J/AJ/161/191 Hα photometry in NGC 7020 (Dottori+, 2021)
The Population of HII regions in NGC 7020.
Dottori H., Diaz R.J., Grosbol P., Bueno A., Gimeno G.
<Astron. J., 161, 191 (2021)>
=2021AJ....161..191D 2021AJ....161..191D
ADC_Keywords: Galaxies; H II regions; Photometry, H-alpha
Keywords: Galaxies ; Galaxy nuclei ; H II regions ; Barred spiral galaxies ;
Narrow band photometry
Abstract:
The galaxy NGC7020 displays an exotic hexagonal ringlike central
structure with conspicuous ansae located at two opposite vertices and
a tenuous external ring populated by H ii regions. Inside and around
the hexagonal structure, Hα emission is also present at the
inner disk. To characterize the population of the HII regions, as well
as their ionizing clusters, we imaged NGC7020 with narrowband Hα
and nearby continuum filters attached to GMOS-S installed on the
Gemini South telescope. We found 202 HII regions or complexes of HII
regions evenly distributed between the outer ring and the central disk
The nucleus and ansae also present Hα emission. The equivalent
width of the Hα line (WHα) is systematically greater at
the regions of the outer ring relative to those of the inner disk. We
discuss the influence of the metallicity gradient of the disk and the
upper limit of the masses of the initial mass function on WHα,
and we conclude that the data are still consistent with the occurrence
of a younger burst of HII region formation in the outer ring. The
central regions present more massive clusters, M≳106M☉, than
those of the outer ring (M≲106M☉). Three clusters within 5" of
the nucleus present masses higher than 108M☉. The presence of
diffuse Hα emission in the inner 5" suggests gas flows in the
nuclear region.
Description:
The observations were carried out within the program GS-2007B-Q-236 on
the night of 2007 September 17 at Gemini South, with GMOS-S in imaging
mode. The spatial sampling was 0.146"/pixel (GMOS-S detector 2x2
binning).
The seeing during the observations for filters G0336 and G0337 was
0.99"±0.06", and for filter r', it was 1.09"±0.13". Due to the
galaxy redshift (z=0.0107), the emission line Hα falls within
the filter G0337, with practically maximum transmission, filter G0336
was used to observe the corresponding Hα continuum.
Objects:
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RA (2000) DE Designation(s)
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21 11 20.04 -64 01 31.994 NGC 7020 = NGC 7020
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 74 201 HII region physical parameters
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See also:
J/A+A/542/A39 : NIR photometry in 10 nearby spiral galaxies (Grosboel+, 2012)
J/A+A/587/A135 : Halpha images of NGC 6334 and NGC 6357 (Russeil+, 2016)
J/MNRAS/465/3461 : Halpha maps of 3 LIRGS (Zaragoza-Cardiel+, 2017)
J/A+A/644/A38 : Halpha images of stellar bars in galaxies (Diaz-Garcia+, 2020)
J/A+A/646/A139 : IC 3476 Halpha image (Boselli+, 2021)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/202] Sequential identifier
5- 10 F6.2 arcsec RAoff [-71.2/73.1] Offset Right Ascension from origin
12- 17 F6.2 arcsec DEoff [-68.7/76.2] Offset, Declination, from origin
19- 27 E9 W/m2 IHa [1.43E-19/1.17E-16] true Hα emission line
intensity
29- 36 E8 W/m2 e_IHa [3E-20/6E-19] Uncertainty in IHa
38- 45 E8 W/m2/nm FHa [4.68E-22/1.58E-15] Contamination corrected
flux, Hα
47- 55 E9 W/m2/nm e_FHa [1E-21/6E-18] Uncertainty in FHa
57- 62 F6.2 nm EWHa [0.02/791] Equivalent width, Hα
64- 70 F7.3 nm e_EWHa [0.01/928] Uncertainty in WHa
72- 72 A1 --- Note [*] *=See section 3.1 (7 occurrences)
74- 74 A1 --- Flag [an] a = ansae (2 occurrences), n = galactic
nucleus (1 occurrence)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 02-Aug-2021