scholarly journals Far-Infrared [C II] Properties of Low-Metallicity Galaxies

1998 ◽  
Vol 11 (1) ◽  
pp. 123-124
Author(s):  
K. Mochizuki ◽  
T. Onaka ◽  
T. Nakagawa
Keyword(s):  
Fine Structure ◽  
Interstellar Medium ◽  
Dwarf Galaxies ◽  
Flux Ratio ◽  
Far Infrared ◽  
Line Flux ◽  
Massive Galaxies ◽  
Physical Conditions ◽  
Different Types ◽  
Low Metallicity

The line flux ratio of the [C II] 158 μm fine-structure (2P3/2 → 2P3/2) emission to CO rotational emission is a probe of the intensity of the interstellar UV radiation in galaxies. The largest values for the [C II]/CO (J = 1-0) line ratios are found in starburst galaxies, none of which, however, show values larger than 6 ×103 (Stacey et al. 1991). The exception ([CII]/CO ≃ 2 × 104) are galaxies of Magellanic type which have low metallicity, an intense interstellar UV field, and irregular morphology (Table 1). Mochizuki et al. (1994) showed that the two conditions, a low metallicity and an intense UV field are expected to result in the large [C II]/CO ratios in the Magellanic types. These conditions are likely to be common in more massive galaxies as well, but at an early epoch in their evolution. This suggests that bright [C II] emission can be a good indicator of young galaxies. However, the metal-poor galaxies previously observed in the [C II] line were exclusively Magellanic types. Observations of different types of dwarf galaxies are necessary to help us understand the physical conditions in the interstellar medium of low-metallicity systems.

scholarly journals A dense, solar metallicity ISM in the z = 4.2 dusty star-forming galaxy SPT 0418−47

2019 ◽  
Vol 631 ◽  
pp. A167 ◽  
Author(s):  
Carlos De Breuck ◽  
Axel Weiß ◽  
Matthieu Béthermin ◽  
Daniel Cunningham ◽  
Yordanka Apostolovski ◽  
...  
Keyword(s):  
Fine Structure ◽  
Interstellar Medium ◽  
Far Infrared ◽  
Line Ratio ◽  
Star Forming ◽  
Physical Conditions ◽  
Solar Metallicity ◽  
Fine Structure Lines ◽  
Compact Array

We present a study of six far-infrared fine structure lines in the z = 4.225 lensed dusty star-forming galaxy SPT 0418−47 to probe the physical conditions of its interstellar medium (ISM). In particular, we report Atacama Pathfinder EXperiment (APEX) detections of the [OI] 145 μm and [OIII] 88 μm lines and Atacama Compact Array (ACA) detections of the [NII] 122 and 205 μm lines. The [OI] 145 μm/[CII] 158 μm line ratio is ∼5× higher compared to the average of local galaxies. We interpret this as evidence that the ISM is dominated by photo-dissociation regions with high gas densities. The line ratios, and in particular those of [OIII] 88 μm and [NII] 122 μm imply that the ISM in SPT 0418−47 is already chemically enriched to nearly solar metallicity. While the strong gravitational amplification was required to detect these lines with APEX, larger samples can be observed with the Atacama Large Millimeter/submillimeter Array (ALMA), and should allow observers to determine if the dense, solar metallicity ISM is common among these highly star-forming galaxies.

scholarly journals The Orion Nebula in the Far-Infrared: High-J CO and fine-structure lines mapped by FIFI-LS/SOFIA

2015 ◽  
Vol 12 (S316) ◽  
pp. 153-154
Author(s):  
Randolf Klein ◽  
Leslie W. Looney ◽  
Erin Cox ◽  
Christian Fischer ◽  
Christof Iserlohe ◽  
...  
Keyword(s):  
Fine Structure ◽  
Far Infrared ◽  
Molecular Gas ◽  
Orion Nebula ◽  
Star Forming ◽  
Physical Conditions ◽  
Molecular Outflow ◽  
Integral Field ◽  
Fine Structure Lines ◽  
Co Observations

AbstractThe Orion Nebula is the closest massive star forming region allowing us to study the physical conditions in such a region with high spatial resolution. We used the far infrared integral-field spectrometer, FIFI-LS, on-board the airborne observatory SOFIA to study the atomic and molecular gas in the Orion Nebula at medium spectral resolution.The large maps obtained with FIFI-LS cover the nebula from the BN/KL-object to the bar in several fine structure lines. They allow us to study the conditions of the photon-dominated region and the interface to the molecular cloud with unprecedented detail.Another investigation targeted the molecular gas in the BN/KL region of the Orion Nebula, which is stirred up by a violent explosion about 500 years ago. The explosion drives a wide angled molecular outflow. We present maps of several high-J CO observations, allowing us to analyze the heated molecular gas.

