Lockman Hole

The Lockman Hole is located at about RA 10h 45m, Dec. +58° and is defined by a region of low neutral hydrogen gas and dust column density.{{ cite journal |vauthors=Lockman FJ, Jahoda K, McCammon D |title=The structure of galactic HI in directions of low total column density |journal=Astrophys. J. |date=Mar 1986 |volume=302 |issue=3 |pages=432–49 |doi=10.1086/164002 |bibcode=1986ApJ...302..432L |hdl=2060/19850019473 |s2cid=118595586 |hdl-access=free }} Column density is a commonly used measure in astronomy for the quantity of a given chemical element or molecule in a certain direction. In this region, the typical column density of neutral hydrogen is N_H = 0.6 x 10²⁰ cm⁻². This column density is moderately lower than typical values near the galactic poles, where N_H $\backslash sim$ 10²⁰ cm⁻², and H I column densities of N_H > 10²¹ cm⁻² are common at low galactic latitudes and towards H I clouds.{{ cite journal |vauthors=Dickey JM, Lockman FJ |title= H I in the Galaxy|journal=Annu. Rev. Astron. Astrophys. |date=1990 |volume=28 |issue= 1|pages=215–61 |bibcode=1990ARA&A..28..215D |doi=10.1146/annurev.aa.28.090190.001243 }}

The region around B1950.0 RA {{RA|10|45}} Dec {{Dec|57|20}} has a minimum N_H of 4.5 x 10¹⁹ cm⁻². There is a diffuse cloud covering half of the field.{{ cite journal |vauthors=Schlegel DJ, Finkbeiner P, Davis M |title=Maps of dust infrared emission for use in estimation of reddening and cosmic microwave background radiation foregrounds |journal=Astrophys. J. |date=Jun 1998 |volume=500 |issue=2 |pages=525–53 |bibcode=1998ApJ...500..525S |doi=10.1086/305772 |arxiv = astro-ph/9710327 |s2cid=59512299 }}

The Lockman Hole East is a subregion of the Lockman Hole centered at J2000.0 RA {{RA|10|52}} Dec {{Dec|+57}}.{{cite web

| url=http://www.roe.ac.uk/ifa/shades/maps.html

| title=SHADES: SCUBA Half Degree Extragalactic Survey

| access-date=2011-12-10 }}

The Lockman Hole North-west (LHNW) is a region that appears about as wide as the moon centered at J2000.0 RA {{RA|10|34}} Dec {{Dec|+57|40}}.,{{cite news

| url=http://www.spaceflightnow.com/news/n0303/28chandra/

| title=Shape of Universe seen during adolescent years

| work=Spaceflight Now

| date=2003-03-23

| access-date=2011-12-10 }}

{{ cite journal |vauthors=Yang Y, Mushotzky RF, Steffen AT, Barger AJ, Cowie LL |title=The Chandra Large Area Synoptic X-Ray Survey (CLASXS) of the Lockman Hole-Northwest: The X-Ray Catalog |journal=Astron. J. |date=Oct 2004 |volume=128 |issue=4 |pages=1501–23 |doi=10.1086/423996 |bibcode=2004AJ....128.1501Y|arxiv = astro-ph/0409087 |s2cid=8216340 }} with a column density of N_H = 5.72 x 10¹⁹ cm⁻².

Clouds of neutral hydrogen are ubiquitous in the Milky Way galaxy, and effectively absorb photons that are energetic enough to ionize hydrogen, which requires an energy of 13.6 electron volts (in the extreme ultraviolet range). Even the relatively small amounts of hydrogen in the Lockman Hole absorb most radiation at and just above energies of 13.6 electron volts, but even so it transmits extreme ultraviolet and soft x-ray radiation from extragalactic objects to a greater degree than other areas of the sky.

Neutral hydrogen is also associated with diffuse emission at infrared wavelengths that can confuse observations of faint infrared sources.

The relatively clear field of view offered by the Lockman Hole has allowed its use to view extremely distant regions of the universe. Observations by the Spectral and Photometric Imaging Receiver (SPIRE) instrument aboard the Herschel Space Telescope of the Lockman Hole have imaged thousands of extremely distant galaxies that appear as they did 10–12 billion years ago.{{cite web |title=Star-forming galaxies like grains of sand |url=http://oshi.esa.int/#detail=image.html?id=36 |access-date=2010-06-01 |archive-url=https://web.archive.org/web/20110614104930/http://oshi.esa.int/#detail=image.html?id=36 |archive-date=2011-06-14 }}

This field of view also contains hundreds of astronomical X-ray sources, some of them supermassive black holes.

