We observed with the Submillimeter Array and IRAM 30 m telescope three high-mass star-forming regions in different evolutionary stages in the W3 high-mass star formation complex. These regions, i.e. W3 SMS1 (W3 IRS5), SMS2 (W3 IRS4) and SMS3, are located within the same large-scale environment, which allows us to study rotation and outflows as well as chemical properties in an evolutionary sense. While we find multiple mm continuum sources toward all regions, these three subregions exhibit different dynamical and chemical properties, which indicates that they are in different evolutionary stages. Even within each sub-region, massive cores of different ages are found, e.g. in SMS2, sub-sources from the most evolved UCHii region to potential starless cores exist within 30 000 AU (left panel, Fig. 1). Outflows and rotational structures are found in SMS1 and SMS2. Evidence for interactions between the molecular cloud and the HII regions is found in the 13CO channel maps (right panel, Fig. 1), which may indicate triggered star formation.

Several recent surveys (HERACLES, NGLS, KINGFISH, VNGS) have provided us with sensitive high-resolution observations of the molecular gas and dust content in spiral galaxies within 25 Mpc. I review recent results on the molecular gas content and its relation to star formation, as well as on the gas to dust ratio and the dust heating in spiral galaxies. I also present new results on the effect of environment on the molecular gas content of spiral galaxies.

The wide variety of low metallicity galaxies of the local universe serve as convenient laboratories to study the evolution of gas and dust and conditions for star formation in environments which may resemble those of the early universe. The Herschel Dwarf Galaxy Survey is studying the far infrared (FIR) and submillimeter (submm) properties of the gas and dust in galaxies with metallicity values as low as 1/45 that of solar. With complementary Spitzer, Laboca/APEX, Scuba/JCMT data, the dust spectral energy distributions are well constrained now, providing more accurate dust masses. We find a steep drop in dust-to-gas mass ratio (D/G) when the metallicity is below 12+log(O/H) ∼ 8. A submillimeter excess can be found in some low metallicity galaxies, which, when present, becomes apparent at wavelengths at or longer than 500 μm. While CO is difficult to observe in low metallicity gas, the FIR fine structure lines, on the other hand, are very luminous and highlight a potentially important reservoir of CO-free molecular gas, better traced by the 158 μm [CII] line.

A very sensitive survey of the CO(2−1) emission of the entire disk of the Local Group galaxy M 33 is virtually complete. Hundreds of clouds down to a mass of 10000M⊙ are detected and we show that the cloud mass function (assuming a constant ratio between CO emission and H2 mass) steepens away from the center of M 33. Through comparison with dust emission and cloud Virial masses, we estimate a N(H2)/ICO factor roughly twice Galactic.

We present an overview of the latest results from the PdBI Arcsecond Whirlpool Survey (PAWS, PI: E. Schinnerer), which has mapped CO(1-0) emission in the nearby grand-design spiral galaxy M51 at 40pc resolution. Our data are sensitive to GMCs above 105 M⊙, allowing the construction of the largest GMC catalog to date – containing over 1500 objects – using the CPROPS algorithm (Rosolowsky & Leroy 2006). In the inner disk of M51, the properties of the CO emission show significant variation that can be linked to the dynamical environment in which the molecular gas is located. We find that dynamically distinct regions host clouds with different properties and exhibit different GMC mass spectra, as well as distinct patterns of star formation. To understand how this sensitivity to environment emerges, we consider the role of pressure on GMC stabilization (including shear and star formation feedback-driven turbulence). We suggest that, in the presence of significant external pressure, streaming motions driven by the spiral arm can act to reduce the surface pressure on clouds. The resulting stabilization impacts the global pattern of star formation and can account for the observed non-monotonic radial dependence of the gas depletion time. Our findings have implications for the observed scatter in the standard GMC relations and extragalactic star formation laws.

