Hα star formation rates for a sample of star-forming galaxies from SDSS (DR1)
A study of current star formation rates (SFRs) derived from Hα emission of ionized hydrogen for 1305 star-forming galaxies from the Sloan Digital Sky Survey (Data Release 1) is carried out. Current SFRs are derived from the Hα flux corrected for interstellar extinction and aperture. For a subsample...
Gespeichert in:
| Datum: | 2005 |
|---|---|
| Hauptverfasser: | , , |
| Format: | Artikel |
| Sprache: | English |
| Veröffentlicht: |
Головна астрономічна обсерваторія НАН України
2005
|
| Schriftenreihe: | Кинематика и физика небесных тел |
| Schlagworte: | |
| Online Zugang: | http://dspace.nbuv.gov.ua/handle/123456789/79654 |
| Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Zitieren: | Hα star formation rates for a sample of star-forming galaxies from SDSS (DR1) / I.Y. Izotova, S.L. Parnovsky, Y.I. Izotov // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 262-265. — Бібліогр.: 13 назв. — англ. |
Institution
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
irk-123456789-79654 |
|---|---|
| record_format |
dspace |
| spelling |
irk-123456789-796542015-04-04T03:01:40Z Hα star formation rates for a sample of star-forming galaxies from SDSS (DR1) Izotova, I.Y. Parnovsky, S.L. Izotov, Y.I. MS3: Physics of Stars and Galaxies A study of current star formation rates (SFRs) derived from Hα emission of ionized hydrogen for 1305 star-forming galaxies from the Sloan Digital Sky Survey (Data Release 1) is carried out. Current SFRs are derived from the Hα flux corrected for interstellar extinction and aperture. For a subsample of 45 galaxies the current SFRs are derived using simultaneously three parameters: the galaxy luminosity in the far infrared range (IRAS data), the monochromatic radio continuum luminosity at 1.4 GHz (NVSS data), and the Hα emission of ionized hydrogen (SDSS DR1 data). The results obtained are discussed and compared with the similar ones for the Markarian galaxies. 2005 Article Hα star formation rates for a sample of star-forming galaxies from SDSS (DR1) / I.Y. Izotova, S.L. Parnovsky, Y.I. Izotov // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 262-265. — Бібліогр.: 13 назв. — англ. 0233-7665 http://dspace.nbuv.gov.ua/handle/123456789/79654 en Кинематика и физика небесных тел Головна астрономічна обсерваторія НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| topic |
MS3: Physics of Stars and Galaxies MS3: Physics of Stars and Galaxies |
| spellingShingle |
MS3: Physics of Stars and Galaxies MS3: Physics of Stars and Galaxies Izotova, I.Y. Parnovsky, S.L. Izotov, Y.I. Hα star formation rates for a sample of star-forming galaxies from SDSS (DR1) Кинематика и физика небесных тел |
| description |
A study of current star formation rates (SFRs) derived from Hα emission of ionized hydrogen for 1305 star-forming galaxies from the Sloan Digital Sky Survey (Data Release 1) is carried out. Current SFRs are derived from the Hα flux corrected for interstellar extinction and aperture. For a subsample of 45 galaxies the current SFRs are derived using simultaneously three parameters: the galaxy luminosity in the far infrared range (IRAS data), the monochromatic radio continuum luminosity at 1.4 GHz (NVSS data), and the Hα emission of ionized hydrogen (SDSS DR1 data). The results obtained are discussed and compared with the similar ones for the Markarian galaxies. |
| format |
Article |
| author |
Izotova, I.Y. Parnovsky, S.L. Izotov, Y.I. |
| author_facet |
Izotova, I.Y. Parnovsky, S.L. Izotov, Y.I. |
| author_sort |
Izotova, I.Y. |
| title |
Hα star formation rates for a sample of star-forming galaxies from SDSS (DR1) |
| title_short |
Hα star formation rates for a sample of star-forming galaxies from SDSS (DR1) |
| title_full |
Hα star formation rates for a sample of star-forming galaxies from SDSS (DR1) |
| title_fullStr |
Hα star formation rates for a sample of star-forming galaxies from SDSS (DR1) |
| title_full_unstemmed |
Hα star formation rates for a sample of star-forming galaxies from SDSS (DR1) |
