flux error
(H-alpha=100)
47- 50 F4.2 --- Z ? Metallicity Z(O3/N2) 12 + log(O/H) (3)
52- 55 F4.2 --- e_Z ? Metallicity Z(O3/N2) error
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Note (1): Total flux of H-alpha (HaFl) in units of 10-17ergs/cm2/s
corrected for the extinction to NGC 4361
Note (2): Relative intensities of [OIII], [NII] and [SII] lines with
respect to H-alpha = 100.0
Note (3): Metallicity, Z, from O3N2 calibration (Marino et al.,
2013A&A...559A.114M 2013A&A...559A.114M, Cat. J/A+A/559/A114) for those HII regions where
H-alpha, [O III] and [N II] line fluxes measured
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Acknowledgements:
Jeremy R. Walsh, jwalsh(at)eso.org
(End) Jeremy R. Walsh [ESO], Patricia Vannier [CDS] 29-Aug-2024