arXiv subjects

Tomoka Tosaki

Publications and source records attributed to Tomoka Tosaki.

At least 55 records · Page 3Linked to original sources

arXiv2012

Properties of Molecular Gas in Galaxies in Early and Mid Stage of the Interaction: I. Distribution of Molecular Gas

We present the results of 12CO(J = 1-0) mapping observations toward four interacting galaxies in early and mid stages of the interaction to understand the behavior of molecular gas in galaxy-galaxy interaction. The observations were carried out using the 45-m telescope at Nobeyama Radio Observatory (NRO). We compared our CO total flux to those previously obtained with single-dish observations and found that there are no discrepancy between them. Applying a typical CO-H2 conversion factor, all constituent galaxies have molecular gas mass more than 10^9 M_sun. Comparisons to HI, Ks and tracers of SF such as Halpha, FUV, 8 um and 24 um revealed that the distribution of molecular gas in interacting galaxies in the early stage of the interaction differs from atomic gas, stars and star-forming regions. These differences are not explained without the result of the interaction. Central concentration of molecular gas of interacting galaxies in the early stage of the interaction is lower than that of isolated galaxies, which suggests molecular gas is distributed off-centre and/or extends in the beginning of the interaction.

astro-ph.GA↗

arXiv2011

13CO(J=1-0) On-the-fly Mapping of the Giant HII Region NGC 604: Variation in Molecular Gas Density and Temperature due to Sequential Star Formation

We present 13CO(J=1-0) line emission observations with the Nobeyama 45-m telescope toward the giant HII region NGC 604 in the spiral galaxy M 33. We detected 13CO(J=1-0) line emission in 3 major giant molecular clouds (GMCs) labeled as GMC-A, B, and C beginning at the north. We derived two line intensity ratios, 13CO(J=1-0)/12CO(J =1-0), R13/12, and 12CO(J=3-2)/12CO(J =1-0), R31, for each GMC at an angular resolution of 25" (100 pc). Averaged values of R13/12 and R31 are 0.06 and 0.31 within the whole GMC-A, 0.11 and 0.67 within the whole GMC-B, and 0.05 and 0.36 within the whole GMC-C, respectively. In addition, we obtained R13/12=0.09\pm0.02 and R31=0.76\pm0.06 at the 12CO(J=1-0) peak position of the GMC-B. Under the Large Velocity Gradient approximation, we determined gas density of 2.8 \times10^3 cm^-3 and kinetic temperature of 33+9-5 K at the 12CO(J=1-0) peak position of the GMC-B. Moreover, we determined 2.5 \times10^3 cm^-3 and 25\pm2 K as averaged values within the whole GMC-B. We concluded that dense molecular gas is formed everywhere in the GMC-B because derived gas density not only at the peak position of the GMC but also averaged over the whole GMC exceeds 10^3 cm^-3. On the other hand, kinetic temperature averaged over the whole GM-B, 25 K, is significantly lower than that at the peak position, 33 K. This is because HII regions are lopsided to the northern part of the GMC-B, thus OB stars can heat only the northern part, including the 12CO(J=1-0) peak position, of this GMC.

astro-ph.CO↗

arXiv2011

Giant Molecular Clouds in the Spiral Arm of IC 342

We present results of 12CO (1--0) and 13CO (1--0) observations of the northeastern spiral arm segment of IC 342 with a ~50pc resolution carried out with the Nobeyama Millimeter Array. Zero-spacing components were recovered by combining with the existing data taken with the Nobeyama 45m telescope. The objective of this study is to investigate the variation of cloud properties across the spiral arm with a resolution comparable to the size of giant molecular clouds (GMCs). The observations cover a 1 kpc times 1.5 kpc region located ~2 kpc away from the galactic center, where a giant molecular association is located at trailing side and associated star forming regions at leading side. The spiral arm segment was resolved into a number of clouds whose size, temperature and surface mass density are comparable to typical GMCs in the Galaxy. Twenty-six clouds were identified from the combined data cube and the identified clouds followed the line width-size relation of the Galactic GMCs. The identified GMCs were divided into two categories according to whether they are associated with star formation activity or not. Comparison between both categories indicated that the active GMCs are more massive, have smaller line width, and are closer to virial equilibrium compared to the quiescent GMCs. These variations of the GMC properties suggest that dissipation of excess kinetic energy of GMC is a required condition for the onset of massive star formation.