The Chandra X-ray Observatory and ROSAT have been used to study X-ray sources from the Lockman Hole.{{ cite journal |author=Hasinger G, Burg R, Giacconi R, Hartner G, Schmidt M, Trumper J, Zamorani G |title=A Deep X-Ray Survey in the Lockman-Hole and the Soft X-Ray N-Log |journal=Astron. Astrophys. |date=Aug 1993 |volume=275 |issue=1 |pages=1–15 |bibcode=1993A&A...275....1H |last2=Burg |last3=Giacconi |last4=Hartner |last5=Schmidt |last6=Trumper |last7=Zamorani }} Some 75 X-ray sources are observed with the PSPC of ROSAT.

Detailed X-ray spectral analysis has been performed on 123 X-ray sources in the Lockman Hole using XMM-Newton.

The diffuse X-ray background (XRB) has also been studied in the area.{{ cite journal |author1=Mather, J. C. |author2=Cheng, E. S. |author3=Cottingham, D. A. |author4=Eplee, R. E. Jr. |author5=Fixsen, D. J. |author6=Hewagama, T. |author7=Isaacman, R. B. |author8=Jensen, K. A. |author9=Meyer, S. S. |author10=Noerdlinger, P. D. |author11=Read, S. M. |author12=Rosen, L. P. |author13=Shafer, R. A. |author14=Wright, E. L. |author15=Bennett, C. L. |author16=Boggess, N. W. |author-link16=Nancy Boggess|author17=Hauser, M. G. |author18=Kelsall, T. |author19=Moseley, S. H. Jr. |author20=Silverberg, R. F. |author21=Smoot, G. F. |author22=Weiss, R. |author23=Wilkinson, D. T. |title=Measurement of the cosmic microwave background spectrum by the COBE FIRAS instrument |journal=The Astrophysical Journal |date=January 1994 |volume=420 |issue=2 |pages=439–44 |bibcode=1994ApJ...420..439M |doi=10.1086/173574 |doi-access=free }}{{ cite journal |doi=10.1086/185717 |author=Mather |last2=Cheng |first2=E. S. |last3=Eplee |first3=R. E. Jr. |last4=Isaacman |first4=R. B. |last5=Meyer |first5=S. S. |last6=Shafer |first6=R. A. |last7=Weiss |first7=R. |last8=Wright |first8=E. L. |last9=Bennett |first9=C. L. |title= A preliminary measurement of the cosmic microwave background spectrum by the Cosmic Background Explorer (COBE) satellite|journal=Astrophys. J. |date=1990 |volume=354 |pages=L37 |bibcode=1990ApJ...354L..37M |display-authors=1|doi-access=free }}

Active galactic nuclei have also been studied in the area, for example MBC2005.{{ cite journal |vauthors=Mateos S, Barcons X, Carrera FJ, Ceballos MT, Hasinger G, Lehmann I, Fabian AC, Streblyanska A |title=XMM-Newton observations of the Lockman Hole: search for AGNs |journal=Astron. Astrophys. |date=Dec 2005 |volume=444 |issue=1 |pages=79–99 |bibcode=2005A&A...444...79M |doi=10.1051/0004-6361:20052881 |arxiv = astro-ph/0506718 |s2cid=211409 }}

• Chandra Deep Field South - a similar clear field-of-view
• Interstellar medium
• Local Bubble
• Local Interstellar Cloud

{{reflist|2}}

• {{ cite journal |vauthors=Lockman FJ, Jahoda K, McCammon D |title=The structure of galactic HI in directions of low total column density |journal=Astrophys. J. |date=Mar 1986 |volume=302 |issue=3 |pages=432–49 |doi=10.1086/164002 |bibcode=1986ApJ...302..432L |hdl=2060/19850019473 |s2cid=118595586 |hdl-access=free }}

• [http://chandra.harvard.edu/photo/2005/bhlock/index.html Lockman Hole at Chandra]
• [http://chandra.harvard.edu/photo/2005/bhlock/animations.html Animations of Lockman Hole]
• [https://web.archive.org/web/20190708014607/http://herschel.cf.ac.uk/results/lockman-hole The Lockman Hole by the Herschel Space Observatory]
• [http://www.asu.edu/clas/hst/classes/ast494+591/2009-04-03/sdunn090403.pdf Spitzer Space Telescope and the Lockman Hole]
• [https://web.archive.org/web/20101124090146/http://www.mpe.mpg.de/heg/www/VAB2010/2010_05-18_FB_PB_high_neu1%20131.pdf XMM-Newton Observations of the Lockman Hole]
• [https://web.archive.org/web/20160303231447/http://www.mpe.mpg.de/xray/wave/rosat/gallery/calendar/1997/oct.php The Lockman Hole from the Max-Planck-Institut für extraterrestrische Physik]

Category:Interstellar media

Category:Observational astronomy

Category:Ursa Major

Category:X-ray astronomy