| title_sort |
hα star formation rates for a sample of star-forming galaxies from sdss (dr1) |
| publisher |
Головна астрономічна обсерваторія НАН України |
| publishDate |
2005 |
| topic_facet |
MS3: Physics of Stars and Galaxies |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/79654 |
| citation_txt |
Hα star formation rates for a sample of star-forming galaxies from SDSS (DR1) / I.Y. Izotova, S.L. Parnovsky, Y.I. Izotov // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 262-265. — Бібліогр.: 13 назв. — англ. |
| series |
Кинематика и физика небесных тел |
| work_keys_str_mv |
AT izotovaiy hastarformationratesforasampleofstarforminggalaxiesfromsdssdr1 AT parnovskysl hastarformationratesforasampleofstarforminggalaxiesfromsdssdr1 AT izotovyi hastarformationratesforasampleofstarforminggalaxiesfromsdssdr1 |
| first_indexed |
2025-07-06T03:40:45Z |
| last_indexed |
2025-07-06T03:40:45Z |
| _version_ |
1836867382615736320 |
| fulltext |
Hα STAR FORMATION RATES FOR A SAMPLE
OF STAR-FORMING GALAXIES FROM SDSS (DR1)
I. Y. Izotova1, S. L. Parnovsky1, Y. I. Izotov2
1Astronomical Observatory, National Taras Shevchenko University of Kyiv
3 Observatorna Str., 04053 Kyiv, Ukraine
e-mail: izotova@observ.univ.kiev.ua
2Main Astronomical Observatory, NAS of Ukraine
27 Akademika Zabolotnoho Str., 03680 Kyiv, Ukraine
A study of current star formation rates (SFRs) derived from Hα emission of ionized hydrogen
for 1305 star-forming galaxies from the Sloan Digital Sky Survey (Data Release 1) is carried out.
Current SFRs are derived from the Hα flux corrected for interstellar extinction and aperture. For
a subsample of 45 galaxies the current SFRs are derived using simultaneously three parameters:
the galaxy luminosity in the far infrared range (IRAS data), the monochromatic radio continuum
luminosity at 1.4 GHz (NVSS data), and the Hα emission of ionized hydrogen (SDSS DR1 data).
The results obtained are discussed and compared with the similar ones for the Markarian galaxies.
INTRODUCTION
Star formation in a galaxy is characterized by two main parameters: the initial mass function (IMF) and
the total star formation rate (SFR). The emission in the far infrared range (FIR), the radio continuum emission
at 1.4 GHz, and the Hα emission of ionized hydrogen are the main indicators of star-forming processes in
the galaxy. A star formation rate averaged over a timescale of 107–108 yr is defined as a current SFR. Studies
of current SFRs have been carried out in [4–6, 9–13]. In this paper we present a study of current SFRs for
a homogeneous sample of 1305 galaxies with active star formation processes using data from the Data Release 1
of the Sloan Digital Sky Survey (SDSS DR1). Throughout the paper we assume the Hubble constant to be
H0 = 75 km s−1 Mpc−1.
THE SAMPLE
The Sloan Digital Sky Survey is a photometric and spectroscopic survey which was carried out with a dedicated
2.5-m telescope at the Apache Point Observatory in New Mexico and was aimed to get a digital map of the North
Galactic Cap in the area of 10 000 deg2. The SDSS Data Release 1 [1] has been released in 2003. SDSS DR1
covers the sky region of 2099 deg2 with imaging data in five bands u, g, r, i, z (at wavelengths 3551 Å, 4886 Å,
6166 Å, 7480 Å, and 8932 Å, respectively), more than 180000 spectra of galaxies, quasars, and stars selected over
1360 deg2 of this area. The imaging data stretch to a depth of about r ∼ 22.6, the spectra cover the wavelength
interval 3800–9200 Å with a resolution of 1800–2100.
For SFRs study we use a sample of 1338 emission-line galaxies which were extracted from SDSS DR1
after an examination of all ∼ 180 000 spectra [8]. The galaxies from this sample have an emission feature at
the wavelength of the [O III] 4363. The presence of this emission line allows one to provide the direct model-
independent determination of the electron temperature and abundance. The Hα fluxes have been corrected for
interstellar extinction using the observed hydrogen Balmer emission-line fluxes [8] as well as for aperture effect.
