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Life’s Ingredients in a Distant Galaxy

We spend so much time talking about the Arecibo radio telescope with regard to planetary radar that it’s nice to come back to its applications in deep space. Thus the news that astronomers using the instrument have found key ingredients of amino acids in a galaxy 250 million light years from Earth in the constellation Serpens. The molecules are methanimine and hydrogen cyanide which, with the addition of water, form the amino acid glycine, considered a key ingredient in life on Earth.

Arp 220 galaxy

Arp 220 is known for a high rate of new star formation, and recent Hubble work has discovered more than 200 star clusters at its heart. Observing it at a range of frequencies and using the wide-band mode of the main spectrometer, the team, led by Arecibo astronomer Christopher Salter, found the characteristic emission of the molecules clearly evident. Says Emmanuel Momjian (NRAO), “The fact that we can observe these substances at such a vast distance means that there are huge amounts of them in Arp 220. It is indeed very intriguing to find that the ingredients of life appear in large quantities where new stars and planets are born.” This Cornell news release has more.

Image: The galaxy Arp 220, where the recent finds were made. The Hubble Space Telescope’s Advanced Camera for Surveys has uncovered more than 200 mammoth star clusters in its heart. The clusters are the bluish-white dots scattered throughout the image. The heftiest Arp 220 cluster — about 10 million solar masses — is twice as massive as any comparable star cluster in the Milky Way. Arp 220 collided with another galaxy about 700 million years ago, fueling the frenzy of star birth in a small region about 5,000 light-years across. The galaxy is a nearby example of the aftermath of two colliding galaxies. Credit: Credit: NASA, ESA, and C. Wilson (McMaster University, Hamilton, Ontario, Canada).

Bear in mind that Arecibo has recently been ugraded with new receivers, thus allowing the 800-MHz wide-band study the team performed on Arp 220. The galaxy itself has been the subject of intense scrutiny. Classed as an ultra-luminous infrared galaxy (ULIRG), it seems to have an active galactic nucleus (AGN) at its core. The high level of new star formation is thought to be related to a collision between two galaxies, making Arp 220 the brightest of the three galactic mergers closest to Earth. The star formation itself is occurring in a region about 5000 light years across, where gas and dust are dense enough to equal all gas and dust in the Milky Way. More on the latter finding in this Hubble news release.

Comments on this entry are closed.

  • david January 18, 2008, 22:22

    Just idle wondering, but I wonder if space is expanding then if a race has just beamed us a signal from 250 million light years away then it will actually take longer than 250 million years to reach the earth. And a reply would take even longer. I wonder at what distance would they need to be now so that their message could never reach us due to space expanding faster than the signal could travel. And at what distance would their signal reach us but our reply would never reach them. Assuming space is expanding.

    Just idle wondering on my part. 250 million light years is a long distance and a lot of time for a signal traveling at light speed. If the universe has spawned multiple intelligences it might be impossible for us to ever know it if we are separated by a large enough distance.

  • ljk February 1, 2008, 17:11

    Silicates in Ultra-Luminous Infrared Galaxies

    Authors: M. M. Sirocky, N. A. Levenson, M. Elitzur, H. W. W. Spoon, L. Armus

    (Submitted on 30 Jan 2008)

    Abstract: We analyze the mid-infrared (MIR) spectra of ultraluminous infrared galaxies (ULIRGs) observed with the Spitzer Space Telescope’s Infrared Spectrograph. Dust emission dominates the MIR spectra of ULIRGs, and the reprocessed radiation that emerges is independent of the underlying heating spectrum. Instead, the resulting emission depends sensitively on the geometric distribution of the dust, which we diagnose with comparisons of numerical simulations of radiative transfer. Quantifying the silicate emission and absorption features that appear near 10 and 18um requires a reliable determination of the continuum, and we demonstrate that including a measurement of the continuum at intermediate wavelength (between the features) produces accurate results at all optical depths. With high-quality spectra, we successfully use the silicate features to constrain the dust chemistry. The observations of the ULIRGs and local sightlines require dust that has a relatively high 18/10um absorption ratio of the silicate features (around 0.5). Specifically, the cold dust of Ossenkopf et al. (1992) is consistent with the observations, while other dust models are not. We use the silicate feature strengths to identify two families of ULIRGs, in which the dust distributions are fundamentally different. Optical spectral classifications are related to these families. In ULIRGs that harbor an active galactic nucleus, the spectrally broad lines are detected only when the nuclear surroundings are clumpy. In contrast, the sources of lower ionization optical spectra are deeply embedded in smooth distributions of optically thick dust.