astro-ph.CO↗

arXiv2011

NRO M33 All Disk Survey of Giant Molecular Clouds (NRO MAGiC): I. HI to H_2 Transition

We present the results of the Nobeyama Radio Observatory (NRO) M33 All Disk (30'x30' or 7.3 kpc x 7.3 kpc) Survey of Giant Molecular Clouds (NRO MAGiC) based on 12CO (1-0) observations using the NRO 45-m telescope. The spatial resolution of the resultant map is 19".3, corresponding to 81 pc, which is sufficient to identify each Giant Molecular Cloud (GMC) in the disk. We found clumpy structures with a typical spatial scale of ~100 pc, corresponding to GMCs, and no diffuse, smoothly distributed component of molecular gas at this sensitivity. Closer inspection of the CO and HI maps suggests that not every CO emission is associated with local HI peaks, particularly in the inner portion of the disk (r < 2 kpc), although most of CO emission is located at the local HI peaks in the outer radii. We found that most uncovered GMCs are accompanied by massive star-forming regions, although the star formation rates (SFRs) vary widely from cloud to cloud. The azimuthally averaged H{\sc i} gas surface density exhibits a flat radial distribution. However, the CO radial distribution shows a significant enhancement within the central 1-2 kpc region, which is very similar to that of the SFR. We obtained a map of the molecular fraction, f_mol = Sigma_H_2/(Sigma_HI+Sigma_H_2, at a 100-pc resolution. This is the first f_mol map covering an entire galaxy with a GMC-scale resolution. We find that f_mol tends to be high near the center. The correlation between f_mol and gas surface density shows two distinct sequences. The presence of two correlation sequences can be explained by differences in metallicity, i.e., higher (~ 2-fold) metallicity in the central region (r< 1.5 kpc) than in the outer parts. Alternatively, differences in scale height can also account for the two sequences, i.e., increased scale height toward the outer disk.

astro-ph.GA↗

arXiv2010

Aperture Synthesis Observations of CO, HCN, and 89GHz Continuum Emission toward NGC 604 in M 33: Sequential Star Formation Induced by Supergiant Hii region

We present the results from new Nobeyama Millimeter Array observations of CO(1-0), HCN(1-0), and 89-GHz continuum emissions toward NGC 604, known as the supergiant H ii region in a nearby galaxy M 33. Our high spatial resolution images of CO emission allowed us to uncover ten individual molecular clouds that have masses of (0.8 -7.4) 10$^5$M$_{\sun }$ and sizes of 5 -- 29 pc, comparable to those of typical Galactic giant molecular clouds (GMCs). Moreover, we detected for the first time HCN emission in the two most massive clouds and 89 GHz continuum emission at the rims of the "H$α$ shells". Three out of ten CO clouds are well correlated with the H$α$ shells both in spatial and velocity domains, implying an interaction between molecular gas and the expanding H ii region. Furthermore, we estimated star formation efficiencies (SFEs) for each cloud from the 89-GHz and combination of H$α$ and 24-$μ$m data, and found that the SFEs decrease with increasing projected distance measured from the heart of the central OB star cluster in NGC 604, suggesting the radial changes in evolutionary stages of the molecular clouds in course of stellar cluster formation. Our results provide further support to the picture of sequential star formation in NGC604 initially proposed by Tosaki et al. (2007) with the higher spatially resolved molecular clouds, in which an isotropic expansion of the H ii region pushes gases outward and accumulates them to consecutively form dense molecular clouds, and then induces massive star formations.

astro-ph.GA↗

arXiv2010

Breakdown of Kennicutt-Schmidt Law at GMC Scales in M33

We have mapped the northern area (30'\times 20') of a local group spiral galaxy M33 in 12CO(1-0) line with the 45-m telescope at the Nobeyama Radio Observatory. Along with Halpha and Spitzer 24-micron data, we have investigated the relationship between the surface density of molecular gas mass and that of star formation rate (SFR) in an external galaxy (Kennicutt-Schmidt law) with the highest spatial resolution (~80pc) to date, which is comparable to scales of giant molecular clouds (GMCs). At positions where CO is significantly detected, the SFR surface density exhibits a wide range of over four orders of magnitude, from Sigma{SFR}<10^{-10} to ~10^{-6} M_solar yr^{-1}pc^{-2}, whereas the Sigma_{H2} values are mostly within 10-40 M_solar pc^{-2}. The surface density of gas and that of SFR correlate well at a ~1-kpc resolution, but the correlation becomes looser with higher resolution and breaks down at GMC scales. The scatter of the Sigma_{SFR}-Sigma_{H2} relationship in the ~80-pc resolution results from the variety of star forming activity among GMCs, which is attributed to the various evolutionary stages of GMCs and to the drift of young clusters from their parent GMCs. This result shows that the Kennicutt-Schmidt law is valid only in scales larger than that of GMCs, when we average the spatial offset between GMCs and star forming regions, and their various evolutionary stages.

