My research focuses on nearby galaxies, with the prime goal of understanding the environmental and chemical mechanisms that regulate star formation. This includes studying a variety of physical and density scales: from individual proto-star clusters in nearby galaxies to entire ensembles of (giant) molecular clouds in extragalactic systems. To do this, I employ an extensive set of spectroscopic tracers of molecular gas. I have recently began applying my expertise to studying the effects of cluster galaxies' environment on their dense molecular, star-forming gas.

For my research, I make extensive use of radio and sub-mm observations taken with a variety of telescopes (interferometric and single dish: SMA, ALMA, NOEMA, GBT, IRAM-30m), but also combines this information with data taken at shorter wavelengths (VLT/MUSE, HST, Spitzer, Herschel).

Dense gas in nearby galaxies

Density plays a key role in any star formation theories because it directly governs the free-fall time in molecular clouds. Estimating gas density across galaxies is therefore crucial. As the lead observer of the IRAM-30m Large Program EMPIRE, I obtained exceptional data of dense gas tracers across entire disks of 9 nearby spiral galaxies. By combining these data with a suite of multiwavelength observations, I found evidence for a variable star formation efficiency of the dense gas, which anti-correlates with increasing hydrostatic pressure. Thus, although dense gas appears abundant the central regions of many spiral galaxies, this gas appears relatively inefficient at forming stars.

Extragalactic Chemical Complexity

High critical density molecular lines represent our best tool currently to study star-forming, dense molecular gas at extragalactic distances. However, the emission coming from common dense gas tracers like HCN, HCO+ and HNC is often found to be optically thick. Estimating the optical depth of these lines is essential to derive the mass and density structure of the dense ISM. Building up on the EMPIRE survey, in Jiménez-Donaire+17a I presented IRAM 30m and ALMA measurements of dense gas isotopologues for the first time spatially resolved across the disks of five nearby galaxies. This had only been possible in very bright systems such as U(LIRGS), starbursts or galaxy centers .

The EMPIRE deep observations alsp offered me the chance to trace the variation of isotopic abundances across the disks of galaxies by analyzing CO isotopologues such as 13CO and C18O. In Jiménez-Donaire+17b I found clear evidence for a varying C18O-to-13CO ratio across wide areas in the disks of nine nearby galaxies. This variations can be linked to a combination of abundance differences and fractionation (rather than an optical depth effect).

Molecular gas and star formation in cluster environments

The recent VERTICO CO ALMA Large program systematically probes sub-kpc scale observations of molecular gas in Virgo cluster galaxies. Based on the analysis of this pioneer dataset and multiwavelength supporting data, I found strong evidence that the large-scale environmental mechanisms affecting the HI galaxy content also have a direct impact in the star formation efficiency of molecular gas in cluster galaxies, leading to longer depletion times in HI-deficient members.

Embedded proto-star cluster formation

Super star clusters have extraordinary mass (>10^5 Msun) and compactness (few pc), producing intense radiation fields and strong winds, which power the large-scale outflows of material from these galaxies. Little is known about the life cycles of these massive clusters of stars, in part because extremely high-resolution, multi-wavelength observations are required. I have carried an ambitious campaign with the SMA to obtain new sub-arcsecond data in dust and gas tracers of M82, our closest northern nuclear starburst, to characterize its SSC population (Jiménez-Donaire et al. in prep.).

My office



mdonaire *at*


Observatorio Astronómico Nacional
C/Alfonso XII, 3
28014 Madrid, Spain