The latter procedure is done using the ratio of the fluxes corresponding to the total galaxy magnitude m and
the magnitude m (3′′) “through the fiber” in the r band (for redshifts z < 0.04) and in the i band (for redshifts
z ≥ 0.04) (N = 1305). The fiber magnitude is taken from a photometric measurement in a 3′′ fiber aperture.
The aperture correction factor can be expressed as A = 10−0.4[mr,i−mr,i(3
′′)].
This galaxy sample was cross-identified with the NVSS sources [3] having the 1.4 GHz radio continuum
radiation and the IRAS/IRASF catalogue sources [7]. For this purpose, we combine NVSS, IRAS/IRASF,
NED1 data and SDSS images with due regard for size of radio sources. We have revealed that 100 galaxies
from our sample are NVSS sources, 102 galaxies are IRAS/IRASF sources, and 45 emission-line galaxies are
c© I. Y. Izotova, S. L. Parnovsky, Y. I. Izotov, 2004
1The NASA/IPAC Extragalactic Database operated by the Jet Propulsion Laboratory, California Institute of Technology.
262
Figure 1. (a) Distribution of the galaxy absolute magnitudes. (b) Redshift distribution for a sample of galaxies.
(c) Comparison of uncorrected values of SFR(Hα) derived from the luminosity in the Hα line of ionized hydrogen with
the corrected ones
Figure 2. (a) Distribution of SFRs derived from the luminosity in the Hα line of ionized hydrogen. (b) Distribution of
SFRs derived from the radio continuum emission at 1.4 GHz
the sources found both in NVSS and IRAS/IRASF. The distributions of the galaxy absolute magnitudes M
and redshifts z for the whole sample of 1338 galaxies are shown in Figs. 1a – 1b with a median M = −17.6 and
a median z = 0.046.
STAR FORMATION RATES
The current star formation rate can be obtained from the luminosity of a H II region in the Hα emission line or
in the radio continuum. For deriving of the SFRs, the free-free radiation in the radio continuum is preferable in
general because of negligible extinction in the radio range, but this method is limited by a lower sensitivity and
confusion with non-thermal sources. Both optical and radio methods suffer from absorption of Ly-c photons by
dust that re-radiates energy in the far infrared range. Following to the approach in [4, 6], we assume the Salpeter
IMF with a slope coefficient α = 2.35, low- and high- star mass cut-offs of 0.1 M� and 100 M�, respectively.
Then, the current SFR (averaged over star lifetime of ∼ 3 · 106 yr) is defined as
SFR(Hα) = 7.07 · 10−42L(Hα), (1)
where L(Hα) is the galaxy luminosity in the Hα emission line of ionized hydrogen corrected for interstellar
extinction and aperture effect, it is in erg s−1; SFR(Hα) is in M� yr−1.
It is assumed in Eq. (1) that 1/3 of the Ly-c flux is lost due to dust absorption or escapes from the galaxy.
The coefficient in the relation between SFR(Hα) and L(Hα) in Eq. (1) depends on the adopted IMF and
metallicity [13].
The luminosities L(Hα) corrected for interstellar extinction and aperture effect in individual galaxies are
a few times larger than the uncorrected ones (Fig. 1c). The individual SFRs(Hα) for the total sample vary in
a wide range of 10−3÷ 439.6 M�yr−1 with a median SFR(Hα) = 1.6 M�yr−1 (Fig. 2a).
To obtain SFR(1.4GHz), we assume that the radiation at 1.4 GHz is thermal [9]. In fact, a substantial
part of this radiation can be a non-thermal one produced by young supernovae or old supernovae remnants.
263
Figure 3. (a) The luminosity log L(FIR) dependence on the luminosity log L(1.4GHz). (b) The luminosity log L(1.4GHz)
dependence on the luminosity log L(Hα)
The fraction of thermal radiation is shown to be about 10% of the total flux for normal galaxies [2]. Taking
into account this fraction, we obtain in accordance with [9]:
SFR(1.4 GHz) = 2.5 · 106αL(1.4 GHz)/L� M�yr−1, (2)
where α = 0.1, L(1.4GHz)/L� = 3.07 · 10−7D2f1.4 is the galaxy radio continuum luminosity, D is the distance
in Mpc, f1.4 is the flux density in Jy.