astro-ph.GA↗

arXiv2010

Breakdown of Kennicutt-Schmidt Law at GMC Scales in M33

We have mapped the northern area (30' times 20') of a local group spiral galaxy M33 in 12CO(J=1-0) line with the 45-m telescope at the Nobeyama Radio Observatory. Along with Halpha and Spitzer 24-micron data, we have investigated the relationship between the surface density of molecular gas mass and that of star formation rate (SFR) in an external galaxy (Kennicutt-Schmidt law) with the highest spatial resolution (~80pc) to date, which is comparable to scales of giant molecular clouds (GMCs). At positions where CO is significantly detected, the SFR surface density exhibits a wide range of over four orders of magnitude, from Sigma(SFR)<10^{-10} to ~10^{-6}M_solar yr^{-1} pc^{-2}, whereas the Sigma(H2) values are mostly within 10 to 40 M_solar pc^{-2}. The surface density of gas and that of SFR correlate well at a 1-kpc resolution, but the correlation becomes looser with higher resolution and breaks down at GMC scales. The scatter of the Sigma(SFR)-Sigma(H2) relationship in the 80-pc resolution results from the variety of star forming activity among GMCs, which is attributed to the various evolutionary stages of GMCs and to the drift of young clusters from their parent GMCs. This result shows that the Kennicutt-Schmidt law is valid only in scales larger than that of GMCs, when we average the spatial offset between GMCs and star forming regions, and their various evolutionary stages.

astro-ph.GA↗

arXiv2010

Dense and Warm Molecular Gas and Warm Dust in Nearby Galaxies

We performed 12CO(1-0), 13CO(1-0), and HCN(1-0) single-dish observations (beam size ~14"-18") toward nearby starburst and non-starburst galaxies using the Nobeyama 45 m telescope. The 13CO(1-0) and HCN(1-0) emissions were detected from all the seven starburst galaxies, with the intensities of both lines being similar (i.e., the ratios are around unity). On the other hand, for case of the non-starburst galaxies, the 13CO(1-0) emission was detected from all three galaxies, while the HCN(1-0) emission was weakly or not detected in past observations. This result indicates that the HCN/13CO intensity ratios are significantly larger (~1.15+-0.32) in the starburst galaxy samples than the non-starburst galaxy samples (<0.31+-0.14). The large-velocity-gradient model suggests that the molecular gas in the starburst galaxies have warmer and denser conditions than that in the non-starburst galaxies, and the photon-dominated-region model suggests that the denser molecular gas is irradiated by stronger interstellar radiation field in the starburst galaxies than that in the non-starburst galaxies. In addition, HCN/13CO in our sample galaxies exhibit strong correlations with the IRAS 25 micron flux ratios. It is a well established fact that there exists a strong correlation between dense molecular gas and star formation activities, but our results suggest that molecular gas temperature is also an important parameter.

astro-ph.GA↗

arXiv2009

ASTE CO(3-2) Mapping toward the Whole Optical Disk of M 83: Properties of Inter-arm GMAs

We present a new on-the-fly (OTF) mapping of CO(J=3-2) line emission with the Atacama Submillimeter Telescope Experiment (ASTE) toward the 8' x 8' (or 10.5 x 10.5 kpc at the distance of 4.5 Mpc) region of the nearby barred spiral galaxy M 83 at an effective resolution of 25''. Due to its very high sensitivity, our CO(J=3-2) map can depict not only spiral arm structures but also spur-like substructures extended in inter-arm regions. This spur-like substructures in CO(J=3-2) emission are well coincident with the distribution of massive star forming regions traced by Halpha luminosity and Spitzer/IRAC 8 um emission. We have identified 54 CO(J=3-2) clumps as Giant Molecular-cloud Associations (GMAs) employing the CLUMPFIND algorithm, and have obtained their sizes, velocity dispersions, virial masses, and CO luminosity masses. We found that the virial parameter alpha, which is defined as the ratio of the virial mass to the CO luminosity mass, is almost unity for GMAs in spiral arms, whereas there exist some GMAs whose alpha are 3 -- 10 in the inter-arm region. We found that GMAs with higher $α$ tend not to be associated with massive star forming regions, while other virialized GMAs are. Since alpha mainly depends on velocity dispersion of the GMA, we suppose the onset of star formation in these unvirialized GMAs with higher alpha are suppressed by an increase in internal velocity dispersions of Giant Molecular Clouds within these GMAs due to shear motion.

