Facts about SNe and their remnants

• Evolution of an SNR sensitively depends on its environment.

• Observed SNRs are typically produced by SNe in relative dense environments.

• But most (> 80%) of core-collapsed SNe explode in superbubbles (e.g., van Dyk et al. 1996; Higdon et al. 1998).

• Most of Type Ia SNe probably also occur in low density regions (Galactic halo and bulge).

Most of SNRs are “missing”!

Missing Supernova Remnants

Q. Daniel Wang

(Univ. of Massachusetts Amherst)

In collaboration with

Shukui Tang, Yang Chen, David Smith, Fangjun Lu, et al.

• Characteristics of SNRs in low density regions

• Accumulated X-ray emission from such SNRs

Examples of SNRs in low density evironments

Name L, b shell PWN X-ray

Crab Nebula

184.6, -5.8 NO Yes Nonthermal

G54.1+0.3 54.1, 0.3 NO Yes Nonthermal

DA 530 93.3, 6.9 D=27’in radio

NO ?

RX J1932 64, 5.3 2.4’ in X-ray

NO ?

G28.6–0.1 28.6, –0.1 10’ x 8’ in X-ray

No Nonthermal?

DA 530

1420 MHz (Landecker et al. 1999)

 

PSPC observation:n0 ~ 0.02-0.05 cm-3

kT ~ 10-15 keVnet ~ 8 × 1010 cm-3 s

RX 193214.6+300741

• Exposure: PSPC 3.3 ks• Diameter: ~7 pc (D/10kpc)

vertial distance: ~ 1 kpc • L(0.1-2.4): ~1034 ergs/s• Mass: ~ 0.7Msun

• n0 ~ 0.02 cm-3

• Age: ~ 7 x 103 yrs (Ve/103

km/s) • Thermal spectrum of a very

high T or a Power law• No optical and radio

counterparts yet.• 40 ks Chandra obs. approved

G28.6–0.1

Image: Chandra ACIS-I observationsContours: VLA 20cm radio

Ueno et al. 2003

•Diameter: ~20 (D/8kpc) •L(2-10): ~3 x 1032 ergs/s

•ne t ~ 1011 cm-3 s

•Thermal spectrum of T ~ 5.4 keV or a Power law of a photon index ~ 2

T ≤107 K

SNRs in superbubbles

30 Dor C in the LMC

East half

West half

Smith & Wang 2004

100 pc

SNRs in the 3-phase ISM SNRs in the 3-phase ISM

McKee & Ostriker 1977

The interstellar space is dominated by a hot phase maintained by SNe and/or superbubbles.

Missing SNRs and Galactic ridge X-ray emission

A toy model for the GRXE:• SNRs are in a hot medium and emit thermal X-ray emission.• A GRXE spectrum samples the entire evolution of an SNR,

according to the model of McKee & Ostriker (1977).• The intermixing between the X-ray emission and absorption

is approximately uniform.

T0 ≤106 K

Galactic ridge X-ray spectrum in the Chandra deep survey field

SNR thermal

Nonthermal (Valinia et al.

2000) Extragalactic

• SN rate ~ 1/(15-30)yr

• Total NH~1.51023 cm-

2

• T0 ~ 0.01 keV

• Abundance: 0.50.1

• Luminosity (0.8-10keV) ~ 91038 erg s-1

Conclusions

• Candidates of SNRs in low density medium have been identified and are yet to be carefully examined.

• Most of such SNRs are not observed individually.

• They can be detected collectively and may explain the GRXE.

• They may have lasting impacts on the Galactic ecosystem.

~ 1055 erg, or ~ 104

Type Ia SNe over the past ~ a few x 107 years.

Snowden et al. 1997