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TRANSCRIPT
Monique C. Aller (Georgia Southern University)
Varsha P. Kulkarni (University of South Carolina) Eli Dwek (NASA-‐GSFC)
Donald G. York & Daniel E. Welty (University of Chicago) Giovanni Vladilo (Osservatorio Astronomico di Trieste)
¡ Introduction – Quasar Absorption Systems (QASs) § How we can use QASs to study dust in distant galaxies § Evidence for dust in QASs
¡ Silicate dust in QASs § Dedicated Spitzer IRS mini-‐survey to study silicate dust in gas and dust-‐rich QASs è results, trends
§ NASA-‐ADAP ongoing archival study to silicate dust in moderately gas-‐rich QASs with archival Spitzer IRS quasar spectra ècurrent results, open questions
¡ Summary & Future Work
Peeples 2015
Impact param
eter
Cartoon of QAS
Sightlines to distant quasars pass through foreground (still distant) galaxies
• Galaxies sampled by gas cross-‐section, independent of galaxy brightness • Primary neutral gas reservoir for star-‐formation (e.g., Storrie-‐Lombardi & Wolfe 2000):
• Damped Lyman-‐α absorbers (DLAs): NHI ≥ 2×1020cm-‐2
• sub-‐DLAs: 1019≤NHI<2×1020cm-‐2
Credit: A Pontzen
UV/Optical Spectra (gas properties): abundances; kinematics; temperature; density; ionization parameter
From Webb; Pettini 2003
Si IV (1393 Å)
C IV (1548 Å)
Lyman limit
Cartoon of QAS
Infrared Spectra (silicate dust): grain property constraints from 10 and 18 μm absorption features
York et al. 2006
809 SDSS absorbers 1<z<2
SMC-‐like reddening for absorbers
Statistical evidence of reddening for quasars with foreground
absorption systems è dust in QASs
– 23 –
Zn Si Mn Fe Cr Ti
[X/H
] = lo
g (X
/H) -
log
(X/H
) sun
Solar&Level&(0%&dust)&
-2.5 -2 -1.5 -1 -0.5 0 0.5Metallicity [X/H]
-1.5
-1
-0.5
0
Dep
letio
n [F
e/X
]
Fig. 1.— Left panel: (a) Abundances of a few key elements in DLAs and sub-DLAs, based
on data from Meiring et al. (2009) and references therein. Also shown for comparison are
the abundance patterns observed for the Galactic halo ISM, warm Galactic ISM, and the
SMC ISM. The depletion patterns are similar for DLAs and sub-DLAs, except the pattern
for sub-DLAs is o↵set to higher abundances. Both the DLA and sub-DLA depletion patterns
appear to be roughly similar to the Galactic halo ISM pattern. Right panel: (b) Depletion
of Fe relative to Zn or S (if Zn is not available) vs. the metallicity based on Zn or S, for the
sample of quasar DLAs analyzed in Kulkarni et al. (2015). A trend of increasing depletion
level with increasing metallicity is seen.
X = Zn or S (if Zn unavailable)
Kulkarni et al. 2016
Dust depletion appears anti-‐correlated with metallicity (e.g., Ledoux et al. 2003; Meiring et al. 2006, 2009)
Noterdaeme et al. 2009
Dust extinction is present based on 2175 Å bump (carbonaceous)
zabs=1.64 like LMC2
estimated by varying E(B! V ) and comparing, by eye, thedepth of the resulting 2175 8 feature to the observed data. Therange of values found is from E(B! V ) ¼ 0:12 to 0.19, andthis range is used later to estimate part of the systematic errorsin the parameters to fit 1 (Table 1), which is our best estimate
for the dust parameters at za ¼ 0:524 along the AO 0235+164line of sight.Galactic-type dust extinction at za ¼ 0:524 produces the
best fit to the AO 0235+164 spectrum when comparing Ga-lactic-, SMC-, and LMC-type dust. The observed spectrum
Fig. 5.—HST STIS spectra of AO 0235+164 from Fig. 1 and Galactic, LMC, and SMC dust model !2 fits. The data are binned 2:1. For clarity, the continua of thefitting functions are shown displaced above the data. Superposed on the data is the Galactic model.
TABLE 1
AO 0235+164 Spectral Fits with Dust Extinction
Fit Dust Type Referencea E(B !V )b RVb "c, b
k1d
(8)k2
d
(8) !2#
1.............. Galactic 1 0.227# 0.003 2.51# 0.03 !1.75# 0.01 2500 8700 2.67
2.............. LMC 2 0.281# 0.004 3.16 !1.40# 0.02 2500 8700 5.31
3.............. SMC 2 0.161# 0.006 2.93 !1.63# 0.03 2500 8700 14.2
4.............. LMC 2 0.396# 0.005 3.16 !0.72# 0.03 2800 6000 2.50
5.............. Mod. Gal.e 3 0.211# 0.002 3.08 !1.76# 0.01 1690 8700 3.08
6.............. Gal. + LMCf 1+2 0.267# 0.003 2.95# 0.02 !1.60# 0.01 1690 8700 3.72
7.............. Galactic 1 0.223# 0.003 2.43# 0.03 !1.75# 0.01 2549 8700 2.44
7b............ . . . . . . . . . . . . +0.28# 0.06 1690 2549 . . .
