J/ApJ/910/95 METAL Hubble prog. II. LMC dust-to-gas ratio (Roman-Duval+, 2021)
METAL: The Metal Evolution, Transport, and Abundance in the Large Magellanic
Cloud Hubble program.
II. Variations of interstellar depletions and dust-to-gas ratio within the LMC.
Roman-Duval J., Jenkins E.B., Tchernyshyov K., Williams B., Clark C.J.R.,
Gordon K.D., Meixner M., Hagen L., Peek J., Sandstrom K., Werk J.,
Yanchulova Merica-Jones P.
<Astrophys. J., 910, 95 (2021)>
=2021ApJ...910...95R 2021ApJ...910...95R
ADC_Keywords: Spectra, ultraviolet; Interstellar medium; Equivalent widths;
Abundances; Magellanic Clouds
Keywords: Interstellar medium ; Interstellar line absorption ;
Interstellar abundances ; Interstellar atomic gas ;
Interstellar dust ; Interstellar phases ; Metallicity ;
Chemical abundances ; Local Group ; Chemical enrichment ;
Galaxy chemical evolution
Abstract:
A key component of the baryon cycle in galaxies is the depletion of
metals from the gas to the dust phase in the neutral interstellar
medium (ISM). The METAL (Metal Evolution, Transport, and Abundance in
the Large Magellanic Cloud) program on the Hubble Space Telescope
acquired UV spectra toward 32 sight lines in the half-solar
metallicity LMC, from which we derive interstellar depletions
(gas-phase fractions) of Mg, Si, Fe, Ni, S, Zn, Cr, and Cu. The
depletions of different elements are tightly correlated, indicating a
common origin. Hydrogen column density is the main driver for
depletion variations. Correlations are weaker with volume density,
probed by CI fine-structure lines, and distance to the LMC center. The
latter correlation results from an east-west variation of the
gas-phase metallicity. Gas in the east, compressed side of the LMC
encompassing 30 Doradus and the southeast HI over-density is enriched
by up to +0.3dex, while gas in the west side is metal deficient by up
to -0.5dex. Within the parameter space probed by METAL, no correlation
with molecular fraction or radiation-field intensity are found. We
confirm the factor of three to four increase in dust-to-metal and
dust-to-gas ratios between the diffuse (logN(H)∼20cm-2) and
molecular (logN(H)∼22cm-2) ISM observed from far-infrared, 21cm, and
CO observations. The variations of dust-to-metal and dust-to-gas
ratios with column density have important implications for the
sub-grid physics of chemical evolution, gas and dust mass estimates
throughout cosmic times, and for the chemical enrichment of the
Universe measured via spectroscopy of damped Lyα systems.
Description:
The details of the observing strategy, sample properties, and survey
parameters were covered in the Metal Evolution, Transport, and
Abundance in the Large Magellanic Cloud (METAL) Survey paper
(see Paper I; Roman-Duval+ 2019, J/ApJ/871/151).
