J/MNRAS/494/4751 Light attenuation in star-forming regions (Molina+, 2020)
A cautionary tale of attenuation in star-forming regions.
Molina M., Ajgaonkar N., Yan R., Ciardullo R., Gronwall C., Eracleous M.,
Boquien M., Schneider D.P.
<Mon. Not. R. Astron. Soc., 494, 4751-4770 (2020)>
=2020MNRAS.494.4751M 2020MNRAS.494.4751M (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Star Forming Region ; Redshifts ; Positional data ;
Photometry, ultraviolet ; Spectra, optical
Keywords: dust, extinction - galaxies: general - galaxies: ISM
Abstract:
The attenuation of light from star-forming galaxies is correlated with
a multitude of physical parameters including star formation rate,
metallicity and total dust content. This variation in attenuation is
even more evident on kiloparsec scales, which is the relevant size for
many current spectroscopic integral field unit surveys. To understand
the cause of this variation, we present and analyse Swift/UVOT near-UV
(NUV) images and SDSS/MaNGA emission-line maps of 29 nearby (z<0.084)
star-forming galaxies. We resolve kiloparsec-sized star-forming
regions within the galaxies and compare their optical nebular
attenuation (i.e. the Balmer emission line optical depth,
τlB~τHβ-τHα) and NUV stellar continuum
attenuation (via the NUV power-law index, β) to the attenuation
law described by Battisti et al. We show the data agree with that
model, albeit with significant scatter. We explore the dependence of
the scatter of the β-τlB measurements from the
star-forming regions on different physical parameters, including
distance from the nucleus, star formation rate and total dust content.
Finally, we compare the measured τlB and β values for the
individual star-forming regions with those of the integrated galaxy
light. We find a strong variation in β between the kiloparsec
scale and the larger galaxy scale that is not seen in τlB. We
conclude that the sightline dependence of UV attenuation and the
reddening of β due to the light from older stellar populations
could contribute to the scatter in the β-τlB relation.
Description:
This paper explores a subset of a larger sample that was chosen to
study star formation and its quenching in the local Universe. Our
approach is to simultaneously analyse the near-UV (NUV) stellar
continuum and optical nebular emission lines across the faces of
galaxies, using data that are well matched in depth and physical
scale.
In order to simultaneously study NUV and optical properties, we
cross-referenced the MaNGA Product Launch 7 (MPL-7), corresponding to
the SDSS Data Release 15, or DR15 (Aguado et al. 2019ApJS..240...23A 2019ApJS..240...23A),
with the Swift/UVOT NUV archive as of 2018 April 26. UVOT is a 30cm
telescope that has a field of view (FOV) of 17arcminx17arcmin with an
effective plate scale of 1arcsec/pixel.
Since this project aims to study the NUV slope, we required that all
objects in our sample have UVOT images in both the uvw1 and uvw2
filters. We place a secondary constraint on the X-ray emission,
LX(2-10)keV~<1041erg/s, to exclude luminous active galactic nuclei
(AGNs), using the Swift X-ray Telescope (XRT) point source catalogue
(Evans et al. 2014ApJS..210....8E 2014ApJS..210....8E, Cat. IX/43). These requirements
produce a sample of 139 galaxies. From the sample of 139 galaxies, we
select 29 galaxies with SFRs appropriate for our study.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 152 29 Basic properties of star-forming galaxies and
UVOT images
table3.dat 68 56 Flux measurements of star-forming regions
table4.dat 75 56 Derived quantities of star-forming regions
tablea1.dat 43 56 Aperture Definitions for Star Forming Regions
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See also:
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020)
IX/43 : 1SXPS Swift X-ray telescope point source catalogue (Evans+ 2014)
II/298 : AKARI/FIS All-Sky Survey Point Source Catalogues (ISAS/JAXA, 2010)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID [1/29] Internal object
identifier
4- 27 A24 --- Name Galaxy name
29 A1 --- f_Name [*] Flag on Name (1)
31- 33 A3 --- Class SDSS galaxy classification (2)
35- 39 F5.3 --- z Redshift (3)
41- 45 F5.3 mag E(B-V) Extinction from Schlegel et al.