scholarly journals Probing Globular Cluster Formation in Low Metallicity Dwarf Galaxies

2008 ◽  
Vol 4 (S255) ◽  
pp. 366-369
Author(s):  
Kelsey E. Johnson ◽  
Leslie K. Hunt ◽  
Amy E. Reines
Keyword(s):  
Globular Clusters ◽  
Massive Star ◽  
Dwarf Galaxies ◽  
Cluster Formation ◽  
Formation Rate ◽  
Star Clusters ◽  
Initial Study ◽  
Spectral Energy ◽  
Massive Galaxies ◽  
Low Metallicity

AbstractThe ubiquitous presence of globular clusters around massive galaxies today suggests that these extreme star clusters must have been formed prolifically in the earlier universe in low-metallicity galaxies. Numerous adolescent and massive star clusters are already known to be present in a variety of galaxies in the local universe; however most of these systems have metallicities of 12 + log(O/H) > 8, and are thus not representative of the galaxies in which today's ancient globular clusters were formed. In order to better understand the formation and evolution of these massive clusters in environments with few heavy elements, we have targeted several low-metallicity dwarf galaxies with radio observations, searching for newly-formed massive star clusters still embedded in their birth material. The galaxies in this initial study are HS 0822+3542, UGC 4483, Pox 186, and SBS 0335-052, all of which have metallicities of 12 + log(O/H) < 7.75. While no thermal radio sources, indicative of natal massive star clusters, are found in three of the four galaxies, SBS 0335-052 hosts two such objects, which are incredibly luminous. The radio spectral energy distributions of these intense star-forming regions in SBS 0335-052 suggest the presence of ~12,000 equivalent O-type stars, and the implied star formation rate is nearing the maximum starburst intensity limit.

scholarly journals Low Metallicity ISM: excess submillimetre emission and CO-free H2 gas

2011 ◽  
Vol 7 (S284) ◽  
pp. 141-148 ◽  
Author(s):  
Suzanne C. Madden ◽  
Aurélie Rémy ◽  
Frédéric Galliano ◽  
Maud Galametz ◽  
George Bendo ◽  
...  
Keyword(s):  
Linear Relationship ◽  
Dwarf Galaxies ◽  
Far Infrared ◽  
Spectral Energy ◽  
Molecular Gas ◽  
Energy Distributions ◽  
Gas Reservoir ◽  
Excess Emission ◽  
Dust Component ◽  
Low Metallicity

AbstractThe low metallicity interstellar medium of dwarf galaxies gives a different picture in the far infrared(FIR)/submillimetre(submm)wavelengths than the more metal-rich galaxies. Excess emission is often found in the submm beginning at or beyond 500 μm. Even without taking this excess emission into account as a possible dust component, higher dust-to-gas mass ratios (DGR) are often observed compared to that expected from their metallicity for moderately metal-poor galaxies. The Spectral Energy Distributions (SEDs) of the lowest metallicity galaxies, however, give very low dust masses and excessively low values of DGR, inconsistent with the amount of metals expected to be captured into dust if we presume the usual linear relationship holding for all metallicities, including the more metal-rich galaxies. This transition seems to appear near metalllicities of 12 + log(O/H) 8.0 - 8.2. These results rely on accurately quantifying the total molecular gas reservoir, which is uncertain in low metallicity galaxies due to the difficulty in detecting CO(1-0) emission. Dwarf galaxies show an exceptionally high [CII] 158 μm/CO (1-0) ratio which may be indicative of a significant reservoir of ‘CO-free’ molecular gas residing in the photodissociated envelope, and not traced by the small CO cores.

scholarly journals The interacting nature of dwarf galaxies hosting superluminous supernovae

2020 ◽  
Vol 643 ◽  
pp. A47
Author(s):  
Simon Vanggaard Ørum ◽  
David Lykke Ivens ◽  
Patrick Strandberg ◽  
Giorgos Leloudas ◽  
Allison W. S. Man ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Star Formation ◽  
Dwarf Galaxies ◽  
Flux Ratio ◽  
Host Galaxy ◽  
Type I ◽  
Host Galaxies ◽  
Redshift Range ◽  
Low Metallicity ◽  
The Difference

