@article {220, title = {{The molecular gas reservoir of 6 low-metallicity galaxies from the Herschel Dwarf Galaxy Survey. A ground-based follow-up survey of CO(1-0), CO(2-1), and CO(3-2)}}, journal = {\aap}, volume = {564}, year = {2014}, pages = {A121}, keywords = {galaxies: dwarf, galaxies: ISM, infrared: galaxies, ISM: molecules, radio lines: galaxies}, doi = {10.1051/0004-6361/201322096}, author = {Cormier, D. and Madden, S.~C. and Lebouteiller, V. and Hony, S. and Aalto, S. and Costagliola, F. and Hughes, A. and R{\'e}my-Ruyer, A. and Abel, N. and Bayet, E. and Bigiel, F. and Cannon, J.~M. and Cumming, R.~J. and Galametz, M. and Galliano, F. and Viti, S. and Wu, R.} } @article {2014A\&A...564A.121C, title = {{The molecular gas reservoir of 6 low-metallicity galaxies from the Herschel Dwarf Galaxy Survey. A ground-based follow-up survey of CO(1-0), CO(2-1), and CO(3-2)}}, journal = {Astronomy and Astrophysics}, volume = {564}, year = {2014}, month = {apr}, pages = {A121}, abstract = {Context. Observations of nearby starburst and spiral galaxies have revealed that molecular gas is the driver of star formation. However, some nearby low-metallicity dwarf galaxies are actively forming stars, but CO, the most common tracer of this reservoir, is faint, leaving us with a puzzle about how star formation proceeds in these environments.
Aims: We aim to quantify the molecular gas reservoir in a subset of 6 galaxies from the Herschel Dwarf Galaxy Survey with newly acquired CO data and to link this reservoir to the observed star formation activity.
Methods: We present CO(1-0), CO(2-1), and CO(3-2) observations obtained at the ATNF Mopra 22-m, APEX, and IRAM 30-m telescopes, as well as [C ii] 157{$μ$}m and [O i] 63{$μ$}m observations obtained with the Herschel/PACS spectrometer in the 6 low-metallicity dwarf galaxies: Haro 11, Mrk 1089, Mrk 930, NGC 4861, NGC 625, and UM 311. We derived their molecular gas masses from several methods, including using the CO-to-H$_{2}$ conversion factor X$_{CO}$ (both Galactic and metallicity-scaled values) and dust measurements. The molecular and atomic gas reservoirs were compared to the star formation activity. We also constrained the physical conditions of the molecular clouds using the non-LTE code RADEX and the spectral synthesis code Cloudy.
Results: We detect CO in 5 of the 6 galaxies, including first detections in Haro 11 (Z \~{} 0.4 Z$_{\&sun;}$), Mrk 930 (0.2 Z$_{\&sun;}$), and UM 311 (0.5 Z$_{\&sun;}$), but CO remains undetected in NGC 4861 (0.2 Z$_{\&sun;}$). The CO luminosities are low, while [C ii] is bright in these galaxies, resulting in [C ii]/CO(1-0) {\ge} 10 000. Our dwarf galaxies are in relatively good agreement with the Schmidt-Kennicutt relation for total gas. They show short molecular depletion timescales, even when considering metallicity-scaled X$_{CO}$ factors. Those galaxies are dominated by their H i gas, except Haro 11, which has high star formation efficiency and is dominated by ionized and molecular gas. We determine the mass of each ISM phase in Haro 11 using Cloudy and estimate an equivalent X$_{CO}$ factor that is 10 times higher than the Galactic value. Overall, our results confirm the emerging picture that CO suffers from significant selective photodissociation in low-metallicity dwarf galaxies.}, keywords = {galaxies: dwarf, galaxies: ISM, infrared: galaxies, ISM: molecules, radio lines: galaxies}, doi = {10.1051/0004-6361/201322096}, url = {http://adsabs.harvard.edu/abs/2014A\%26A...564A.121C}, author = {Cormier, D. and Madden, S.~C. and Lebouteiller, V. and Hony, S. and Aalto, S. and F. Costagliola and Hughes, A. and R{\'e}my-Ruyer, A. and Abel, N. and Bayet, E. and Bigiel, F. and Cannon, J.~M. and Cumming, R.~J. and Galametz, M. and Galliano, F. and Viti, S. and Wu, R.