J/ApJ/892/23 Pa-beta, Ha and attenuation in NGC5194 & NGC6946 (Kessler+, 2020)
Paβ, Hα, and attenuation in NGC 5194 and NGC 6946.
Kessler S., Leroy A., Querejeta M., Murphy E., Rebolledo D., Sandstrom K.,
Schinnerer E., Wong T.
<Astrophys. J., 892, 23-23 (2020)>
=2020ApJ...892...23K 2020ApJ...892...23K (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby; Photometry, H-alpha; Infrared; Extinction;
Interstellar medium
Keywords: Galaxies; Interstellar dust extinction; Star formation
Abstract:
We combine Hubble Space Telescope Paschen β (Paβ) imaging
with ground-based, previously published Hα maps to estimate the
attenuation affecting Hα, A(Hα), across the nearby,
face-on galaxies NGC 5194 and NGC 6946. We estimate A(Hα) in
∼2000 independent 2" ∼75pc diameter apertures in each galaxy, spanning
out to a galactocentric radius of almost 10kpc. In both galaxies,
A(Hα) drops with radius, with a bright, high-attenuation inner
region, though in detail the profiles differ between the two galaxies.
Regions with the highest attenuation-corrected Hα luminosity
show the highest attenuation, but the observed Hα luminosity of
a region is not a good predictor of attenuation in our data.
Consistent with much previous work, the IR-to-Hα color does a
good job of predicting A(Hα). We calculate the best-fit
empirical coefficients for use combining Hα with 8, 12, 24, 70,
or 100µm to correct for attenuation. These agree well with previous
work, but we also measure significant scatter around each of these
linear relations. The local atomic plus molecular gas column density,
N(H), also predicts A(Hα) well. We show that a screen with
magnitude ∼0.2 times that expected for a Milky Way gas-to-dust value
does a reasonable job of explaining A(Hα) as a function of N(H).
This could be expected if only ∼40% of gas and dust directly overlap
regions of Hα emission.
Description:
We observed NGC 6946 (Proposal ID 14156) in Paβ with HST/WFC3.
NGC 5194 was observed in Paβ by HST as part of Proposal 12490
(P.I.: J. Koda). We retrieve these data from the archive.
Both observations used WFC3's F110W (wide J) and F128N (narrow
Paβ; peak wavelength of 1.284um and FWHM of 0.0128um) filters and
have a native point-spread function (PSF) of 0.1".
We combine archival narrowband Hα images with our Paβ maps
to estimate the amount of dust attenuation in each region.
See Section 2.3.
We compare the attenuation estimated from recombination lines to
archival maps of IR emission at 8-100um. Both galaxies were
observed by Spitzer at 8 and 24um as part of SINGS
(Kennicutt+ 2003PASP..115..928K 2003PASP..115..928K).
NGC 6946 was observed at 70 and 100um by Herschel as part of KINGFISH
(Kennicutt+ 2011PASP..123.1347K 2011PASP..123.1347K). NGC 5194 was also observed by
Herschel as part of the Very Nearby Galaxy Survey (VNGS;
Bendo+ 2012, J/MNRAS/423/197 and Mentuch Cooper+ 2012ApJ...755..165M 2012ApJ...755..165M)
but only at 70um.
We also compare to 12um data from WISE, using the maps constructed
by Leroy+ (2019ApJS..244...24L 2019ApJS..244...24L).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 134 1822 Measured line luminosities and estimated
attenuation in NGC 6946
table3.dat 123 2075 Measured line luminosities and estimated
attenuation in NGC 5194
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/MNRAS/423/197 : MIPS photometry for Herschel SAG2 Programs (Bendo+, 2012)
J/ApJ/864/136 : Star-forming regions multiwavelength study (Binder+, 2018)
J/ApJ/704/842 : VIRUS-P spectroscopy of NGC 5194 (Blanc+, 2009)
J/ApJ/633/871 : Positions & photometry of HII knots in M51 (Calzetti+, 2005)
J/ApJ/714/1256 : Far-IR star formation rate indicators (Calzetti+, 2010)
J/A+A/584/A87 : CALIFA sample SFR calibration (Catalan-Torrecilla+, 2015)
J/ApJ/784/3 : The PAWS catalogs of GMCs and islands in M51 (Colombo+, 2014)
J/ApJ/808/42 : Abundances of Spirals (CHAOS) II. M51 (Croxall+, 2015)
J/MNRAS/388/500 : GHASP: Hα data cubes for 108 galaxies (Epinat+, 2008)
J/ApJ/671/333 : Aperture photometry in NGC 5194 (Kennicutt+, 2007)
J/ApJ/875/85 : SNRSs opt. search in NGC6946 with WIYN & GMOS (Long+, 2019)
J/ApJ/761/97 : Star Formation in Radio Survey (SFRS): 33GHz (Murphy+, 2012)
J/ApJS/234/24 : VLA 33GHz obs. of star-forming regions (Murphy+, 2018)
J/AJ/156/18 : Binary companions of evolved stars (Price-Whelan+, 2018)
J/A+A/625/A19 : 33 GHz continuum map of M51 (Querejeta+, 2019)
J/ApJ/656/770 : Mid-IR spectrum of star-forming galaxies (Smith+, 2007)
J/AJ/136/2563 : HI Nearby Galaxy Survey, THINGS (Walter+, 2008)
Byte-by-byte Description of file: table[23].dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq Internal index identifier
6- 13 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
15- 21 F7.4 deg DEdeg Declination in decimal degrees (J2000)
23- 32 E10.4 10-7W LHa Hα luminosity; erg/s (1)
34- 43 E10.4 10-7W e_LHa Uncertainty in LHa ; erg/s (1)
45- 54 E10.4 10-7W LPab Paβ luminosity; erg/s (1)
56- 65 E10.4 10-7W e_LPab Uncertainty in LPab; erg/s (1)
67- 72 F6.4 mag AHa [0.0009/9.9] Hα attenuation (1)
74- 79 F6.4 mag e_AHa [0.02/3.7] Uncertainty in AHa (1)
81- 90 E10.4 --- Ha/24um [0.0003/0.3] Hα to Spitzer 24um band
ratio
92-101 E10.4 --- Ha/70um Hα to Herschel 70 micron band ratio
103-112 E10.4 --- Ha/8um [0.0002/0.09] Hα to Spitzer 8um band
ratio
114-123 E10.4 --- Ha/12um [0.0007/0.3] Hα to WISE 12um band ratio
125-134 E10.4 --- Ha/100um [0.0001/0.06]? Hα to Herschel 100um
band ratio (only for NGC 6946)
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Note (1): Luminosities and estimated attenuation for 2" diameter apertures.
Luminosities assume the distances in Table 1:
8.58±0.10Mpc for NGC5194 (McQuinn+ 2016ApJ...826...21M 2016ApJ...826...21M) and
7.72±0.32Mpc for NGC6946 (Anand+ 2018AJ....156..105A 2018AJ....156..105A and
Eldridge & Xiao 2019MNRAS.485L..58E 2019MNRAS.485L..58E).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 11-Aug-2021