Context. Type I superluminous supernovae (SLSNe I) are rare, powerful explosions whose mechanism and progenitors remain elusive. Several studies have shown a preference for SLSNe I to occur in low-metallicity, actively star-forming dwarf galaxies. Aims. We investigate whether the host galaxies of SLSNe I show increased evidence for interaction. Galaxy interaction can trigger star formation and provide favourable conditions for these exceptional explosions to take place. Methods. Based on SLSN host galaxy images obtained with the Hubble Space Telescope (HST), we narrowed down a sample of 42 images obtained in the rest-frame ultraviolet over the redshift range between 0 <  z <  2. The number of host galaxy companions was measured by counting the number of objects detected within a given projected radius from the host. As a comparison, we used two different Monte Carlo-based methods to estimate the expected average number of companion objects in the same HST images, as well as a sample of 32 dwarf galaxies that have hosted long gamma-ray bursts (GRBs). Results. About 50% of SLSN I host galaxies have at least one major companion (within a flux ratio of 1:4) within 5 kpc. The average number of major companions per SLSN I host galaxy is 0.70−0.14+0.19. Our two Monte Carlo comparison methods yield a lower number of companions for random objects of similar brightness in the same image or for the SLSN host after randomly redistributing the sources in the same image. The Anderson-Darling test shows that this difference is statistically significant (p-value < 10−3) independent of the redshift range. The same is true for the projected distance distribution of the companions. The SLSN I hosts are, thus, found in areas of their images, where the object number density is greater than average. The SLSN I hosts have more companions than GRB hosts (0.44−0.13+0.25 companions per host distributed over 25% of the hosts) but the difference is not statistically significant. The difference between their separations is, however, marginally significant with SLSN companions being closer, on average, than those of GRBs. Conclusions. The dwarf galaxies hosting SLSNe I are often part of interacting systems. This suggests that SLSNe I progenitors are formed after a recent burst of star formation. Low metallicity alone cannot explain this tendency.

scholarly journals Full of Orions: a 200-pc mapping of the interstellar medium in the redshift-3 lensed dusty star-forming galaxy SDP.81

2020 ◽  
Vol 494 (4) ◽  
pp. 5542-5567 ◽  
Author(s):  
Matus Rybak ◽  
J A Hodge ◽  
S Vegetti ◽  
P van der Werf ◽  
P Andreani ◽  
...  
Keyword(s):  
Field Strength ◽  
Interstellar Medium ◽  
Far Infrared ◽  
Source Plane ◽  
Star Forming ◽  
Physical Conditions ◽  
Orion Trapezium ◽  
Thermal Saturation ◽  
Continuum Data ◽  
Far Ultraviolet

ABSTRACT We present a sub-kpc resolved study of the interstellar medium properties in SDP.81, a $z$ = 3.042 strongly gravitationally lensed, dusty star-forming galaxy, based on high-resolution, multiband ALMA observations of the far-infrared (FIR) continuum, CO ladder, and the [C ii] line. Using a visibility-plane lens modelling code, we achieve a median source-plane resolution of ∼200 pc. We use photon-dominated region (PDR) models to infer the physical conditions – far-ultraviolet (FUV) field strength, density, and PDR surface temperature – of the star-forming gas on 200-pc scales, finding a FUV field strength of ∼103−104G0, gas density of ∼105 cm−3, and cloud surface temperatures up to 1500 K, similar to those in the Orion Trapezium region. The [C ii] emission is significantly more extended than that FIR continuum: ∼50 per cent of [C ii] emission arises outside the FIR-bright region. The resolved [C ii]/FIR ratio varies by almost 2 dex across the source, down to ∼2 × 10−4 in the star-forming clumps. The observed [C ii]/FIR deficit trend is consistent with thermal saturation of the C+ fine-structure-level occupancy at high gas temperatures. We make the source-plane reconstructions of all emission lines and continuum data publicly available.

scholarly journals Far‐Infrared Spectroscopy of Normal Galaxies: Physical Conditions in the Interstellar Medium

2001 ◽  
Vol 561 (2) ◽  
pp. 766-786 ◽  
Author(s):  
S. Malhotra ◽  
M. J. Kaufman ◽  
D. Hollenbach ◽  
G. Helou ◽  
R. H. Rubin ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Interstellar Medium ◽  
Far Infrared ◽  
Far Infrared Spectroscopy ◽  
Normal Galaxies ◽  
Physical Conditions

scholarly journals Characterisation of the submillimeter excess in dwarf galaxies: Presentation of the Herschel Dwarf Galaxies Survey

2011 ◽  
Vol 7 (S284) ◽  
pp. 149-151
Author(s):  
Aurélie Rémy ◽  
Suzanne C. Madden ◽  
Frederic Galliano ◽  
Maud Galametz ◽  
Sacha Hony ◽  
...  
Keyword(s):  
Dwarf Galaxies ◽  
High Sensitivity ◽  
Far Infrared ◽  
Space Observatory ◽  
Low Metallicity ◽  
Survey Sample

AbstractThe Herschel Space Observatory is revolutionizing our view of dust in galaxies with high sensitivity observations in the far infrared(FIR)/submillimeter (submm) regime from 70 to 500 μm. Herschel is confirming the submm excess that has been noted previously in low metallicity dwarfs. We present here the Dwarf Galaxies Survey sample through a Herschel colour-colour diagram. We will then focus on two galaxies, Haro11 and NGC4449 presenting different interesting behaviours in the FIR as revealed by Herschel.

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