} } @article {2014ApJ...786..156H, title = {{A Multi-wavelength View of the Central Kiloparsec Region in the Luminous Infrared Galaxy NGC 1614}}, journal = {The Astrophysical Journal}, volume = {786}, year = {2014}, month = {may}, pages = {156}, abstract = {The Luminous Infrared Galaxy NGC 1614 hosts a prominent circumnuclear ring of star formation. However, the nature of the dominant emitting mechanism in its central \~{}100 pc is still under debate. We present sub-arcsecond angular resolution radio, mid-infrared, Pa{$\alpha$}, optical, and X-ray observations of NGC 1614, aimed at studying in detail both the circumnuclear ring and the nuclear region. The 8.4 GHz continuum emission traced by the Very Large Array and the Gemini/T-ReCS 8.7 {$μ$}m emission, as well as the Pa{$\alpha$} line emission, show remarkable morphological similarities within the star-forming ring, suggesting that the underlying emission mechanisms are tightly related. We used a Hubble Space Telescope/NICMOS Pa{$\alpha$} map of similar resolution to our radio maps to disentangle the thermal free-free and non-thermal synchrotron radio emission, from which we obtained the intrinsic synchrotron power law for each individual region within the central kiloparsec of NGC 1614. The radio ring surrounds a relatively faint, steep-spectrum source at the very center of the galaxy, suggesting that the central source is not powered by an active galactic nucleus (AGN), but rather by a compact (r {\l}t}\~{} 90 pc) starburst (SB). Chandra X-ray data also show that the central kiloparsec region is dominated by SB activity, without requiring the existence of an AGN. We also used publicly available infrared data to model-fit the spectral energy distribution of both the SB ring and a putative AGN in NGC 1614. In summary, we conclude that there is no need to invoke an AGN to explain the observed bolometric properties of the galaxy.}, keywords = {galaxies: individual: NGC 1614, galaxies: nuclei, galaxies: starburst, infrared: galaxies, radio continuum: galaxies, supernovae: general}, doi = {10.1088/0004-637X/786/2/156}, url = {http://adsabs.harvard.edu/abs/2014ApJ...786..156H}, author = {R. Herrero-Illana and M. A. P{\'e}rez-Torres and Alonso-Herrero, A. and Alberdi, A. and Colina, L. and Efstathiou, A. and Hern{\'a}ndez-Garc{\'\i}a, L. and Miralles-Caballero, D. and V{\"a}is{\"a}nen, P. and Packham, C.~C. and Rajpaul, V. and Zijlstra, A.~A.} } @article {2014MNRAS.440.1052K, title = {{The nature of supernovae 2010O and 2010P in Arp 299 - I. Near-infrared and optical evolution}}, journal = {Monthly Notices of the Royal Astronomical Society}, volume = {440}, year = {2014}, month = {may}, pages = {1052-1066}, abstract = {We present near-infrared and optical photometry, plus optical spectroscopy of two stripped-envelope supernovae (SNe) 2010O and 2010P that exploded in two different components of an interacting luminous infrared galaxy Arp 299 within only a few days of one another. SN 2010O is found to be photometrically and spectroscopically similar to many normal Type Ib SNe and our multiwavelength observations of SN 2010P suggest it to be a Type IIb SN. No signs of clear hydrogen features or interaction with the circumstellar medium are evident in the optical spectrum of SN 2010P. We derive estimates for the host galaxy line-of-sight extinctions for both SNe, based on both light curve and spectroscopic comparison finding consistent results. These methods are also found to provide much more robust estimates of the SN host galaxy reddening than the commonly used empirical relations between extinction and equivalent width of Na I D absorption features. The SN observations also suggest that different extinction laws are present in different components of Arp 299. For completeness, we study high-resolution pre-explosion images of Arp 299 and find both SNe to be close to, but not coincident with, extended sources that are likely massive clusters. A very simple model applied to the bolometric light curve of SN 2010O implies a rough estimate for the explosion parameters of E$_{k}$ {\ap} 3 {\times} 10$^{51}$ erg, M$_{ej}$ {\ap} 2.9 M$_{\&sun;}$ and M$_{Ni}$ {\ap} 0.16 M$_{\&sun;}$.}, keywords = {galaxies: individual: Arp 299, galaxies: starburst, infrared: galaxies, supernovae: general, supernovae: individual: SN 2010O, supernovae: individual: SN 2010P}, doi = {10.1093/mnras/stt2289}, url = {http://adsabs.harvard.edu/abs/2014MNRAS.440.1052K}, author = {Kankare, E. and Mattila, S. and Ryder, S. and Fraser, M. and Pastorello, A. and Elias-Rosa, N. and Romero-Ca{\~n}izales, C. and Alberdi, A. and Hentunen, V.