J/AJ/109/2503 Synthesis model in HII regions. II. (Mayya 1995)
Embedded clusters in giant extragalactic H II regions. II.
Evolutionary population synthesis model
Mayya Y.D.
<Astron. J. 109, 2503 (1995)>
=1995AJ....109.2503M 1995AJ....109.2503M
ADC_Keywords: H II regions ; Models, evolutionary
Abstract:
A stellar population synthesis model, suitable for comparison with
Giant Extragalactic H II Regions (GEHRs), is constructed incorporating
the recent developments in modeling stellar evolution by Maeder and
co-workers and stellar atmospheres by Kurucz. A number of quantities
suitable for comparison with broadband data of GEHRs in visible and
near-infrared parts of the spectrum are synthesized in addition to the
hydrogen and helium ionizing photon production rates at solar
metallicities, for three scenarios of star formation -
(i) instantaneous burst (IB); (ii) continuous star formation (CSF);
and (iii) two bursts of star formation, with the older burst rich in
red supergiants. For the IB case, evolution of color indexes shows
three distinct phases - an initial steady blue phase, followed by a
red bump (5-15Myr) and another steady phase with color indexes
intermediate to the earlier two phases. CSF color indexes
asymptotically reach peak values at ∼10Myr, never reaching the reddest
IB color indexes. Ionizing photon production rate falls off by an order
of magnitude in 6Myr for IB, whereas it almost remains constant for
the CSF model. Two-burst models with burst separations ∼10Myr have
properties of both IB and CSF, simultaneously producing the red IB
color indexes and high ionizing photon rate, making such regions easily
distinguishable using optical observations. Flat IMFs result in bluest
color indexes when the massive stars are on the main sequence and
reddest color indexes during the red supergiant phase of the evolving
massive stars. Errors on the computed quantities due to the
statistical uncertainties inherent in the process of star formation
become negligible for cluster masses in excess of 10^5 M☉. Our
GEHR spectra in the range 200nm to 3um are found to be in good
agreement with the computations of
Mas-Hesse & Kunth (1991A&AS...88..399M 1991A&AS...88..399M)
Description:
Tables 3, 4, and 5 are given. Each table has been split into three
parts, a, b, and c, where each part includes derived quantities for
Initial Mass Functions (IMF) defined by slope, lower cutoff (Ml),
and upper cutoff (Mu), as follows:
part a: slope = 2.5, Ml = 1, Mu = 60
part b: slope = 3.5, Ml = 1, Mu = 30
part c: slope = 1.0, Ml = 1, Mu = 120
Tabulated quantities are smoothed over a period of 0.5Myr to
suppress the short term fluctuations on the computer quantities.
For the continuous star-formation model, constant star-formation
rate (SFR) is assumed in computations of the tabulated quantities.
Table 5 give the ages of the young and old bursts for the
two-burst models.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3a.dat 97 41 Derived quantities for star clusters with IB
table3b.dat 97 41 Derived quantities for star clusters with IB
table3c.dat 97 41 Derived quantities for star clusters with IB
table4a.dat 97 41 Derived quantities for star clusters with CSF
table4b.dat 97 41 Derived quantities for star clusters with CSF
table4c.dat 97 41 Derived quantities for star clusters with CSF
table5a.dat 104 68 Der. quantities for star clusters w/ two bursts
table5b.dat 104 68 Der. quantities for star clusters w/ two bursts
table5c.dat 104 68 Der. quantities for star clusters w/ two bursts
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Byte-by-byte Description of file: table3?.dat table4?.dat
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Bytes Format Units Label Explanations
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1- 5 F5.2 Myr Age Age of the cluster
7- 12 F6.2 solMass/solLum M/L Ratio of total mass to bolometric lum.
14- 19 F6.2 solMass/solLum M/Lv Ratio of total mass to visual luminosity
21- 26 F6.2 ph/s/solMass NLy Lyman continuum photon production rate
per unit mass of the cluster
28- 33 F6.2 --- fHe Fraction of hydrogen ionizing photons
which are capable of ionizing helium
35- 40 F6.2 --- Phi/Lb Ratio of expected Hbeta to blue band
luminosity (1)
42- 47 F6.2 mag B-V B-V color index
49- 54 F6.2 mag V-R V-R color index
56- 61 F6.2 mag V-I V-I color index
63- 68 F6.2 mag J-H J-H color index
70- 75 F6.2 mag H-K H-K color index
77- 82 F6.2 mag V-K V-K color index
84- 89 F6.2 0.1nm WHb Hbeta equivalent width (2)
91- 97 F7.2 0.1nm WHa Halpha equivalent width (2)
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Note (1): Lyman continuum photon rate NL is also expressed in units or
expected Hbeta luminosity φ from a nebula at 10,000K, and defined
as: φ=4.78x10-13NL. φ in this equation has dimensions
or erg/s/M☉, and NL in ph/s/M☉.
Note (2): Equivalent widths assuming a gas temperature of 10,000K.
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Byte-by-byte Description of file: table5?.dat
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Bytes Format Units Label Explanations
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1- 5 F5.2 Myr T(yng) Age of the younger burst
7- 12 F6.2 Myr T(old) Age of the older burst
14- 19 F6.2 solMass/solLum M/L Ratio of total mass to bolometric lum.
21- 26 F6.2 solMass/solLum M/Lv Ratio of total mass to visual luminosity
28- 33 F6.2 ph/s/solMass NLy Lyman continuum photon production rate
per unit mass of the cluster
35- 40 F6.2 --- fHe Fraction of hydrogen ionizing photons
which are capable of ionizing helium
42- 47 F6.2 --- Phi/Lb Ratio of expected Hbeta to blue band
lum.(1)
49- 54 F6.2 mag B-V B-V color index
56- 61 F6.2 mag V-R V-R color index
63- 68 F6.2 mag V-I V-I color index
70- 75 F6.2 mag J-H J-H color index
77- 82 F6.2 mag H-K H-K color index
84- 89 F6.2 mag V-K V-K color index
91- 96 F6.2 0.1nm WHb Hbeta emission line equivalent width (2)
98-104 F7.2 0.1nm WHa Halpha emission line equivalent width (2)
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Note (1): Lyman continuum photon rate NL is also expressed in units or
expected Hbeta luminosity φ from a nebula at 10,000K, and defined
as: φ=4.78x10-13NL. φ in this equation has dimensions
or erg/s/M☉, and NL in ph/s/M☉.
Note (2): Equivalent widths assuming a gas temperature of 10,000K.
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Origin: AAS CD-ROM series, Volume 5, 1995 Lee Brotzman [ADS] 19-Jul-1995
References:
Mayya, Paper I. =1994AJ....108.1276M 1994AJ....108.1276M
Mayya & Prabhu, Paper III. =1996AJ....111.1252M 1996AJ....111.1252M
(End) [CDS] 09-Jan-1996