GLIMPSE results on the Mid IR Stellar and Diffuse Emission in the Galactic

Plane

Robert Benjamin (UW-W) and the GLIMPSE teamwith special thanks to SSC and the IRAC team

Spitzer Science Center 2005 ConferenceIR Diagnostics of Galaxy Evolution (Nov 14-16,2005)

GLIMPSE(Galactic Legacy Infrared Mid-Plane Survey

Extraordinaire)• PI: Ed Churchwell (UW-Madison)• Galactic Spitzer Legacy Program• Over 320,000 Spitzer /IRAC frames

• bandsurveymicrons

• GalacticLatitudeb| < 1 degree

• GalacticLongitudel-degrees

• Totalsurveytimehours

• Angular Resolution: <2 arcseconds

(Almost) no extinction!http://www.astro.wisc.edu/glimpse

Benjamin et al (2003)

PASP, 115, 953

Data Products GLIMPSE Point Source Catalog (> 99.5% reliable)GLIMPSE Point Source Archive (~5)Mosaicked Images in 4 bands

“Web Infrared Tool Shed” Mid-IR models of circumstellar dust and PDRsGLIMPSE Point Source Catalog and Archive msel mbr msens Catalog Archive3.55 m 14.2 7.0 13.3-13.6 29.0 million 42.4 million4.49 m 14.1 6.5 13.3-13.6 29.0 million 39.1 million5.66 m 11.9 4.0 11.7-12.3 11.1 million 11.7 million7.84 m 9.5 4.0 11.0-12.4 8.4 million 9.0 million TOTAL 31 million 43 million

Note: ~85% of sources expected to be between K2 giants (d<7 kpc) and M5 giants (d<124 kpc).

http://data.spitzer.caltech.edu/popular/glimpse

Mean Free Path in Galactic ISM

X-ray opacity (Benjamin 2004), UV/Optical (Clayton, Cardelli, Mathis 1989), IR (Li & Draine 2001)Assuming nH=1 cm-3

Indebetouw et al. 2005, ApJ 619, 931

• Extinction in mid IR is nearly flat across IRAC bands!

A[3.6] /AK=0.56±0.06

A[4.5] /AK=0.56±0.08

A[5.8] /AK=0.43±0.10

A[8.0] /AK=0.43±0.10

Objects Uncovered by GLIMPSE

329 PAH Bubbles Churchwell et al (2005), in prep

Supernova Remnant Survey Reach et al (2005), astro-ph/0510630

IR Dark Cloud Survey Devine et al (2005), in prep

New Planetary Nebulae Cohen et al (2005), ApJ, 627, 446

24 New Mid IR Stellar Bowshocks Benjamin et al (2005), in prep

Large (R>9000 AU) Circumstellar Disk Candidate Walker et al (2005), in prep

92 New Open Stellar Clusters Mercer et al (2005), ApJ in press

New Galactic Globular Cluster Kobulnicky et al (2005) AJ 129, 239

RCW 79

G311.5-0.3K

IRAS 16205-5729(near RCW49) GLIMPSE-C01

Galaxy Cluster?

• Edge-on spiral, face-on spiral, eight other candidates seen at l=317o b=-0.5o • “Transparency” of Galactic ISM at midplane relevant to search for “Zone of Avoidance” galaxies and using light profiles of external edge-on systems.

Galaxy Cluster?

Associated with Great Attractor? (10 kpc=30”)

10 deg to Galactic Center

• Extinction still affects star counts for some small areas with dense CO clouds.• 25 % more stars to the left of Galactic Center (l=10-30) than to the right (l=350-330)

• Galaxy approx. axisymmetric outside l=30o, but some enhancements, e.g. l=307o

• Fit by N=No(l/lo)K1(l/l0) where lo=24±4o [4.5 band] (17-30o)

Redleft of G.C.

(l=10-65)

Blueright of G.C.

(l=350-295)

Redleft of G.C.

(l=10-65)

Blueright of G.C.

(l=350-295)

?

Fits of data to n=no(S/So)- yield avg=1.83-1.95

Fewer sources: Bright and large l

More sources: Faint and small l

Molecular cloud/W41/W42 at l=23-25

34o

54o

Sun

G.C.

Galactic Longitude

Galactic structure parameters

(Benjamin et al 2005 ApJL 630, 149) BAR

Rbar=4.4±0.5 kpc

bar=44 ±10o

M[4.5]=-2.15 ±0.2 mag (early K giants)

DISK

N=No(l/lo)K1(l/l0)

lo=24±4o (17-30o)

Rdisk=3.5 ±0.5 kpc

SPIRAL ARMS

Clear enhancement at

l=306-309 (Centaurus)

No enhancement at

l= 49 (Sagittarius)

Credit: Robert Hurt (SSC/JPL/NASA)

Galactic Longitude Asymmetry

l=30o

l=-16o

(344o)

GLIMPSE: A Legacy for Galactic AND Extragalactic Research

• GLIMPSE is uncovering a plethora of objects (clusters, star formation regions, PAH rings, planetary nebulae, SNR, mid IR stellar bowshocks, protostellar jets, other galaxies, etc.) that will provide detailed understanding of emission mechanisms for distant sources.

• Mid IR star counts can now be used for the study of Galactic stellar structure to yield the scale-length of the stellar disk, the angle and size of the bar, and the locations of stellar spiral arms.* The bar seems to be enhanced in early K giants (lucky for us).

• Coming up soon: – GLIMPSE II (the inner 20 degrees)– Refined Galactic modelling results (including amplitudes of

bar/disk/arms).– Diffuse emission variation vs. location in Galaxy

• Data is available to you now for FREE from SSC website.

THANK YOU, SPITZER LEGACY PROGRAM!

* [The length and] angle of the bar are also new”, said astronomer Michael Merrifield, “It’s a very different angle from the 10-30 degrees of previous analyses. In some sense, the new method is really pretty elegant but it’s at odds with previous estimates using different methods. Clearly, at least one of them is definitely wrong. ” [discoverychannel.com, Sept 9, 2005]

SSC website: data.spitzer.caltech.edu/popular/glimpseGLIMPSE website: www.astro.wisc.edu/glimpse (includes this talk)