In short, this study of interstellar depletions in the LMC is based on
STIS and COS medium-resolution spectra of 32 massive stars, obtained
predominantly as part of the METAL large HST program (GO-14675), but
also from archival HST spectra of the same target sample (DOI
10.17909/t9-g6d9-rj76). The target sample used in this analysis is
listed in Table 1. The complete list of medium-resolution spectra used
in this analysis, including the program IDs of archival data, is
included in Paper I.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 65 32 Spectroscopic targets and their interstellar
parameters
table3.dat 61 454 Equivalent widths and individual AOD and column
density measurements for the STIS observations
table5.dat 70 257 Column densities and depletions
table6.dat 101 32 Measurements of the CI, CI*, and CI** column
densities and ratios, derived radiation fields,
volume densities, and electron densities
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See also:
J/AJ/132/1630 : CaII spectroscopy in MC clusters (Grocholski+, 2006)
J/AJ/132/2268 : SAGE calibration stars (Meixner+, 2006)
J/A+A/471/625 : VLT-FLAMES survey of massive stars (Trundle+, 2007)
J/ApJS/176/59 : FUSE survey of OVI in the MW disk (Bowen+, 2008)
J/ApJ/700/1299 : Gas-phase element depletions in the ISM (Jenkins, 2009)
J/MNRAS/404/1321 : TiII in Milky way and Magellanic clouds (Welty+, 2010)
J/ApJ/734/65 : CI radial velocities with HST/STIS (Jenkins+, 2011)
J/ApJ/755/89 : Metallicities of damped Lyα systems (Rafelski+, 2012)
J/ApJ/753/71 : Mass-loss return from LMC evolved stars. VI. (Riebel+, 2012)
J/ApJ/745/173 : UV absorption sight lines of LMC and SMC (Welty+, 2012)
J/ApJ/780/76 : SII energy levels and line strengths (Kisielius+, 2014)
J/ApJ/804/76 : ZnII lines and collision strengths (Kisielius+, 2015)
J/ApJ/811/78 : Elemental depletions in the MCs (Tchernyshyov+, 2015)
J/MNRAS/457/2814 : SAGE SMC evolved stars candidates (Srinivasan+, 2016)
J/A+A/606/A50 : Fe-rich silicate analogues (Demyk+, 2017)
J/ApJS/236/36 : Ga, Ge, As, Kr, Cd, Sn & Pb col. densities (Ritchey+, 2018)
J/A+A/623/A5 : DustPedia metallicities and HI masses (De Vis+, 2019)
J/ApJ/871/151 : METAL Hubble program. I. (Roman-Duval+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Target Target or Sight-line
11- 12 I2 h RAh [4/5] Hour of Right Ascension (J2000)
14- 15 I2 min RAm Minute of Right Ascension (J2000)
17- 22 F6.3 s RAs Second of Right Ascension (J2000)
24- 24 A1 --- DE- Sign of the Declination (J2000)
25- 26 I2 deg DEd [65/71] Degree of Declination (J2000)
28- 29 I2 arcmin DEm Arcminute of Declination (J2000)
31- 35 F5.2 arcsec DEs Arcsecond of Declination (J2000)
37- 40 F4.2 mag E(B-V) [0.08/0.4] E(B-V) color excess
42- 46 F5.2 [cm-2] logN(HI) [19.57/21.85] log of LMC HI column density
(1)
48- 51 F4.2 [cm-2] e_logN(HI) [0.02/0.7] Uncertainty in logN(HI)LMC
53- 57 F5.2 [cm-2] logN(H2) [13.98/20.95] log of LMC H2 column
density (2)
59- 61 I3 km/s Vhelio-min [180/240] Heliocentric velocity range, min
63- 65 I3 km/s Vhelio-max [270/370] Heliocentric velocity range, max
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Note (1): HI column densities are from Roman-Duval+ (2019, J/ApJ/871/151)
Note (2): H2 column densities are from Welty+ (2012, J/ApJ/745/173)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Target Target or Sight-line
11- 11 A1 --- Grat Grating
13- 16 A4 --- El Element
18- 25 F8.3 0.1nm lambda [1152.81/2260.78]? Wavelength
27- 32 F6.3 [0.1nm] logfl [-2.81/3.11]? log oscillator strength,
logλf_λ in Angstrom units
34- 38 F5.1 0.1pm EW [-21.2/387.1]? Equivalent width, mÅ unit
40- 43 F4.1 0.1pm e_EW [2.6/90.0]? Uncertainty on EW