(1998ApJ...500..525S 1998ApJ...500..525S)
47- 50 F4.2 --- b/a Axial ratio (3)
52- 53 I2 arcsec Rpet Petrosian radius calculated
using the uvw2 filter
55- 59 F5.2 [Msun] logMass Logarithm of the stellar mass
(4)
61- 65 F5.2 [Msun/yr] logSFR Logarithm of the star formation
rate (5)
67- 71 I5 s tuvw2 Exposure time on the uvw2
filter
73- 77 I5 s tuvw1 Exposure time on the uvw1
filter
79- 82 F4.1 10-18W/m2/nm fuvw2 Minimum flux density detection
in the uvw2 filter (6)
84- 87 F4.1 10-18W/m2/nm fuvw1 Minimum flux density detection
in the uvw1 filter (6)
89- 93 F5.2 10-18W/m2/nm/arcsec2 Suvw2 Surface density in the uvw2
filter (7)
95- 98 F4.2 10-18W/m2/nm/arcsec2 e_Suvw2 Error on Suvw2
100- 104 F5.2 10-18W/m2/nm/arcsec2 Suvw1 Surface density in the uvw1
filter (7)
106- 109 F4.2 10-18W/m2/nm/arcsec2 e_Suvw1 Error on Suvw1
111- 115 F5.2 mag uvw2mag ? Swift uvw2 AB magnitude
without K-corrections
117- 120 F4.2 mag e_uvw2mag ? Error on uvw2mag
122- 126 F5.2 mag uvw1mag ? Swift uvw1 AB magnitude
without K-corrections
128- 131 F4.2 mag e_uvw1mag ? Error on uvw1mag
133- 137 F5.3 --- taulB ? Balmer emission line optical
depth τlB (8)
139- 143 F5.3 --- e_taulB ? Error on taulB (9)
145- 148 F4.1 --- beta ? NUV power-law index (8)
150- 152 F3.1 --- e_beta ? Error on beta (10)
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Note (1): Flag as follows:
* = The MaNGA IFU does not cover a majority of the galaxy disc, so no
{taui}lB,int and βint are reported
Note (2): The SDSS classification of the galaxy (Bolton et al.
2012AJ....144..144B 2012AJ....144..144B) as follows:
SB = Starburst
SF = Star-forming galaxy
G = Galaxy
Note (3): The redshift and b/a values are taken from the NASA-Sloan Atlas
(http://nsatlas.org; Blanton et al. 2011AJ....142...31B 2011AJ....142...31B)
Note (4): Stellar masses are taken from the SED fits from the MaNGA DRP
(Law et al. 2016AJ....152...83L 2016AJ....152...83L)
Note (5): The SFRs within 1Re using the Hα luminosity are drawn from
the MaNGA Data Analysis Pipeline (Westfall et al. 2019AJ....158..231W 2019AJ....158..231W)
Note (6): fuvw2 and fuvw1 represent the minimum flux density detections for a
point source with a diameter of 2.5arcsec at the redshift of the
galaxy with S/N=3
Note (7): The UV surface densities are calculated by dividing the integrated,
observed fluxes by the area of the integrated aperture
Note (8): The Balmer optical depth and UV spectral slope are for the integrated
light in the galaxy, see Section 4.2.3 for details
Note (9): The systematic uncertainty in the emission line flux as described by
Belfiore et al. (2019AJ....158..160B 2019AJ....158..160B) is included in the reported
error
Note (10): The systematic uncertainty of 0.03mag due to choice in foreground
attenuation curves is not included in these 1σ errors, as the
βSwift-β 'conversion' dominates the error budget.
