The understanding of the interstellar medium (ISM) and star formation in the low-metallicity environment is crucial to constrain formation of stars and galaxies of the first generation. The local extremely low-metallicity galaxies (XMPGs) with Z<Zsun/20 offer the unique laboratory with nearly metal-free environment that mimics the condition in the early universe. Previous infrared studies have focused on their integrated properties due to their small sizes and faint brightness. The general conclusion is that they show dramatic different ISM and star formation properties from more metal-rich galaxies, and that a large diversity in the properties is also seen among XMPGs alone. The high resolution combined with its multiple far-IR bands of Herschel will revolutionize the study of ISM and star formation in XMPGs through the spatially-resolved images of dust properties (mass and temperature) and SFRs. By relating the dust and star formation properties to the local physical conditions, we can start to understand the underlying physical mechanisms that regulate ISM and star formation processes in the extremely low-metallicity environment. We propose to obtain deep map of the dust emission in three XMPGs with Herschel PACS and SPIRE photometer. These three objects are carefully selected to facilitate the spatially-resolved study, i.e. the large size and previous IR detections by Spitzer. Combined with a rich ancillary data, we will (1) model dust emission to derive dust properties and then relate it to the local physical properties; (2) derive reliable SFRs by combining IR-based obscured SFRs and UV-based unobscured ones, from which we then can understand the star formation processes at sub-kpc scales.
Publication
Spatially resolved dust emission of extremely metal-poor galaxies* . Zhou Luwenjia et al. . Monthly Notices of the Royal Astronomical Society, Volume 458, Issue 1, p.772-780 . 458 . 10.1093\/mnras\/stw345 . 2016MNRAS.458..772Z , Inefficient star formation in extremely metal poor galaxies . Shi Yong et al. . Nature, Volume 514, Issue 7522, pp. 335-338 (2014). . 514 . 10.1038\/nature13820 . 2014Natur.514..335S ,
Instrument
PACS_PacsPhoto_largeScan, SPIRE_SpirePhoto_small
Temporal Coverage
2012-04-06T00:34:48Z/2012-11-19T05:55:03Z
Version
SPG v14.2.0
Mission Description
Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
European Space Agency, 2013, Extremely-Metal Poor Galaxies: Mapping Dust Emission, SPG v14.2.0, European Space Agency, https://doi.org/10.5270/esa-q4fbs1o
