English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present Herschel SPIRE FTS spectroscopy of the nearby luminous infraredgalaxy NGC 6240. In total 20 lines are detected, including CO J=4-3 throughJ=13-12, 6 H2O rotational lines, and [CI] and [NII] fine-structure lines. TheCO to continuum luminosity ratio is 10 times higher in NGC 6240 than Mrk 231.Although the CO ladders of NGC 6240 and Mrk 231 are very similar, UV and/orX-ray irradiation are unlikely to be responsible for the excitation of the gasin NGC 6240. We applied both C and J shock models to the H2 v=1-0 S(1) andv=2-1 S(1) lines and the CO rotational ladder. The CO ladder is best reproducedby a model with shock velocity v_s=10 km s^-1 and a pre-shock density n_H=5 *10^4 cm^-3. We find that the solution best fitting the H2 lines is degenerate:The shock velocities and number densities range between v_s = 17 - 47 km s^-1and n_H=10^7 - 5 * 10^4 cm^-3, respectively. The H2 lines thus need a much morepowerful shock than the CO lines. We deduce that most of the gas is currentlymoderately stirred up by slow (10 km s^-1) shocks while only a small fraction(< 1 percent) of the ISM is exposed to the high velocity shocks. This impliesthat the gas is rapidly loosing its highly turbulent motions. We argue that ahigh CO line-to-continuum ratio is a key diagnostic for the presence of shocks.

Evidence for CO shock excitation in NGC 6240 from Herschel SPIRE spectroscopy