SMA observations of molecular gas and dust in nearby galactic centers are presented to showcase remarkable ISM properties including warm to very hot gas, molecular clouds producing massive star clusters, and mechanical feedback through bubbles and outflows.

Effects of galaxy environment on its cold gas content are studied in detail using different date sets and statistics. These include measuring the clustering of galaxies as a function of their Hi mass fraction, quantifying the depletion of Hi gas content of cluster galaxies as a function of cluster-centric radius, and comparing the dependence of environmental density on galaxy star formation rate with the dependence on Hi gas mass fraction. Results from these studies are all consistent with a picture in which ram-pressure stripping may play an important role in removing atomic gas from the outer disks of low mass satellite galaxies.

Lenticular (S0) galaxies are a morphological transition class between ellipticals and early-type spirals. Recent studies indicate that the formation scenario for lenticular galaxies depends on their near-IR luminosity (Barway et al. 2007;2009;2011). Low-luminosity lenticular galaxies likely formed by the stripping of gas from the disc of late-type spiral galaxies, which in turn formed their pseudo bulges through secular evolution processes, possibly involving multiple episodes of star formation. On the other hand, more luminous lenticulars likely formed at early epochs through a rapid collapse followed by rapid star formation, similar to the formation process of elliptical galaxies, and are characterized by a old coeval stellar population in the bulge. To investigate the imprint of these distinct formation scenarios on stellar populations, we combine GALEX/SDSS/2MASS photometry to construct color-color diagrams for a carefully defined sample of ~400 lenticular galaxies. We divide the sample into bright and faint groups as suggested by Barway et al. (2007). We find the (FUV-NUV) versus (NUV-K) color-color diagram shows larger scatter for faint lenticular galaxies while bright lenticular galaxies show a much tighter relation similar to that of ellipticals. Simple Stellar Population (SSP) analysis shows that ellipticals and bright lenticulars are dominated by a stellar population of age >109 years while faint lenticular galaxies are as young as 108 years, providing evidence for relatively recent star formation activity. Further, if we use the (NUV-r) < 5.4 color criterion to identify galaxies with recent (within 500 Myr) star formation, most faint lenticular galaxies fall into this category; bright lenticulars are mostly quiescent. Most faint lenticular galaxies generally have lower velocity dispersions. If we consider velocity as a virial mass indicator, majority of faint, recently star forming, lenticular galaxies have low virial masses compared to brighter lenticular galaxies. Such systematic differences in star formation history between bright and faint lenticular galaxies are consistent with the expectations from the luminosity dependent formation scenario described above.

We study the stellar populations of a large sample of nearly face-on disk Low Surface Brightness Galaxies (LSBGs), with B-band central surface brightness μ0(B) > 22 mag arcsec−2, selected from the Sloan Digital Sky Survey Data Release 4 (SDSS-DR4) main galaxy sample (similar to Zhong et al. 2008; Liang et al. 2010).

We present a study of the morphology, kinematics and star formation of a sample of 27 isolated spiral galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S4G), on the basis of Hα Fabry-Perot (FP) data from the GHαFaS instrument at the William Herschel Telescope (WHT) in La Palma, complemented with images at 3.6 micron from the Spitzer Space Telescope, and with images in the R-band and in Hα taken with the ACAM instrument mounted on the WHT. With the FP data we can investigate the gas kinematics in terms of velocity maps and position-velocity diagrams, keys to constrain the secular evolution processes. We can also analyse the morphology and compute the star formation rate (SFR) with the ancillary data.