We can derive the current SFR in the galaxy from its far infrared luminosity following to [12]:
SFR(FIR) = 6.5 · 10−10LFIR/L� M�yr−1. (3)
Eq. (3) is obtained assuming that UV radiation of the massive OB-stars is completely absorbed by dust and re-
emitted in the far-infrared range. The far infrared 60 μm and 100 μm emission flux densities from IRAS/IRASF
catalogues are used to derive the total galaxy FIR luminosity
LFIR/L� = 3.89 · 105[2.58 S60(Jy) + S100(Jy)]D2. (4)
Note that Eqs. (1) and (3) are obtained assuming the same IMF and masses, and star lifetime of ∼ 3 · 106 yr.
We derive the current SFR(FIR) and SFR(1.4GHz) for those galaxies from our sample of emission-
line galaxies from SDSS which match with sources from the IRAS/IRASF catalogues and NVSS data.
Similar to SFR(Hα), the individual values of the SFR(FIR) and SFR(1.4GHz) vary in the large inter-
vals: SFR(FIR) = 0.03 ÷ 162.1 M�yr−1 (N = 102) with a median SFR(FIR) = 2.8 M�yr−1 and
SFR(1.4GHz) = 0.02 ÷ 114.8 M�yr−1 (N = 100) with a median SFR(1.4GHz) = 4.2 M�yr−1 (Fig. 2b).
For comparison, H II galaxies from the First Byurakan Survey (FBS) detected by IRAS have a median
SFR(FIR)FBS = 16.1 M�yr−1 (N = 442), a median SFR(1.4GHz)FBS = 4.9 M�yr−1 (N = 435), in ac-
cordance with [10], if one takes into account the fraction of thermal radiation for normal galaxies from [2]. Thus
on the face of it, the SDSS emission-line galaxies are characterized by lower star formation rates derived from
FIR luminosities in comparison with the Markarian ones. This is mainly caused by the fact that Markarian
galaxies are brighter as compared with the SDSS emission-line ones and, hence, they are more metal-rich and
contain more dust.
The dependence of the 1.4 GHz luminosity on the FIR luminosity in log scale (Fig. 3a) for a SDSS galaxies
sample has the same tight linear correlation (with coefficient R = 0.92, slope of 1.02) as it was revealed earlier
for Markarian galaxies. Tight correlation implies the common origin of the FIR radiation and radio continuum
emission in the star-forming regions. However, contrary to expectations, no tight correlation was obtained
between the Hα luminosities and 1.4 GHz luminosities (Fig. 3b). The possible reason for such differences might
be due to the inhomogeneous distribution of dust in star-forming regions and uncertainties in the interstellar
extinction. Hα luminosity is most subject to this effect while the 1.4 GHz and FIR luminosities are not.
Some characteristics such as redshift z, absolute magnitude M(r) in the r band as well as SFR(Hα),
SFR(FIR), and SFR(1.4GHz) derived from Eqs. (1)–(3) for emission-line galaxies from SDSS and H II
Markarian galaxies detected by IRAS are shown in Table 1. In the paper by Hopkins et al. [5],
the current star formation rates based on the Hα, FIR, and 1.4 GHz luminosities are derived using
other relations between the SFRs and respective luminosities. Adopting Eqs. (1)–(2), (7)–(8) from [5]
264
we obtain for our sample: SFR(FIR)H = 0.07 ÷ 72.6 M�yr−1 with a median SFR(FIR)H = 1.4 M�yr−1;
SFR(1.4GHz)H = 0.07 ÷ 98 M�yr−1 with a median SFR(1.4GHz)H = 2.4 M�yr−1. Thus, calibrations used
in the present paper do not differ significantly from those used by Hopkins et al. [5].
