J/A+A/601/A95 Star-forming dwarfs at intermediate-z in VUDS (Calabro+, 2017)
Characterization of star-forming dwarf galaxies at 0. 1 ~< z ~< 0. 9 in VUDS:
probing the low-mass end of the mass-metallicity relation.
Calabro A., Amorin R., Fontana A., Perez-Montero E., Lemaux B.C.,
Ribeiro B., Bardelli S., Castellano M., Contini T., de Barros S.,
Garilli B., Grazian A., Guaita L., Hathi N.P., Koekemoer A.M., Le Fevre O.,
Maccagni D., Pentericci L., Schaerer D., Talia M., Tasca L.A.M., Zucca E.
<Astron. Astrophys. 601, A95 (2017)>
=2017A&A...601A..95C 2017A&A...601A..95C (SIMBAD/NED BibCode)
ADC_Keywords: Galaxy catalogs ; Spectroscopy ; Abundances
Keywords: galaxies: evolution - galaxies: high redshift -
galaxies: dwarf - galaxies: abundances - galaxies: starbursts
Abstract:
We present emission line measurements and the main physical properties
of a sample of 164 star-forming dwarf galaxies (SFDGs) in the VIMOS
Ultra Deep Survey (VUDS, Le Fevre et al., 2015A&A...576A..79L 2015A&A...576A..79L). VUDS
is one of the largest programs on the ESO-VLT with 640 hours of
observing time, and covers a total of one square degree in three
separate fields: COSMOS, ECDFS, and VVDS-02h. The spectroscopic
observations were carried out at the VLT with the VIMOS Multi-Object
Spectrograph (MOS) with two grisms (LRBLUE and LRRED) covering a
wavelength range of 365<lambda<935nm at uniform spectral resolution of
R=180 and R=210, respectively. The integration time (on-source) is
∼14-hours per target for each grism, which allows to detect the
continuum at 850nm for iAB=25, and emission lines with an observed
flux limit F=1.5*10-18erg/s/cm2 at S/N∼5. Redshift measurements in
VUDS were performed using the EZ code (Garilli et al.,
2010PASP..122..827G 2010PASP..122..827G), both in automatic and manual modes (by two
persons independently) for each spectrum. The overall redshift
accuracy is dz/(1+z)=0.0005-0.0007. The spectra had already been fully
calibrated in wavelength and flux by the VUDS team, which also did the
sky subtraction. Emission lines fluxes and equivalent widths are
measured manually on a one-by- one basis using the task 'splot' of
IRAF by direct integration of the line profile after linear
subtraction of the continuum. These fluxes are given in units of
10-18erg/s/cm2. The uncertainties in the line measurements were
computed from the dispersion of values provided by multiple
measurements adopting different possible band-passes (free of lines
and strong residuals from sky subtraction) for the local continuum
determination, which is fitted using a second order polynomial. No
extinction correction has been applied to these fluxes. The EW
measurements of Hγ, Hβ and Hα lines have been already
corrected for absorption by +0.1nm for all galaxies, following Ly et
al. (2014ApJ...780..122L 2014ApJ...780..122L). For each galaxy the reddening constant,
c(Hβ), is presented. These values and their uncertainties have
been derived from the Hα/Hβ or Hγ/Hβ ratios,
whenever possible. We adopted the reddening constant from the best-fit
SED, using the relations of Calzetti et al. (2000ApJ...533..682C 2000ApJ...533..682C), for
(a) galaxies where the computation of c(Hβ) from emission lines
is not possible because the lines are not present, or (b) the line
ratios give a negative extinction correction (i.e.,
Hα/Hβ<2.82 or Hγ/Hβ<0.47, assuming Case B
recombination with Te=2*104K, ne=100cm-3).
Description:
Stellar masses (Ms) and 1-sigma uncertainties have been derived from
the SED fitting code Le Phare (Ilbert et al., 2006A&A...524A..76B 2006A&A...524A..76B). A
Chabrier (2003PASP..115..763C 2003PASP..115..763C) IMF and Calzetti et al.
(2000ApJ...533..682C 2000ApJ...533..682C) extinction law are adopted, while the
contribution of emission lines to the stellar templates have been
considered following Ilbert et al. (2009ApJ..690..1236I 2009ApJ..690..1236I). Typical
1-sigma uncertainties in Ms are ∼0.2dex and are obtained from the
median of the probability distribution function (PDF). Thus, they do
not account for possible systematic error (e.g., IMF variations). Star
formation rates have been derived from Hα or Hβ luminosity
(IMF from Chabrier et al. (2003PASP..115..763C 2003PASP..115..763C) and assuming a
theoretical ratio Hα/Hβ=2.82) following Kennicutt
(1998ApJ...498..541K 1998ApJ...498..541K). Uncertainties in SFR account for the
propagation of errors in line fluxes. Gas-phase metallicities,
ionization parameters, and their uncertainties, have been derived
using the code HII-CHI-mistry (HCm, Perez-Montero et al.,
2014MNRAS.441.2663P 2014MNRAS.441.2663P), which is based on the comparison between a set
of observed line ratios ([OII]3727,[OIII]4363,[OIII]5007,[NII]6584,
[SII]6717+6731, all relative to Hβ) and the predictions of
photoionization models. HCm provides abundances that are consistent
with those derived from the direct method. Morphological type for each
galaxy is based on HST-ACS F814W band images, available for COSMOS and
ECDFS fields, and follows the criteria of Amorin et al.