We have used the package CLOUDPROPS (Rosolowsky & Leroy 2008) in order to identify clouds, which are contained in data cubes of molecular/Hα line emission, and extract their properties. The molecular data cube is taken from the ALMA public archive and the ionized hydrogen data cube was obtained with the Fabry-Perot interferometer, GHαFaS, on the 4.2 m WHT in La Palma. In our study of the overlap region of the Antennae galaxies we have identified two populations of molecular clouds, above and below log M/M⊙ = 6.75 (in agreement with Wei et al. 2012 who find the break in mass at log M/M⊙ = 6.5) and two different populations of ionized gas clouds; the break in the luminosity occurs near log L = 37.6 (see Fig. 1). We have measured the masses, velocity dispersions and luminosities of the clouds, and derived relation between them for each population. Population II clouds (both molecular and ionized) tend to be located in the most luminous regions, while population I clouds can be found in the outskirts. This work will be published in Font et al. (2013).

Lyman Break Analogs (LBAs) are a population of star-forming galaxies at low redshift (z ∼ 0.2). These objects present metallicities, morphologies and other physical properties similar to higher redshift Lyman Break Galaxies (LBGs), motivating their detailed study as potential local analogs to high-redshift starburst galaxies (Hoopes et al. 2007, Basu-Zych et al. 2009, Overzier et al. 2010, Overzier et al. 2011).

Our recent integral-field spectroscopy survey of LBAs with Keck/OSIRIS shows that these galaxies have the same nebular gas kinematic properties as high-redshift LBGs. We argue that such kinematic studies are not an appropriate diagnostic to rule out major merger events as the trigger for the observed starburst. Comparison between kinematic analysis and morphological indices from HST imaging disagree with respect to merger identification, with no correlation between the two methods. Artificial redshifting of our data indicates the merger detection rate is even worse at high redshift due to surface brightness dimming and resolution loss. For more details, we refer the reader to Gonçalves et al. (2010).

More recently, we have initiated a program with the CARMA array to detect molecular gas in these galaxies (Gonçalves et al. 2013, in prep.). Our results show that LBAs present strong emission in CO(1-0), with similar gas fractions to those observed in high-redshift starburst galaxies. Moreover, the objects observed thus far follow the same Schmidt-Kennicutt law as local galaxies, albeit at much higher surface densities, as found in BzK galaxies at z ∼ 2 (Daddi et al. 2010). This distinguishes our sample from dusty starburst galaxies, such as ULIRGs and SMGs.

The upcoming operations of ALMA will definitely make a great impact on this project. We will be able to observe fainter, lower metallicity objects, and at the same time we will map the CO emission at sub-kpc resolutions. Once those data become available, we hope the scenario for the physical processes regarding the collapse of the molecular clouds and subsequent star formation will become clearer.

We present detailed integral field unit observations of the central few kiloparsecs of the ionized nebulae surrounding four active central cluster galaxies (CCGs) in cooling flow clusters (Abell 0496, 0780, 1644 and 2052). Our sample consists of CCGs with Hα filaments, and have existing data from the X-ray to radio wavelength regimes available, but lacked the detailed optical emission-line (and simultaneous absorption line) data over a broad wavelength range to probe the dominant ionisation processes, excitation sources, morphology and kinematics of the hot gas (as well as the morphology and kinematics of the stars). This, combined with the other multiwavelength data, will form a complete view of the different phases (hot and cold gas and stars) and how they interact in the processes of star formation and feedback detected in central galaxies in cooling flow clusters, as well as the influence of the host cluster. We derive the optical dust extinction maps of the four nebulae. We also derive a range of different kinematic properties, given the small sample size. For Abell 0496 and 0780, we find that the stars and gas are kinematically decoupled, and in the case of Abell 1644 we find that these components are aligned. For Abell 2052, we find that the gaseous components show rotation even though no rotation is apparent in the stellar components. To the degree that our spatial resolution reveals, it appears that all the optical forbidden and hydrogen recombination lines originate in the same gas for all the galaxies. Based on optical diagnostic ratios ([OIII]λ5007/Hβ against [NII]λ6584/Hα, [SII]λ6717,6731/Hα, and [OI]λ6300/Hα), all objects contain a LINER nucleus and show extended LINER-like gas emission. We also show that the hardness of the ionizing continuum does not decrease radially within our field-of-view as the emission line ratios do not vary significantly with radius, thus the derived nebular properties are spatially homogeneous. We fit AGN and pAGB stars photoionisation models as well as shock excitation models to our derived diagnostic ratios. We suggest that AGN photoionisation is the most likely ionisation mechanism even though shocks and pAGB stars can not be conclusively eliminated.