-P. and R. Herrero-Illana and Kotilainen, J. and M. A. P{\'e}rez-Torres and V{\"a}is{\"a}nen, P.} } @article {2012ApJ...756..111M, title = {{Core-collapse Supernovae Missed by Optical Surveys}}, journal = {The Astrophysical Journal}, volume = {756}, year = {2012}, month = {sep}, pages = {111}, abstract = {We estimate the fraction of core-collapse supernovae (CCSNe) that remain undetected by optical SN searches due to obscuration by large amounts of dust in their host galaxies. This effect is especially important in luminous and ultraluminous infrared galaxies, which are locally rare but dominate the star formation at redshifts of z \~{} 1-2. We perform a detailed investigation of the SN activity in the nearby luminous infrared galaxy Arp 299 and estimate that up to 83\% of the SNe in Arp 299 and in similar galaxies in the local universe are missed by observations at optical wavelengths. For rest-frame optical surveys we find the fraction of SNe missed due to high dust extinction to increase from the average local value of \~{}19\% to \~{}38\% at z \~{} 1.2 and then remain roughly constant up to z \~{} 2. It is therefore crucial to take into account the effects of obscuration by dust when determining SN rates at high redshift and when predicting the number of CCSNe detectable by future high-z surveys such as LSST, JWST, and Euclid. For a sample of nearby CCSNe (distances 6-15 Mpc) detected during the last 12 yr, we find a lower limit for the local CCSN rate of 1.5$^{+0.4}$ $_{- 0.3}$ {\times} 10$^{-4}$ yr$^{-1}$ Mpc$^{-3}$, consistent with that expected from the star formation rate. Even closer, at distances less than \~{}6 Mpc, we find a significant increase in the CCSN rate, indicating a local overdensity of star formation caused by a small number of galaxies that have each hosted multiple SNe.}, keywords = {galaxies: individual: Arp 299, galaxies: starburst, infrared: galaxies, supernovae: general, supernovae: individual: SN 2005at SN 2010P}, doi = {10.1088/0004-637X/756/2/111}, url = {http://adsabs.harvard.edu/abs/2012ApJ...756..111M}, author = {Mattila, S. and Dahlen, T. and Efstathiou, A. and Kankare, E. and Melinder, J. and Alonso-Herrero, A. and M. A. P{\'e}rez-Torres and Ryder, S. and V{\"a}is{\"a}nen, P. and {\"O}stlin, G.} } @article {2012ApJ...744L..19K, title = {{Discovery of Two Supernovae in the Nuclear Regions of the Luminous Infrared Galaxy IC 883}}, journal = {The Astrophysical Journal Letters}, volume = {744}, year = {2012}, pages = {L19}, abstract = {We report the discovery of two consecutive supernovae (SNe), 2010cu and 2011hi, located at 0farcs37 (180 pc) and 0farcs79 (380 pc) projected distance, respectively, from the center of the K-band nucleus of the luminous infrared galaxy (LIRG) IC 883. The SNe were discovered in an ongoing near-infrared K-band search for core-collapse SNe in such galaxies using the ALTAIR/NIRI adaptive optics system with laser guide star at the Gemini-North Telescope. These are thus the closest SNe yet discovered to an LIRG nucleus in optical or near-infrared wavelengths. The near-infrared light curves and colors of both SNe are consistent with core-collapse events. Both SNe seem to suffer from relatively low host galaxy extinction suggesting that regardless of their low projected galactocentric distances, they are not deeply buried in the nuclear regions of the host galaxy.}, keywords = {galaxies: individual: IC 883, galaxies: starburst, infrared: galaxies, instrumentation: adaptive optics, supernovae: individual: SN 2010cu SN 2011hi}, doi = {10.1088/2041-8205/744/2/L19}, url = {http://adsabs.harvard.edu/abs/2012ApJ...744L..19K}, author = {Kankare, E. and Mattila, S. and Ryder, S. and V{\"a}is{\"a}nen, P. and Alberdi, A. and Alonso-Herrero, A. and Colina, L. and Efstathiou, A. and Kotilainen, J. and Melinder, J. and M. A. P{\'e}rez-Torres and Romero-Ca{\~n}izales, C. and Takalo, A.} }