J/ApJ/789/81   Multiwavelength survey of HII regions in NGC 300   (Faesi+, 2014)

Molecular cloud-scale star formation in NGC 300. Faesi C.M., Lada C.J., Forbrich J., Menten K.M., Bouy H. <Astrophys. J., 789, 81 (2014)> =2014ApJ...789...81F 2014ApJ...789...81F (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Radio lines ; Photometry, H-alpha ; Photometry, ultraviolet ; Photometry, infrared ; Extinction ; Millimetric/submm sources Keywords: galaxies: individual: NGC 300; galaxies: ISM; galaxies: star formation; H II regions; stars: formation Abstract: We present the results of a galaxy-wide study of molecular gas and star formation in a sample of 76 H II regions in the nearby spiral galaxy NGC 300. We have measured the molecular gas at 250pc scales using pointed CO(J=2-1) observations with the Atacama Pathfinder Experiment telescope. We detect CO in 42 of our targets, deriving molecular gas masses ranging from our sensitivity limit of ∼105M to 7x105M. We find a clear decline in the CO detection rate with galactocentric distance, which we attribute primarily to the decreasing radial metallicity gradient in NGC 300. We combine Galaxy Evolution Explorer far-ultraviolet, Spitzer 24µm, and Hα narrowband imaging to measure the star formation activity in our sample. We have developed a new direct modeling approach for computing star formation rates (SFRs) that utilizes these data and population synthesis models to derive the masses and ages of the young stellar clusters associated with each of our H II region targets. We find a characteristic gas depletion time of 230Myr at 250pc scales in NGC 300, more similar to the results obtained for Milky Way giant molecular clouds than the longer (>2Gyr) global depletion times derived for entire galaxies and kiloparsec-sized regions within them. This difference is partially due to the fact that our study accounts for only the gas and stars within the youngest star-forming regions. We also note a large scatter in the NGC 300 SFR-molecular gas mass scaling relation that is furthermore consistent with the Milky Way cloud results. This scatter likely represents real differences in giant molecular cloud physical properties such as the dense gas fraction. Description: Our sample of star-forming regions in NGC 300 consists of 76 HII regions from the catalog of Deharveng et al. (1988A&AS...73..407D 1988A&AS...73..407D). To measure the molecular gas content in our sample of 76 star-forming regions, we obtained 12CO(J=2-1; rest frequency: 230.538GHz) observations with the APEX-1 facility heterodyne receiver on the APEX 12m diameter submillimeter telescope. Observations took place over several epochs between 2011 April 8 and December 16. We obtained over 100hr of observation time divided amongst three project IDs: 13hr between 2011 May 5 and May 12 under European Southern Observatory (ESO) project E-087.C-0507A-2011, and the remainder of the time under Max-Planck-Gesellschaft projects M-087.F-0033-2011 (2011 April 8-18 and June 4-August 7) and M-088.F-0022-2011 (2011 October 10-December 16; PI: J. Forbrich for all three projects). NGC 300 was observed on 2000 August 5 with the Wide-Field Imager (WFI) on the Max Planck Gesellschaft/ESO 2.2m telescope at La Silla, Chile, using the Hα narrowband filter (central wavelength 6588.27Å, FWHM 74.31Å). GALEX FUV images were downloaded from the MAST data archive using the GalexView tool. Observations were taken under the auspices of the Guest Investigator program GI1_061002 between 2004 October 26 and December 15, with a total exposure time of 12988s. NGC 300 was observed with the Spitzer Space Telescope's Multiband Imaging Photometer for Spitzer (MIPS) on 2004 October 26. BCDs from AOR 6070016 (PI: G. Helou) were downloaded directly from the Spitzer Heritage archive. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 59 76 Summary of APEX observations table3.dat 114 76 Tabulated photometry and results -------------------------------------------------------------------------------- See also: J/ApJ/821/125 : SMA obs. of giant molecular clouds in NGC 300 (Faesi+, 2016) J/ApJ/723/1019 : Galactic SFR and gas surface densities (Heiderman+, 2010) J/ApJ/723/492 : Physical data of GRS molecular clouds (Roman-Duval+, 20110) J/ApJ/706/599 : Hα and UV SFR in the local volume (Lee+, 2009) J/ApJ/703/1672 : Far-IR and Hα fluxes in galaxies (Kennicutt+, 2009) J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009) J/AJ/136/2782 : Star formation efficiency in nearby galaxies (Leroy+, 2008) J/ApJS/173/293 : UV-Optical galaxy color-magnitude diagram I. (Wyder+, 2007) J/AJ/128/1167 : ARAUCARIA project : NGC 300 Cepheids. II (Gieren+, 2004) J/ApJS/100/125 : CO(J=2-1) Survey of the Milky Way (Sakamoto+, 1995) Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 A4 --- [DCL88] HII region catalog identifier (Deharveng et al. 1988A&AS...73..407D 1988A&AS...73..407D) 6- 14 F9.6 deg RAdeg Right Ascension in decimal degrees (J2000) 16- 25 F10.6 deg DEdeg Declination in decimal degrees (J2000) 27- 30 F4.1 mK TRMS [5/23] APEX RMS main beam temperature 32- 36 F5.1 km/s vHI [78/197] H I velocity 38- 40 F3.1 kpc RGal [0/7] Deprojected galactocentric distance 42 A1 --- l_ICO Limit flag on ICO 43- 46 I4 mK.km/s ICO [48/1140] Spectrally-integrated CO intensity 48- 50 I3 mK.km/s e_ICO [37/113]? Uncertainty in ICO 52 A1 --- f_ICO [a] a = Gaussian-derived ICO 54- 57 F4.1 km/s W(CO) [2/21]? CO linewidth 59 A1 --- Type Detection type (G1) -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 A4 --- [DCL88] HII region catalog identifier 6 A1 --- l_FHa Limit flag on FHa 7- 12 F6.2 10-17W/m2 FHa [0.5/137]? ESO/WFI Hα flux; in 1e-14erg/s/cm2 14- 17 F4.2 10-17W/m2 e_FHa [0.2/6]? Uncertainty in FHa 19 A1 --- l_FFUV Limit flag on FFUV 20- 25 F6.1 uJy FFUV [8/5780] GALEX/FUV band flux density 27- 31 F5.1 uJy e_FFUV [2/290]? Uncertainty in FFUV 33 A1 --- l_F24 Limit flag on F24 34- 38 F5.2 mJy F24 [0.01/65] Spitzer/MIPS 24um flux density 40- 43 F4.2 mJy e_F24 [0.02/4.2]? Uncertainty in F24 45- 48 F4.2 mag AHa [0.01/0.7]? Hα extinction 50- 53 F4.2 mag e_AHa [0/0.2]? Uncertainty in AHa 55- 58 F4.2 mag AFUV [0.01/1.6]? FUV extinction 60- 63 F4.2 mag e_AFUV [0.01/0.5]? Uncertainty in AFUV 65 A1 --- l_M(GMCC) Limit flag on M(GMCC) 66- 69 F4.2 10+5Msun M(GMCC) [0.4/7] Giant Molecular Cloud Complex mass 71- 74 F4.2 10+5Msun e_M(GMCC) [0.1/0.7]? Uncertainty in M(GMCC) 76- 79 F4.1 10+3Msun M* [1/38]? Stellar mass 81- 83 F3.1 10+3Msun e_M* [0.2/7]? Uncertainty in M* 85- 87 F3.1 Myr Age [1.8/10]? Age 89- 91 F3.1 Myr e_Age [0.3/4]? Uncertainty in Age 93- 98 E6.1 Msun/yr SFR [0.0002/0.01]? Star Formation Rate 100-105 E6.1 Msun/yr E_SFR [0.0001/0.003]? Upper uncertainty in SFR 107-112 E6.1 Msun/yr e_SFR [0.0001/0.002]? Lower uncertainty in SFR 114 A1 --- Type Detection type (G1) -------------------------------------------------------------------------------- Global note: Note (G1): Detection type as follows: D = A CO detection source; M = A marginal CO detection source; N = A source with CO upper limits. -------------------------------------------------------------------------------- History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 29-Jul-2016
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