HERUS: A CO ATLAS FROM SPIRE SPECTROSCOPY OF LOCAL ULIRGs

Abstract

We present the Herschel SPIRE Fourier Transform Spectroscopy (FTS) atlas for a complete flux-limited sample of local ultraluminous infrared galaxies (ULIRGs) as part of the HERschel Ultra Luminous InfraRed Galaxy Survey (HERUS). The data reduction is described in detail and was optimized for faint FTS sources ,with particular care being taken for the subtraction of the background, which dominates the continuum shape of the spectra. To improve the final spectra, special treatment in the data reduction has been given to any observation suffering from artifacts in the data caused by anomalous instrumental effects. Complete spectra are shown covering 200-671 μm, with photometry in the SPIRE bands at 250, 350, and 500 μm. The spectra include near complete CO ladders for over half of our sample, as well as fine structure lines from [C I] 370 μm, [C I] 609 μm, and [N II] 205 μm. We also detect H 2 O lines in several objects. We construct CO spectral line energy distributions (SLEDs) for the sample, and compare their slopes with the far-infrared (FIR) colors and luminosities. We show that the CO SLEDs of ULIRGs can be broadly grouped into three classes based on their excitation. We find that the mid-J (5<J<8) lines are better correlated with the total FIR luminosity, suggesting that the warm gas component is closely linked to recent star formation. The higher J transitions do not linearly correlate with the FIR luminosity, consistent with them originating in hotter, denser gas that is unconnected to the current star formation. We conclude that in most cases more than one temperature component is required to model the CO SLEDs.

HERUS: the far-IR/submm spectral energy distributions of local ULIRGs and photometric atlas

“…Photometry of the HERUS galaxies in the SPIRE bands PSW (250µm), PMW (350µm), PLW (500µm). These fluxes originally appeared in Pearson et al (2016) ters of our model are thus A, β and T. We fit these to the data for each individual HERUS ULIRG using the emcee Markov Chain Monte Carlo package 1 (Foreman-Mackey et al, 2013, for the general approach see also Lewis & Bridle 2002, Jaynes 2003 to probe the parameter space, equivalent to an exploration of the χ 2 surface with a nonlinear parameterization. We apply the following priors for our parameter values: for temperature (T) we adopt a uniform prior between 3 and 100K; for emissivity (β) we adopt a uniform prior between 0 and 3; for A, because the wide range of distances for our sources implies a range of amplitudes covering several orders 1 http://dan.iel.fm/emcee/current/ of magnitude, we adopt a uniform prior on log(A) between -3 and 10.…”

“…Other observations for this sample are also available at a range of resolutions and wavelengths. For more details on the SPIRE spectroscopic observations see Pearson et al (2016).…”

AGN feedback in a galaxy merger: multi-phase, galaxy-scale outflows with a fast molecular gas blob ∼6 kpc away from IRAS F08572+3915

“…We note, however, that there are examples of radio-quiet galaxies with jet-like winds indicating the existence of either a faint ongoing jet or a past jet event (e.g., Aalto et al 2016;Fernández-Ontiveros et al 2019). Finally, the CO spectral line energy distribution (SLED) up to J = 11 reveals highly excited gas in IRAS F08572+3915 (Papadopoulos et al 2010;Pearson et al 2016). While the strong AGN and starburst activity contribute significantly to the high molecular gas excitation, we cannot rule out that shocks resulting from a potential jet-dense ISM play a role in shaping the SLED beyond J ≈ 7 (e.g., Papadopoulos et al 2008;Pellegrini et al 2013).…”

The Near-infrared CO Absorption Band as a Probe to the Innermost Part of an AGN-obscuring Material

“…To make a similar analysis, we referred to Pearson et al (2016), who observed the CO emission lines from J = 5-4 to J = 13-12 in 43 ULIRGs using the Herschel Space Observatory. Seven of their sample galaxies are included in our targets, namely, all of the AKARI targets and IRAS 00397−1312.…”