We use the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) project as a template to demonstrate how deep spectrophotometric surveys covering large cosmological volumes over extended fields (1– $15\, \rm{deg^2}$ ) with a mid-IR imaging spectrometer (17– $36\, \rm{\rm{\upmu m}}$ ) in conjunction with deep $70\, \rm{\rm{\upmu m}}$ photometry with a far-IR camera, at wavelengths which are not affected by dust extinction can answer the most crucial questions in current galaxy evolution studies. A SPICA-like mission will be able for the first time to provide an unobscured three-dimensional (3D, i.e. x, y, and redshift z) view of galaxy evolution back to an age of the universe of less than $\sim$ 2 Gyrs, in the mid-IR rest frame. This survey strategy will produce a full census of the Star Formation Rate (SFR) in the universe, using polycyclic aromatic hydrocarbons (PAH) bands and fine-structure ionic lines, reaching the characteristic knee of the galaxy luminosity function, where the bulk of the population is distributed, at any redshift up to $z \sim 3.5$ . Deep follow-up pointed spectroscopic observations with grating spectrometers onboard the satellite, across the full IR spectral range (17– $210\, \rm{\rm{\upmu m}}$ ), would simultaneously measure Black Hole Accretion Rate (BHAR), from high-ionisation fine-structure lines, and SFR, from PAH and low- to mid-ionisation lines in thousands of galaxies from solar to low metallicities, down to the knee of their luminosity functions. The analysis of the resulting atlas of IR spectra will reveal the physical processes at play in evolving galaxies across cosmic time, especially its heavily dust-embedded phase during the activity peak at the cosmic noon ( $z \sim 1$ –3), through IR emission lines and features that are insensitive to the dust obscuration.

We present ALMA [CII] line and far-infrared (FIR) continuum observations of seven z > 6 low-luminosity quasars (M1450 > −25 mag) discovered by our on-going Subaru Hyper Suprime-Cam survey. The [CII] line was detected in all targets with luminosities of ∼(2−10) × 108 L⊙, about one order of magnitude smaller than optically luminous quasars. Also found was a wide scatter of FIR continuum luminosity, ranging from LFIR < 1011L⊙ to ∼2 × 1012L⊙. With the [CII]-based dynamical mass, we suggest that a significant fraction of low-luminosity quasars are located on or even below the local Magorrian relation, particularly at the massive end of the galaxy mass distribution. This is a clear contrast to the previous finding that luminous quasars tend to have overmassive black holes relative to the relation. Our result is expected to show a less-biased nature of the early co-evolution of black holes and their host galaxies.

To investigate molecular composition of low-metallicity environments, we conducted spectral line survey observations in the 3 mm band toward three dwarf galaxies, the Large Magellanic Cloud, IC 10, and NGC 6822 with the Mopra 22 m, the Nobeyama 45 m and the IRAM 30 m, respectively. The rotational transitions of CCH, HCN, HCO+, HNC, CS, SO, 13CO, and 12CO were detected in all three galaxies. We found that the spectral intensity patterns are similar to one another regardless of star formation activities. Compared with Solar-metallicity environments, the molecular compositions of dwarf galaxies are characterized by (1) deficient nitrogen-bearing molecules and (2) enhanced CCH and suppressed CH3OH. These are interpreted (1) as a direct consequence of the lower elemental abundance of nitrogen, and (2) as a consequence of extended photon dominated regions in cloud peripheries due to the lower abundance of dust grains, respectively.

We detected CO line and 1.2-mm continuum emission from the two GRB host galaxies (GRB 020819B and GRB 051022) by using the Atacama Large Millimeter/submillimeter Array (ALMA). This is the first case for detecting molecular gas emission in GRB hosts. The ratio of molecular gas to dust mass of the GRB 020819B site is significantly lower than those of the Milky Way and nearby star-forming galaxies, suggesting that the star-forming environment where the GRB occur is different from those in local galaxies. The possible reason is that much of the dense gas is dissipated by a strong interstellar ultraviolet radiation field.

