Synchrotron spectral index and interstellar medium densities of star-forming galaxies

ABSTRACT The [O iii] 88 $\mu$m fine-structure emission line has been detected into the Epoch of Reionization (EoR) from star-forming galaxies at redshifts 6 < z ≲ 9 with ALMA. These measurements provide valuable information regarding the properties of the interstellar medium (ISM) in the highest redshift galaxies discovered thus far. The [O iii] 88 $\mu$m line observations leave, however, a degeneracy between the gas density and metallicity in these systems. Here, we quantify the prospects for breaking this degeneracy using future ALMA observations of the [O iii] 52 $\mu$m line. Among the current set of 10 [O iii] 88 $\mu$m emitters at 6 < z ≲ 9, we forecast 52 $\mu$m detections (at 6σ) in SXDF-NB1006-2, B14-6566, J0217-0208, and J1211-0118 within on-source observing times of 2–10 h, provided their gas densities are larger than about nH ≳ 102–103 cm−3. Other targets generally require much longer integration times for a 6σ detection. Either successful detections of the 52 $\mu$m line or reliable upper limits will lead to significantly tighter constraints on ISM parameters. The forecasted improvements are as large as ∼3 dex in gas density and ∼1 dex in metallicity for some regions of parameter space. We suggest SXDF-NB1006-2 as a promising first target for 52 $\mu$m line measurements. We discuss how such measurements will help in understanding the mass–metallicity relationship during the EoR.

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The Violent Interstellar Medium of Nearby Dwarf Galaxies

Publications of the Astronomical Society of Australia ◽

10.1071/as99106 ◽

1999 ◽

Vol 16 (1) ◽

pp. 106-112 ◽

Cited By ~ 9

Author(s):

Fabian Walter

Keyword(s):

Interstellar Medium ◽

Gamma Ray ◽

Dwarf Galaxies ◽

Young Star ◽

Stellar Winds ◽

Star Forming ◽

Star Forming Regions ◽

Supernova Explosions ◽

High Velocity Clouds ◽

Ob Associations

AbstractHigh resolution HI observations of nearby dwarf galaxies (most of which are situated in the M81 group at a distance of about 3·2 Mpc) reveal that their neutral interstellar medium (ISM) is dominated by hole-like features most of which are expanding. A comparison of the physical properties of these holes with the ones found in more massive spiral galaxies (such as M31 and M33) shows that they tend to reach much larger sizes in dwarf galaxies. This can be understood in terms of the galaxy's gravitational potential. The origin of these features is still a matter of debate. In general, young star forming regions (OB-associations) are held responsible for their formation. This picture, however, is not without its critics and other mechanisms such as the infall of high velocity clouds, turbulent motions or even gamma ray bursters have been recently proposed. Here I will present one example of a supergiant shell in IC 2574 which corroborates the picture that OB associations are indeed creating these structures. This particular supergiant shell is currently the most promising case to study the effects of the combined effects of stellar winds and supernova explosions which shape the neutral interstellar medium of (dwarf) galaxies.

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Observations of [OI]63 μm line emission in main-sequence galaxies at z ∼ 1.5

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2884 ◽

2020 ◽

Vol 499 (2) ◽

pp. 1788-1794

Author(s):

J Wagg ◽

M Aravena ◽

D Brisbin ◽

I Valtchanov ◽

C Carilli ◽

...

Keyword(s):

Field Strength ◽

Interstellar Medium ◽

Radiation Field ◽

Uv Radiation ◽

Main Sequence ◽

Line Emission ◽

The Other ◽

Low Density ◽

Star Forming ◽

Neutral Gas

ABSTRACT We present Herschel–PACS spectroscopy of four main-sequence star-forming galaxies at z ∼ 1.5. We detect [OI]63 μm line emission in BzK-21000 at z = 1.5213, and measure a line luminosity, $L_{\rm [O\, {\small I}]63\, \mu m} = (3.9\pm 0.7)\times 10^9$ L⊙. Our PDR modelling of the interstellar medium in BzK-21000 suggests a UV radiation field strength, G ∼ 320G0, and gas density, n ∼ 1800 cm−3, consistent with previous LVG modelling of the molecular CO line excitation. The other three targets in our sample are individually undetected in these data, and we perform a spectral stacking analysis which yields a detection of their average emission and an [O i]63 μm line luminosity, $L_{\rm [O\, {\small I}]63\, \mu m} = (1.1\pm 0.2)\times 10^9$ L⊙. We find that the implied luminosity ratio, $L_{\rm [O\, {\small I}]63\, \mu m}/L_{\rm IR}$, of the undetected BzK-selected star-forming galaxies broadly agrees with that of low-redshift star-forming galaxies, while BzK-21000 has a similar ratio to that of a dusty star-forming galaxy at z ∼ 6. The high [O i]63 μm line luminosities observed in BzK-21000 and the z ∼ 1−3 dusty and sub-mm luminous star-forming galaxies may be associated with extended reservoirs of low density, cool neutral gas.