    Comments: 38 pages, 11 figures; to appear in ApJ v679 (May 20)

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0801.4776v1 [astro-ph]

    Submission history

    From: N. A. Levenson [view email]

    [v1] Wed, 30 Jan 2008 21:53:46 GMT (61kb)

    http://arxiv.org/abs/0801.4776

  • ljk March 10, 2008, 23:45

    Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical Model

    Authors: Robin T. Garrod, Susanna L. Widicus Weaver, Eric Herbst

    (Submitted on 8 Mar 2008)

    Abstract: Gas-phase processes were long thought to be the key formation mechanisms for complex organic molecules in star-forming regions. However, recent experimental and theoretical evidence has cast doubt on the efficiency of such processes. Grain-surface chemistry is frequently invoked as a solution, but until now there have been no quantitative models taking into account both the high degree of chemical complexity and the evolving physical conditions of star-forming regions.

    Here, we introduce a new gas-grain chemical network, wherein a wide array of complex species may be formed by reactions involving radicals. The radicals we consider (H, OH, CO, HCO, CH3, CH3O, CH2OH, NH and NH2) are produced primarily by cosmic ray-induced photodissociation of the granular ices formed during the colder, earlier stages of evolution. The gradual warm-up of the hot core is crucial to the formation of complex molecules, allowing the more strongly-bound radicals to become mobile on grain surfaces.

    This type of chemistry is capable of reproducing the high degree of complexity seen in Sgr B2(N), and can explain the observed abundances and temperatures of a variety of previously detected complex organic molecules, including structural isomers. Many other complex species are predicted by this model, and several of these species may be detectable in hot cores. Differences in the chemistry of high- and low-mass star-formation are also addressed; greater chemical complexity is expected where evolution timescales are longer.

    Comments: Accepted for publication in ApJ (57 pages, 9 figures)

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0803.1214v1 [astro-ph]

    Submission history

    From: Robin Garrod [view email]

    [v1] Sat, 8 Mar 2008 04:38:25 GMT (351kb)

    http://arxiv.org/abs/0803.1214

  • ljk May 7, 2008, 6:58

    Detection of Extended Hot Water in the Outflow from NGC 2071

    Authors: Gary J. Melnick, Volker Tolls, David A. Neufeld, Yuan Yuan, Paule Sonnentrucker, Dan M. Watson, Edwin A. Bergin, Michael J. Kaufman

    (Submitted on 5 May 2008)

    Abstract: We report the results of spectroscopic mapping observations carried out toward a ~1 min x 1 min region within the northern lobe of the outflow from NGC 2071 using the Infrared Spectrograph (IRS) of the Spitzer Space Telescope. These observations covered the 5.2-37 um spectral region and have led to the detection of a number of ionic, atomic, and molecular lines, including fine-structure emission of Si+, Fe+, S++, S, the S(0)-S(7) pure rotational lines of H2, the R(3) and R(4) transitions of HD, and at least 11 transitions of H2O. In addition, the 6.2, 7.4, 7.6, 7.9, 8.6 and 11.3 um PAH emission bands were also observed and several transitions of OH were tentatively detected. Most of the detected line transitions were strong enough to map including, for the first time, three transitions of hot H2O.

    We find that: (1) the water emission is extended; (2) the extended emission is aligned with the outflow; and, (3) the spatial distribution of the water emission generally follows that observed for H2. Based on the measured line intensities, we derive an HD abundance relative to H2 of 1.1-1.8 10^-5 and an H2O number density of 12-2 cm^3. The H2 density in the water-emitting region is not well constrained by our observations, but is likely between 3 10^4 and 10^6 cm^3, yielding an H2O abundance relative to H2 of between 2 10^-5 and 6 10^-4.

    Future observations planned for the Herschel Space Observatory should greatly improve the density estimate, and thus our knowledge of the H2O abundance, for the water-emitting regions reported here. Finally, we note a possible departure from the H2O ortho-to-para ratio of 3:1 expected for water formed in hot post-shocked gas, suggesting that a significant fraction of the water vapor we detect may arise from H2O sputtered from cold dust grains.

    Comments: 35 pages, 15 figures, 4 tables, accepted for publication in ApJ

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0805.0573v1 [astro-ph]

    Submission history

    From: Gary Melnick [view email]

    [v1] Mon, 5 May 2008 17:02:20 GMT (2937kb)

    http://arxiv.org/abs/0805.0573

  • ljk May 13, 2008, 15:04

    A Molecular Thermometer for the Distant Universe (ESO 13/08)

    Astronomers have detected for the first time in the ultraviolet the
    carbon monoxide molecule in a galaxy located almost 11 billion light-
    years away, a feat that had remained elusive for 25 years. This
    detection allows them to obtain the most precise measurement of the
    cosmic temperature at such a remote epoch. Read more about this
    discovery in ESO 13/08 at:

    http://www.eso.org/public/outreach/press-rel/pr-2008/pr-13-08.html

  • ljk December 17, 2008, 17:49

    Water is detected in a galaxy 7 billion light years from Earth:

    http://www.universetoday.com/2008/12/17/water-way-out-there/