astro-ph.CO↗

arXiv2009

Suzaku and Multi-wavelength Observations of OJ 287 during the Periodic Optical Outburst in 2007

Suzaku observations of the blazar OJ 287 were performed in 2007 April 10--13 and November 7--9. They correspond to a quiescent and a flaring state, respectively. The X-ray spectra can be well described with single power-law models in both exposures. The derived X-ray photon index and the flux density at 1 keV were found to be Gamma = 1.65 +- 0.02 and S_{1 keV} = 215 +- 5 nJy, in the quiescent state. In the flaring state, the source exhibited a harder X-ray spectrum (Gamma = 1.50 +- 0.01) with a nearly doubled X-ray flux density S_{1 keV} = 404^{+6}_{-5} nJy. Moreover, significant hard X-ray signals were detected up to ~ 27 keV. In cooperation with the Suzaku, simultaneous radio, optical, and very-high-energy gamma-ray observations were performed with the Nobeyama Millimeter Array, the KANATA telescope, and the MAGIC telescope, respectively. The radio and optical fluxes in the flaring state (3.04 +- 0.46 Jy and 8.93 +- 0.05 mJy at 86.75 Hz and in the V-band, respectively) were found to be higher by a factor of 2--3 than those in the quiescent state (1.73 +- 0.26 Jy and 3.03 +- 0.01 mJy at 86.75 Hz and in the V-band, respectively). No notable gamma-ray events were detected in either observation. The spectral energy distribution indicated that the X-ray spectrum was dominated by inverse Compton radiation in both observations, while synchrotron radiation exhibited a spectral cutoff around the optical frequency. Furthermore, no significant difference in the synchrotron cutoff frequency was found between the quiescent and flaring states. According to a simple synchrotron self-Compton model, the change of the spectral energy distribution is due to an increase in the energy density of electrons with small changes of both the magnetic field strength and the maximum Lorentz factor of electrons.

astro-ph.CO↗

arXiv2009

Spatial correlation between submillimetre and Lyman-alpha galaxies in the SSA 22 protocluster

Lyman-alpha emitters are thought to be young, low-mass galaxies with ages of ~10^8 yr. An overdensity of them in one region of the sky (the SSA 22 field) traces out a filamentary structure in the early Universe at a redshift of z = 3.1 (equivalent to 15 per cent of the age of the Universe) and is believed to mark a forming protocluster. Galaxies that are bright at (sub)millimetre wavelengths are undergoing violent episodes of star formation, and there is evidence that they are preferentially associated with high-redshift radio galaxies, so the question of whether they are also associated with the most significant large-scale structure growing at high redshift (as outlined by Lyman-alpha emitters) naturally arises. Here we report an imaging survey of 1,100-um emission in the SSA 22 region. We find an enhancement of submillimetre galaxies near the core of the protocluster, and a large-scale correlation between the submillimetre galaxies and the low-mass Lyman-alpha emitters, suggesting synchronous formation of the two very different types of star-forming galaxy within the same structure at high redshift. These results are in general agreement with our understanding of the formation of cosmic structure.

astro-ph.CO↗

arXiv2008

Nobeyama Millimeter Array Observations of the Nuclear Starburst of M83: A GMA Scale Correlation between Dense Gas Fraction and Star Formation Efficiency

