We present FIR[50 − 300 µm]−CO luminosity relations (i.e., log L FIR = α log L CO + β) for the full CO rotational ladder from J = 1 − 0 up to J = 13 − 12 for a sample of 62 local (z ≤ 0.1) (Ultra) Luminous Infrared Galaxies (LIRGs; L IR[8−1000 µm] > 10 11 L ) using data from Herschel SPIRE-FTS and ground-based telescopes. We extend our sample to high redshifts (z > 1) by including 35 (sub)millimeter selected dusty star forming galaxies from the literature with robust CO observations, and sufficiently well-sampled FIR/sub-millimeter spectral energy distributions (SEDs) so that accurate FIR luminosities can be deduced. The addition of luminous starbursts at high redshifts enlarge the range of the FIR−CO luminosity relations towards the high-IR-luminosity end while also significantly increasing the small amount of mid-J/high-J CO line data (J = 5 − 4 and higher) that was available prior to Herschel. This new data-set (both in terms of IR luminosity and J-ladder) reveals linear FIR−CO luminosity relations (i.e., α 1) for J = 1 − 0 up to J = 5 − 4, with a nearly constant normalization (β ∼ 2). In the simplest physical scenario this is expected from the (also) linear FIR−(molecular line) relations recently found for the dense gas tracer lines (HCN and CS), as long as the dense gas mass fraction does not vary strongly within our (merger/starburst)-dominated sample. However from J = 6 − 5 and up to the J = 13 − 12 transition we find an increasingly sub-linear slope and higher normalization constant with increasing J. We argue that these are caused by a warm (∼ 100 K) and dense (> 10 4 cm −3 ) gas component whose thermal state is unlikely to be maintained by star formation powered far-UV radiation fields (and thus is no longer directly tied to the star formation rate). We suggest that mechanical heating (e.g., supernova driven turbulence and shocks), and not cosmic rays, is the more likely source of energy for this component. The global CO spectral line energy distributions (SLEDs), which remain highly excited from J = 6 − 5 up to J = 13 − 12, are found to be a generic feature of the (U)LIRGs in our sample, and further support the presence of this gas component.

We present results from a study of optically emitting Supernova Remnants (SNRs) in six nearby galaxies (NGC 2403, NGC 3077, NGC 4214, NGC 4395, NGC 4449 and NGC 5204) based on deep narrow band Hα and [S II] images as well as spectroscopic observations. The SNR classification was based on the detected sources that fulfill the well-established emission line flux criterion of [S II]/Hα> 0.4. This study revealed ∼400 photometric SNRs down to a limiting Hα flux of 10 −15 erg sec −1 cm −2 . Spectroscopic observations confirmed the shockexcited nature of 56 out of the 96 sources with ([S II]/Hα) phot > 0.3 (our limit for an SNR classification) for which we obtained spectra. 11 more sources were spectroscopically identified as SNRs although their photometric [S II]/Hα ratio was below 0.3. We discuss the properties of the optically-detected SNRs in our sample for different types of galaxies and hence different environments, in order to address their connection with the surrounding interstellar medium. We find that there is a difference in [N II]/Hα line ratios of the SNR populations between different types of galaxies which indicates that this happens due to metallicity. We cross-correlate parameters of the optically detected SNRs ([S II]/Hα ratio, luminosity) with parameters of coincident X-ray emitting SNRs, resulted from our previous studies in the same sample of galaxies, in order to understand their evolution and investigate possible selection effects. We do not find a correlation between their Hα and X-ray luminosities, which we attribute to the presence of material in a wide range of temperatures. We also find evidence for a linear relation between the number of luminous optical SNRs (10 37 erg sec −1 ) and SFR in our sample of galaxies.

This paper uses the first XMM–Newton Serendipitous Source Catalog compiled by the XMM–Newton Science Centre to identify low‐z X‐ray selected normal galaxy candidates. Our sample covers a total area of ≈6 deg2 to the 0.5–2 keV limit ≈10−15 erg s−1 cm−2. A total of 23 sources are selected on the basis of low X‐ray to optical flux ratio log fX/fopt < −2, soft X‐ray spectral properties and optical spectra, when available, consistent with stellar formation rather than active galactic nucleus (AGN) processes. This sample is combined with similarly selected systems from the Needles in the Haystack Survey to provide a total of 46 unique (z≲ 0.2) X‐ray detected normal galaxies, the largest low‐z sample yet available. This is first used to constrain the normal galaxy log N–log S at bright fluxes (10−15–10−13 erg s−1 cm−2). We estimate a slope of −1.46 ± 0.13 for the cumulative number counts consistent with the Euclidean prediction. We further combine our sample with 23 local (z≲ 0.2) galaxies from the Chandra Deep Field‐North and ‐South surveys to construct the local X‐ray luminosity function of normal galaxies. A Schechter form provides a good fit to the data with a break at log L★= 41.02+0.14−0.12 erg s−1 and a slope of α=−1.76 ± 0.10. Finally, for the sample of 46 systems, we explore the association between X‐ray luminosity and host galaxy properties, such as star formation rate (SFR) and stellar mass. We find that the LX of the emission‐line systems correlates with Hα luminosity and 1.4‐GHz radio power, both providing an estimate of the current SFR. In the case of early‐type galaxies with absorption‐line optical spectra, we use the K band as an approximation of stellar mass and find a correlation of the form LX∝L1.5K. This is flatter than the LX–LB relation for local ellipticals. This may be due to either LK providing a better approximation of galaxy mass or selection effects biasing our sample against very luminous early‐type galaxies, LX > 1042 erg s−1.

We present new diagnostic tools for distinguishing supernova remnants (SNRs) from HII regions. Up to now, sources with flux ratio [S II]/Hα higher than 0.4 have been considered as SNRs. Here, we present the combinations of three or two line ratios as more effective tools for the separation of these two kinds of nebulae, depicting them as 3D surfaces or 2D lines. The diagnostics are based on photoionization and shock excitation models (MAPPINGS III) analysed with Support Vector Machine (SVM) models for classification. The line-ratio combination that gives the most efficient diagnostic is: [O I]/Hα -[O II]/Hβ -[O III]/Hβ. This method gives 98.95% completeness in the SNR selection and 1.20% contamination. We also define the [O I]/Hα SNR selection criterion and we measure its efficiency in comparison to other selection criteria.