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O/H Abundances in the Ringed Galaxy NGC 4736: Mixing Processes in the Interstellar Medium

International Astronomical Union Colloquium ◽

10.1017/s0252921100049563 ◽

1996 ◽

Vol 157 ◽

pp. 111-113

Author(s):

P. Martin ◽

J. Belley

Keyword(s):

Interstellar Medium ◽

H Ii Regions ◽

Mixing Processes ◽

Star Forming ◽

The Past ◽

Star Forming Regions ◽

Central Regions ◽

65 H ◽

Oval Distortion

AbstractImaging spectrophotometry in the main nebular lines has been performed on 65 H ɪɪ regions in the ringed galaxy NGC 4736. O/H abundances were derived using the line ratios [O ɪɪɪ]/Hβ and [N ɪɪ]/[O ɪɪɪ] calibrated by Edmunds & Pagel (1984). We show that the O/H scatter in the resonance ring of star forming regions is small, no greater than normally expected in the well-mixed ISM of disks of gas-rich galaxies. The global O/H gradient (−0.046 dex/kpc) in the disk of NGC 4736 is shallower than gradients of normal spirals but comparable to gradients observed in weakly barred spirals. This last result could indicate that radial mixing is or was present in NGC 4736. The oval distortion in the central regions can be responsible for this homogenization but it is also possible that a strong bar was present in the past.

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Protostellar Outflows at the EarliesT Stages (POETS)

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833573 ◽

2018 ◽

Vol 619 ◽

pp. A107 ◽

Cited By ~ 13

Author(s):

A. Sanna ◽

L. Moscadelli ◽

C. Goddi ◽

V. Krishnan ◽

F. Massi

Keyword(s):

Spectral Index ◽

Young Stars ◽

Radio Continuum ◽

Continuum Emission ◽

Stellar Winds ◽

Distance Measurements ◽

Very Large Array ◽

Star Forming ◽

Continuum Source ◽

Star Forming Regions

Context. Weak and compact radio continuum and H2O masers are preferred tracers of the outflow activity nearby very young stars. Aims. We want to image the centimeter free–free continuum emission in the range 1–7 cm (26–4 GHz), which arises in the inner few 1000 au from those young stars also associated with bright H2O masers. We seek to study the radio continuum properties in combination with the H2O maser kinematics to quantify the outflow energetics powered by single young stars. Methods. We made use of the Karl G. Jansky Very Large Array (VLA) in the B configuration at K band and the A configuration at both Ku and C bands in order to image the radio continuum emission toward 25 H2O maser sites with an angular resolution and thermal rms on the order of 0.′′1 and 10 μJy beam−1, respectively. These targets add to our pilot study of 11 maser sites previously presented. The sample of H2O maser sites was selected among those regions that have accurate distance measurements, obtained through maser trigonometric parallaxes, and H2O maser luminosities in excess of 10−6 L⊙. Results. We present high-resolution radio continuum images of 33 sources belonging to 25 star-forming regions. In each region, we detect radio continuum emission within a few 1000 au of the H2O masers’ position; 50% of the radio continuum sources are associated with bolometric luminosities exceeding 5 × 103 L⊙, including W33A and G240.32 + 0.07. We provide a detailed spectral index analysis for each radio continuum source, based on the integrated fluxes at each frequency, and produce spectral index maps with the multifrequency synthesis deconvolution algorithm of CASA. The radio continuum emission traces thermal bremsstrahlung in (proto)stellar winds and jets that have flux densities at 22 GHz below 3 mJy and spectral index values between − 0.1 and 1.3. We prove a strong correlation (r > 0.8) between the radio continuum luminosity (Lrad) and the H2O maser luminosity (LH2O) of (L8 GHz∕mJy kpc2) = 103.8 × (LH2O L⊙)0.74. This power-law relation is similar to that between the radio continuum and bolometric luminosities, which confirms earlier studies. Since H2O masers are excited through shocks driven by (proto)stellar winds and jets, these results provide support to the idea that the radio continuum emission around young stars is dominated by shock ionization, and this holds over several orders of magnitude of stellar luminosites (1–105 L⊙).

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Nuclear molecular gas in the Virgo Cluster S0 galaxy NGC 4710

Symposium - International Astronomical Union ◽

10.1017/s0074180900123976 ◽

1993 ◽

Vol 153 ◽

pp. 439-440

Author(s):

J.M. Wrobel ◽

J.D.P. Kenney

Keyword(s):

Interstellar Medium ◽

Emission Line ◽

Optical Emission ◽

Virgo Cluster ◽

Gas Analysis ◽

Molecular Gas ◽

Star Forming ◽

The Galaxy

The CO(J=1→0) emission from NGC 4710, a star–forming S0 galaxy in the Virgo Cluster, was synthesized with spatial and velocity resolutions of 7″ and 26 km s—1, respectively. The CO shows a compact morphology and co–rotates with the galaxy's stars and nuclear optical emission line gas. Analysis of the CO distribution and kinematics indicates that the nuclear molecular gas is probably gravitationally unstable, and this may explain why the galaxy is presently forming stars. Four possible origins for the nuclear molecular gas are considered. An origin via bulge star ejecta being deposited into a residual interstellar medium is favored.

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