ALFA

Arecibo 305 m

GALSPECT

GALFA-HI is a 4′, large area, Galactic HI survey

WNSHS/GAMESWALLABY/GASKAP

EBHIS

GALFA-HI compared to past, present, future surveys

IGPS

JEGP+ 11

•Arecibo Surveys

ALFA Surveys Other instrument surveys

PALFA EALFA GALFA

ALFALFA ZOAAGES AUDS

GALFA-HI GALFACTS GALFA-RRL

TOGS TOGS2 I-GALFA PIs

(some data taken contemporarily)

GALFA-HI owes a lot of commensal observing!

GALFA-HI DR1 is available to the public. DR2 soon!

JEGP+ 11

baselineripple

calibration

x

crossing-pointgain

calibration

x

first sidelobecalibratio

n

x

baselineripple

calibration

√

crossing-pointgain

calibration

√

first sidelobecalibratio

n

√

GALFA-HI matches IRAS and Planck resolutions

Extinction

HI FIR

GALFA-HI matches IRAS and Planck resolutions

Extinction

HI FIR

Interstellar morphologies:Cigars, Filaments,

Needles

Pancakes, Sheets

Blobs

Even Bicycle Wheels!

GALFA FINDS HI BLOBS

(Ap J, In press)

Both small and

weak!

GALFA finds long, straight HI FILAMENTS!

SHEETS are old hat. Consider this famous paper—

the earliest known (to me) example of this geometry

in the normal ISM…

Here’s our Arecibo Millennium-survey friend

3C225b, showing prominent HI absorption.

We measure the temperature (17 K); we use ISM pressure (4000

cm-3 K) to get volume density.

N(HI) ~ 1019 cm-2 n(HI) ~ 200 cm-3

N(HI)=n(HI) * L

WHAT’S L????

Arecibo (GALFA) map of the

Knapp ultrathin

sheet.

Haud (2010) mapped the narrowest HI emission component: our cold thin cloud is part of a much

larger structure, well-fit by an expanding ring! The whole structure is half in, half out of the Local

Bubble…

Our two ultrathin sheets

A crude sketch of Haud’s

rotating, expanding, translating

“bicycle wheel in space”,

looking down onto the

Galaxy…