The Byurakan-IRAS Galaxy (BIG) sample (Mickaelian 1995) is the result of optical identifications of IRAS PSC sources at high-galactic latitudes using the First Byurakan Survey (FBS) low-dispersion spectra (Markarian et al. 1989). Among the 1577 objects 1178 galaxies have been identified. Most are dusty spiral galaxies and there are a number of ULIRGs among these objects. Our spectroscopic observations carried out with three telescopes (Byurakan Astrophysical Observatory 2.6m, Russian Special Astrophysical Observatory 6m and Observatoire de Haute Provence 1.93m) (Mickaelian & Sargsyan 2010) for 172 galaxies, as well as the SDSS DR8 spectra for 83 galaxies make up the list of 255 spectroscopically studied BIG objects. The classification to activity types for narrow-line emission galaxies has been carried out using the diagnostic diagrams by Veilleux & Osterbrock (1987). All possible physical characteristics have been measured and/or calculated, including radial velocities and distances, angular and physical sizes, absolute magnitudes and luminosities (both optical and IR). IR luminosities and star-formation rates have been calculated from the IR fluxes (Duc et al. 1997).

Among the 172 observed galaxies, 102 starburst (HII) ones, 29 AGN (Sy or LINER), and 19 galaxies with composite spectrum have been revealed; spectra of 12 galaxies show emission features but without a possibility for more accurate classification, 9 galaxies are presented as galaxies where the star formation rate does not exceed normal one, and 1 galaxy is an absorption galaxy. Among the 83 objects having SDSS spectra, there are 55 HIIs, 8 Seyferts, 2 LINERs, 4 other AGN (without accurate classification), 6 composite spectrum objects and 8 other emission-line galaxies. In our spectroscopic sample we have 43 (17%) AGN, 25 (10%) composite spectrum objects, 157 (62%) starbursts, 29 emission-line galaxies without a definite type, and 1 absorption-line galaxy. There are 3 Ultra-Luminous InfraRed Galaxies (ULIRG).

Various multiwavelength (MW) data have been retrieved for the full sample of 1178 objects from recent catalogs from X-ray to radio (ROSAT, GALEX, APM, MAPS, USNO, GSC, SDSS, 2MASS, WISE, IRAS, AKARI, NVSS, FIRST, etc.) to make a complete study of these galaxies possible. MW SEDs have been built, which have been matched to their optical classifications. Star-formation rates have been calculated to compare to their other physical characteristics, such as morphology, activity types, UV, optical, IR and radio luminosities, etc.

The UK InfraRed Telescope/UFTI instrument was used to analyse stars in the central region (square kpc) of the M33 galaxy over 3 nights in August 2005 with observations in K-band. Photometry was obtained for all stars by fitting appropriate PSF models, using DAOPHOT package (Stetson 1987). Around 18500 stars were detected. A master image was produced by applying an appropriate shift to each image and combining all 30 images. The final catalogue was obtained by assigning unique ID numbers to all stars and calibrating instrumental magnitudes. Comparing the UFTI and the UIST catalogues (Javadi et al. 2011) shows that a larger number of stars were detected with the UFTI, reaching a K-band limiting magnitude of 18.5 mag. Cross correlation methods were employed to cross match our catalogue with a previous monitoring survey in the near-infrared, the UIST catalogue. As a result, we assigned J magnitude and J-K color index to those stars which were found in both catalogues. Using these stars, a color-magnitude diagram was produced which shows populations of RGB, AGB and Carbon stars. Isochrones from Marigo et al. (2008) for solar metallicity and a distance modulus of 24.9 magnitude were used to identify different populations in the central region of the M33 galaxy. We will merge the UFTI catalogue with the UIST and the WFCAM, to get better coverage of stars in the central square kiloparsec.