Table 1. Comparison of SFRs and other characteristics for the SDSS emission-line galaxies and Markarian H II galaxies
SDSS emission-line galaxies Markarian H II galaxies (with FIR)
Parameter Interval Median Interval Median
z 0.000142÷ 0.538 0.046 0.001÷ 0.163 0.022
M(r) −8.7÷−21.8 −17.60 −15.7÷−22.2 −19.7
SFR(Hα), M�yr−1 10−3 ÷ 439.6 1.6 − −
SFR(FIR), M�yr−1 0.03÷ 162.1 2.8 0.2÷ 344.3 16.1
SFR(1.4GHz), M�yr−1 0.02÷ 114.8 4.2 0.3÷ 3.2 · 103 4.9
CONCLUSION
For a sample of the SDSS emission-line galaxies we derived the current star formation rates SFR(Hα), SFR(FIR),
SFR(1.4GHz) based on the following indicators: the Hα emission of ionized hydrogen, galaxy emission in the far
infrared range (60 μm and 100 μm), and radio continuum radiation at 1.4 GHz.
SDSS emission-line galaxies are shown to be characterized by lower star formation rates derived from FIR
luminosities in comparison with the Markarian galaxies. This difference is mainly because of the lower luminosi-
ties of the SDSS galaxies. Hence, SDSS galaxies are more metal-poor and contain less dust which is responsible
for FIR emission but not for the Hα or 1.4 GHz emission. The fact that the SFRs in SDSS galaxies derived
from the Hα luminosity are lower than SFRs(FIR), and SFRs(1.4GHz) implies the inhomogeneous distribution
of dust in star-forming regions. Therefore, the large fraction of Hα emission is probably hidden in the densest
central parts of star-forming regions due to higher interstellar extinction.
[1] Abazajian K., Adelman-McCarthy J. K., Agueros M. A., et al. The First Data Release of the Sloan Digital Sky
Survey // Astron. J.–2003.–126, N 4.–P. 2081–2086.
[2] Condon J. J. Radio emission from normal galaxies // Annu. Rev. Astron. and Astrophys.–1995.–30.–P. 575–611.
[3] Condon J. J., Cotton W. D., Greisen E. W., et al. The NRAO VLA Sky Survey // Astron. J.–1998.–115, N 5.–
P. 1693–1716.
[4] Gallagher III J. S., Hunter D. A., Tutukov A. V. Star formation histories of irregular galaxies // Astrophys.
J.–1984.–284, N 2.–P. 544–556.
[5] Hopkins A. M., Miller C. J., Nichol R. C., et al. Star Formation Rate Indicators in the Sloan Digital Sky Survey //
Astrophys. J.–2003.–599, N 2.–P. 971–991.
[6] Hunter D. A., Gallagher III J. S. Stellar populations and star formation in irregular galaxies // Publ. Astron. Soc.
Pacif.–1986.–98, N 1.–P. 5–28.
[7] IRAS catalog and Atlases: Explanatory Supplement / Eds C. A. Beichman, G. Neugebauer, H. J. Habing,
P. E. Clegg, T. J. Chester, 2004.–80 p.
[8] Izotov Y. I., Stasińska G., Guseva N. G., Thuan T. X. Abundance patterns in the low-metallicity emission-
line galaxies from the Early Data Release of the Sloan Digital Sky Survey // Astron. and Astrophys.–2004.–415,
N 1.–P. 87–94.
[9] Izotova I. Y., Izotov Y. I. Star formation rate in blue compact galaxies from the Second Byurakan Survey //
Kinematics and Physics of Celestial Bodies.–1999.–15, N 3.–P. 195–205.
[10] Izotova I. Y., Parnovsky S. L. Star formation rate in Markarian galaxies // Kinematics and Physics of Celestial
Bodies. Suppl. Ser.–2000.–N 3.–P. 99–100.
[11] Izotova I. Y., Parnovsky S. L., Izotov Y. I. Star Formation Rate in Starburst Galaxies // New Astron. Rev.–
2000.–44, N 3.–P. 283–285.
[12] Thronson H. A., Telesco C. H. Star formation in active dwarf galaxies // Astrophys. J.–1986.–311, N 1.–P. 98–112.
[13] Zasov A. V. The efficiency of star formation in spiral galaxies // Astron. Lett.–1995.–21, N 5.–P. 652–662.
265
|