(2015A&A...578A.105A 2015A&A...578A.105A). The effective radius and axis ratio have been
derived on the same images using GALFIT (Peng et al.,
2002AJ....124..266P 2002AJ....124..266P, 2010AJ....139.2097P 2010AJ....139.2097P) , following the methodology
presented in Ribeiro et al. (2016A&A...593A..22R 2016A&A...593A..22R), in those cases when
no error is found in the fitting procedure. The gas surface densities
'sgas' and total gas masses 'Mgas' were derived by inverting an
assumedly non-variable Kennicutt-Schmidt (KS) law (Kennicutt & Evans,
2012ARA&A..50..531K 2012ARA&A..50..531K) with exponent n=1.4. Then, gas fractions are
calculated as: Mgas/(Mgas+Ms). For sgas and fgas, we should consider
an uncertainty of at least 0.2-0.3dex (∼ a factor of two), which comes
both from the uncertainties of the size and from the KS law.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 56 164 Positions, redshifts and selection magnitudes
tableb2.dat 183 164 Emission line fluxes and reddening
tableb3.dat 103 164 Derived physical properties of SFDGs in VUDS
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See also:
J/A+A/568/L8 : VUDS extreme emission line 0.2≲z≲0.9 galaxies (Amorin+, 2014)
J/A+A/572/A41 : VUDS Dicovery of a high-redshift protocluster (Lemaux+, 2014)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 I10 --- VUDS VUDS ID number
12- 21 F10.6 deg RAdeg Right ascension (J2000.0)
23- 32 F10.6 deg DEdeg Declination (J2000.0)
34- 39 F6.4 --- z Spectroscopic redshift
41- 46 F6.3 mag imag Selection magnitude (i-band) (AB)
48- 54 F7.3 mag iMAG ?=-99.990 Rest-frame absolute magnitude in the
i band (AB)
56 A1 --- Field [0-2] Field (1)
--------------------------------------------------------------------------------
Note (1): VUDS field as follows:
0 = COSMOS
1 = ECDFS
2 = VVDS-02h
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tableb2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 I10 --- VUDS VUDS ID number
12- 16 F5.1 10-21W/m2 F(3727) ?=-9.9 [OII]3727 line flux
18- 21 F4.1 10-21W/m2 e_F(3727) ?=-9.9 Error in [OII]3727 line flux
24- 28 F5.1 0.1nm EW(3727) ?=-9.9 [OII]3727 EW
30- 34 F5.1 0.1nm e_EW(3727) ?=-9.9 Error in [OII]3727 EW
36- 39 F4.1 10-21W/m2 F(3868) ?=-9.9 [NeIII]3868 line flux
41- 44 F4.1 10-21W/m2 e_F(3868) ?=-9.9 Error in [NeIII]3868 line flux
46- 49 F4.1 10-21W/m2 F(Hg) ?=-9.9 Hγ line flux
51- 54 F4.1 10-21W/m2 e_F(Hg) ?=-9.9 Error in Hg line flux
56- 59 F4.1 10-21W/m2 F(4363) ?=-9.9 [OIII]4363 line flux
61- 64 F4.1 10-21W/m2 e_F(4363) ?=-9.9 Error in [OIII]4363 line flux
66- 70 F5.1 10-21W/m2 F(Hb) ?=-9.9 Hβ line flux
72- 75 F4.1 10-21W/m2 e_F(Hb) ?=-9.9 Error in Hb line flux
77- 81 F5.1 0.1nm EW(Hb) ?=-9.9 Hβ EW
83- 87 F5.1 0.1nm e_EW(Hb) ?=-9.9 Error in Hb EW
89- 93 F5.1 10-21W/m2 F(4959) ?=-9.9 [OIII]4959 line flux
95- 98 F4.1 10-21W/m2 e_F(4959) ?=-9.9 Error in [OIII]4959 line flux
100-104 F5.1 10-21W/m2 F(5007) ?=-9.9 [OIII]5007 line flux
106-109 F4.1 10-21W/m2 e_F(5007) ?=-9.9 Error in [OIII]5007 line flux
111-116 F6.1 0.1nm EW(5007) ?=-9.9 [OIII]5007 EW
118-122 F5.1 0.1nm e_EW(5007) ?=-9.9 Error in [OIII]5007 EW
124-128 F5.1 10-21W/m2 F(Ha) ?=-9.9 Hα line flux
130-133 F4.1 10-21W/m2 e_F(Ha) ?=-9.9 Error in Ha line flux
135-139 F5.1 0.1nm EW(Ha) ?=-9.9 Hα EW
141-145 F5.1 0.1nm e_EW(Ha) ?=-9.9 Error in Ha EW
147-150 F4.1 10-21W/m2 F(6584) ?=-9.9 [NII]6584 line flux