We present aperture synthesis high-resolution (~ 7" x 3") observations in CO(J=1-0) line, HCN(J=1-0) line, and 95 GHz continuum emission toward the central (~ 1.5 kpc) region of the nearby barred spiral galaxy M 83 with the Nobeyama Millimeter Array. Our high-resolution CO(J=1-0) mosaic map depicts the presence of molecular ridges along the leading sides of the stellar bar and nuclear twin peak structure. On the other hand, we found the distribution of the HCN(J=1-0) line emission which traces dense molecular gas (nH2 > a few x 10^4 cm^-3) shows nuclear single peak structure and coincides well with that of the 95 GHz continuum emission which traces massive starburst. The peaks of the HCN(J=1-0) line and the 95 GHz continuum emission are not spatially coincident with the optical starburst regions traced by the HST V-band image. This suggests the existence of deeply buried ongoing starburst due to strong extinction (A_v ~ 5 mag) near the peaks of the HCN(J=1-0) line and the 95 GHz continuum emission. We found that the HCN(J=1-0)/CO(J=1-0) intensity ratio R_HCN/CO correlates well with extinction-corrected SFE in the central region of M 83 at a resolution of 7.5" (~ 160 pc). This suggests that SFE is controlled by dense gas fraction traced by R_HCN/CO even on a Giant Molecular cloud Association (GMA) scale. Moreover, the correlation between R_HCN/CO and the SFE in the central region of M 83 seems to be almost coincident with that of the Gao & Solomon (2004a) sample. This suggests that the correlation between R_HCN/CO and the SFE on a GMA (~ 160 pc) scale found in M 83 is the origin of the global correlation on a few kpc scale shown by Gao & Solomon (2004a).

astro-ph↗

arXiv2007

A Search for CO(J=3-2) Emission from the Host Galaxy of GRB 980425 with the Atacama Submillimeter Telescope Experiment

We report on a deep search for CO(J=3-2) line emission from the host galaxy of GRB 980425 with the Atacama Submillimeter Telescope Experiment (ASTE). We observed five points of the galaxy covering the entire region. After combining all of the spectra, we obtained a global spectrum with the rms noise level of 3.3 mK in T_mb scale at a velocity resolution of 10 km s^-1. No significant emission was detected, though we find a marginal emission feature in the velocity range corresponding to the redshift of the galaxy. We derive 3 sigma upper limits on the global properties: the velocity-integrated CO(3-2) intensity of I_CO(3-2) < 0.26 K km s^-1 by adopting a velocity width of 67 km s^-1; the H_2 column density of N(H_2) < 3 x 10^20 cm^-2; the molecular gas mass of M(H_2) < 3 x 10^8 M_sun, by assuming a CO line luminosity to H_2 molecular gas mass conversion factor of X_CO = 5.0 x 10^20 cm^-2 (K km s^-1)^-1; and the star formation rate of SFR < 0.1 M_sun yr^-1, based on the Schmidt law. The SFR is consistent with the previous results of H_alpha and mid-IR observations, thereby suggesting that there is no significant obscured star formation in the host galaxy of GRB 980425. This result implies that there is a variety of GRB hosts with regard to the presence of obscured star formation.

astro-ph↗

arXiv2007

A Revised Estimate of the CO (J=1-0) Emission from the Host Galaxy of GRB 030329 Using the Nobeyama Millimeter Array

A sensitive observation of the CO (J=1-0) molecular line emission in the host galaxy of GRB 030329 (z =0.1685) has been performed using the Nobeyama Millimeter Array in order to detect molecular gas and hidden star formation. No sign of CO emission was detected, which invalidates our previous report on the presence of molecular gas. The 3sigma upperlimit on the CO line luminosity (L'_CO) of the host galaxy is 6.9 x 10^8 K km s^-1 pc^2. The lowerlimit of the host galaxy's metallicity is estimated to be 12+log(O/H) ~ 7.9, which yields a CO line luminosity to H_2 conversion factor of alpha_CO = 40 Msun (K km s^-1 pc^2)^-1. Assuming this alpha_CO factor, the 3sigma upperlimit on the molecular gas mass of the host galaxy is 2.8 x 10^10 Msun. Based on the Schmidt law, the 3sigma upperlimit of the total star formation rate (SFR) of the host galaxy is estimated to be 38 Msun yr^-1. These results independently confirm the inferences of previous observations in the optical, submillimeter, and X-ray band, which regard this host galaxy as a compact dwarf galaxy, and not a massive, aggressively star forming galaxy.

astro-ph↗

arXiv2007

ASTE CO(3-2) Observations of the Barred Spiral Galaxy M 83: I. Correlation between CO(3-2)/CO(1-0) Ratios and Star Formation Efficiencies

