------------------------------------------------------------------------ ms_NRAO.tex ApJS, December 2004 Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-MailScanner-Information: Please contact postmaster@aoc.nrao.edu for more information X-MailScanner: Found to be clean X-MailScanner-SpamCheck: not spam, SpamAssassin (score=-5.1, required 7, BAYES_10 -4.70, USER_AGENT_PINE 0.00, X_AUTH_WARNING -0.40) % astro-ph/0409292 \documentstyle[11pt,aasms4,epsf]{article} % no no. on page 1 \def\folio{\ifnum\pageno<2\nopagenumbers\else\number\pageno\fi} \newtoks\headline \headline={\hss\twelverm\folio\hss} % page no at top of page \newtoks\footline \footline={{\hfil}} % no footer \font\reallybigbf=cmbx12 scaled 1440 %title font for cover page, next line is % \font\reallybigbf=cmbx10 scaled 1728 % an alternative if the first is unavailable \font\bigbf=cmbx10 scaled 1440 % title font for second page \font\mathbf=cmmib10 scaled 1000 % bold math font for tenpoint \def\phihat{\hat {\hbox{\mathbf \char"1E}}} %bold phi with a hat \font\twelvess=cmss10 scaled 1000 %\font\twelvess=cmss10 scaled 1200 % The following handle references for ApJ \def\ref{\par\noindent\hangindent=2pc \hangafter=1 } \def\amin{\ifmmode^{\prime}\else$^{\prime}$\fi} \def\asec{\ifmmode^{\prime\prime}\else$^{\prime\prime}$\fi} %\newcommand\iras{{\it IRAS}} %\newcommand\asca{{\it ASCA}} %\newcommand\rosat{{\it ROSAT}} %\newcommand\hii{\ion{H}{2}} \def\cc{\hbox{G0.121+0.017}} \def\gc{\hbox{Galactic center}} \def\ApJ{ApJ} \def\MNRAS{MNRAS} \def\ARAA{ARA\&A} \def\ApJLett{ApJ} \def\PASJ{PASJ} \def\ANYAS{Ann NY Acad Sci} \def\ApJS{ApJS} % \def\AA{A\&A} \def\Nature{Nature} \def\etal{{et al. }} % cappage puts a figure caption and page no. on a page \def\cappage #1 #2 #3 {\vfill\eject\pageno=#1 \vglue 10 true in minus 10 true in \noindent{\bf Figure #2.} #3} % Definitions of useful things % the following have to be used in mathmode \def\ee #1 {\times 10^{#1}} \def\ut #1 #2 { \, \hbox{#1}^{#2}} \def\u #1 { \, \hbox{#1}} \def\lsol{\, \hbox{$\hbox{L}_\odot$}} \def\msol{\, \hbox{$\hbox{M}_\odot$}} \def\kms {\, \hbox{km}\,\hbox{s}^{-1}} \def\persec {\, \hbox{s}^{-1}} \def\percc {\, \hbox{cm}^{-3}} \def\persqcm {\, \hbox{cm}^{-2}} \def\mic {\, \mu \hbox{m}} \def\half{{\textstyle {1\over 2}}} \def\thalf{{\textstyle{ 3\over 2}}} \let\grad=\nabla \def\cross{{\bf \times}} \def\curl #1 {\grad \cross #1} \def\div #1 {\grad \cdot #1} \def\nh{{n_{\rm H}}} \tighten \doublespace %\twocolumn \def\msol {\hbox{$M_\odot$}} % Solar mass \def\sec {$^{\rm s}$} % Second of time \def\kms {\hbox{km{\hskip0.1em}s$^{-1}$}} % km/s \def\i {\hbox{\it I}} % italic I \def\etal {{\it et al. }} % et al. \begin{document} \title{A $\lambda$20cm Survey of the Galactic Center Region I: Detection of Numerous Linear Filaments} \author{F. Yusef-Zadeh} \affil{Department of Physics and Astronomy, Northwestern University, Evanston, Il. 60208 (zadeh@northwestern.edu)} \author{J. Hewitt} \affil{Department of Physics and Astronomy, Northwestern University, Evanston, Il. 60208 (j-hewitt@northwestern.edu)} \author{W. Cotton} \affil{National Radio Astronomy Observatory, Charlottesville, VA 22903 (bcotton@nrao.edu)} This is a first in a series of papers presenting a sensitive $\lambda$20cm VLA continuum survey of the Galactic center region using new and archival data based on multi-configuration observations taken with relatively uniform {\it uv} coverage. The high dynamic range images cover the regions within $-2^\circ < l < 5^\circ$ and $-40' < b < 40'$ with a spatial resolution of $\approx30''$ and 10$''$. The wide field imaging technique is used to construct a low-resolution mosaic of 40 overlapping pointings. The mosaic image includes the Effelsburg observations filling the low spatial frequency {\it uv} data. We also present high resolution images of twenty three overlapping fields using DnC and CnB array configurations. These high-resolution images are sensitive to both compact and extended continuum features with a wide range of angular scales with rms noise of 0.2 mJy beam$^{-1}$ in the outer parts of the Galactic center region. The survey has resulted in a catalog of 345 discrete sources as well as 140 images revealing structural details of HII regions, SNRs, pulsar wind nebulae and more than 80 linear filaments distributed toward the complex region of the Galactic center. These observations show the evidence for an order of magnitude increase in the number of faint linear filaments with typical lengths of few arcminutes. Many of the filaments show morphological characteristics similar to the Galactic center nonthermal radio filaments (NRFs). The linear filaments are not isolated but are generally clustered in star forming regions where prominent NRFs had been detected previously. The extensions of many of these linear filaments appear to terminate at either a compact source or a resolved shell-like thermal source. A relationship between the filaments, the compact and extended thermal sources as well as a lack of preferred orientation for many RFs should constrain models that are proposed to explain the origin of nonthermal radio filaments in the Galactic center. \end{document}