152-155 F4.1 10-21W/m2 e_F(6584) ?=-9.9 Error in [NII]6584 line flux
157-160 F4.1 10-21W/m2 F(6717) ?=-9.9 [SII]6717 line flux
162-165 F4.1 10-21W/m2 e_F(6717) ?=-9.9 Error in [SII]6717 line flux
167-170 F4.1 10-21W/m2 F(6730) ?=-9.9 [SII]6730 line flux
172-175 F4.1 10-21W/m2 e_F(6730) ?=-9.9 Error in [SII]6730 line flux
177-181 F5.3 --- c(Hb) ?=-9.9 Reddening constant, c(Hb)
183 A1 --- n_c(Hb) [abc] Method for the reddening constant (1)
--------------------------------------------------------------------------------
Note (1): Method for the reddening constant as follows:
a = from Hα/Hβ
b = from Hγ/Hβ
c = from the SED best-fitting
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tableb3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 I10 --- VUDS VUDS ID number
12- 16 F5.2 [Msun] logMs ?=-9.9 Logarithm of stellar mass (2)
18- 22 F5.2 [Msun] e_logMs ?=-9.9 Uncertainty in stellar mass (3)
24- 29 F6.3 [Msun/yr] logSFR ?=-9.9 Logarithm of star formation rate (4)
31- 35 F5.3 [Msun/yr] e_logSFR ?=-9.9 Uncertainty in log_SFR (5)
37- 42 F6.3 kpc re ?=-9.9 Effective radius in i-band (6)
44- 49 F6.3 kpc e_re ?=-9.9 Uncertainty in effective radius (6)
51- 56 F6.3 --- q ?=-9.9 Axis ratio in i-band (6)(7)
58- 63 F6.3 --- e_q ?=-9.9 Uncertainty in axis ratio (6)
65- 71 F7.2 Msun/pc2 sgas ?=-9.9 Gas mass surface density (8)
73- 77 F5.2 --- fgas ?=-9.9 Gas fraction (8)(9)
79- 83 F5.2 --- Ab(O) ?=-9.9 Gas-phase metallicity 12+log(O/H) (10)
85- 89 F5.2 --- e_Ab(O) ?=-9.9 Uncertainty in metallicity (10)
91- 95 F5.2 --- log(U) ?=-9.9 Ionization parameter log(U) (10)
97-101 F5.2 --- e_log(U) ?=-9.9 Uncertainty in ionization
parameter (10)
103 A1 --- MType [0-6] Morphological Type (11)
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Note (2): We adopted a Chabrier IMF.
Note (3): They account for the statistical uncertainties in the SED fitting.
Note (4): It is computed from Hα or Hβ luminosity and adopting the
Kennicutt (1998ApJ...498..541K 1998ApJ...498..541K) calibration (by assuming a Chabrier et al.,
2003PASP..115..763C 2003PASP..115..763C) IMF and a theoretical ratio Hα/Hβ=2.82).
Note (5): 1-sigma error, it accounts for the propagation of errors in emission
line fluxes
Note (6): derived applying GALFIT to F814W-band ACS-HST images.
A value of -9.9 is given for those cases in which:
(a) GALFIT is not applied (VVDS-02h field) or
(b) GALFIT returns an error at the end of the fitting procedure
Note (7): Ratio between the minor and major axis of the ellipse enclosing half
of the total luminosity of the galaxy in the F814W filter
Note (8): derived inverting a Kennicutt-Schmidt law (Kennicutt & Evans,
2012ARA&A..50..531K 2012ARA&A..50..531K) with exponent n=1.4. From gas surface density, total gas
mass in solar units was calculated as: sgas*2pi(re_)2*106.
Note (9): derived from the total gas mass and total stellar mass as:
fgas=Mgas/(Mgas+Ms)
Note (10): derived using the code HII-CHI-mistry (Perez-Montero et al.,
2014MNRAS..441.2663P)
Note (11): Morphological Type as follows:
0 = Round/nucleated
1 = Tadpole/cometary
2 = Clumpy/Chain
3 = Merger/interacting
4 = Low surface brightness
5 = unresolved
6 = not available
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Acknowledgements:
Antonello Calabro, nillo2412(at)gmail.com
(End) Patricia Vannier [CDS] 14-Feb-2017