See Section 4.3 for details.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID [1/29] Internal object identifier
4- 7 F4.1 --- Region Region identifier
9- 13 F5.1 10-19W/m2/nm Fuvw2 Flux density for the Swift uvw2 filter
(1)
15- 17 F3.1 10-19W/m2/nm e_Fuvw2 Error on Fuvw2
19- 22 F4.1 10-19W/m2/nm Fuvw1 Flux density for the Swift uvw1 filter
(1)
24- 26 F3.1 10-19W/m2/nm e_Fuvw1 Error on Fuvw1
28- 30 I3 10-17mW/m2 FHb Flux on the Hβ λ4861 line
corrected for foreground extinction
32 I1 10-17mW/m2 e_FHb Error on FHb (2)
34- 36 I3 10-17mW/m2 FO3 Flux on the [OIII]λ5007 line
corrected for foreground extinction
38 I1 10-17mW/m2 e_FO3 Error on FO3 (2)
40- 41 I2 10-17mW/m2 FO1 Flux on the [OI]λ6300 line
corrected for foreground extinction
43 I1 10-17mW/m2 e_FO1 Error on FO1 (2)
45- 48 I4 10-17mW/m2 FHa Flux on the Hα λ6563 line
corrected for foreground extinction
50 I1 10-17mW/m2 e_FHa Error on FHa (2)
52- 54 I3 10-17mW/m2 FN2 Flux on the [NII]λ6583 line
corrected for foreground extinction
56 I1 10-17mW/m2 e_FN2 Error on FN2 (2)
58- 60 I3 10-17mW/m2 FS26716 Flux on the [SII]λ6716 line
corrected for foreground extinction
62 I1 10-17mW/m2 e_FS26716 Error on FS26716 (2)
64- 66 I3 10-17mW/m2 FS26731 Flux on the [SII]λ6731 line
corrected for foreground extinction
68 I1 10-17mW/m2 e_FS26731 Error on FS26731 (2)
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Note (1): Swift flux densities are given without a K-correction, but are
corrected for foreground extinction
Note (2): The systematic uncertainty in emission line flux as described by
Belfiore et al. (2019AJ....158..160B 2019AJ....158..160B) is included in the reported
error
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 F4.1 --- Region Region identifier
6- 8 F3.1 kpc Dist Difference between the nuclear
coordinate of the galaxy and the
centre of the region's aperture
10- 13 F4.1 kpc2 Area Area
15- 20 F6.3 [10-7W/kpc2] logSHa Logarithm of the Hα surface
brightness
22- 26 F5.3 [10-7W/kpc2] e_logSHa Error on logSHa
28- 31 F4.1 --- beta NUV power-law index β
33- 35 F3.1 --- e_beta Error on beta
37- 41 F5.3 --- taulB Balmer emission line optical depth
τlB
43- 47 F5.3 --- e_taulB Error on taulB (1)
49- 51 F3.1 --- log[O/H] Oxygen abundance (2)
53- 55 F3.1 --- e_log[O/H] Error on 12+log[O/H] (3)
57- 60 F4.2 --- Dn(4000) Dn(4000) spectroscopic index
62- 65 F4.2 --- e_Dn(4000) Error on Dn(4000) (4)
67- 71 F5.1 0.1nm EW(Ha) Hα equivalent width
73- 75 F3.1 0.1nm e_EW(Ha) Error on EW(Ha) (1)
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Note (1): The systematic uncertainty in emission line flux as described by
Belfiore et al. (2019AJ....158..160B 2019AJ....158..160B) is included in the reported
error
Note (2): Metallicity is calculated using the ([OIII]/Hβ)/([NII]/Hα)
ratio as described in as described in Pettini & Pagel
(2004MNRAS.348L..59P 2004MNRAS.348L..59P), and converted to Tremonti et al.
(2004ApJ...613..898T 2004ApJ...613..898T) via Kewley & Ellison (2008ApJ...681.1183K 2008ApJ...681.1183K)
Note (3): The error bar includes the 0.3dex uncertainty in the Pettini & Pagel
(2004MNRAS.348L..59P 2004MNRAS.348L..59P) relation, which is the largest uncertainty
associated with the measurement. See Section 6.3 for details.
Note (4): The systematic uncertainty in Dn(4000) as described by Westfall et al.
(2019AJ....158..231W 2019AJ....158..231W) is included in the reported error
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Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 F4.1 --- Region Region identifier
6- 14 F9.5 deg RAdeg Right ascension (J2000)
16- 23 F8.5 deg DEdeg Declination (J2000)
25- 31 F7.5 arcsec a Aperture size
33- 39 F7.5 --- b/a Axial ratio
41- 43 I3 deg theta ? Aperture position angle
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 02-Jun-2023