The tidal interactions between galaxies are believed to be the main mechanism responsible for Wolf-Rayet (WR) phases in galaxies. The HI 21 cm-line is the best tracer for detecting tidal features in galaxies. We are studying WR galaxies in the HI line using GMRT and in the Hα line using Devasthal Optical telescope. Signatures of tidal interactions in Mrk 996 and Mrk 005, previously believed to be in non-interacting environment, have been detected using both HI and Hα images.

HI absorption-line studies provide a unique probe of the gas distribution and kinematics in galaxies well beyond the local universe (z ≳ 0.3). HI absorption-line surveys with next-generation radio telescopes will provide the first large-scale studies of HI in a redshift regime which is poorly understood. However, we currently lack the understanding to infer galaxy properties from absorption-line observations alone. To address this issue, we are conducting a search for intervening HI absorption in a sample of 20 nearby galaxies. Our aim is to investigate how the detection rate varies with distance from the galaxy. We target sight-lines to bright continuum sources, which intercept known gas-rich galaxies, selected from the HIPASS Bright Galaxy Catalogue (Koribalski et al. 2004). In our pilot sample, six galaxies with impact parameters < 20 kpc, we do not detect any absorption lines — although all are detected in 21cm emission. This indicates that an absorption non-detection cannot simply be interpreted as an absence of neutral gas – see Fig. 1. Our detection rate is low compared to previous surveys e.g. Gupta et al. (2010). This is, at least partially, due to the high resolution of the observations reducing the flux of the background source, which will also be an issue in future surveys, such as ASKAP-FLASH.

In this study, we probe for the first time the molecular gas physical properties of several star forming regions located in the arms and inter-arms of the spiral galaxy NGC 6946. Combining our observations with additional data found in the literature, we provide in this study the most complete CO ladder ever obtained in these inter-arm and arm regions, i.e. the CO(1-0, 2-1, 3-2, 4-3, 6-5) and 13CO(1-0, 2-1) transitions. For each region studied, we use more precisely the large velocity gradient (LVG) assumption in order to derive the beam-averaged molecular gas physical properties. Namely, we obtained the gas kinetic temperature (i.e. 'best' TK), volume number gas density (i.e. 'best' n(H2)) and CO column density (i.e. 'best' N(CO)) which best reproduce the data for 8 regions investigated. Optical depths were also estimated for a large variety of CO lines in these regions. To identify the best values found, we used two complementary theoretical approaches when comparing the model predictions with the observations, i.e. the χ2 minimisation and the likelihood. Very different physical conditions for the molecular gas from a region to another have been obtained: TK ranges from 10 to 250 K, n(H2) ranges from 102.3 to 107.0 cm−3 and N(CO) ranges from 1015.0 to 1019.3 cm−2 among the arm and inter-arm regions. For each region probed, we also published for the first time the CO spectral line energy distribution (SLED) from CO(1-0) to CO(10-9) for this galaxy, mixing observations and model predictions which provide an essential insight for future follow-up observational programmes. Finally, in this work, we discuss the physical properties we obtained for each region in relation with the presence of young stellar population characteristics such as supernovae remnants (SNRs), Hi holes, Hii regions.

We studied the color distribution of satellite galaxies in three groups of galaxies and found that nearly a half of galaxies show statistically significant radial color gradients, which are indicative of changing stellar ages and metallicities. We found that the disk-dominated satellite galaxies with positive color and age gradients (i.e., evolving in outside-in fashion) are residing, predominantly, in the inner, dense group regions, within the characteristic radius R200, while those galaxies, residing in the outer group in-fall region, show typically zero or negative gradients.

This contribution discusses the prospect of using millimeter interferometry to survey molecular gas in a large number of galaxies beyond the distance of Virgo.