45- 45 A1 --- l_logN(X) Limit flag for logn
47- 51 F5.2 [cm-2] logN(X) [12.07/18.31] Column density
53- 56 F4.2 [cm-2] E_logN(X) [0.03/0.3]? Upper uncertainty on logN(X)
58- 61 F4.2 [cm-2] e_logN(X) [0.03/0.69]? Lower uncertainty on logN(X)
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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- 9 A9 --- Target Target or Sight-line
11- 15 F5.2 [cm-2] logN(H) [19.57/21.87] log N(H)
17- 20 F4.2 [cm-2] e_logN(H) [0.02/0.7] Uncertainty in logN(H)
22- 25 A4 --- El Element
27- 32 A6 --- Grat Grating
34- 34 A1 --- l_logN(X) Limit flag on logN(X)
36- 40 F5.2 [cm-2] logN(X) [12.13/18.31] Column density
42- 45 F4.2 [cm-2] e_logN(X) [0.02/0.48]? Uncertainty in logN(X)
47- 47 A1 --- l_log(X/H) Limit flag on log(X/H)
49- 52 F4.2 --- log(X/H) [2.67/8.97] Abundance, 12+log(X/H)LMC,gas
54- 57 F4.2 --- e_log(X/H) [0.03/0.73]? Uncertainty in log(X/H)
59- 59 A1 --- l_d(X) Limit flag for d(X)
61- 65 F5.2 --- d(X) [-2.1/1.5] Depletion
67- 70 F4.2 --- e_d(X) [0.03/0.73]? Uncertainty in d(X) (1)
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Note (1): The statistical uncertainty is listed here. Systematic errors on
the depletions due to uncertainties on the photospheric abundances are
not included, because they do not affect the relative trends examined
here (e.g., environmental parameters). An estimate of these systematic
errors can be found in Table 4 of Tchernyshyov+ (2015, J/ApJ/811/78).
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Target Target or Sight-line
11- 14 A4 --- Inst Instrument
16- 20 F5.1 K T01(H2) [46/270] Rotational temperature (3)
22- 26 F5.2 [cm-2] logN(CI) [13.18/15.56]? log, CI column density
28- 31 F4.2 [cm-2] e_logN(CI) [0.01/0.92]? Uncertainty in logN(CI)
33- 37 F5.2 [cm-2] logN(CII) [16.48/17.62]? log, CII column density
39- 42 F4.2 [cm-2] e_logN(CII) [0.19/0.24]? Uncertainty in logN(CII)
44- 47 F4.2 --- f1 [0.02/0.47]? f1, N(CI*)/N(CI)
49- 52 F4.2 --- e_f1 [0.01/0.23]? Uncertainty in f1
54- 57 F4.2 --- f2 [0/0.33]? f2, N(CI**)/N(CI)
59- 62 F4.2 --- e_f2 [0/0.1]? Uncertainty in f2
64- 67 F4.1 --- I/I0 [0/10.7]? Normalized UV radiation field (4)
69- 71 F3.1 --- e_I/I0 [0/7.2]? Uncertainty in I/I0
73- 75 I3 cm-3 n(H) [4/562]? Hydrogen volume density
77- 79 I3 cm-3 e_n(H) [1/180]? Uncertainty in n(H)
81- 84 F4.2 --- glow [0.37/1]? Fraction of low-pressure gas
86- 89 F4.2 --- e_glow [0/0.2]? Uncertainty in glow
91- 95 F5.3 cm-3 ne [0.002/0.055]? Electron number density
97-101 F5.3 cm-3 e_ne [0.001/0.017]? Uncertainty in ne
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Note (3): Rotational temperatures, T01, computed as in Equation 5 of
Tumlinson+ (2002ApJ...566..857T 2002ApJ...566..857T), are taken from
Welty+ (2012APJ...745..173W 2012APJ...745..173W) and references therein. For Sk-66 172,
the iterative computation of density and radiation field from CI and
CII line ratios diverges with the H2 T01 rotational temperature
given in Welty+ (2012, J/ApJ/745/173) (41+110-140K) input to the
model as the kinetic temperature. The closest temperatures for which
the models converge is 110K, which are well within the error bars of
the temperature estimation.
Note (4): An estimate of the intensity of the UV radiation field, I,
normalized to the value I0 specified by Mathis+ (1983A&A...128..212M 1983A&A...128..212M)
for the average intensity of ultraviolet starlight in the solar
neighborhood.
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History:
From electronic version of the journal
References:
Roman-Duval et al. Paper I. 2019ApJ...871..151R 2019ApJ...871..151R Cat. J/ApJ/871/151
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Aug-2022