In the central regions of active galaxies, dense molecular medium are exposed to various types of radiation and energy injections, such as UV, X-ray, cosmic ray, and shock dissipation. With the rapid progress of chemical models and implementation of new-generation mm/submm interferometry, we are now able to use molecules as powerful diagnostics of the physical and chemical processes in galaxies. Here we give a brief overview on the recent ALMA results to demonstrate how molecules can reveal underlying physical and chemical processes in galaxies. First, new detections of Galactic molecular absorption systems with elevated HCO/H13CO+ column density ratios are reported, indicating that these molecular media are irradiated by intense UV fields. Second, we discuss the spatial distributions of various types of shock tracers including HNCO, CH3OH and SiO in NGC 253 and NGC 1068. Lastly, we provide an overview of proposed diagnostic methods of nuclear energy sources using ALMA, with an emphasis on the synergy with sensitive mid-infrared spectroscopy, which will be implemented by JWST and SPICA to disentangle the complex nature of heavily obscured galaxies across the cosmic time.

We present recent results on Karl Jansky Very Large Array (JVLA) deep S-band (2-4 GHz) observation towards a protocluster 4C23.56 at redshift z ∼ 2.5. The protocluster 4C23.56 is known to have a significant over density (∼ 5 times) of star-burst galaxies selected to be Hα line-bright by a Subaru narrow band imaging. Now we have found 25 HAEs associated with the protocluster. These starburst HAEs are likely to become massive ellipticals at z = 0 in a cluster. Various other galaxy populations also reside in this field and the fact makes the field very unique as a tool to understand galaxy formation in a over dense region. Subsequent deep 1100-μm continuum surveys by the ASTE 10-m dish have discovered that several submillimeter bright galaxies (SMGs) coincide with HAEs, suggesting HAEs undergoing dusty starbursts. As star formation rates (SFRs) of HAEs might have been underestimated, we use radio being resistant to dust extinction. We investigate the correlation between SFR1.4 GHz and SFRHα for radio index α = 0.8 to see if the correlation holds for the sources and to check the number of dusty star forming galaxies. Our final results will allow us to evaluate quantitatively how the galaxy formation channel may be different under the condition of over-densities.

We performed 12CO(J = 2 − 1) and 13CO(J = 2 − 1) line surveys of the galactic plane using the AMANOGAWA telescope (Nakajima et al. 2007) which covers 5° ≤ l ≤ 180° on a 7'.5 grid. The telescope beamsize and velocity resolution are 8.7′ ± 0.4′ and 1.3 km s−1. The resultant rms noise level is typically 0.12 K in TA*. We found a linear correlation between 12CO(J = 2 − 1) and 12CO(J = 1 − 0) and a curved correlation between 12CO(J = 2 − 1) and 13CO (J = 2 − 1), although the intensity ratios of these three lines have intrinsic variation. These correlations can be reproduced with simple radiative transfer equations suggesting some restrictions on the physical quantities of molecular gas on a galactic scale.

We have mapped the nearby face-on spiral galaxy M 33 in the 1.1 mm dust continuum using AzTEC on Atacama Submillimeter Telescope Experiment (ASTE). The preliminary results are presented here. The observed dust has a characteristic temperature of ~ 21 K in the central kpc, radially declining down to ~ 13 K at the edge of the star forming disk. We compare the dust temperatures with KS band flux and star formation tracers. Our results imply that cold dust heating may be driven by long-lived stars even nearby star forming regions.

We present a new diagnosis method for determining physical properties of star-forming gas in high-z galaxies. In this method, we employed three key observational quantities, [CI], CO, and FIR luminosities, including our new detections of CO J = 4–3 emission from the pure-starburst (non-AGN) submm galaxy SMM J14011+0252 (z = 2.6) and the type-2 AGN IRAS FSC 10214+4724 (z = 2.3) obtained with the Nobeyama Millimeter Array (NMA) at the Nobeyama Radio Observatory. These two sources have extremely high star formation rate, and exhibit strong emission of CO and [CI] 609 μm lines. We determined ISM physical conditions for the two objects and another three high-z quasars in order to investigate the relationship between their ISM and power sources (i.e., massive star formation or AGN). A new PDR analysis (Wolfire et al. 2005, private communication) using CO, [CI], and FIR on five high-z sources provides new evidence that AGN host galaxies harbor denser (log nH ~ 5–6) ISM exposed to stronger far-UV fluxes of log G0 ~ 3.5–4 than the non-AGN submm galaxy. Volume filling factors of the star-forming dense gas in the AGN hosts are an order of magnitude smaller than that of the pure-starburst submm galaxy. This suggests that, in these AGN hosts, dense molecular clouds are dominating the central kpc around AGN, triggering extensive circumnuclear starbursts, and possibly feeding their central supermassive black hole simultaneously.

