J/MNRAS/478/5579 Refined sample of Lyman excess H II regions (Marshall+, 2018)
A refined sample of Lyman excess H II regions.
Marshall B., Kerton C.R.
<Mon. Not. R. Astron. Soc., 478, 5579-5590 (2018)>
=2018MNRAS.478.5579M 2018MNRAS.478.5579M (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Millimetric/submm sources
Keywords: stars: early-type - stars: formation - H II regions
Abstract:
A large number (67) of the compact/ultra-compact HII regions
identified in the Coordinated Radio and Infrared Survey for High-Mass
Star Formation catalogue were determined to be powered by a Lyman
continuum flux in excess of what was expected given their
corresponding luminosity. In this study we attempt to reasonably
explain the Lyman excess phenomenon in as many of the 67 HII regions
as possible through a variety of observational and astrophysical means
including new luminosity estimates, new Herschel photometry, new
distance determinations, the use of different models for dust and
ionized gas covering factors, and the use of different stellar
calibrations. This phenomenon has been observed before; however, the
objects shown to exhibit this behaviour in the literature have
decidedly different physical properties than the regions in our
sample, and thus the origin of the excess is not the same. We find
that the excess can be reproduced using OB stellar atmosphere models
that have been slightly modified in the extreme ultraviolet. Though
the exact mechanism producing the excess is still uncertain, we do
find that a scaled up magnetospheric accretion model, often used to
explain similar emission from T Tauri stars, is unable to match our
observations. Our results suggest that the Lyman excess may be
associated with younger HII regions, and that it is more commonly
found in early B-type stars. Our refined sample of 24 Lyman excess HII
regions provides an ideal sample for comparative studies with regular
HII regions, and can act as the basis for the further detailed study
of individual regions.
Description:
The initial sample consists of the 67 HII regions that were
identified by C15 (Cesaroni et al. (2015A&A...579A..71C 2015A&A...579A..71C, Cat.
J/A+A/579/A71) as having an excess of LyC photons for a given
luminosity, out of the total 200 regions. Each of these sources has
been identified in the CORNISH catalogue as being either a compact or
ultra-compact HII region. The sources have NLy values consistent with
main sequence spectral types ranging from approximately B1 to earlier
than O6 for both the Panagia (1973AJ.....78..929P 1973AJ.....78..929P) calibration
(hereafter PAN73) and the more recent Conti, Crowther & Leitherer
(2008, From Luminous Hot Stars to Starburst Galaxies. Cambridge
University Press) calibration. The remaining HII regions catalogued in
C15 already lie outside of the forbidden region of the NLy-L plot,
and we do not consider them in detail any further.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 42 67 New flux densities for the 67 LERs categorized
by C15 ( Cesaroni et al., 2015A&A...579A..71C 2015A&A...579A..71C)
table4.dat 80 24 The refined sample of LERs
tablea1.dat 61 43 Sources removed from the original LER sample
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See also:
J/A+A/579/A71 : Infrared emission of young HII regions (Cesaroni+, 2015)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- C15 Cesaroni et al. (2015A&A...579A..71C 2015A&A...579A..71C,
Cat. J/A+A/579/A71) identification number
5- 11 F7.2 Jy S70um Flux density at 70um
13- 20 F8.3 Jy S160um Flux density at 160um
22- 28 F7.2 Jy S250um Flux density at 250um
30- 35 F6.2 Jy S350um Flux density at 350um
37- 42 F6.2 Jy S500um Flux density at 500um
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- C15 Cesaroni et al. (2015A&A...579A..71C 2015A&A...579A..71C,
Cat. J/A+A/579/A71) identification number
5- 21 A17 --- CORNISH CORNISH designation (GLLL.llll+BB.bbbb)
23- 29 F7.4 deg GLON Galactic longitude
31- 37 F7.4 deg GLAT Galactic latitude
39- 42 F4.2 [Lsun] logL log10 Luminosity
44- 48 F5.2 [s-1] log(NLy) log10 ionizing photon flux
50- 54 F5.2 kpc d Distance (reflect our new photometry and
new kinematic distances)
56- 59 F4.2 pc r Radius determined using Spitzer 8um images
61- 65 F5.2 10+3cm-3 ne Electron density
67- 69 A3 --- SpType ZAMS spectral type (1)
71- 75 F5.2 --- alpha ?=- Spectral index (2)
77- 80 F4.2 --- e_alpha ? Spectral index error (2)
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Note (1): Spectral type consistent with NLy from Panagia (1973AJ.....78..929P 1973AJ.....78..929P).
Note (2): The spectral index was calculated from data available in the
literature with the error associated with the data fit.
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- C15 Cesaroni et al. (2015A&A...579A..71C 2015A&A...579A..71C,
Cat. J/A+A/579/A71) identification number
5- 21 A17 --- CORNISH CORNISH designation (GLLL.llll+BB.bbbb)
23- 26 F4.2 [Lsun] logL log10 Luminosity
28- 32 F5.2 [s-1] logNLy log10 photon flux
34- 38 F5.2 kpc d Distance value based on our new photometry
and kinematic distance
40- 44 F5.2 10+3cm-3 ne Electron density
46- 61 A16 --- Notes Notes (1)
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Note (1): Indicates the factor(s) which recategorized the source as no longer
being a LER as follows:
P17 = is using new photometry at the MK18 (this paper) distance
P15 = is using new photometry at the C15 (Cesaroni et al.,
2015A&A...579A..71C 2015A&A...579A..71C) distance
S = is scaling the distance only
C = is using new photometry at the MK18 (this paper) distance and
a fc=0.8
PC = is reflective of a medium/low photometry confidence level
L15 = is using new luminosity calculated using C15 (Cesaroni et al.,
2015A&A...579A..71C 2015A&A...579A..71C) flux densities with C15 (Cesaroni et al.,
2015A&A...579A..71C 2015A&A...579A..71C) distances
L17 = is using new luminosity calculated using Cesaroni et al.
(2015A&A...579A..71C 2015A&A...579A..71C) flux densities with MK18 (this paper) distances
D = is using the ZAMS stellar parameters from Davies et al.
(2011MNRAS.416..972D 2011MNRAS.416..972D) only
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History:
From electronic version
(End) Patricia Vannier [CDS] 20-Jan-2022