a Reference for extinction formulae: (1) CCM89; (2) Pei (1992); (3) Pei (1992) modified to allow a variable far-UVextinction component. RV is a fixed value in the models using the Pei (1992) formulae for extinction and a variable inthe models using the CCM89 formulae.
b Only the formal error; systematic errors probably dominate and are much larger.c Power-law spectral index for the continuum modeled as f# / # " . For model 7 a broken power law was used, and
the continuum parameters for the blue part are given in line 7b.d Beginning and end wavelength of the spectral region modeled as a power law and included in the fit.e A modified Galactic extinction with a reduced far-UV component (see text).f A model with both Galactic- and LMC-type absorbers at za ¼ 0:524. The best fit found required no LMC-type
absorption [E(B! V ) $ 0:005].
JUNKKARINEN ET AL.664 Vol. 614
zabs=0.524 Galactic
Junkkarinen et al. 2004
15σ (in EW)
detection of silicate dust in z=0.524
DLA using Spitzer IRS Feature best-‐matched by profiles for diffuse Galactic
interstellar clouds or laboratory amorphous olivine – with a shallow peak optical depth (~0.08)
Kulkarni et al. 2007
¡ Select 12 additional QASs abundant in gas (and dust): § Expected to be DLAs or sub-DLAs; i.e. most NH1>1020 cm-2
§ Signatures of dust à 2175 Å bump detected; reddening; large extinctions (AV >0.4); and/or gas-phase depletions
§ Signatures of molecular absorption in a few QASs (PKS 1830-211, TXS 0218+357)
¡ Spitzer IRS spectra (PI proposals: V.P. Kulkarni) § Data in low-‐resolution mode (SL, LL) § Cover 10 µm feature every QAS; (part of) 18 µm feature in 6 QASs
¡ QASs redshifts sample 0.156≤zabs≤1.388; quasars 0.87≤zem≤2.51
10 µm silicate dust
absorption detected at >4σ in each
system
Kulkarni et al. 2011
Grav. Lensed Blazar (z=2.507)
Absorber (z=0.886): Ø Face-‐on (Sb/Sc) spiral galaxy Ø Molecule-‐rich: CO, HCO+, HCN, HS, H2O, NH3
Ø Neutral gas rich: 21-‐cm (HI) absorption 10 µm absorption
Aller et al. 2012
18 µm absorption
HST F814W image, Winn et al. 2002
galaxy lensed
quasar
12.7σ (in EW) detection of 10 µm feature
(=7.78 kpc QAS)
Examined fits with >100 optical depth templates (observed & lab sources) è laboratory crystalline olivine (Mg2xFe2-‐2xSiO4) silicates è unusually high crystallinity (Galactic ISM = amorphous)
PKS 1830-‐211
Amorphous olivines provide poor fit
(x=0.94) (x=1.0)
(x=0.0) (x=0.55) (Mg,Fe)3Si2O5(OH)4 SiO2
Aller et al. 2012
Aller et al. 2014
Grav. Lensed Blazar (z=0.944) Absorber (z=0.685): Ø Face-‐on spiral galaxy Ø Molecule-‐rich: CO, HCO+, HCN, H2O, NH3, LiH
Ø Neutral gas rich: 21-‐cm (HI) absorption
HST imaging, Jackson et al. 2000
10 µm 18 µm
Sep: 335mas~2.4 kpc in QAS
Detections of both the 10µm and the 18µm silicate absorption features: ¡ Significant detections -‐10µm (10.7-σ in EW) and 18µm (>3σ) abs. ¡ Highest peak optical depth (τ10=0.49±0.02) for any QAS so far
AMORPHOUS OLIVINE
Aller et al. 2014
Like PKS 1830-‐211 is gravitationally-‐lensed, molecule-‐rich BUT unlike PKS 1830-‐211 BOTH the 10 and 18 µm absorption matched by amorphous olivine profile
Comparing 10 micron absorption feature in different QASs:
• Variations in depth of feature • Variations in breadth of feature • Variations in peak wavelength • Variations in substructure
è may suggest variations in silicate dust grain properties between different QASs è variations do not clearly correlate with other QAS parameters like presence of molecules, absorber redshift
Aller et al. 2014b
Milky Way diffuse clouds
extrapolation
• Grain differences? e.g. larger grains-‐low UV extinction • Sampling different dust grain population? e.g. face-‐on vs. through MW disk • Different stellar populations? e.g. more O-‐rich
Slope of relation is 3-‐6x higher for QASs than for Milky Way diffuse clouds
Aller et al. 2014
fcov=1 assumed in all QASs
Kulkarni et al. 2011
Hint of an anti-‐correlation between carbonaceous and
silicate dust absorption strengths
à is dust
predominately carbonaceous or silicate along a
sightline?