Long-duration gamma-ray bursts (GRBs) are considered to be due to the death of massive stars. Therefore, GRBs are closely associated with the star formation of host galaxies. Since GRBs can be detected at cosmological distances, they are expected to be probes of the star formation history of the Universe. In order to determine the use of GRBs, it is essential to understand the star formation of their hosts. Multi-wavelength observations have shown that the star formation rates (SFRs) of GRB hosts derived from submillimeter/radio observations are generally higher than those from optical/UV observations (Berger et al. 2003). This implies that GRB hosts have a large amount of molecular gas and massive star formation obscured by dust. In order to solve this problem, it is necessary to derive the SFRs in a method which is independent of existing methods and not affected by dust extinction.

We observed 12CO (J = 3–2) line emission from the host galaxy of GRB 980425 using the Atacama Submillimeter Telescope Experiment (ASTE). Five points were observed covering the entire region of the galaxy, and we find possible emission features (S/N ~ 3 σ) at the velocity range corresponding to the redshift of the galaxy. By combining all spectra of five points, we obtain a global spectrum with a ~4 σ emission feature. If the features are real, this is the first detection of CO among GRB hosts. We derive the total gas mass of M(H2)=7 ± 2× 108M⊙ assuming a CO-to-H2 conversion factor of αCO = 8.0M⊙ (K km s−1 pc2)−1, which is deduced using the correlation between the αCO and the metallicity. The dynamical mass is calculated to be Mdyn=2× 1010M⊙, and M(H2)/Mdyn~3% is consistent with those of nearby dwarfs and normal spirals. The derived SFR is 0.5 ± 0.1 M⊙ yr−1 based on the Schmidt law. This SFR agrees with the results of previous Hα observations, suggesting that there is no significant obscured star formation in this host galaxy. This result implies that there is a variety of GRB hosts in terms of the presence of obscured star formation.

In order to study the spatial variation of molecular gas properties and their relation to the nuclear activities of galaxies, we have conducted an imaging survey of HCN(1-0) and CO(1-0) emission from nearby active galaxies with the Nobeyama Millimeter Array. Here we present the results of three galaxies, NGC 3504 (Starburst nucleus), NGC 4736 (Post-Starburst nucleus), and NGC 6951 (Seyfert nucleus with a circumnuclear star-forming ring).

In the observations of these three galaxies, we find that (1) the HCN distribution is significantly different from that of CO, and that (2) the HCN emission spatially correlates better with the massive star-forming region than CO emission (Figure 1, 2(a), and 2(b)). For instance, in the Post-Starburst nucleus of NGC 4736, we find a remarkable decrease of the HCN emission, despite of strong CO nuclear concentration. The upper limit (2σ) of the integrated intensity ratio I(HCN)/I(CO) within the central r < 150 pc region is 0.04, which is surprisingly low compared with the value in other galactic nucleus (cf. ratio = 0.08 within r < 300 pc in Milky Way, Jackson et al. 1996, ApJ, 456, 91). Presumably the dense molecular gas must have been consumed by a past starburst event in the nucleus. These results suggest a tight correlation between the gas density measured by the I(HCN)/I(CO) ratio and the star-forming activities in the central region of galaxies.

It seems that there exist a spatial anti-correlation between the I(HCN)/ I(CO) ratio and the gas velocity dispersion in NGC 6951 (Figure 2(c)). The ratio is not enhanced in the CO twin peaks which are interpreted as shock regions due to gas orbit crowding. These imply the importance of gravitational instability on the formation of dense molecular gas and successive massive starformation in this region.