EAYAM 2017 in Ishigaki

What Makes Red Quasars Red?:
Observational Evidence for Dust Extinction

Seoul National University
Dohyeong Kim

Galaxies in the Universe:
Why are they different?

ⓒ CANDELS

Evolution!

ⓒ http://www.yourgenome.org

How Do Galaxies Evolve?

Hopkins+ 08

ULIRGs

Quasarsvs.

3C273 NASA A. Martel (JHU) J. Bahcall (IAS) and ESA• Merging features• Starburst& buried AGN• Obscured in optical• Tidal features fade rapidly• Powerful BH activity• Dust removed

Possible Scenarios
ULIRGsQuasarsvs.

ULIRGsA Galaxies

B Galaxies

QuasarsConnection?
They are too different!

ULIRGs• Merging features• Starburst& buried AGN• Obscured in optical

Quasars•••

Tidal features fade rapidly
Powerful BH activity
Dust removed

ULIRGs• Merging features• Starburst& buried AGN• Obscured in optical?

Quasars•••

Tidal features fade rapidly
Powerful BH activity
Dust removed

How Do Galaxies Evolve?

Hopkins+ 08

“Blowout” phase
Hopkins+08

Red Quasars
Urrutia+08• Broad emission lined d(Glikman+07; Urrutia+09)• Red colors (r’-K >5 mag)d(Glikman+07; Urrutia+09)• Ongoing SF in their host(Georgakakis+09)
d• Merging features(Urrutia+08; Glikman+15)dRed Quasars
Why are they red?

Urrutia+08• Dust reddened by merging

host galaxies (Glikman+07; Urrutia+09)
Support the merging scenario• Moderate viewing angled• Intrinsic red colors(Whiting+01; Young+08)
d-Unusual CF of dust torus(Rose+14)
d-Unusual physical condition(Wilkes+02; Rose+13)• Broad emission lined d(Glikman+07; Urrutia+09)• Red colors (r’-K >5 mag)d(Glikman+07; Urrutia+09)• Ongoing SF in their host(Georgakakis+09)
d• Merging features(Urrutia+08; Glikman+15)dWhy are they red?
• Dust reddened by merging

host galaxies (Glikman+07; Urrutia+09)

Dust reddened: O High Edd: O

Support the merging scenario• Moderate viewing angled• Intrinsic red colors(Whiting+01; Young+08)
d-Unusual CF of dust torus(Rose+14)
d-Unusual physical condition

Dust reddened: O High Edd: X(Wilkes+02; Rose+13)

Dust reddened: X High Edd: ?
Dust reddened: X High Edd: ?
Dust reddened: X High Edd: ?

1. BH Accretion Rates ofRed Quasars

BH Mass Estimators
Balmer lines

Vanden Berk+ 01

log (MBH/M☉) based on existing method

New NIR BH Mass Estimators-Paschen and Brackett linesKim+ 10log (MLPβ,FWHMPβ /M☉)

Kim+ 15aKim+ 15b

Sample: 16 red quasars at z~0.7
Observation: NASA IRTF

Kim+ 15b

BH accretion rateof Red quasars
λEDD of red quasars~ 0.69λEDD of normal quasars~ 0.16

High Edd ratio!

Why are they red?
• Dust reddened by merging

host galaxies (Glikman+07; Urrutia+09)

Dust reddened: O High Edd: O

Support the merging scenario• Moderate viewing angled• Intrinsic red colors(Whiting+01; Young+08)
d-Unusual CF of dust torus(Rose+14)
d-Unusual physical condition

Dust reddened: O High Edd: X(Wilkes+02; Rose+13)

Dust reddened: X High Edd: ?
Dust reddened: X High Edd: ?
Dust reddened: X High Edd: ?

2. What Makes Red Quasars
Red?

Measured Line:Hβ, Hα, Pβ, and Pα

Kim& Im in press

Sample: 20 red quasars at z~0.3 and 0.7
Observation: NASA IRTF

Kim& Im in press
Local Red AGNs (Rose+ 13)

Red Quasar (1307+2338)

Red Quasar (0036-0113)

CLOUDY code (Ferland 98)• α= -2~2• nH= 107~1014 cm-3
• U= 10-5~105
Possible line luminosity ratios
w/o the dust extinction

6/11 (55%) cannot be explainedby any physical condition

Dust reddened!

Why are they red?
• Dust reddened by merging

host galaxies (Glikman+07; Urrutia+09)

Dust reddened: O High Edd: O

Support the merging scenario• Moderate viewing angled• Intrinsic red colors(Whiting+01; Young+08)
d-Unusual CF of dust torus(Rose+14)
d-Unusual physical condition

Dust reddened: O High Edd: X(Wilkes+02; Rose+13)

Dust reddened: X High Edd: ?
Dust reddened: X High Edd: ?
Dust reddened: X High Edd: ?

SUMMARY
1. BH accretion rates of red quasars (λEDD ~ 0.69)
is significantly higher than those of unobscured
type 1 quasars (λEDD ~ 0.16)
2. The line luminosity ratios of red quasars fromHβ(0.48μm) to Pβ(1.87μm) cannot be explained byany physical conditions of BLRs.
3. These pieces of observational evidence support
that red quasars are dust-obscured quasars in theintermediate stage between ULIRGs and unobscured
type 1 quasars.

20 Red Quasars at z~0.3& 0.7
Kim+ In
press

Pβ vs.
HβE(B-V) values(Glikman+ 07& Urrutia+09)
measured bycontinuum fit
Kim+
10

Kim+ In
press

Red Quasars(Dust corr.)

Unobscured
Type 1 Quasars

Red Quasars(Dust uncorr.)

Kim+ 15b

Accretion Rates ofRed Quasars from
Hydrogen Pβ Line
Kim+ 15b

Sample-16 red quasars at z~0.7

Observation

Edd ratio ⬆

-SpeX on IRTF/NASABH mass estimator-Pβ line (1.28 μm; Kim+10)

Control sample-410 SDSS quasars withsame criteria

Edd ratio ⬇

What Makes Red Quasars Red?:
Unusual CF of Hot Dust Torus
Warm Dust
Hot Dust
Power-law

Kim+ Inpress

Unusual CFof HD torus?
Unobscured Quasars• Kim+ 15b• 18 local type 1 quasars• CF= ~0.4

Red Quasars• 16 red quasars at z~0.3• CF= ~0.5

Kim+ In
press