Aller et al. 2014
Suggestion of trend between Mg II EW and silicate 10 µm peak optical depth:
Are silicate-‐rich QASs more massive?
Mg II saturated in most systems, and is proxy for velocity spread (QAS mass; outflows)
TXS 0218+357
DUST MEASUREMENTS IN QASS: ¡ Silicate dust 10 µm feature in ≥50 QASs toward quasars with Spitzer IRS data ¡ Signatures of silicate crystallinity (substructure, longer-‐λ resonance features)? ¡ Determine shapes of extinction curves for ≥70 individual QASs ¡ Examine relative abundances of carbon:silicate dust (~35 QASs)
GAS MEASUREMENTS IN QASS WITH DUST INFORMATION:
¡ Ascertain gas metallicity and depletions (e.g. Fe, Cr, Si) ¡ Estimate gas kinematics (e.g. velocity structure, widths)
CONNECTIONS BETWEEN DUST/GAS AND MODELS: ¡ Examine interrelation between gas and dust properties in connection to dust/ chemical evolution models V. P. Kulkarni (PI, U. South Carolina); M.C. Aller (co-‐I/Science-‐PI; Ga. Southern U.); E. Dwek (co-‐I; NASA-‐GSFC)
¡ Quasars with archival Spitzer IRS spectra § Most in low resolution (SL,LL) stare mode § Several mapped, higher resolution spectra
¡ Cataloged foreground absorbers with moderate gas § Log NHI≥18.0 (most not DLAs or sub-‐DLAs, median=18.23) § EWMg II≥0.5 Å (median ~0.9) or EWNa I≥1.0 Å § Absorbers 10 μm or 18 μm silicate feature would fall within observed spectrum
¡ QASs are purely gas-‐selected (no prior requirements for evidence of QAS dust or molecules)
èfinal sample of 37 quasars (some with multiple absorbers) § median zquasar=1.0 (0.3<zquasar<4.4) § median zQAS= 0.7 (0.1<zQAS<2.8)
SBS#09009+532#Spectrum#3C#175#Spectrum#
3C 175 • z=0.77 Seyfert (1.2) • Optically variable
Absorber (zQAS=0.46) • NH I<18.30 Rao et al. 2011
• EWMg II=0.62 Å Rao et al.2011
3C 196 • z=0.87 QSO • Optically variable
Absorber (zQAS=0.44) • NH I=20.8 (DLA) Boisse et al. 1998 • ~ 0.8-‐2.0 x solar metallicity • SFR ~5 M⊙ yr-1 Gharanfoli et al. 2007
• Barred spiral
SBS 0909+532 • z=1.38 AGN • Grav. Lensed
Absorber (zQAS=0.83) • NH I≥21.14 (DLA) • EWMg II=2.o; 0.7 Å • 2175 Å bump Motta et al. 2012 • Early type galaxy
3C#196#Spectrum# SBS 0909+532 Spectrum 3C 196 Spectrum 3C 175 Spectrum
Aller et al. in prep
3C#175#QAS#Amorph.#Olvine# 3C#175#QAS#Amorph.#Pyroxene# SBS0909+532#QAS#Amorph.#Olvine#
Some uncertainty on the intrinsic shape of the quasar continuum (limited continuum bracketing absorption features) ècurrently
exploring what range of grain properties would be consistent with plausible quasar continuum normalizations
τ10=0.32 τ10=0.28 τ10=0.19
¡ Silicate grain variations?
¡ Silicate absorption (QAS) blended with silicate emission (quasar) in some systems?
¡ Differences in sightline to quasar?
3C#175#QAS#Amorph.#Olvine#
What is the origin of these poor(er) fits?
¡ Silicate grain variations?
¡ Silicate absorption (QAS) blended with silicate emission (quasar) in some systems?
¡ Differences in sightlines èPKS 1830-‐211; AO 0235+164; TXS 0218+357 are blazars è Systems with poor(er) fits are not blazars; sightline intersecting dust torus?
Credit: Pierre Auger Observatory
¡ Silicate dust in absorption in QASs § Evidence of 10 µm (and 18 µm) absorption seen in QASs at z<1.4 with
strong low-‐ion metal absorption lines and/or signatures of dust § Variation in shape, breadth of absorption feature
¡ Trends of τ10 with other dust and gas properties of QAS § Correlation with E(B-‐V) – but steeper slope than in MW clouds § Correlation with Mg II EW – silicate rich are more massive? § Suggestion of anti-‐correlation with carbonaceous dust abs. strength
¡ Some systems show evidence of possible silicate emission in quasar (as well) § Currently exploring more sophisticated quasar continuum
normalizations accounting for this
¡ Final analysis with expanded sample will better constrain silicate dust trends, and explore prevalence of silicate dust in distant galaxies