We present CO(J=3-2) emission observations with the Atacama Submillimeter Telescope Experiment (ASTE) toward the 5' x 5' (or 6.6 x 6.6 kpc at the distance D = 4.5 Mpc) region of the nearby barred spiral galaxy M 83. We successfully resolved the major structures, i.e., the nuclear starburst region, bar, and inner spiral arms in CO(J=3-2) emission at a resolution of 22'' (or 480 pc), showing a good spatial coincidence between CO(J=3-2) and 6 cm continuum emissions. We found a global CO(J=3-2) luminosity L'_CO(3-2) of 5.1 x 10^8 K km s^-1 pc^2 within the observed region. We also found L'_CO(3-2) in the disk region (0.5 < r < 3.5 kpc) of 4.2 x 10^8 K km s^-1 pc^2, indicating that CO(J=3-2) emission in the disk region significantly contributes to the global L'_CO(3-2). From a comparison of a CO(J=3-2) data with CO(J=1-0) intensities measured with Nobeyama 45-m telescope, we found that the radial profile of CO(J=3-2)/CO(J=1-0) integrated intensity ratio R_3-2/1-0 is almost unity in the central region (r < 0.25 kpc), whereas it drops to a constant value, 0.6--0.7, in the disk region. The radial profile of star formation efficiencies (SFEs), determined from 6 cm radio continuum and CO(J=1-0) emission, shows the same trend as that of R_3-2/1-0. At the bar-end (r ~ 2.4 kpc), the amounts of molecular gas and the massive stars are enhanced when compared with other disk regions, whereas there is no excess of R_3-2/1-0 and SFE in that region. This means that a simple summation of the star forming regions at the bar-end and the disk cannot reproduce the nuclear starburst of M 83, implying that the spatial variation of the dense gas fraction traced by R_3-2/1-0 governs the spatial variation of SFE in M 83.

astro-ph↗

arXiv2006

ASTE $^{12}$CO($J=$3--2) Survey of Elliptical Galaxies

We report $^{12}$CO($J=$3--2) observations of 15 nearby elliptical galaxies carried out with the ASTE telescope. Thirteen were selected without regard to the presence of other tracers of cold interstellar matter. CO emission was detected from three of the galaxies, two of which are undetected by IRAS at 100 microns, suggesting that cold ISM may be present in more ellipticals than previously thought. The molecular gas masses range from $2.2 \times 10^6$ to $4.3 \times 10^8$ $M_\odot$. The ratio of the CO(3--2) and (1--0) lines, $R_{31}$, has a lower value for elliptical galaxies than for spiral galaxies except for NGC 855, for which the value is close to the mean for spirals. The molecular gas in NGC 855 has a mean density in the range 300 -- 1000 cm$^{-3}$ adopting a temperature range of 15 -- 100 K.

astro-ph↗

arXiv2006

Environmental Effects on Gaseous Disks of the Virgo Spiral Galaxies

We found high molecular fractions ($f_{\rm mol}$; ratio of the molecular to total gas surface densities) in three of five Virgo spiral galaxies in spite of their low total gas column density, based on $^{12}$CO$(J=1-0)$ observations with the Nobeyama 45 m telescope equipped with a multi-beam receiver, BEARS. We interpret this as a result of environmental effects. Combining the CO data with HI data, the relationship between the surface density of the total gas (HI plus H$_2$) and $f_{\rm mol}$ indicates that the three galaxies near the cluster center have larger $f_{\rm mol}$ values than expected for field galaxies, while the others show normal $f_{\rm mol}$. The large $f_{\rm mol}$ is interpreted as being due either to effective HI gas stripping, even in the inner disks, or to large ISM pressure induced by the high ICM pressure and/or ram pressure, although the possibility of an unusually high metallicity cannot be ruled out.

astro-ph↗

arXiv2006

ASTE observations of nearby galaxies: A tight correlation between CO(J=3-2) emission and Halpha

Star formation rates (SFRs) obtained via extinction corrected H alpha are compared to dense gas as traced by CO(J=3-2) emission at the centers of nearby galaxies, observed with the ASTE telescope. It is found that, although many of the observed positions are dusty and therefore heavily absorbed at H alpha, the SFR shows a striking correlation with dense gas in the form of the Schmidt law with an index 1.0. The correlation is also compared between gas traced by CO(J=1-0) and application of H alpha extinction correction. We find that dense gas produces a far better correlation with SFR in view of surface density values.

astro-ph↗